Thread: 3.125 stroke

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I have a real nice 3.125 stroke Bryant crank and a stock 350 block, can any one tell me a good piston and rod combo to use? Crank came from a race engine but I just want to build a strong street rod. Thanks

I would suggest using Eagle or SCAT 5.7 inch I-beam rods and TRW forged flat top pistons. Unfortunately, SRP, JE, Wiseco do not make lightweight forged pistons for it. I have used TRW forged pistons in the past without any problems. They are just heavier than the newer style forged pistons mentioned above. I am not a fan of KB hypereutectic pistons. A lot of people use them successfully in street-driven cars but I have always preferred the strength of forged pistons.

This is an oddball stroke crank and as far as I know, there are no off the shelf piston/rod combinations to make it work. The block deck height on your 350 in 9.025" if the block is virgin and has never been decked, so you need to add up a "stack" of parts that will get you close to that.

The radius of your crank is 1.5625". A 350 piston has a piston compression height of 1.560". Oliver makes a 5.875" rod for the SBC. Add this stack up and get 8.9975", close enough for a 0.027" piston deck height or you could cut the decks to 8.9975" for a zero deck motor. I suspect that by the time you find out what a set of Oliver rods will cost, you'll lose interest and sell the crank to a roundy-round racer who can afford high-buck rods or custom pistons with off the shelf rods.

Oops! My bad. Mea culpa! I was thinking 327 and 3.125 stroke instead of 3.250 stroke. Brain fart! Sorry about that. Forget what I said about TRW, okay. Let me rephrase this. You can call Ross pistons and find out what a custom set would be if you are determined on using that crankshaft. They will be able to tell you what standard-length rods to use and suggest something that works with a particular piston. They will not be cheap, but if that is a top-of-the-line forged crankshaft, and if it is important for you to be different, then it may be worthwhile. Let us know what you decide.

Your right, I,m guilty of trying to be different along with trying to make what I have work. I have the custom pistons that were used with this combo but the compression would be way to high and they are hollow domed so I can't cut them. I guess I'm backing myself in a corner here and better just stick with a standard set-up. Thanks for all your advice

You might be able to use heads with 76cc chambers to lower the compression and use a cam with enough overlap to bleed off some more. How much of a pop-up do the pistons have? Do you have a manufacturer and part number for them? I would not give up unless you know the cost far outweighs the benefits. A small cubic inch engine in a light weight street rod can be pretty cool.

Here we go again, with a 3.125 stroke and a 6" rod speed pro makes a piston with a 1.430 compression height used for the 383, The block should be decked to true it up. so what do you think about this combo? Thanks for all your advice


Just having fun

Originally Posted by mitchell.adams

Here we go again, with a 3.125 stroke and a 6" rod speed pro makes a piston with a 1.430 compression height used for the 383, The block should be decked to true it up. so what do you think about this combo? Thanks for all your advice


Just having fun

Sounds good to me.

Originally Posted by techinspector1

Sounds good to me.

Me, too! It should give you good performance in a light-weight car.