whats the max stroke you can put in a gen 4 bowtie 9.8 deck

4.25

The truth is, the book says 4.6 but when you get into that kind of stroke you get into maximum piston pin height, which is ok. The problem comes when you have to use a really short rod. Your piston speed increases which promotes increased ware and will also lower your rpm limits.

In my opinion I wouldn't put anything bigger than a 4.37 stroke in a 9.8 block.

my .02
DAVE

I know that you can go to 4.5", but there are rod angle problems and cam clearance issues. Not to mention a ton of machining that would be required to the pan rail. By the time you are done, you'd be better off going with a merlin II block. Now if practicality is an issue, then it's 4.25".

Hey Cord,
Do you know if it is practical to go with a 4.5" stroke in a Merlin II short deck?

VETTE ITS NOT A GOOD IDEA TO GO WITH 4.5 STROKE IN A SHORT DECK MOTOR ,NOTHING SEEMS TO WORK OUT RIGHT WITH THE COMBO ,IT HAS BEEN DONE THOUGH !!!!!!!


4.25 /250 ROD WORKS GREAT 4.600 BORE
HAVE A GOOD NEW YEAR

That is what I thought! Thanks

I agree with Bobby, you can do a lot of things that are not really practical. 4.25 with a 6.385" rod still leaves room for rings and gives more power in the 5,000 and up rpm range. The bigger the bore, the more you unshroud the valves and the bigger surface for the cylinder pressure to act on(MORE POWER). A 4.25" stroke and 4.31" bore is a 496, a great engine if you have a Chevy block!

thanks i was thinking of either using 4.25 or 4.375 with a 4.530 bore

Hello MTM,
The 4.25" stroke will give you almost as much torque and 6.385" rods are a common set up. The bigger the bore, the better they run-even better than the displacement increase would indicate because of better air flow. Depending on your block, we like to bore 4.560-4.600", leaving one more boring to 4.625" if ever needed.