Bigger cam!

 

did you have those heads cc'd? are you sure they are 54 some people have had stockers with 58cc heads.

 

Yes, for 68° IVC ABDC. The DCR result will vary depending on the actual head cc and cam timing....Given the current engine combination, the numbers are going to reflect the same condition that Rich describes unless 64cc+ heads or -16cc or deeper pistons are installed (I would not go to thicker gaskets).

 

well no i did not get those cc'd but they are the stock heads with a port and polish and a very mild resurfacing (milled)...I believe that stock is 54 and with a small amount of material removed and the mill I would think they would be around 54. I really wish I would have gotten them measured

 

so what happens if i run it as is...detonation?? or something more?
I did compression check on all of the cylinders and had around 275psi which is quite a bit considering its not boken in yet. by they way the surface of the block did not seem to look like it was resurfaced milled as I could barely an imprint of the last head gasket, so I am not sure if it is zero decked.. anyone know what the height would be from the factory with this assembly

 

The stock LT1 heads are 56cc.

Are you sure about the 275 psig? Did you check with another gauge?

A gasket imprint is not an assurance the block was not previously decked. You need to find out what was done to the block, get the actual measurements. If this info is not available, you're going to have to measure everything again.

The wrong (low) octane gasoline for the engine (high) CR usually results in catastrophic failure.

 

I didnt check the 275 psi with another gauge but I am fairly sure it is correct. I have read a few different methods about how to perform the compression check one stating crank the motor 3-5 times and and others sayin to crank it till it maxes out. I cranked it till it would not go up anymore. Does anyone know what is safe for cylinder pressure or is there a way to determine the DCR using it

 

275 psig results in 8.4 DCR

 

How do you figure that?

The motor hasn't been run yet, right? And the cranking pressure is going to probably be way off, as the lifters aren't full of oil, making the cam look small, which will make the cranking pressure too high.

A dynamic compression of 9.86 is far too high for pump gas.

 

its been run for about a 30 min period...Im not sure how he reached 8.4 DCR but I love to know. After using various calcs I think my DCR is 9:3:1....Since its already together Im goin to see how it runs after a thorough tune. Things goin for me are the aluminum heads small quench (around .05) electric water pump 160 stat, msd box and coil. Two things Im considering to possibly maintain pump gas would be a timing retard module for my msd box and installing a finch fuel catalyst and maintain my knock sensor. plus maybe a little juice

 

On one of my 383 setups, I am running 9.2 DCR in Phoenix with no issues and my new 383 setup will be 9.4 DCR.

Granted I know how to tune and that has saved me.

 

good to hear that makes me feel much better! Just curious what ur running for a cam

 

Chevy,

I modified my sig to answer your questions. You can PM me if you have specific questions on tuning.

 

I used the equation below, which is derived from the gas law equation. Since you measured actual pressures without fuel, I used the heat capacity ratio of air (1.4). All pressures are absolute, so your 275 psig becomes 289.7 psia. Po is atmospheric, which at sea level is 14.7 psia.

P=Po*DCR^1.4.

 

Thanks Tito and Blackhawk...I think I'm goin to run it and see how it goes.