My heads are milled down to 59cc chambers and I use a .040 Cometic head gaskets for a nice tight quench. Compression is 11.4-11.5 and with a proper tune it runs great. As sorry as the gasoline is getting now days that is about as high as I want to go on a street car. High Compression is free HP/TQ..

 

Iv been talking to tsp about rotating assemblies but never mentioned compression. I think Il send a pm

 

This!

 

FWIW, I'm running 8.65:1 DCR, stock 243 heads, .040 gaskets, LS1 block, elevation: 1000 ft, no detonation/retard.

 

If you have a rotating asembly out of the block and are gonna run near 12 to 1. Open the ring end gaps up a little to like .025 from stock.This keeps the ring land from breaking when the rings run out of clearance due to too much heat and or detonation.This will help it survive if the tune is spot on.

 

Your pistons and rod lengths make a big difference also. I would not buy nothing, except maybe a crank if I knew I was not going to stroke it. You can play around with rod length to your compression height of your pistons to change CR'S. You have deck height and all that stuff to consider. And there right, It's all about the tune also. Lot of factors to think about. I am runnin a LQ4 block which is a 9.230 deck with flat top pistons with Patriot 59cc head and .051 gaskets with no problems. Pistons come up above deck .008. Just remember- stroke divided by 2 plus rod length plus compression height gives you total height. You can play around with different pistons to get different results.

 

I already had the crank and rods and heads, so THIS is why it took me a month to finally pick my cam and then pistons

 

Sounds like me; took me sometime too. Good luck on your build...

 

This is confusing lol

 

Can anyone tell me a formula to figure out dynamic compression? I read the page from the link twice and it didn't out right tell u the formula to figure it out. Can some one help me lol

 

Try this
http://www.wallaceracing.com/dynamic-cr.php

 

I tried that and I'm lost lol Im just going to keep trying to figure all this out some how

 

It can be if you go too far into the rabbit hole. You can end up with over analysis paralysis.

You can avoid the rabbit hole by just using fellow racers practical experience. With that being said, here is mine: I have 10.9:1 static, 8.4 dynamic with a smallish 224 camshaft and I run 93 pump gas at sea level in serious Florida summer heat with no problems.

If you are the theoretical type, I will go against the grain here and tell you that dynamic compression is one factor but more important is volumetric efficiency. All of these dynamic compression ratio calculators that people use are using a generate a figure that will have more to do with a cranking compression test than an actual running engine. For this reason, I don't put a lot of stock in the generic dynamic compression calculators. So, I can see using it as a general guide, but certainly not the definitive science that some people think it is.

This is why I like the fellow racers practical experience approach. There are tons of guys on here with working combinations along with a slew of vendors with tons of practical experience. I bet you can come up with a proven combo without too much "engineering".

 

If only there were others with 383 that puts down 500-550 na so I could just use there setup. I figure if you can get 500 out of a 347, you can get 550 out of a 383

 

550 out of a 383 n/a is absolutely possible. Whether or not it is doable with pump gas is a good question. If Patrick got to 500, it surely would be worth while to study that build thread.

 

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