SwampWS6

iTrader: (7)

This may be a dumb question, but im kinda a noob with the technical apsect of the LT1.

So my question is; Is compression more important than quench? I know ideally one would want to have both, but is one better than the other? If so, then why? I have 11:1 CR now.

The reason im asking is my current 383 project seem to a little low on CR. I dont want to go with too thin of a gasket and hurt my quench. I hope you guys understand the question im asking. Please help if you can.. . . . .

VAformula

iTrader: (8)

What's your current quench? That will be a good starting point for us to know. A good quench would be .35-.40 so if you're above that, I would move down. 11:1 isn't extremely low, but you would benefit being higher. With my new build I'm aiming for 11.75:1 CR. So more details please!

za355tx

iTrader: (108)

Lloyd Elliott has always told me the optimum quench is .031. Which is a .026 gasket with the pistons .005 in the hole. The last couple of motors we've done have been .031 and they ran like raped apes. That also puts compression over 12 to 1 with a small combustion chambered like the LTx heads have. Pump gas friendly as well (93 octane). Hope this helps some.

NewOrleansLT1

Is .028 a good quench?

VAformula

iTrader: (8)

The only problem I have with going anything closer than .30 would be that in a tight quench area, the mixture of air and gas trapped there is not burnable, it won't ignite, simply not enough space for the flame to expand.

Obviously this is when you get super close, like .20 or less, but I wouldn't want to find out exactly how close you can get and spend all this money just to have to change the head gasket when you are done. With a .28 quench you should be able to get away with it and be fine. I personally have seen LTX's between .30-.50 and I don't think much has changed due to the quench area alone. I think once you hit the sweet spot you're pretty even. I would like to hear if anyone has any evidence to prove otherwise??

SwampWS6

iTrader: (7)

Thing is, I am in the middle of my build. I haven't checked the piston to deck height just yet. I just installed my crank and was checking clearances and got to thinking. Im just wondering which is more important. . . . . . to have good CR or to have good Quench? I just calculated head gaskets and psiton cc and came up with my 11:1.

Its just one of those things that I didn't want to screw myself on because I didn't ask enough questions.

I didn't want to raise my CR and get screwed on Quench or get a good Quench and get screwed on my CR. Basically I want to find that perfect balance!

SwampWS6

iTrader: (7)

That's the same thing he told me, I just don't know how far the piston is in the hole at this time. . . . . . .

Ed Wright

iTrader: (1)

It would be hard on parts to run .020" quench. The pistons would smack the heads. Could get expensive.
At .032" mine just kissed the heads. A lower RPM engine would be fine at .031". At .035" the quench area would stay clean. No black. No marks.
Bumping the heads upsets ring seal. Ring seal is a big deal.
Clean quench=good. Touching=bad.

VAformula

iTrader: (8)

Well if you don't know how far the piston is in the hole then you don't exactly know your CR? The ratio needs to know where the piston is in the hole to get the final answer. The calculator I use says "Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : "

SwampWS6

iTrader: (7)

The calculator from http://www.gtsparkplugs.com/CompRatioCalc.html didn't ask to "Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : . I guess I used a simple calculator. . . . .

KW Baraka

iTrader: (7)

Look at it like this.

11:1 CR with poor quench will probably lead to chronic detonation (especially in warm weather), poor fuel economy, poor emmissions and, to a degree.....a lack of power due to incomplete fuel burn.

On the other hand, optimal quench with low compression will lead, to a degree.....a lack of power due to the limitations of low compression in a NA application.

One will actually hurt your engine.....and the other won't.

KW

KW Baraka

iTrader: (7)

BTW.....has you block ever been decked?

If so.....by how much?

KW

KW Baraka

iTrader: (7)

One last comment......you want quench between .030" and .040" (I'd aim for .035")

and

You'll want dynamic compression (something else for you to learn about) in the neighborhood of 9:1 in a LT1/4 engine.

KW

SwampWS6

iTrader: (7)

That is what I wanted to know.

The block has been zero decked. Around .001 I think.

So which will have a more potential HP loss? Low CR or to much Quench, or are they even?

Ive understood generally from research and talking to people that perfect quench is .035 - .040.

SwampWS6

iTrader: (7)

Does a cam affect your dynamic CR or your static CR? I cant really find to much info on this topic!

Ed Wright

iTrader: (1)

Compression makes more difference in power than quench.

11-1 with too much quench clearance won't be a detonation problem with any kind of performance cam and reverse cooling. It won't damage your engine.

If your block actually is zero decked just use the .038" Fel Pro gaskets.

VAformula

iTrader: (8)

^Everything they have said, plus, your "Piston To Deck Height" is where it asks that question. So mine is zero decked so the answer is zero.

SwampWS6

iTrader: (7)

No matter what my piston to deck height is????

NewOrleansLT1

Hey Ed... What's your opinion on a .028 quench??

VAformula

iTrader: (8)

Zero decked means your pistons are flush with the deck, so then add a .38 gasket and you will end up with .38 quench. If you're not zero decked then add or subtract the distance the pistons are in or out of the hole.