300 Stroker questions?

[mgb260]

Quench doesn't factor with open chambers like the 300 heads, If you used the later Rover with 29cc chamber or the TA heads I would try to get Quench. Small wedge chambers need Quench. Open chamber and Hemi's do not. With high compression small chamber heads with Quench are less detonation prone. If you want a little lower compression unshroud the valves on the outside and clean up around the spark plug hole. Probably get it down to 10.2. 10.5 with aluminum heads is about the same as 9.5 with iron as for detonation. You can retard your cam 4 degrees and lower your Dynamic compression. I would still run pump premium.

[mgb260]

Interesting discussion on open chamber vs closed chamber and Quench:

https://www.tapatalk.com/groups/clevelands/open-vs-quench-george-dan-jones-t17441.html?

[Airwreckc]

Jim,

Learn something new every day--I had no idea that quench related to the shape of the combustion chamber.  Thanks for setting me straight.  

It seems like I need to keep my eyes open for a good late (?) 350 crank.  Do you have an opinion on whether these cranks need heat treating after the mains are ground so much?

[mgb260]

Eric I added a little to the thread above. Not heat treated but I would polish the journals. The oiling holes move a little and need to be moved over to center, I would take the 300 crank to the machineshop so they can compare.

[Airwreckc]

Again, great advice.  Thanks. Sounds like with my aluminum heads, I could run 10.5 assuming I ran pump premium (which I plan to do, anyway.  I could even run Sunoco 93, if necessary).  But perhaps, unshrouding the valves and cleaning up around the spark plugs is not a bad idea, anyway.

[BlownMGB-V8]

In addition to turning down the mains 1/2" you will need to thin down the oil slinger to fit the 300 block. The rear seal journal should be ground just enough to remove the hash marks if using neoprene seals.

Jim

[Airwreckc]

Thanks Jim,

Is there a list anywhere of all the things needed to do the 350 stroker properly?

[mgb260]

Other than the crank mods and different stroke everything is the same as the 300. V6 3 keyway roller timing set and front seal. Best Gasket co make a specific 300 neoprene rear seal. I have heard the V6 rear seal works but haven't tried it. 350 HEI distributor works. There is an MSD offshore clone distributor on Ebay that Clinton used on his 300 build. Search on the MGexperience Swaps board for a lot of Chris's stroker info and Clifton's 300 build. V8Buick board too. Jim B and I are on all these boards with info.

[mgb260]

This chart is helpful, rod bearing clearance is wrong though. Should be .0007-.0015 same as mains:

https://www.teambuick.com/reference/300-340_engine_specs.php

[Airwreckc]

Great, thanks!

[Wilitrun]

Hey JN,
Thanks very much for helping chase down my manual approval on v8buick, it's very much appreciated.
I'm very motivated to use cast exhaust manifolds on my build, do you have any input on whether the 1st set of Rover manifolds fit better on an MGB, and where to find them? My understanding is the second set pictured is for the GTV8 and are quite rare.
I can't see my stock 300 manifolds fitting unless I flipped them upside down and backwards, and fair-play I guess but it's not the look I'm going for. Cheers.

[MGBV8]

Not that difficult to get 300 RWHP from the 300 & forget all the time, money, & headaches with the stroker build.

[mgb260]

David, You're welcome. I have no idea on the Rover exhaust fitment . They look like you would have a better chance with them. Still would require fender massaging and that pesky steering shaft may be an issue.

[Airwreckc]

Carl, yeah, it's a conundrum.  Either way, it's a very fast car.  Really fast or scary.

[BriansMGBV8]

"Not that difficult to get 300 RWHP from the 300 & forget all the time, money, & headaches with the stroker build."

Amen to that......sporty 300 build in these cars should work well.


Thanks Jim, I was also was approved on the BuickV8 site.

[BlownMGB-V8]

I can tell you from experience that a totally stock iron head 2bbl 300 fitted with a 4bbl intake in the MGB will do just fine.

Jim

[Wilitrun]

Not to challenge that point of view as I don't have a sentimental attachment to the idea, but can we talk about that for a minute?
Is the idea of using the 350 crank to improve rod ratio, reduce thrust and overall stress at the power level I want really not worth the bother?
By my read, while the engine is apart for a regular overhaul, we are looking at the following:
-find a viable 74-80 core and pay the labour to turn down the journals
-secure a suitable set of rods with the length and clearance we need
-order a set of custom pistons in the dimensions needed (one of the big ticket items at $1000+)
This is what's being added considering the existing crank will require regrinding, speedi-sleeve and new pistons, rod resizing and dynamic balance of the rotating assembly.
Since the cam is roached we need to replace it anyway, and the extra work of
-ordering a custom ground cam meant for roller followers (the other big ticket item at about $1000 so split the difference with a stock/reground flat cam, where do we land here: about $6-700?)
-a set of roller followers to reduce wear and the need for oil additives
by my read will pay for itself the first time we would need to replace a flat-tappet cam, as Jim B. already pointed out.
With the goal of not increasing power output as it's not needed, but reducing wear and improving reliability with likely some low-end torque gains, are we saying this isn't a worthwhile exercise? If we are, that's a welcome perspective and feel free to elaborate, I won't be offended. What's fueling my enthusiasm for the idea most is the notion we can take a stock crank of little value from another engine and for relatively little money, solve the crankshaft part of the stroker build equation. Seems like a valuable gimme. Cheers.

[Airwreckc]

Hi David, I like your thought process.  IF I'm correct, I picked up the necessary rods for $100.  And the pistons are about $150 (plus the labor to hone the pin holes a bit--I'd probably pay to have the pins fitted anyway).  So, I *think* my cost is the 350 crank and grinding the mains--and if I buy a reconditioned crank, I don't have to pay for the rod journals to be ground (not that that's equal),

[BlownMGB-V8]

You have a strong grasp of the situation. My TA cams that just came in cost me $850 ea. but if the low lift blanks had been in stock might have cost a bit less, say around $750 perhaps. What you need for rockers depends on the heads you use. With stock heads you can use stock rockers. The Wiseco pistons were about $1150. Cost of the rods were on par with reconditioning.

The crank can be an expense. In my case I have a lathe and was able to cut down the mains myself but it took time. So if you figure $500 for that you are looking at about $2500 extra to do the stroker and roller cam setup with forged rods and pistons. Not bad for what you get, and probably worth it even without the extra stroke, pushing the potential redline up as far as you like below about 7500rpm. If power is your goal, add TA heads, a porting job, and that new intake and then about all you need is a good set of equal length headers which you'd have to make yourself. By that point, depending on cam specs you could be well over 700hp.

But let's be reasonable. Anything over 300 hp is plenty in the MGB and you don't need all that to get there. So with the exception of bragging rights, grudge races, and just being able to run with the hot shoes (which it doesn't take power to do, just ask Carl), you can get there cheaply. OTOH, say you stay stock or near stock with the stroker/roller combo. Now your oil change intervals just went to modern standards, perhaps as much as 15K+ miles, a 5 fold improvement and with cheaper but better oil. No more worries about flattening cam lobes. Your torque curve just got wider, flatter and higher so driveability improved considerably, and your overall power level went up. All this while remaining understressed for great durability, which these engines were renowned for in the first place. Mileage might improve as well. Add efi and you now have a thoroughly modern engine and very likely the last one the car ever needs. Does that make it worth it? Some would say yes and some would say no. Dealer's Choice.

Jim

[BlownMGB-V8]

Can't talk about pistons without considering the heads. Our choices are:

-Stock alloy heads 57cc
-Stock iron heads 57cc

-Late Rover heads (4.6L etc) 29cc
-TA heads 31cc

As is clear they fall into two categories based on chamber volume so the pistons need to be selected with the correct head in mind. Likewise the heads need to be selected with the future in mind. For instance, if you can foresee ultimately ponying up the big bucks to get the best heads but want to do that later, the Rover heads would be a good choice. I don't have the valve sizes but maybe someone can post them here. The iron heads do have larger valves and ports and probably the most flow of the stock heads, followed by the 300 alloy heads and the 4.6 heads close behind. Weight difference from a single iron head to a 300 alloy head is 17lbs. The rover head is a couple pounds heavier than the 300 head and the TA head is about 10lbs heavier. so the economy performance build would favor the iron head despite the weight disadvantage. Bearing in mind of course that the stock iron intake adds an equal weight penalty. To put this into perspective, the 300 with alloy heads and intake comes in at 50lbs more than the 1800. With Iron heads this increases to 85lbs. In terms of front/rear balance, use of a D44 or 8.8 axle balances this out pretty well and any remaining concerns can be dealt with via swaybar sizes and tire pressures.

The small chamber heads can benefit from pistons which provide a squish area whereas the larger chamber heads, not so much as there is only a very small area that would allow this. Using a conventional .040" thick head gasket, about 65cc of total volume excluding the squish height works out to around a 10.5 CR in the stroker engine. That would be at zero deck.

Jim

[Airwreckc]

Great discussion, information, and perspectives. I had a beautiful 1980 with a mildly modified original engine.  It was really no fun--just felt crude, ran hot, and was unreliable.  I'm looking for a vehicle that will be reliable, because without that, it'll sit there most of the time and never get used.

[MGBV8]

I have read on another forum that the answer is always..........................Miata.  

[Airwreckc]

Hahaha,  Yes, with a Ford V8.

[MGBV8]

No way.  They started using Chevy LS engines years ago.  

[Airwreckc]

I'm on the lookout for a 350 crank, if anyone knows of one.  I have found a few reman cranks, but not too sure if I want to go that route as I'm concerned about whether they may have the rod journals reground significantly.  I see mention of preferring the "late" cranks if you're using heavier rods (as I likely am)--can anyone confirm the year range for that version?  Thanks much.