Ive been doing some studying for me an engine build and all of the similiar builds with zero deck height seem to be putting out a little more horsepower than the others tht were not zero deck height.The build was the basic KB hyper pistons,eddy 84cc,eddy performer intake,your choice of cam build.Was the difference the cam,differnt dynos or was it the zero deck height?

Back in the early 80's , I, built a 351w ford motor with a set of the smallest 54 cc heads from a 289 engine that i had custom ported and polished with bigger 327 Chevy valves and a set of custom forged trw pistons .
The funny thing here besides( being a ford i know )Is the pistons that trw made at the time were pop up dome style made for open chamber heads . and had a big cheese wedge cut in them on the other side of the dome for valve clearance.
As fate had it i machine the dome off and made the pistons zero deck flat tops . at the time the machine shop had never done an engine this way the always done 289 with bigger 351 heads so my motor was the opposite .
After assembled the motor had exactly .039 quench with the close chamber heads and flat tops with a big valve relief wedge the acted like a reverse dome and compression came in at 10.5 to one i was told .
That motor ran harder at the track the all my friends 351w's at the time and the always asked me what the heck I had in it?
I would just lol& say nothin special it just runns , now that i have learned about quench i would say that was the reason ,By accident ! So there u have it this was before any body was talking about quench benefits and before i could afford mopar.

Thanks for your detailed and knowledgeable reply. Even taking into account a "foggy" 15 m/s, that seems slow only IMO, wonder how that speed/distance correlates with burn time at 7k? And is one of the main effect of quench to reduce fuel droplets, and not seperate them out, which means? higher velocity in that regard would not be any issue. I like the point? I think regarding "pumping losses"? regarding making quench in the first place and reaching a point of little gain.

I'll throw out my .02 and you can take it for FWIW....

I called Ross pistons a few months ago to see if they could cut a dish in some pistons I have for a 470. With a standard head gasket, zero deck height (may end up .005 or so out of the hole, the compression height on these pistons puts on paper puts the piston at zero with a stock deck height) and the heads (iron) that are going on this motor, compression would be in the low 11s. I wanted a dish cut in the pistons to lower the comp to 10 to 1 with .040 quench. I chatted with the guy at Ross for quite a while. He said he could cut a dish in the pistons, but we ran quite a bit of numbers, he guessed on how much he could actually cut out of the pistons, etc. It would have been border line to have gotten a big enough dish in them. He tells me that he would just put some thicker head gaskets on it with the pistons as is and go on. He said that a tight quench does make more HP, but for what Im doing maybe only 5 or so more. This combo should go low-mid 11s in a heavy 73 RR. Pump gas, street car. So was it worth 400 bucks for 5 to 10 HP??


As far as detonation and quench, the last 3 motors Ive had in this car, havent had proper quench or anywhere near it.

1. First motor came in the car when I bought it. Didnt have a clue what pistons were in the motor. I was 15 when I bought the car, so I had no clue what I was doing. Motor didnt ping a bit when I first got it. Stock cam, manifolds, CH4B intake, etc. Started playing with it. Gave it some timing, small hyd cam, etc. Pinged like flippin mad. Pulled timing out of it (I think it was down to 30 or so total). Had everything from 87 to 110 race fuel in it. Pulled the motor down a few years down the road, had 2295 TRWs in it. Comp was about 11.5 to 1. No quench to speak of...Pistons showed signs of detonation on the ring lands. I was told to not resuse them by one machinist. Another said he didnt see anything wrong with them. Sold them to a local guy who used them and AFAIK didnt have a lick of problem with them.

2. Second motor used KB step head pistons with 452s. Quench worked out to be something like .080 or so. Static was 10.5 to 1, .509 cam. Never heard it ping a bit on pump 91 with 36 degrees of timing. Pistons showed no signs of detonation on the ring lands.

3. Current motor is a flat top piston, same 452s as above. No quench at all, .100 at minimum. Static is 10.6 to 1, 259@.050 solid on a 108, in at 102. Will ping on 91 with 38 degrees in it on a hot humid day. Pull timing back to 34 and no pinging.

Take it FWIW, your experiences may vary!

I'm a believer in obtaining it. Quench will in all likelyhood give a slight amt of HP increase from better homogenizing of the mixture but the tremendous benefit of it is it lets your run a much higher CR on the exact same octane WO pinging that would for sure ping at the same CR and No quench and CR is one of the most important parameters of an engines power potential. Squeeze is power. If your building from scratch get quench (.035"-.040")/select your cam/ You know the octane you will run/then build the SCR to keep you under the pinging limit keeping in mind that you want a fast ign curve (which also demands more octane) and you'll fine tune (staying under the pinging point) by working w the curve. Do the homework to get what you are after w no dissapointments & nothing left on the table