Buick 300 Stroker - One More Time

[Roverbeam]

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?

[Airwreckc]

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.

[MGBV8]

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.

[mgb260]

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

[mgb260]

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

[Roverbeam]

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?

[Airwreckc]

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?

[mgb260]

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

[Roverbeam]

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!

[mgb260]

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.

[MGBV8]

" 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.

[BlownMGB-V8]

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

[mgb260]

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

[BlownMGB-V8]

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

Jim

[MGBV8]

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

[Airwreckc]

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.

[BlownMGB-V8]

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

[Roverbeam]

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.

[mgb260]

Chad, what with the 29cc heads?

[Roverbeam]

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

[Airwreckc]

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

[Roverbeam]

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

[BlownMGB-V8]

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

[Roverbeam]

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.

[roverman]

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.