CK5
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Fragmented piston
- Thread starter Rugger187
- Start date
my guess is it was a bit high. Maybe I am a stick in the mud but I don't like to push 9 on a truck engine. This is why I only like forged pistons. Forged will still get beat up but won't explode.
Fueled and timed right I don't see why 9.5:1 won't work. Vortecs are good for it, proper quench and you should be good to go. I'm somewhere between 9 and 9.5:1 (built before I knew better about CC'ing the chamber) and by all accounts I abused mine by not fixing fueling earlier, but didn't have your results. Then again, I was running the same displacement motor, just different everything else. 
I'm on the borderline about calling dished pistons crap, GM felt the need to run them, but they ruin quench, which is a major benefit of the Vortec/Fast Burn chamber.
I'm on the borderline about calling dished pistons crap, GM felt the need to run them, but they ruin quench, which is a major benefit of the Vortec/Fast Burn chamber.
If you run zero deck and a shim gasket, assuming the dish is .025" itself.
With a .038" dish, the closest you'd get on most "stock" assemblies is .015+.025+.038=.078", no? Or is the pad actually raised like a dome to take up the deck height and gasket thickness?
With common parts, .025" deck with a flat top piston and .015" gasket will get you to the "ideal" .040". No idea if flat tops and dished are the same price. Maybe cheaper because you can get cast dish?
With common parts, .025" deck with a flat top piston and .015" gasket will get you to the "ideal" .040". No idea if flat tops and dished are the same price. Maybe cheaper because you can get cast dish?
http://i860.photobucket.com/albums/ab168/skipwhite/Pistons/427PISTONS005-1.jpg
The quench pad on the edge matches the quench pad on the head. It is the same height as a flat top in this area. I nearly always 0 deck. Shims are OK but I have seen them leak.
The quench pad on the edge matches the quench pad on the head. It is the same height as a flat top in this area. I nearly always 0 deck. Shims are OK but I have seen them leak.
Sorry if I miss understand on a "stock" block you will have to run a shim.
If you are zero-decked I can see the need to do something to reduce compression, but if deck height is stock at .025", you should be able to run flat tops and a .015 gasket to get proper quench with enough valve clearance.
Otherwise if zero-decked, why not run a .040" gasket and flat tops?
Otherwise if zero-decked, why not run a .040" gasket and flat tops?
To keep the quench tight while lowering the compression. I have built 11 to one pump gas engines but on a big heavy vehicle like a blazer truck I feel that place just before the down shift in an auto or lugging in a manual is much worse than a light street car. That is why I like 9 to one. Can it be driven properly with more compression, yes but you never know who may sit behind the wheel. A TBI 350 is only 8.5 to one stock and gets up to approx 9 with flattops. A 383 with flattop s a vortex heads will be much higher. I just like to be conservative. A half a point of compression isn't really a huge amount of power loss.
I see what you are saying now...you can still keep quench around .040", but the compression will be lower due to the dish volume.
You certainly want to build with "worst case" in mind IMO. Once I got timing and fueling right, but the Vortecs/compression were certainly not tolerant when things were a bit off, that is for certain. It did not take much at all (slight lugging, bit of a hill) before detonation set in. A 383 with Vortecs running on TBI timing/fueling should certainly be even worse than mine was.
You certainly want to build with "worst case" in mind IMO. Once I got timing and fueling right, but the Vortecs/compression were certainly not tolerant when things were a bit off, that is for certain. It did not take much at all (slight lugging, bit of a hill) before detonation set in. A 383 with Vortecs running on TBI timing/fueling should certainly be even worse than mine was.
The vortec heads are 64cc and I will be getting a set icon forged pistons with a 18cc dish. Should put me right around 9.7:1 compression. The pistons will run $367 which seems like a really good price.
Iron heads and running 9.7:1 compression in a heavy vehicle is asking for detonation AGAIN. You want to keep CR at or under 9:1 with an iron head in a heavy vehicle and could go to 10:1 with aluminum heads.
trust 4x4high on his info he knows motors 
Dont know if it was mentioned before but watch for different pin heights also, changes everything.
The engine I built that is currently in my rig is a 350 bored +.030" with a zero decked block and a 12cc D dish piston running a Fel-Pro .039" compressed gasket and that gets me exactly 9.48:1 with the 65cc AFR heads.
