What is the stock compression for the 2.8, 3.1 and 3.4? and how do you increase the compression besides Boring the block?

 

im not sure about the compression ratios of the engines, but you can get different pistons, mill the heads or deck the block. but if you take too much off the heads then you have to do the intake as well so it lines back up properly. increasing the stroke will also increase compression. im not sure how much of this you can do on these engines, im just speaking generally.

 

well heck, after u mill the heads and deck the block , then go buy some dome topped pistons, that'll help you out also....but if you go to radical say w/ a cam, one of those valves might decide to meet Mr. Piston and send Mr. Motor to the hospital.

 

yea that is a possibility. i didnt mean do all of them though. youd have to see what kind of clearances you have. id say go with pistons and see once what you have left from there. i havent done much with the internals of one of these engines (yet )

 

If you are looking to buy Dowards turbo kit, you will actually need to lower your compression to around 8:1 to get full benefits. Stock compression for the 2.8L is 8.9:1

 

i thought flat topped pistons were better? when i bought my car the guy told me it had flat topped pistons, i even put it in my sig.. am i just like a total sucker or what?

 

Probably does have flat tops. Most stocks are flat, or chamfered (have a nice ring cut out around them, to lower compression ratio (cr)

2.8 - 8.9:1
3.1 - 8.5:1 (perfect for a turbo!)
3.4 - I don't know. Everything I have found points to around 9:1 cr. Anyone know for sure?

 

so if mine are flat thats better then ringed chamfered right?

 

no.

Chamfered (inverted dome) offer more headroom for radical cams.

Flat pistons usually do not offer very much headroom for radical cams unless they have valve reliefs in them.

 

A couple things here...

Inverted dome pistons are known as 'dished' pistons. Different than chamered (chamfered are flat tops, with a 'ring' cut out around the outside of it. They look like dome, but aren't)

With a radical cam, you want high compression, whether by domed (aka pop up) pistons, or milling the heads. You have a high static compression ratio, but the increased overlap of the radical camshaft lowers the dynamic compression, allowing the use of pump gas. Old trick, there.

Actually, you'll have better - you'll have a bigger turbo (16g vs 14b) more airflow = more power) and bigger injectors (24 instead of my 19). I think you'll be happy with the results.

The 3.1 will be the 'power house' engine though. With the lower compression, I won't hesistate to set the kit at 10psi stock, and I'm sure it'll get 220hp+. Now, with the larger injectors and turbo, the kit I sell will run up to the MAF's limit of 10-14psi, and run more than that, I'm sure. I'm going to go 2 bar on the 3.1 MAP systems as well, so they'll max out at 14 psi.

This whole last paragraph is all theory tho. I won't know until I do it. Turbo will be in by next weekend. I've got to get the lines for the oil/water cooling system next...

 

One other point there Xopher... you have 15x7 snowflakes, not 15x6

 

i don't have a turbo, nor do i plan on getting one. my question is "when the previose owner told me i had flat topped pistons and said they were better then regular ones, was he lieing to me"?

if i was i gonna be pissed!!!

 

lol, sorry.. thought you were asking cr because of a turbo...

Flat tops are regular pistons. It's like saying, yeah, it's got a torque arm, and lower control arms... yeah, big deal, they all do!

 

LONG time ago
DOMED pistons were the thing for raising compression.
Domed pistons are like ice cream "scoop" in the cone.
Flat top pistons are pretty much the "norm" these days, tho.
Yeah compression in the 3.4 is high at 9.0+. I still run regular 87 octane with no problems or change in "power" due to usage of premimum gas.
IF ya do a swap boogie BE SURE YOU insert the correct spark plug (ask for a plug for a 3.4 1995 F Body).
When I first did the 3.4 swap in the Firebird I had wrong plug in engine.
Upon changing to correct plug, no more "ping" upon uphill acceleration.
The 60* engine family has "some" Hi Po parts available.
BUT compared to the V8 stuff, no.
Compression is "raised" by milling or changing to thinner head gaskets.
OR THE WISEST OPTION FOR BUMPING COMPRESSION
is installing a 3.4 mill from the get go!

 

Thanks for the info guys.
I don't plan on doing a 3.4 swap I plan on getting a turbo but I am thinking about a 3.1 now thanks to Doward! 220hp+ sounds good to me I'm going to look around for a low mileage 3.1 that will fit my budget and then I can throw that 2.8 out of the 85 Camaro in to my 89 RS

 

Used complete running 3.4 long blocks
Have been purchased for as low as $210 up to $800 & $900.
My examples below cost me the high numbers & came as 44K & 50K mile engines, each.
Cost me about $100+ to install with the "new" parts (timing chain & gasket kit).
Then I sell the left over stuff.
My Firebird example actually cost me a total of $800 as I sold left over 3.4 stuff.
Good luck on your decisons, yet I wouldn't waste the time on the small things.
Installing the right solution from beginning & getting it running real quick spoiled me.
You can easily find a good used 3.4 in your area.
EASILY, as you are rental car heaven area!