de-stroker

[wjvo]

When you DE-stroke an engine I was wondering if you had to do anything to the block like boring it. I know you have to bore it when you stroke it, I think, but I'm not sure about de-stroking

 

[butelja]

The only reason I know of that you would have to bore an engine when stroking it would be to add clearance for the connecting rods so they don't hit the cylinder.&nbsp;&nbsp;However, most hot rodders would probably bore and stroke at the same time to add the maximum cubic inches possible.<br><br>When destroking an engine, there will not be potential connecting rod clearance problems as when stroking.&nbsp;&nbsp;However, either the rod length, piston pin height, or deck height will need to be changed.&nbsp;&nbsp;Otherwise, the piston will never come all the way to the top of the cylinder.&nbsp;&nbsp;This would create seriously low compression.&nbsp;&nbsp;If the deck height is machined down, it would cause fit-up problems for the intake manifold on a V8 engine unless it is altered too.

 

When you DE-stroke an engine I was wondering if you had to do anything to the block like boring it. I know you have to bore it when you stroke it, I think, but I'm not sure about de-stroking
When destroking and engine you don't have to bore it over. You do want to check the main journals. Some cranks have smaller journals depending on a number of things. For example if you are stroking out a 350 to a 383 you would use a 400 crank shaft and 400 rods, but the cranks mains will have to be turned. You could also use special pistons with the pin deck raised and use longer rods and decrease the rod angle ratio. The only thing you would have to do hear is possibly notch the block to allow for rod to block clearance and also check rod to cam shaft clearance(for really stroking out). To destroke a 400 you could use a 350 crank and 350 rods, but will have to use special bearing to compensate for smaller journals and you'll end up with a 377 yuck.

 

i'm thinking of building a377 a400 block bored 40 over and a350 crank but instead of 5.7 rods i would use 6.0 rods.how will this effect;head clearece compression ratio .with 9.5 comp. pistons

 

[evelrod]

Lets assume you have solved all the revelant deck clearance problems, and deal with the LONGER RODS. In all cases, the piston dwell time at TDC will be substantially longer therby putting a piston in the way of the valves unless some work is done in the area of valve clearance. Do not assume that by de-stroking and correcting the deck ht. problem with longer rods that all valve clearances will remain the same. On one of my engines, a 0.25 in. longer rod resulted in 0.105 in. deeper valve pockets in the pistons , all else remaining the same!