Comprestion Ratio
04-24-2005, 08:33 PM
#21
Originally Posted by Cal
Well I have a good welder for welding aluminum, but I'm a pretty shitty porter! However, I'm trying to improve.
What general areas in the combustion chamber would be best for depositing some aditional metal? I assume away from the valves to avoid blocking flow. I need some more compression, but I would rather not mill the heads.
What general areas in the combustion chamber would be best for depositing some aditional metal? I assume away from the valves to avoid blocking flow. I need some more compression, but I would rather not mill the heads.
04-27-2005, 06:31 PM
#29
Cal, I wouldnt run off and fire that thing up just yet. Going in and welding heads for compression takes a ton of skill and know how. Otherwise your playing with fire. If you didnt get a solid weld in any of those points, chances are your going to have chuncks of it floating around in the cyl. once it gets hot enough. Welding chambers is something probably left up to a pro.
For anyone that is looking for more compression with a reletively stock or slightly modded motor the best way is just mill the heads and/or run a thinner gasket. Only downside to milling the heads is that you start running in to the already discussed P2V issues.
Anyone that is serious about getting big compression is more than likely going to have aftermarket pistons to allow for the high compression and still be able to run the fat cam. For 99% of the applications on this board, more compression isnt needed. You can make it up in other areas. Once you start getting into higher compression you need to worry about fuel. All it takes is one bad fill of **** gas and your car will run like crap. Especially if you live in an area that has alot of summer heat and you spend alot of time on the road.
You wont see alot (if any) gains going from 10.8:1 to 11.0 (if you do they will be minimal at best). General rule of thumb I have always used and alot of race engine builders use is for every full point of compression you pick up about 15rwhp. So going from 10.8 to 11.2 or 11.5 your only going to pick up power that could have been made by a good tune or by a cheap (sometimes not so cheap) bolt on.
My new motor is going to make 14.0:1 on a 347ci N/A motor. Heads milled .030, GM graphite gasket, 57cc chamber, Diamond +10cc domed piston with 2cc reliefs. Because of this I will no longer be able to run down to local skivron and pick up a tank of 92-93. It will be on a strict diet of Sonoco 114. Street driving will be borderline out of the question with the boom tube and this much compression (not to mention the cam
). Its going to be a pain in the ***, but this bitch is gonna be FAST 
For anyone that is looking for more compression with a reletively stock or slightly modded motor the best way is just mill the heads and/or run a thinner gasket. Only downside to milling the heads is that you start running in to the already discussed P2V issues.
Anyone that is serious about getting big compression is more than likely going to have aftermarket pistons to allow for the high compression and still be able to run the fat cam. For 99% of the applications on this board, more compression isnt needed. You can make it up in other areas. Once you start getting into higher compression you need to worry about fuel. All it takes is one bad fill of **** gas and your car will run like crap. Especially if you live in an area that has alot of summer heat and you spend alot of time on the road.
You wont see alot (if any) gains going from 10.8:1 to 11.0 (if you do they will be minimal at best). General rule of thumb I have always used and alot of race engine builders use is for every full point of compression you pick up about 15rwhp. So going from 10.8 to 11.2 or 11.5 your only going to pick up power that could have been made by a good tune or by a cheap (sometimes not so cheap) bolt on.
My new motor is going to make 14.0:1 on a 347ci N/A motor. Heads milled .030, GM graphite gasket, 57cc chamber, Diamond +10cc domed piston with 2cc reliefs. Because of this I will no longer be able to run down to local skivron and pick up a tank of 92-93. It will be on a strict diet of Sonoco 114. Street driving will be borderline out of the question with the boom tube and this much compression (not to mention the cam
). Its going to be a pain in the ***, but this bitch is gonna be FAST
04-27-2005, 06:38 PM
#31
Originally Posted by MUSTANGEATER
Why did you pick domes over smaller chambers?
The C5R heads would be perfect for what I need but require to much other custom crap that I dont want to mess with. Custom intake, headers etc.
04-27-2005, 07:15 PM
#33
I'm pretty confident about my welding abilities, and my cam doesn't allow any extra P2V for milling the heads. I also don't like how milling heads throws off the valvetrain geometry and intake manifold fit. I'm running a cam with about 12 degrees of overlap but still have stock compression, so it would seem appropiate to raise the compression some. Some domed pistons are a good idea, but I assume that could be a pricey option. Maybe I'll have to use my old motorcycle as a guinea pig to see how good I am at welding up chambers. 
