Raise Compression

[Alxsmt]

i say just get pistons

[Z26-T]

Yeah, I talked to a few guys, such as Ben about what heads to go when I go through and build a engine for mine. The 3400 ported heads are the best for boostage.

My friend just put a 4k yank stall in his T/A. Took his 13.99 ET to 14.1...

[loner666]

I know. Its the least of my worries. I only plan to do that when/if I ever pull the engine apart again to do the bottom end

[IsaacHayes]

I wouldn't worry about the compression loner, you are turbo and it's a small amount less than stock. You have turbo as the power adder. N/A needs every bit of compression to make power.

[loner666]

More compression+less boost=better power then less compression+more boost

But yes I do have boost and that why its getting upped to 12 either this weekend or next. Im working on getting slicks. Found a brand new set for my 14 for $330. Still going to suck with an open diff though

[3400-95-Modified]

Higher stall is going to make you spin even more because its going to dump you further into your powerband... You need slicks with your setup.

And you dont need compression you have boost... 9.15:1 is enough for what you want to do.

[loner666]

Yea but that wont be my track toy. The Corsica is going to remain my track toy but with a different idea in mind for engine and drive train. All will be decided later and put in its own topic if I decide to do what I want

[IsaacHayes]

Impala is just more weight! Like 400lbs at least.

[loner666]

This is why Im putting 3400 heads back on if I keep my motor setup. I want my compression back, maybe alittle more since Ill get forged pistons and Ive heard/read the 3400 head flow better then the 3500 when ported for boost, or am I wrong still?

Either way, the decision of keeping this motor when/if my trans goes again is still up in the air. Id really love to put it into an Imala

And Jon you bastard, why couldnt get make a choice on that convertor before I did my trans agian? I could go for a higher stall.............once I have some better rubber for the track. I cant even fully stall right now, which would be around 3k or I make a smoke show all the way to the 1/8. Damn street tires and open diff

[IsaacHayes]

How come you are not running way faster than Asylum? Is the 4T60-E really that much of a power hog over the 3TXX?

Hopefully it's just the stall eating up a ton of power. I still think a stock one would be good for you, and it would be higher stall anyways with the power you are making.

But more compression always helps with power. That's why the LS1/Quad4/etc have high compression stock. And that's why when they were messing around with engines to get better emissions back when they first started caring, they tried things like lowering compression and those motors horsepower went down the toilet. No whither or not the decrease from 9.8:1 to 9.15?:1 is enough to take away a big chunk of power I don't know. But going higher than stock would be nice too.

[3400-95-Modified]

Yeah, I'm trying to stay away from a 2700, thats why I went with 2095... the stall i have now is just way too agressive.

And for those that think .020 is alot off a piston... Take a set of calipers, set it at .020" if you dont have a set, for reference a standard CD is about .055" thick... so less than half of that thickness... I gotta double check a 3400 piston and I do remember quite a bit of material being up there, and Yeah I was gonna say what dave did... .020 quench is asking for issues.

All this compression talk may take place AFTER this year when the car is getting painted... I'm not totally sure yet on what I want to do. There is still quite a bit to finish up the overall car and if I can get low 14's with this combo right now then I'll leave it alone for a little while.

Ben how much are the SI valves and where can I get them from? You dont have them listed in your store, just in the head assy's

[Monzsta]

brake torque is your best guess at stall speed or as close as you'll get, shocking it is a lower stall typically.

3700 rpm according to my data logs before the forward clutch began to slip.

That's with a FAFB Pontiac Sunbird converter, ported heads, and a tune. Stock everything else and a 3100 t/b. FYI, a stock W body 3100 converter stalls at 2700 rpm.

[Superdave]

meh, i wouldnt go into milling the piston tops to reduce dish vol. youre weakening the upper ring land that just loves to break on these engines. SI valves with an undercut and the ironhead gaskets will help.

he can't run the iron head gaskets without cutting the pistons.. he'd have .020" piston to head clearance that way..


there is alot of meat on the 3400 pistons above the upper ring land, .020" shouldn't make too much of a difference in the overall strength.

[34blazer]

meh, i wouldnt go into milling the piston tops to reduce dish vol. youre weakening the upper ring land that just loves to break on these engines. SI valves with an undercut and the ironhead gaskets will help.

[Superdave]

.020 isn't going to be enough to mess it up, I think I still have plenty of room in my lifters to accept more preload.

Either way as noted, converter is getting swapped soon and we'll see what happens there.

Also Dave, how can taking -.020 off the pistons and only dropping to a .040 crush gasket raise compression... isnt that a double negative there... or does the .020 off of the ring make the CC's of the piston low enough to raise it up with .020 off the heads as well? In other words, what is the piston CC's after the .020 is off them?

Basically all you are doing is reducing the dish size.. i had the measurements calculated a while back.. I'll dig out a 3400 piston and do it again tonight if i get the chance.


Most shops charge around $65/hr for machine work.. some might take 2 hrs to do all 6 pistons. they'll usually bitch and moan about having to press out the pins and remove the rods.