Raise Compression

[3400-95-Modified]

I want to bump my compression back up to stock or slightly over. 10:1 or 10.5:1 I'm currently running a 3400 bottom end with 3500 heads... stock measurements, stock pistons, stock headgaskets and whatnot...

Whats the easiest way to do this? Like how much to shave off the head and how to get everything to stay matched up.

Biggest thing I'm lost on, is what is the compression on my stock setup? I dont even know to possibly have an estimate done by a machine shop. I know there are a few "estimates" of what the compression is on the hybrid setups but I don't know if anyone knows for sure or if its been calculated.

Thanks.

[3400-95-Modified]

Well, I just ran the CR checker on the board... forgot that was there...

The following default values have been used.
Bore 3.622"
Stroke 3.310"
Head Gasket Bore 3.75"
Head Gasket Compressed Thickness .060"
Combustion Chamber Volume 32.46
Piston Dome Volume 28.6cc
Piston Deck Clearance -0.020"
Final Displacement 3352 cc
Static Compression Ratio 9.15:1
Quench Interference Ideal Less Power
0.04"

User Notes: 3500 Heads on 3400 Block


SO to get 10.5 I would need 22.7 CC's on the cylinder heads.... OR 26cc's will get me 10:1

Ben, what would that compression increase do for my n/a power? and which one is most obtainable without other alignment issues.

[IsaacHayes]

I wouldn't shave the heads. probably too much to shave to get there, then your LIM won't line up right without more mods.

AlexMT (or is it GT?) ordered 10.5:1 pistons... maybe go that route.

The camaro pistons would be an option too for 11.something... With a good tune you can run pump gas. Not sure if that would fuck up your quench though. If you loose quench you loose power and increase the chance for knock.

[3400-95-Modified]

I'm not tearing into this block. Its shaving the heads or I'm done getting more power the n/a route and its getting sprayed since its low compression now.

Pistons are well over 500 alone for those... Head shaving can be done for WAY cheaper and the LIM can be modified to accept those changes if they are that radical... How do you think they do it with a small block?

Also I would need -.020 deck height pistons to keep my quench at 0.04

[johnnymossville]

Sealed Power Hypereutetic 3.4 iron head replacement pistons from Summit Racing run $28 and change each or around $175 a set of six. Thats what I'm running for 11.56:1 CR. They will handle the bottle also but thats probably too much CR for that.

[3400-95-Modified]

damnit... I really don't want to crack into the block.

[SappySE107]

SI valves will increase compression but to get 10:1 with 3500 heads takes pistons.

[3400-95-Modified]

is the CR calculator correct in saying I currently have 9.15:1? And what would the SI valves get me, and how far can I shave a 3500 head?

Bottom line whats the highest compression I can get with what I currently have?

[SappySE107]

9.16:1 is what I got. SI will give you about .1. I don't know what shaving .020" off will do but I will have a general idea once I finish a set of 3400 heads I am porting for a customer. He wants .020 off and I already cced all the chambers (street/strip).

[3400-95-Modified]

you dont have a set of 3500 heads CC'd with .020 off do you? because technically thats the only number I need to get an estimate

[onefastV6]

I will have to do some digging through 2 year old posts, but If I recall we did CC my heads after they were milled .020"

[3400-95-Modified]

Thank you....

Also was it difficult at all to get the LIM on with them milled 20?

[IsaacHayes]

I forget what is the quench with camaro pistons and 300 heads? Too much right?

[3400-95-Modified]

Whats the deck height of a camaro piston? Anything over .02 and its cutting it close... less and its not enough power, or just below optimal... stock 3500 is .05 quench, 3400 is .04

[onefastV6]

Ahh here we go:

Stock 3500 Combustion Chamber: 32.4cc
Milled .020": 30.7cc or 31.7cc

Either way, you will need pistons get the compression over 9.5:1
I believe milled .020" you will be about 9.2:1

BTW: I didn't have any issued getting the LIM on and sealed.