Here's what I've done on my last 2 motors:

#1: New block, stock pin height, deck block .012" putting piston .012-.013 in the hole, .027" head gasket
#2: Used block, stock pin height, clean up deck to .003" in the hole, .039" gasket

If I build another new motor with a new block, I'd order custom pistons with the pin raised, graze the decks, and use an .039-.040 gasket. However, I wouldn't do this on a combo that didn't have much pin height to begin with though (like a 347 Ford). Lots of ways to skin the cat.

 

I hate to see blocks decked to zero clearance to achieve maximum quench when it has been proven quench doesn't add a bit of power. Modern engines produce around 1-1/2 hp per cubic inch and with ZERO quench.

 

Like I said the chamber is not in the definition of Quench. Quench is the gap or space between the deck and head surface. Chamber is not involved here.

 

What a statement. Zero Quench doesn't add power, but modern engines have zero quench and have more power. What?

 

[QUOTE=NeverTooOld;1596176892]As quench doesn't add a bit of power the deck clearance/quench isn't important. Spend some time in an automotive machine shop and you'll quickly find modern engines with their 4 valves per cylinder and HEMI's don't have any quench and they'll run circles around our C3's. There was a time in which engine builders believed quench increased the burning speed but that was proven wrong 50 years ago when Mopar re-introduced their HEMI.[/QUOTE


I sure get a kick out of you.........can you say "fountain of misinformation"?

Personally I doubt theres any NA production block street drivers on here that run circles around Alans NA production build.

 

Wrong again NeverToOld!

Here is a Dodge Hemi head. It does not have a hemispherical chamber, it is a bathtub, one of the most efficient chambers because it has quench areas on both side of the chamber.

I've done a lot of work with bathtub chambers. They always make more power with tighter quench or squish as some of us call it. In race engines I would tighten the squish until the piston and heads would just start to get leave traces of touching each other and then back off a couple thousandths. Set a lot of records with tight squish.

Mike

 

i dunno what hemi head that is, but this is the one NTO is talking about. and...you are both right. quench is necessary for good even combustion and improves power. but there is an exception to every rule. no big block chevy can beat a true chrysler hemi in top fuel. they stopped trying a long time ago. maybe the big domes form a quench area, but there is no shelf on top of the head next to the combustion chamber.

 

ok, the flats facing the valves may serve as quench pads. i have no idea how close to the valves they are at TDC.

 

That is a late model Mopar Performance Hemi head. Nitro is a different animal. On the blown engines the large hemispherical chamber lends itself to the low compression needed to run high boost with massive volumes of nitromethane injected.

I ran naturally aspirated nitromethane in my Top Fuel Harley. I had bathtub chambers with a 30 degree squish. I ran the squish very tight. Because of this and other things I did to make my engine more efficient, I was able to run less percentage of nitro and less ignition timing. I had no problems with detonation and had very few engine failures, unlike a some of the other fast guys. I also usually ran much higher miles per hour than my competition.

The Billet Top Fuel heads I designed in 1994 are still in use today. They have been on record setting machines and won 5 national championships at IHRA in a row with two differents teams when the Harley's were at IHRA. Doug Vancil ran 6.26 @ 225 about 18 years ago with these heads. These heads had a bathtub chamber with a 30 degree squish and a domed piston to match.

My current Top Fuel heads also are bathtubbed. We ran them at Bonneville in the streamliner and the engine was a beast. We ran 222 MPH in first gear at part throttle testing, but unfortunately, my partner Leo Hess crashed and got hurt on a later pass. A couple of guys are building new bikes with them on them, but haven't made it to the track yet.

Mike

PS: A photo of the chamber. This is for a 5" bore. The valves are 2.500" and 1.980".

 

Sorry for the hijacked thread Muzzy. I just wanted to stress the importance of a tight squish (quench). I've done huge amounts of testing on the dyno, street and track, mild to wild engines, bike and cars. They all respond to tight squish.

Mike

 

Some of you still don't understand "Quench". Google it. Or read this;
definition: The piston to head clearance distance of the top portion of the piston and the cylinder head flat surface. Including the head gaskets compressed thickness, bore, known has head gasket volume.

In other words the chamber is not included. Picture a piston at TDC. Now picture a piece of plexiglass set on top of the head gasket (no cyl head). Now picture a hole in the plexiglass for adding fluid to measure CCs. The fluid fills the bore to the first piston ring and on up to where the head gasket is. Measure that fluid volume. Thats Quench!

 

Well yes and no. The quench area can be at an angle on both the head and the piston. I used anywhere between 10 and 35 degrees. 30 degrees always seemed to produce best power. The valves have less shrouding at 30 degrees and the charge is aimed more towards the center of the combustion chamber, so it only make sense.

The volume from the top ring to the deck of the piston is not part of the quench area. You measure it to get accurate compression ratios, but it is basically lost volume, the less of it the better. Of course then you get into top ringland strength.

Mike

 

Then tell Google they are wrong. From the top piston ring to the deck IS part of the quench. You can also have a negative quench or a positive quench depending on how far the top ring and the flat of the piston is down in the bore. And I say down in the bore but sometimes a piston is above the deck. Headgasket vol is in the equation too.

 

They are using this definition to use the volume to figure compression ratio when all the other values are known such as combustion chamber volume, piston dome volume, etc... So they are completely correct in that instance, but the part of the piston and the part of the head that come close to each other at TDC are the only functioning parts of the quench or squish. These areas are measured in square inches instead of cubic inches. When I design chambers and pistons I typically will run a maximum of 40% square inches of quench square inch to cylinder bore square inch on a higher rpm engine and up to 50 to 55% on a low rpm engine. To high a percentage in a high rpm engine becomes a pumping loss.

Mike

 

 

Tighter the quench, the more efficient and less detonation prone it will be....(to a degree mind you.)..

Zero decking the block, a tight quench is the best for power/efficiency. (assuming you have enough piston to valve clearance and the pistons aren't hitting the head....(at least not too much..:


You can't listen to anything NevertooOld posts...He has no clue about anything. He actually believes headers do nothing....lol

 

Ok let me ask a different question lol.... if I put a 489 stroker from scat with 20cc domed is it going to smack the valves in my 781 heads and launch them into orbit? 😊

 

 

You always have to measure piston to valve clearance. This really has more to do with the camshaft you are running(valve events), then zero decking the block. Basically, you have to check EVERYTHING. A 20cc dome is not THAT tall, and with depending on the cam, I doubt you'll have P to V problems.


There is a LOT more science to engine building then just ordering parts from a catalog and slapping it together. Lots of critical machine work, blue printing and dialing in to make it all work. You are really at the mercy of your local machine shop/builder if you are doing it yourself.

For all of the costs incurred when you really get into doing a real build (like you are now, not just a refreshen of a stock motor), I always recommend people to go to VortecPro performance for BBCs.... You simply can not build one that makes that kind of power, with that kind of quality and proven performance, for that cheap.


Talk to your machine shop, get some ball park pricing on machine work, assembly, then tally up your parts list etc... You will be in for a surprise when all the details add up...

 

Please don't provoke too broke.