I have a 69 351W stroked to a 383, but have a bit of a dilemma regarding quench. Because of the short deck height of the early Windsors, my piston is above the deck from .025 to .018 leaving me a max quench of .022 using a .047 thickness head gasket. That said, I think my best solution is to use a Comedic head gasket at .060 compressed to give me a minimum .035 quench. The rotating assembly is Eagle 4340 crank and H-beam rods with Probe SRS forged pistons.
My question is this, has anyone here run a quench this tight .022?? Just curious.

 

If UR motor turns over free of contact? U may get some erosion on top edges of piston and head gasket life. What are UR plans for this motor when in the 1970? Possibly fuel with Alcohol or Propane ? UR into valve clearances and cam lifts. Not much.

This seems a good thread.
http://forums.corral.net/forums/5-0-...fferences.html
Originally Posted by strokeme View Post
Real simple, 95% of 408 kits will have a piston stack height of 9.480. Meaning half the stroke + the rod length + piston compression height = stack height

Example 4inch stroke /2 = 2
6.200 rod
1.280 compression height piston

Add all this = 9.480, so if the deck is 9.480 now and the stack is 9.480 your at 0 deck. Now you need to cut the deck .010 or .015 to square it up, if you cut .010, you can run the piston as is as it will be .010 above the deck. Use a .047 gasket - .010 your piston is out and you sitting pretty at .037 quench. If the deck is say cut .020 already, sinmply mill .010 to .015 off the top of the piston. Really simple, I do this a few dozen times per year on engine builds.

I believe Probes man is in this thread. PM him.

 

.022 sounds tight. Not to send you to another site... but I know the guys at mustangsteve.com have had experience with this on a 351w. If you don't get a definitive answer here, I would hop over to http://fyi.boardhost.com/ and ask them. Oh... and then come back here so I don't get in trouble

 

This is strictly a N/A street engine for basic cruising so I can show off my tail lights to the looser stop light to stop light

 

Mark mentions a CH piston. I would contact him and follow his knowledge of course.
A few minutes and U can register on that thread. Exact knowledge of that Probe piston is great.
Please say U will use it to speak at the strip and not on the streets.

 

I think you are right on with your plan of using the 0.060" gaskets.

Here's a discussion of the subject from HOT ROD magazine:

Sometimes also called “piston-to-head” clearance, quench height may be defined as the distance between the flat-top portion of the piston and the cylinder head surface at top dead center (TDC), including the head gasket’s compressed thickness and any positive or negative piston deck height that may exist. Proper quench creates turbulence in the combustion chamber, theoretically pushing the mixture toward the spark plug and reducing the possibility of unburned gases at the completion of the combustion cycle, which can play a significant role in reducing detonation and even exhaust emissions.
Quench should be as tight as possible without the piston actually contacting the head. This, in turn, is largely dependent on the type of connecting rods and the engine’s peak rpm. A good rule of thumb is that you can run as little as 0.038 to 0.043 inch with steel connecting rods. Steel-rod street engines that don’t see the far side of 6,000 rpm may even be able to shave this to as close as 0.032 inch. Aluminum rods expand and get longer with heat, so the quench clearance with them should be increased to 0.050–0.065 inch.
It’s not uncommon for old-school, low-compression, smog-motor, stockers to have over 0.060-inch quench at TDC. We’ve even seen some ’70s-era Chrysler 440 engines with the piston 0.150 inch or more down in the hole at TDC. Originally, this was done to lower compression and slow the burn rate in an effort to reduce detonation. Current theory is that this is counterproductive, producing more unburned gases and such a slow burn that the detonation tendency actually increases. Don’t run more than 0.060-inch quench, even if you have a need to run a low compression ratio. And remember, these values include head gasket thickness!

 

thank you for this post,Beanscoot

 

Thanks for sharing , this thread is answering all my questions about my sons build Quench questions.

 

Quench vs. head gasket thickness
The head gasket thickness depends on the desired quench measurement and desired compression ratio. Piston to valve clearance must be verified.

Although static compression ratio should be determined by the piston configuration and the volume of the combustion chamber, small compression ratio adjustments are possible by altering gasket thickness as long as this doesn't cause the quench (or "squish") dimension (piston crown to under side of cylinder head with the piston at TDC) to be out of spec. Generally speaking, this figure is no less than 0.035" to 0.045" for engines built with steel rods. There will be some flex in the crankshaft, rods and pistons as they whip around at speed and this clearance will be diminished as a result\.

The turbulence caused by the piston coming in close proximity of the underside of the cylinder head will "squish" the unburned mixture out of the area and jet it towards the spark plug, thus fully mixing the mixture. This action contributes to a more complete combustion, more power, less emissions and suppresses detonation.



This stock type SBC piston is the least desirable design as far as quench action is concerned


The D-cup design is much better for quench action if a dish is required
The best piston design to use for this is one which has a dead flat area where it will meet the cylinder head. Stock Chevy pistons, for instance, have only a thin band around the perimeter of the piston to accomplish squish. Flat top pistons having minimal valve reliefs will work best. The D-cup pistons offered by various manufacturers also work well (better than a round dish) when a dish is needed.
This is a very important area of engine building and should be considered carefully before ever buying any parts. You must know what the piston deck height (distance from the crown of the piston to the block deck surface with the piston at top dead center) is before continuing.

A 350 Chevy will be used for this explanation: If the piston deck height is 0.025", then a gasket with a thickness of 0.015" (Fel-Pro FPP-1094) would put the squish at 0.040". If the piston deck height is, 0.012", then a gasket with a thickness of 0.028" (GM 10105117) would put the squish at 0.040". Mix and match the piston deck height with the gasket thickness in your particular application to achieve this ideal 0.035" to 0.045" squish.

Another consideration is the type of engine- naturally aspirated, supercharged and so on. It's been said that the Cometic MLS (multi-layered steel) gaskets, although relatively expensive, negate the need to "O" ring the block to accommodate higher boost numbers if used with ARP studs.

I got this from here,http://www.crankshaftcoalition.com/wiki/Head_gasket

 

here is another page i found , this one is easy to understand.
http://www.crankshaftcoalition.com/wiki/Quench

my son and I are building a 351W

found here ,, https://www.ford-trucks.com/forums/1...351-build.html

 

one more from chevy , i dont really seem to find much from ford builders yet.

Piston Head Clearance Guide - Tech Article - Chevy High Performance Magazine

 

a long but informative article,,Racing Engine, How to tips