hi there. Just curious what quench distance people are using for 455s with alum heads? It seems 28-35 thou should be an optimal distance between the pistons and head from what I have researched. What have you guys experienced?
Not more than .045, not less than "piston kisses the quench pad" at maximum RPM. Some of this depend on the piston-to-wall clearance as piston rock affects deck clearance required. I think .028 deck clearance is likely too tight for a big-bore engine. My gut says that anything under .035 is pushing your luck. I've been wrong before.
Felpro .040 (with zero deck) is the way to go. Safe distance and very efficient for street and strip. If detonation occurs, the felpro will likely blow before the engine is destroyed. A more burn resistant gasket may allow damage to the engine. Just my best guess anyway.
So if the 455 block was bored 0.030 over and you were to have a clean up cut on the block, custom pistons to get to 0 deck and use steel shim 0.020 head gaskets would that leave enough quench area? The heads would be iron 68 430 heads and probably aluminum heads down the road.
I think .020 is getting very close. Not sure how much the rods do stretch at rpm and the piston will expand some..........if it clears I would think you would be on the ragged ragged edge. Slot of those steel shim gasket will they allow a .030 over without hanging into they cylinder.......have you measured to bore of the gasket. If your running a true flat piston with the 7ish cc valve notch and a 70cc iron head you would have to pushing over 12.5:1 Dished 22cc would be closer to 10.75 But I would want more space. Between my head and piston.
I will have to measure them when they arrive. I bought a set from Bruno and he thinks they should be good for up to 0.060 over. Maybe stock rods, .030 over pistons, a clean up cut of the block with the 0.020 steel shim head gaskets would be a better option??
If your using zero deck I myself would use the Felpro gaskets that are .040" compressed & you'll be in the .025"-.050" recommended Quench/Squish zone. Not too little OR too much. AND the Felpro gaskets aren't $150.00 for a pair. IF you incest to use the steel shim gaskets at .020" I would go for .010" in "the hole" which leaves you at .030".. Tom T.
I have a set of new felpros hanging on the wall that I was going to use but I've read on this site numerous times about guys trying to use the thinnest gasket possible to up the compression. The price was good so I grabbed a set. Maybe I'll use them on my 72 block that's in the car now? They will probably help that motor out more with the stock iron heads and stock pistons.
If you are talking about the steel shim gaskets, pretty sure you can’t use them on a 72 block, just 71 and earlier?
The idea is to use the thinnest head gaskets possible when NOT doing machine work to raise the compression, i.e. a stock block and heads. If you are decking the block or milling the heads normal .040" gaskets are the easiest/least expensive way to go. The steel shim gaskets would be the way to go to bump up the compression with your current setup as long as it is a '71 or earlier engine. The tighter you can get the quench the better but .040" is usually safe under just about any circumstance and anything tighter would depend on, as mentioned, piston rock and how much carbon will build up on the piston tops after how many miles
Thanks Larry I didn't know that. Well l have a set of each now so no matter what direction I go with my 70 block I got gaskets I'll just keep running my 72 block the way it is until the other one is done.
My block was deck 020 and piston was still down 035 in the hole and went with steel gasket and dished pistons with valve cuts and when I checked clearence barley marked the clay and no problems up to 4800 rpm pulls strong through the gears
