BritishV8 Forum

Hi all,

Does anyone have any idea the potential for the 300 with the 350 crankshaft using the stock aluminum heads (or really, just a good valve job and mild porting) and standard 4BBL manifold (and whatever is an appropriate carb and camshaft)?  Also, I was looking at the Sniper 2BBL EFI unit and noticed it's supposed to be good for engines of "up to 350HP".  I also have a 2BBL manifold and was wondering if this *might* be a good choice for my engine if I decided to use the standard heads and 350 crank.

Just still considering my options before I pull the trigger on the much more expensive TA heads and possibly Brian's new intake manifold.

Any and all opinions are welcomed.  Thanks.

Eric, Glad to have you back! Crower 50233 With Brian's intake with 4 barrel Sniper would be killer combo. 2 barrel combo will cost some HP. If you go to the trouble to stroke it don't skimp.

Thanks Jim--and I appreciate your help!  Any idea what his intake will cost?  I'm starting a list of the parts.  Still on the fence about the heads, but I think the TA heads are the ones, unless that intake is better with something else.

This article on building just such a stroker 300 Buford remains one of the best things Hot Rod Magazine has ever published.

https://www.motortrend.com/how-to/hrdp-1103-how-to-hot-rod-any-engine/

Joe, that is definitely a great article.  Would have been interesting to see what they would have gotten with aftermarket heads and/or EFI, but it remains my inspiration for my build.

Don't overlook the stroker thread on MGE and the 300 thread on the V8Buick small block forum. Lots of good info there.

Bear in mind that the stock SBB heads and the TA heads have different chamber volumes so you can't just swap from one to the other. A good compromise is to build the engine with late Rover heads and have the ability to do a direct swap to TA heads later.

If your target redline is under 6000rpm there is no real need to use forged rods and pistons, but for a stroker custom pistons may be necessary to get the desired squish and CR. If you have to use custom pistons you may as well have the ex-nascar forged rods and some peace of mind about over-reving. I've found Wiseco to be a decent choice. There is an absolutely huge difference between the strength of the stock rods and forged ones. The ex-nascar ones run about $100 a set.

Jim

Thanks Jim B,

My plan is to use Nascar forged rods.  I was able to pick up a set for about $100 awhile ago that I believe will work well with the Ford 2.3 Turbo pistons.   IF that is what I would run with, can you help me understand the pros and cons between using the late model (4.6?) Rover heads and the aluminum 300 heads.  Also, from what I can tell from the Dan Jones chart, the SBB heads flow better than the 4.6 Rover heads, but I *think* I remember that those SBB heads were highly ported and maybe the Rover heads were stock (so maybe not apples-to-apples?)?

300 Buick heads outflow the Rover heads but have a large combustion chamber. The Rover and TA heads have a smaller chamber . So you can use the same pistons if you decide to go with the TA heads later on.

Jim N,

Thanks, that's good to know.   I do like having an upgrade path.  I can't recall the calculations I did when I bought the Nascar rods, but I think at that time, I had the 300 heads in mind.  So now, I have to figure out how the two heads might compare from a CR perspective with those rods and pistons.  Also, I think I recall there being some advantages to the shape of the combustion chamber in one vs the other?

300 large open chamber can run a flat top piston but not at zero deck. Rover and TA require a dished piston outside of dish at zero deck. Chris's combo is about 10.3 compression. 300 head with flat top. Jim B would know cc of dish required for the smaller chamber.

Thanks Jim.

The rods I got are .912 on the small end (SBF) by 2.00 on the big end X 6.320.  When I was previously mulling this over, you told me:

"That pin is typical Ford size. Look at 3.78 Ford Turbo 2.3. pistons. You need 1.52 pin height for zero deck. Those are 1.578 but have an extra thick crown and would be no problem to mill .060 off. With a true flat top I would grind off the lug in the chamber and figure 58cc for chamber in the calculator. I get .005 down from zero deck and 10.3 compression. You would have to measure to be sure."  

I believe your comment was in reference to using the 300 heads.  Do you agree with that?  If so, I assume IF I wanted to use the Rover heads, I'd need to find a different set of pistons, correct?

Yep, For the Rover heads you would need a deep dish probably 30 something cc. Rimmer sells the largest valves for the stock Rover heads. Pretty close to the 300 valve size. You could use spacers and valley plate with the Edelbrock performer intake. You wouldn't make the power that the TA heads and Willpower have but have nice throttle response.

Chamber size for the TA and Rover heads is going to be about 31-32 cc. With a zero deck piston having a 35 cc dish you should come out at about 10.5:1 which is a good ratio for a street engine with alloy heads. The TA and Rover heads are more of a closed chamber design and can make use of squish area. Standard Fel-Pro blue gaskets and a zero deck will give you about .040" squish.

A 6.2" rod with the 350 crank and a 1.405 compression height should put the piston at zero deck height, depending if it's been surfaced. So another .120 on the rod length means cutting the compression height down to around1.280" Should be plenty of room to do that with a standard ring package, even with the dish. I had some Venolias made up with a 1.283" CH and 22 cc dishes and they were a thick crown piston for blower duty and had a standard ring package. Still had room between the oil ring and the piston pin but that was with a 3/4" piston pin. You'll be getting a little close there but it should still work. With a custom piston and a thinner ring package it would not be an issue at all. But, you may not find a suitable off the shelf piston.

Jim

Jim and Jim,

Thanks for the insight.  I feel like the light has finally turned on.  Time to do some more research on pistons, which might drive the head decision.  I already have the 300 heads, so I'm leaning in that direction.  But if I'd need custom pistons for the 300 and could find some off the shelf ones for the Rover, that might change things, especially since the Rover heads are so cheap (and would give me an upgrade path or easier replacement in the future).

As always, I appreciate the guidance!

Eric

Eric, I thought you had 6.2" connecting rods? That is what I calculated. You are close to stock length Buick 350 Rods. Chris used 2.5 Ford SOHC pistons with 1.19 pin height for his build. They have .912 pins. Your rods are 060 shorter than stock 350. I get 1.25 pin height with your rods.

These pistons look good with the small chamber heads. Block should be sonic checked as these would be .060 over. Pin hole would have to be honed for .912 pins.

https://www.ebay.com/itm/273956947909?hash=item3fc91b47c5:g:RKIAAOSwFttdSLG9&amdata=enc%3AAQAHAAAAoHC%2BfWCSmg1Zt4TsYExiLX8mMTL8F6uGDGqqD370g%2B6Cs0xQen1OTZS8yMv5kAwshAJolwssny4HCIaIMVlY475eVb4krp7FLKYPIQtnpPpojzU0vI7h0OL5aHz5BN8eSWQK5V%2BH0ViZRAKNpHTW7tbUWr8%2FCw1lgwLtCtTzLm8Ny%2FgD8MR1Kbz6E2jHO1VK8X0CKtAM5BaT3mADRkqN6fQ%3D%7Ctkp%3ABk9SR57YjYCRYQ
s-l5002.jpg

Jim,

It's distinctly possible (even likely) I made a mistake when I told you what I had--if so, sorry about that.  So, I just checked and sure enough, I have 6.320 rods.  So, I'm confused about what you mean about 1.25 pin height with my rods--do you mean with the turbo pistons?  Would the 2.5 pistons that Chris used work with the large chamber 300 heads and my rods?  

Thanks for the eBay listing for the dished pistons, you save me a lot of searching if I go with the Rover heads.

No, it changes everything. 2.3 Turbo pistons are too tall and Chris's pistons are too short. The one above would work.

Got it.  Makes sense.  Thanks again.

Very good price on those pistons. They don't specify the dish volume but it should be close. Deck height on the 300 is 9.543 so run your numbers on those to see where your pistons end up. I show them .044" down in the hole which means you'd have to use the steel shim head gaskets to get any meaningful squish out of them and then it'd be .054" which is a bit more than optimal but a .014" skim of the decks puts you right there. (Not that I'm a big fan of steel shim gaskets) Can't say what the CR would be without the dish volume.

Jim

Head combustion chamber size:

Early Rover  36-37cc

Late Rover (10 bolt) 28-29cc

300 Buick (alum.)  53-54cc

These are the most common reported CC sizes.

I have all three in my garage.  Some cold, rainy day I need to cc them.

TA should be 1 to 4 CC larger than late Rover heads according to that and my measurements of the TA chambers

Jim

Remember those pistons are for a V6 so you have to buy 2 more.

I do like the pistons Jim N. suggested, but I am concerned about the overbore requirement.  So, I want to look a bit more before I decide.  Can anyone tell me the optimal dimension (at or below the deck) for the combination of the rod length and compression height for both the 300 and Rover/TA heads?  I've tried to verify the dimensions but haven't seen exact numbers and I'm not convinced my backing into it calculations are correct.  I saw Jim B. say earlier that with a 6.2" rod and a 1.405" CH, the dimension is at top of deck--what confuses me is that I have in my notes that the standard rods of 5.963" + Buick 300-4  pistons at 1.859" CH  = 7.822".  I'm not sure where I got that from, but perhaps the Buick V8 site (?).  And I think I understand that, at least for the Rover/TA, we'd want to be at top of deck (whatever that number is) and have a dished piston with about 3-7cc of volume in the dish?

I also prefer, as Jim B. mentioned, to use composite gaskets, so I  know that will make a difference.  This decision seems to be driving a lot in my engine and I don't trust that I have it right yet--so I appreciate your patience with my (lack of) knowledge.  Thanks much.  --Eric

Take your deck height: 9.543"
Subtract half of the stroke: 3.850/2= 1.925
Subtract rod length: 6.320

The result is piston height for zero deck. .040" thick gasket gives .040 squish.

Jim

For my (crank at the machine shop for 6 months) engine build, I first built a spreadsheet.

Using the numbers put up so far (I've made them metric), the Ebay pistons look close, except for the big squish. But decking the block to reduce it, and/or using a thinner gasket will push your compression higher than I think you want?
300:350.jpg

Jim,

Thanks, as always.

Chad, that spreadsheet looks great--any chance you could send it to me?  And I assume these numbers assume using the 300's heads?  If so, just curious if you did a version with Rover 4.6 heads?  I'm comparing both options.

Thanks much to both of you.

Just to stir the muddy water,  I do not think that the stock 300 heads are much, if any, better than the late Rover heads.  Both well ported, the 300 wins easily.

Remember the chamber of the late Rover head is around 29cc and the 300 is around 54cc.

Chad's spread sheet uses 300 heads. if you use the small chamber Rover heads you need around 35cc dish in the pistons.

At 29 cc for the head volume, you end up with ~15.8 compression.

-edit
Ha, Jim out typed me. And I wonder if squish matters much with (heavily) dished pistons and no squish-pad to speak of with the Buick heads?

Ha, I was thinking I was close to figuring it out.  There is a lot of great information here to evaluate.

Carl, I already have some 300 heads.  I was originally leaning in that direction.  One thing that made me think the Rover heads might be better is availability, in case of damage.  What are your thoughts about durability of the 300 heads, especially at high compression?

Chad, subtract 35cc for the dish on the piston.

9.9 with 29cc Rover heads and -35 dished pistons.
But that's assuming the same compression height (or custom?) as the Ebay pistons.
I've spent the time in the past searching the various piston seller's sites, trying to find the magic combo of diameter, compression height, pin size, dish, cost, and quality. I know it's no picnic!

If you deck the block about .030 should put you around 10.3 or so. If you sonic check and bore .060 shouldn't be an issue, They sell .060 over pistons for the 300. I know a few have went .050 over.

" What are your thoughts about durability of the 300 heads, especially at high compression?"

How much compression?

Mike Moor's 1964 Buick 300 is a factory 4bbl 11:1 engine.  He has refreshed it a time or two, but the heads are original.  He swapped out his 215 for the 300 in 1997 or 1998.

I don't think that ad had the dish volume, just the depth which is basically useless. If so, you can't assume a 35cc dish. Did I miss something?

Rover heads are a couple pounds heavier than Buick ones, are made from a little stronger alloy and are a bit denser so they will hold up a little better in a demanding application. In particular the bolt bosses are a little soft in the Buick heads. They can work fine but can also have issues, so be certain to use thick hardened washers under the head bolts and don't over torque the rocker shafts and accessories.

You can buy 4.6 Rover heads for about $200 each on ebay these days. The last set of 300 heads sold on ebay went for $400 + $85 shipping so that's a wash. No need to be tied to the 300 heads. If you end up with the single plane intake you'll be kicking yourself later on for using the Buick heads because you won't be able to swap to the TA heads to take advantage of the intake. This upgrade path can also include a roller cam, which doesn't necessarily have to be particularly radical to let you use modern oils in the engine. With that combo something in the 400 neighborhood should be pretty easy. The MGB can handle that. Just as importantly though the torque output will make driving it a very pleasant experience.

The 300 heads may flow noticeably more than the 4.6 heads or the difference may not be enough to feel, I really don't know. But the TA heads right out of the box are a big step up. Worth the money? I guess that depends on whether you have it to spend. I bought the bare heads and built them myself with used titanium valves and beehive springs for a good bit less than the complete heads cost. Took some machine work to do it but that only cost me time and I gotta say, cutting down titanium intake valves to fit was a very fun experience.

Jim

Jim, Just speculating on the dish cc's, could be 30 or 25. Have to measure.

Always best to measure. Maybe we can persuade Carl to do that. From what I've seen online though it should be 29cc.

Jim

I have seen the late Rover (10 bolt) head combustion chambers listed at both volumes.

<i.You will loose about 0.6:1 CR by using 14 bolt heads with composite gaskets. The exact CR difference will depend upon the gasket manufacturer and the compressed thickness, but 0.6:1 is most you will lose.

I think you may find that it is actually a bit higher than 0.6:1. The compression ratio is calculated by dividing the swept volume and the static volume into the static volume. Therefore if you change the static volume (the bowl in the head and the piston) by 10%, the compression ratio will change by 10%. Rover reduced the capacity of the head from 36CC to 28CC to compensate for the composite gasket. Therefore a rough calculation would suggest that the composite gasket has a volume of around 8CC. The piston bowl on a 4.6 is around 22CC in a 9.35:1 motor. 4.6 bowls are some of the largest you will find in a rover V8. So with the old heads you would have a total static volume of around 58CC (36 ford head and 22 for piston). So if you increase the volume by 8CC by using a composite gasket you will increase the static volume by 8/58 or 14%. 14% of 9.35 is 1.3 change in compression ratio.

For a 4.0 motor the piston bowl is only 13CC, which would make a total volume of 49CC and the change would be 16% or a change in compression ratio of 1.5

I am not attempting to state that the above figures are 100% accurate in their calculation, but I think you will find that the change in ratio is above 1 or the equivalent of going from a High Compression Rover V8 to the standard Low Compression version.

---------------------------

Tempest and Thor. With the introduction of the new Range Rover in 1994 a new head was brought into being, with a revised casting (No 2479) the head had larger ports than the Vitesse heads but retained the same valves and guides which were present from ~1993 onwards. The combustion chamber volume (29cc) was also reduced (by simply machining off more material on the face) to compensate for the increased thickness of the composite head gaskets and probably most noticeable, the 14 head bolts were reduced to 10, the 4 outermost being removed. Incase you're told otherwise, 4.0 and 4.6 litre heads are identical.
Casting Numbers: HRC 2479

Carl, that's interesting--thanks.  I now wonder if anyone had done a specific comparison of these larger port late Rover heads and the 300 heads.

As an aside, I did a rough calculation on the Ford Triton pistons that Jim N. found--I *think* the dish is about 19cc, if my calculation is correct.

Dan Jones has probably done the most flow testing and documentation but we'd need him to say if he has the info needed to do a proper comparison. Should be close but I just don't know. By all rights both heads should be fitted with the same size valves for testing but the thing is, if you are going to fit larger valves you'll tend to go as big as you reasonably can rather than stop at the stock 300 sizes. So it might be relevant to ask if a late Rover head with big valves can flow as much or more than a stock 300 head. But then, big valves aren't free so it's also relevant to ask the results if the 300 heads also have the big valves. Easy enough to see why this might not have been done.

Jim

I think I skimmed the earlier thread and saw JimB's 22cc piston dish mentioned and conflated it with JimN's eBay pistons. Doing a quick cad model of the Ebay pistons, I get 14.6cc's of dish. With a 40 thou skim of the deck, the numbers start to look pretty good with 54cc 300 heads.

Chad, what with the 29cc heads?

14.6cc dish, 29cc heads gives 12.96 compression, 89 thou squish. No bueno.

Jim B,  yes, you're thinking the same thing I was really wondering--has anyone maxed out those late Rover heads and the 300 heads and compared them?  

And Chad's analysis begs the question, what is the maximum compression we'd ever want to see?  

I found a set of forged pistons https://uempistons.com/product/15777/ICON-Premium-Set-IC681CL.020 with 18.33 of dish (and with a bit of machining I think could be machined out to about 22).  With 22cc dish and the 29cc heads, and 51 thou head gasket, the squish is 45 thou, but the compression is 13.11.  But go to .070 head gaskets and the compression is 12.42 and squish is 64 thou--still not ideal.  

Chad, your spreadsheet is making much easier to compare options :)

Below is a link to a cleaned up version of that spreadsheet that anybody can swipe, with imperial and metric units accommodated. When I was piston hunting, I had about a dozen of these going as I compared the trade offs.

Also, here's just a table I've added to as I've seen numbers posted here and elsewhere of the various heads for the RV8.

https://www.dropbox.com/sh/aj86sj1jv7iiuk9/AADfGxZS35tm2zmq3Afnu-qza?dl=0
flownumbers.jpg

I've seen those numbers and they are helpful but what we don't have are unported big valve Rover or 300 numbers. That's what I'd really like to see, then I'd have a very good idea of what just the big valves or just the porting job would do. Well, I guess we have what just the porting job does with the Rover, but not the big valves. Still hard to make a valid comparison and what's the deal with the two 300 columns? Doesn't show what's different. Is one unported and both with big valves? (mislabeled) If that's the case we still have everything BUT what we need to properly compare the heads.

Jim

The two 300 columns were just different sources, different people reporting their numbers. With the stock Rover I stacked the numbers from two sources; not sure why I did it differently with the 300s. Probably just did them at different times, and didn't remember to follow the same format.

I currently have stock/untouched and an unported 300 head cut for big valves that I plan to put onto a flowbench, so that curiosity itch may soon get scratched.

V6 Triton pistons, $170 for (6) spend $340. for almost useable ? "350" crank= 3.8" stroke ? How heavy of a car that "needs" 3.8" stroke ? Cast crank with mains turned down to 2.5" ? How fast could the power of TA heads and a single plane,
destroy this combo ?  What octane requirement with what dynamic compression ratio ?
                    Good luck with a 6k rpm. torque monster, in a 2,200 lb. car.     Art.

The engine is "adequate" with the 3.4" stroke, even with the 2bbl intake. The 3.85" stroke makes it better. Good heads make it better. Light pistons and rods make it better. A roller cam makes it better.  A blower makes it better. TBI and mappable dizzy make it better. It's mostly a question of budget and how carefully you can spend it.

I sort of understand you de-stroker guys a little bit, but it's really going too far in the other direction. A stroker 300 with light rods, pistons, wrist pins, and aluminum flywheel will rev faster than is really comfortable on the street and a 7K redline is as easily achieved as with the short stroke. So what are you gaining? Because it isn't economy.

Here's the thing. You say you want a fast revving engine but it still has to move the car. With any given load and at any given engine speed assuming gear ratios and tire sizes are the same the engine with more power will accelerate the car faster. At any given rpm and assuming equal builds the engine with more displacement will produce more power. So the bigger engine will rev faster. Until you get significantly over 7000 rpm you really aren't going to change that and the 3.850" stroke SBB is quite capable of redlining at 7 grand if it's built right. De-strokers have their place but it is usually in racing where rules restrictions artificially influence natural progression such as F1. On the street things are a bit different. And yes, we all loved the SBC 302, but that was a very special engine built specifically for racing. Again, Rules.

Jim

Back to the heads, big difference between the two 300 heads, too much really for just using a different flow bench it seems. Something there doesn't quite add up.

Jim

Art, I hear what you're saying.  But as Jim says, it's a question of budget.  I think, to a certain extent, those TA heads are probably not necessary (and money that I can use elsewhere--such as having EFI, which will make the car way more drivable).  Without them, I still think I can get to the high 300s in horsepower, which along with the torque curve that engine should have, should make it fun, but not scary.  On the other hand, we haven't been discussing gearing either.  I wonder how much can be gained in having a balanced driving experience by having the right gear ratios.  I am thinking that my rear axle ratio might be around 3.55, to keep me from burning up a set of tires too fast.

Went back and did some more on piston options for the 300 heads.  This one looks very promising.
300HeadsCalculation.jpg

Eric, What piston is this? What pin size?

Jim,

It's a Chevy forged racing piston:  https://www.summitracing.com/parts/dms-1-2803-3780  It has .927 pins, so a bit of honing/reaming and rebushing will be required on my rods, but from what I can tell, it should still leave plenty of material at the small end.  And while they are more expensive than many of the pistons I've been looking at, at $537 they are not unreasonable.

"At any given rpm and assuming equal builds the engine with more displacement will produce more power. So the bigger engine will rev faster."

I don't follow that logic.


" I am thinking that my rear axle ratio might be around 3.55, to keep me from burning up a set of tires too fast."

I think the engine on your drawing board is going to eat up the tires even with that 3:55 gear, Eric.  May want to look into a 3:08.  ;)

Good advice Carl.  I was wondering about that.  I actually might be in luck--I think it's possible that my rear end has a 3:08 gear.  Haven't looked at it in quite awhile, I need to dig it out.

3.08 vs recapture rates.  In other words, pavement velocity vs tire velocity. If you break loose 3.08's in a smoking way, that much harder to recover versus higher numerical ratios.

'Cept 3.55, 3,9, 4.11, etc are easier to smoke.  ;)

Sort of depends on your transmission ratios, particularly 1st and OD.

I think my OD ratio is around .8 and with a 3.54 axle ratio I found I wanted a tall tire. I'm currently running a 26.5" diameter and it's just within the edge of the comfort range but off the line performance is exceptional. I think my 1st gear ratio is probably the 2.95 one or close. Running the larger tires is the equivalent of having a 3.18 axle ratio. If running the .67 OD things would be different and if 1st was over 3.0 with these gears that wouldn't be much fun. A 3.08 could work with the 2.95 1st of course, giving just over 9:1 in 1st but the .67 with the 3.08 gives a 2.06 final ratio and means a big jump from 4th to 5th. I think the 3.08 is a good ratio, just at the opposite edge of the comfort range. Based on the performance of the Roadmaster with it's 2.88 and .67 OD I'd say that's fairly accurate. With a smaller engine you'd find yourself downshifting more often. Luckily you can fine tune things with the tire size to some extent.

Carl, knowing you as I do I do not expect you to agree but if attempting to accelerate a given mass against a standardized resistance, more power is always going to reduce the time needed and increase the acceleration rate. Simple physics there. That's step one. Step two is that a larger displacement engine of a given build type is going to produce more power. Admittedly there's some wiggle room here but not really enough to overcome the displacement advantage unless there are some very radical differences in the build. If it's the same engine, the bigger one will make more power. (Displacement is King) Therefore, more displacement equals faster acceleration. Those monster Hemi's are king of the dragstrip for a reason and you don't see any of them being destroked. I'm not sure how to be any clearer about it, but as we all know opinions will vary and we can believe anything we like. I prefer it that way actually. And of course 600 gram pistons and rods, 100 gram wrist pins, and an 11lb flywheel make all the difference in the world. So much so that I feel the aluminum flywheel is completely unnecessary on the street. But of course there may be some builds where it would seem right. Apparently such is the case with some of the more extreme B series builds.

Jim

Yes. more power will get one down the quarter mile faster (if it hooks up).  Does not always equate to revving faster.  Although, in your case, with lighter reciprocating assembly, it does.  A run of the mill, stock components Buick 300, don't think so.  Compare it to a short stroke Chevy DZ 302.

>Yes. more power will get one down the quarter mile faster (if it hooks up). Does not always equate to revving faster.

Well, see I have a bit of an issue with that statement. It seems to me that less elapsed time is the same thing as accelerating faster.

A given car/engine combo will within reasonable limits turn a rather standard range of engine revolutions in traveling the 1/4 mile, say something in the range of maybe 2000 revolutions given variations in gear ratios, tire size, tire slippage and driver launch characteristics. ( 24" tires=~800rev/mi x axle and transmission ratios / .25 etc, it can be calculated rather more exactly) That being the case, and engine rpm at terminal speed being dependent on elapsed time ie, vehicle speed at the finish line, the more powerful engine not only reaches a higher rpm but does it quicker. How is that not faster acceleration, and likewise how is that not quicker revving?

Inquiring minds want to know.

Jim

I don't equate how quick an engine can get down the drag strip to how quick it can rev or get from zero to redline.  A drag car stays near redline the whole trip.  I have a pneumatic drill that can go from zero to redline pretty damn fast.  Not so quick in the 1/4 mile.   :)

"A given car/engine combo will within reasonable limits turn a rather standard range of engine revolutions in traveling the 1/4 mile, say something in the range of maybe 2000 revolutions"

BTW, a Top Fuel dragster turns a smidge over just one forth of that.

Yep. Well, like I said, fortunately we can believe whatever we like. I do like a peppy engine. And it's not like we are pushing any hard limits here, just have to pay attention to the weight of the internals. Those parts are considerably heavier than they have any need to be.

Jim

Revisiting this discussion.  After a lot of hand wringing, I decided to pull the trigger on getting the TA heads.  Of course, with those heads (and my 6.32" Ford-style connecting rods), that drives a different choice of pistons.  I am still trying to avoid custom pistons, but after a lot of searching, I came across these Mopar V6 pistons: https://www.summitracing.com/parts/uem-3245c-std, which have a 3.78" diameter (in the standard size for these pistons), 1.283" compression height, and are flat top (no dish or crown).  They are *about* $275 for a set of eight.  My initial calculations with this piston and head combination gives the following result:  12.5 compression ratio (with a thin 29 thousands head gasket), 41 thousands quench, and a 1.64 rod ratio.  Anyone have any thoughts on these?  I do know I'll have to re-bush the connecting rods for the slightly smaller Mopar size. And is 12.5 compression too high?  I know there are more variables, such as cam, intake, and exhaust, but trying to establish a baseline for the other variables.  Thanks!

Eric, Way too high! You don't want over 10.5.  What is the ideal pin height, Maybe 1.26? Most figure .020 for steel shim and .040 for composite gaskets. For zero deck with the small chamber heads you can't use a flat top you need a substantial dish. I'll do some calculations and try to find something.

Eric, this first calculator shows ideal pin height for zero deck as 1.295. the second calculator shows ideal dish cc at 37.5 for 10.5 compression. Both for 3.85 stroke and 9.540 deck height and 3.78 bore.

http://www.wallaceracing.com/Calc-Deck-Height-rod-length-new.php

http://www.wallaceracing.com/cr_test2.php

Thanks Jim, I figured you guys would have a better perspective than me.  I'll definitely check out what you sent over.

Eric give these guys a call for custom pistons. We lucked out with Chris's build with off the shelf pistons. Specify 1.29 pin height, 38cc dish and .912 pin. If they can't do 3.78 bore you may have to go 3.8.
https://dssracing.com/

"Eric, Way too high! You don't want over 10.5. "

And you will still be running on 93 octane.

I am hoping I can switch to 87 with about 9.5:1 & an all aluminum engine.

Jim and Carl,

Thanks.  I should be able to get it down to under 10.5.  I actually *may* have found an off the shelf LS piston that may work, although I'm going to look into the link that Jim sent along.

I appreciate the help, as always.

GM 4.8L or 5.3L, no doubt.

IIRC the TA heads have about a 35cc chamber. At zero deck with a composite head gasket that means a 35cc dish gives you right at 10.5:1 compression.

Jim

Carl, you're correct.  GM 5.3.  The OEM LS pistons don't seem to have anything close to the correct configuration, but I found an aftermarket forged piston that gets closer to what Jim N. suggested:  https://www.summitracing.com/parts/dms-1803-3780

The compression height is a bit higher at 1.305" and dish is less at 15cc, but I calculated 10.43 CR and .033 quench with a .040 gasket.  Jim B. mentioned 35cc, but I've seen mention of opening up the TA heads to a volume of 54 cc, but not sure if that's correct.  As GM pistons, the pin size is different from the Ford rods I have, so I need to figure if it's OK to hone the existing wrist pin bushings a bit (from .912 to .927).  Also, if I calculate with a thicker .050 gasket, CR drops a to 10.2 with quench at .043.

With rings and pins, this set runs about $725.

As an aside, IF it's possible to open up the combustion chambers, I'm wondering what would seem to be better--a larger chamber with less dish, or a smaller chamber with more dish.  Either way, there's likely cost (either custom pistons or work on the heads), so it would be interesting to consider what I might get with the two approaches.

And I found an old post from Jim B (to me). suggesting that opening up the TA heads is the wrong idea.  So, it may be custom pistons after all.

"My opinion is that opening up the combustion chambers is the wrong way to go, and for a couple of very good reasons. It may cost you a few hundred more to do but if you are considering the purchase of TA heads you can afford the alternative. And it eliminates probably over 20 hours of labor so if your time is worth more than say $20/hr it is worth it.

If you open up the chambers you lose any squish area the TA heads give you, reducing fuel efficiency and making the engine more prone to "ping" etc. Might just as well sit the pistons down further in the hole, the effect is much the same and is much easier to do.

You would also basically be destroying what are originally a great set of heads. Some may disagree, but really the heads are not the issue and neither is the combustion chamber. The real issue is the pistons. And if you are considering heads that will cost a bare minimum of $1600 even without valves and springs, it only makes sense to pony up the bucks for good pistons. If you do that the manufacturer will make the dish whatever you want it to be so why mess around with counter-productive work on your biggest investment in the engine? My last two sets of custom pistons from Wiseco, bought this year cost me $1100 a set and that was through my local machine shop. You may find cast pistons that won't work for as little as $200 a set but they won't be right for the heads and the engine. You may find forged pistons in the $400-600 range but to match bore, pin size, compression height and dish volume to what you need is going to be very difficult, time consuming, and likely ultimately unsuccessful. You can easily spend enough time on the quest to make the Wiseco pistons look like a very attractive option.

Now, if you've gotten this far, especially if you have the 350 crank and the ex-nascar rods, the next thing is the roller cam. From TA that's going to cost somewhere around $500. The lifters can be aftermarket Chevy at about $400 a set and you'll need a cam stop, so figure that as a $1000 option. By this point the engine cost is approaching $5K if you do most of the work yourself and you should be somewhat adverse to screwing up that size of an investment. So in terms of head work try to be a little more conventional. Sure, if you like, fit nice valves and springs and clean up the bowl areas a little. But remember what this engine is going in, a sub 2500lb car. You can be quite conservative and still have extremely good performance. There is no need to go all-out unless you will be racing it against similarly equipped cars and for the most part the guys in this group have nothing there left to prove. With that combo and a mild cam you should still be comfortably over 300hp, well into the muscle car range.

Which is why I mentioned starting out with the 4.0/4.6L heads. I just grabbed a set from the local pick-n-pull for $150 and the engine was pretty clean inside and had only a quite small ridge in the cylinders. I expect that with new seals I could use them as they are. I plan to use them on my 340 when it goes back together. It means I have to cut the piston dishes deeper but they are thick enough to do that. Then if I later feel a need to bolt on the TA heads it is a simple swap. The set of 300 heads can then go on the stock 300 (mule) and I'll have a set of low mileage iron heads that the Buick guys will likely be interested in.

Yes, you would be correct in thinking that this means I have 3 engines for my car, which does seem a little like overkill even for me and eventually I may let one or even two of them go. OTOH, once I've finished playing around with them the spares won't be eating anything and if I go out and abuse the engine in the car as I am somewhat inclined to do occasionally I won't need to be too concerned about it if there's another on the stand ready to take it's place. The other thing is that this whole scenario is evolving. The 340(350cid) Eaton blower equipped long rod engine was great. With the TA heads it would be even better, but I've retired that intake because it is too tall and won't work with the 300. The next intake will be built for the 300, specifically with the blower dropped down into the lifter valley but I've only just started on that. And nobody knows how long the flat tappet cam in the mule will last. So the 340 will go back together with the Rover heads and a stock (iron) 4bbl intake that will accept the intake system currently on the mule. That gives me more time to build the intake and blower/accessory drive. I do like having a spare available at a moment's notice and also having an engine available for development work. It's really the only way this works out that will allow me to always keep the car driveable."

Eric, I used 29cc for the Rover head in my calculation. Corrected to 37cc I get 10.43 with a 30cc dish.. DSS wants $629 for their standard forged pistons. I wonder how much more for custom?

DSS already have a piston with 29cc dish, they would just have to change pin height to 1.29 and pin diameter to .912, if you went 3.8. Might not charge too much extra for that. Be nice to go down to 3.78 bore size.

Thanks Jim.  I just emailed them with that very question.  I'll report back when I hear something.

As an aside, I did my calculation at 1.295 pin height, 35cc for the CC and 35cc dish, resulting in about 10 CR.