Engine and Transmission Tech

Jim Weise says David and Brian are good to go on V8Buick.

Hello everyone,

I’m new here and planning my engine build (for a MGB-GT Sebring project). I have a Buick 300-4 (aluminum heads and 4 BBL intake). Was planning a non-stroker with the original crankshaft and the following:
- Intake manifold ported and converted using Doc’s dual plane approach
- Holley 650 4 bbl carb
- Original cast iron exhaust manifolds ported, polished and ceramic coated (inside and out)
- 502032 Crower “performance” cam
- .030 cylinder overbore
- Nascar 6.320 connecting rods with Ford Turbo 2.3 flat top pistons—estimated 10.3 compression ratio

Before I commit to this approach, I wonder if anyone has any idea the approximate power difference between my plan and a stroker build using the Buick 350 crankshaft? I realize I’d need to change the pistons (currently looking at some Chrysler V6 flat top pistons with a lower compression height, which I’ll have to hone slightly for the Ford wrist pins)—the goal is a similar 10.3 compression or so.

Also, IF I were to acquire a 350 crank, I see most of them are reground—will that cause any issues with rod bearings for my Nascar rods (which are supposedly 2.0” with bearings)? Any other issues with a stroker build that makes it a lot harder than keeping the original crank and lower CID?
Thanks everyone.



Edited 2 time(s). Last edit at 02/07/2022 11:27AM by Airwreckc.

Eric, Maybe 50HP and 50TQ depending on cam. I'd go up one on the cam. The stock exhaust manifolds won't fit. There are some Rover ones that may but you will have to use a different ujoint on the steering, You can get undersize bearings the same as the rod journals on the crank. What piston are you thinking about trying?



Edited 1 time(s). Last edit at 02/07/2022 11:11AM by mgb260.

Rover exhaust manifolds:

Thanks Jim! Your insight is really appreciated. 50 is definitely a number that makes this worth considering. I guessed I should have also asked what the total HP/TQ numbers might also be, as I want to make sure I'm not going to destroy my transmission (a Tremec 3650--supposedly a lot stronger than a WC T5, but still has its limits). Good to know on the exhaust manifolds, too. The pistons I'm looking at are Chrysler/Dodge minivan 3.8 V6 flat top (3.78 bore and 1.283 compression height). I haven't spent too much time looking at whether the pistons or block deck might need a bit of milling, but it seems to be close (and I'm sure the choice of head gasket will affect the quench number, too). The piston pin hole is a bit smaller than the Ford size (.901 vs .912), but I was thinking that I could use Ford pins and have the piston holes honed to fit.

Jim, in your opinion, which of those two Rover manifolds would flow better? And are the shiny ones aluminum? That might be nice, too.



Edited 1 time(s). Last edit at 02/07/2022 11:18AM by Airwreckc.

Sounds like a plan. I try to build one HP per cubic inch for a strong street motor . 350HP and about 400 TQ if done right. Your transmission will be fine, What length are your rods again? Shiny ones are probably Jet Hot coated. They are also Tri Y design. Two pipes go down from them to a Y on each side. The top one is more conventional,



Edited 2 time(s). Last edit at 02/07/2022 11:34AM by mgb260.

TS import big bore RV8 headers:

I ran those pistons on the calculator and they are .020 below deck and 10.8 . If you remove the lug in the chamber you would be 10.5. Looks good.



Edited 1 time(s). Last edit at 02/22/2022 12:14PM by mgb260.

Jim, thanks for running those numbers. I am not an expert on engine design, obviously. I have done some reading and I read that ideal "quench" clearance seems to be .040" With the pistons .020" below the deck and a composite head gasket, will that give me this optimal quench? Of course, also removing the lug you mentioned.

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.



Edited 2 time(s). Last edit at 02/07/2022 12:59PM by mgb260.

Interesting discussion on open chamber vs closed chamber and Quench:

[www.tapatalk.com]?

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?

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.

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.

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

Thanks Jim,

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

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.



Edited 1 time(s). Last edit at 02/08/2022 12:03PM by mgb260.

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

[www.teambuick.com]



Edited 1 time(s). Last edit at 02/07/2022 04:35PM by mgb260.

Great, thanks!