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namek
03-11-2003, 09:29 AM
Has anyone tried to bump the compression up on their 99+ truck for more power? Just curious... I don't even know if it's possible.
TireFryer30th
03-11-2003, 01:43 PM
Its definitely possible. You would have to remove the heads and have them milled...and since you have the heads off, you might as well have them ported polished and larger valves installed...and since you are doing that...you might as well install a bigger cam to take advantage of the heads increased flow...see where all this goes? :D

TireFryer
namek
03-11-2003, 05:13 PM
I know what you mean. Now if I could ony get this money tree in my back yard to bloom...
Tokez420
03-12-2003, 01:30 AM
whats the compression on the 4.8??
clutchNthrottle
03-12-2003, 01:43 PM
I'm pretty sure it's 9.5:1
namek
03-12-2003, 05:53 PM
Could these motors handle 10.5:1 compression with basically stock internals?
Don454SS
03-12-2003, 10:35 PM
Originally posted by namek
Could these motors handle 10.5:1 compression with basically stock internals? I would certainly believe so. I modified my 97 LT1 Camaro heads. I had the CNC's and had them milled .010". That along with a thinner gasket is giving me about 10.9-11:1. I've had it this way for about 5 years. No problems with any knock or timing getting taken out by the PCM. I only run 93 octane.
clutchNthrottle
03-13-2003, 09:26 AM
Originally posted by namek
Could these motors handle 10.5:1 compression with basically stock internals?

I believe the Silverado SS 6.0L is running 10:1 and the concept reg cab SS 6.0L is squeezing 10.5:1
namek
03-13-2003, 02:40 PM
I would certainly believe so. I modified my 97 LT1 Camaro heads. I had the CNC's and had them milled .010". That along with a thinner gasket is giving me about 10.9-11:1. I've had it this way for about 5 years. No problems with any knock or timing getting taken out by the PCM. I only run 93 octane.

How much would the milling and headwork cost roughly?
Don454SS
03-13-2003, 04:27 PM
Originally posted by namek


How much would the milling and headwork cost roughly?
I regret that I don't recall as it was five years ago. I do recall that it was quite expensive. I sent the heads to CNC in Fl. I lost the link to the CNC website.

A lower cost approach would be to have the heads machined locally. Most decent automotive machine shops can do the work at far less expense than CNC.
namek
03-13-2003, 04:58 PM
What kind of gains did you see with the higher CR? Was it worth it, or should I just keep saving my money for a blower? Thanks again for the help.
Don454SS
03-13-2003, 09:05 PM
In combination with the right mods it is worth it. I got larger stainless steel valves in the process. For your engine mods, it would definitely help, but I wouldn't want to make a blind guess as to how much. I have heard a very general rule of thumb that for every one point compression increase you will see a 4% increase in HP. I don't know how accruate this rule is, cause it doesn't sound like a big gain, does it?

A blower will produce more power, but you don't want high compression with a blower. Also, do you have the right cam installed for a blower? For one item, you don't want anything lower than a 114LSA on the cam.
namek
03-13-2003, 09:27 PM
You're right.. 4% doesn't sound like very much. Thats why I'm still debating between building a NA motor w/ higher CR, or just keeping the same heads and putting a supercharger on it. My friends keep telling me it would be much cooler to have a fast NA motor, and I know it'd definitely be a lot cheaper and probably more reliable. Hmmm decisions decisions :confused: