no difference at all, run it.......................why ask?

 

I want to know exactly what compression distance is... having trouble finding a good definition

 

it's the distance from the center of the wrist pin to the very top of the piston.........

shorter CH will leave the piston down the cylinder lowering the compression.

chart http://victorylibrary.com/mopar/deck-height.htm

 

ok, so when I am looking at pistons I need to find some that have the same or longer compression height than stock 351w pistons, not shorter... next question, how much longer can I go on compression height before I run into deck clearence issues? looking at somewhere around 480 valve lift... and would like to see 9.5:1 comp ratio

 

351W or 302???

 

351w, from a mid 70's granada

 

do the math stroke 3.5 / 2 = 1.75 + the rod 5.954 = 7.704 + 1.796 CH = 9.500 Deck

so on a 9.5 deck you should look for a piston with a 1.796 Compression heigth..or close to it.

get the piston as close to the top as you can...for good quench you want it tight to the head...decking the block is always a good thing to do, it gets the deck nice and straight and you can raise compression a lot quicker than planing the heads. .010 out of the hole is a very doable thing....

 

ok, looks good... but now I gotta find different pistons

 

Valve clearance to the pistons isn't just dependent on total lift, it's also just as dependent on duration and the actual timing events. The contact points are on the exhaust stroke as the piston chases the exhaust valve up the bore, then at or close to TDC, the intake valve starts to open, then it chases the piston back down the bore after TDC. For a .480 lift cam to have problems, the duration would have to be extremely long and have lots of overlap to cause a problem.

 

yeah I get that part... the total lift just gives an idea of the cam.. I can't remember the duration at this moment, but it sounds like it shouldn't be a huge problem.

 

.480 lift sounds like a Ford B303. That's the first one comes to mind.

 

its an edelbrock cam, 2182 I think... the .480 is an approximation of the lift... it may be 482 or something. I can look it up, but I'm not really going for 12:1 or anything... want to be able to run on 87 or 89 octane.

I'm gonna start another thread for my next question, but I will leave it here too since it is somewhat related... anyone know the compression chamber size for a 75-77 granada 351w head? not sure of the casting numbers on them, but its a 2bbl windsor