Pistons Q's and such...

[RedBird]

So, a few of you might recall that i had built a 3400 to go into my sunbird over the spring/summer, and dropped in it back in august. And proceeded to have #3 rod bearing shred and lock the motor up, due to(i think) a warped rod i didn't know about. Puled it and replaced the motor with a stock 3400 for now.
Now i'm rebuilding and i need some assistance. I'm planning on getting the block bored .020 over(as long as that cleans the bores up) and i'm looking at pistons.

Does anyone have any suggestions as to what pistons i might use? This is going to be a N/A motor, *maybe* a small shot of nitrous down the road, but that's only a maybe. the only ones i've found thus far are these -

http://store.summitracing.com/partde...w=1&N=700+150+

And the description says they're flat-tops. Now, i'm looking for a bit more compression than stock, but i know the 3.4 iron head pistons have a slight dish, and they give something like 13:1 compression. This is a DD so i want only about 10.5 or 11:1, MAX. these are shown for 3.4L up to 2005, which would be the 3400.... plans are if i cant find any stock pistons to give me a compression bump, to shave .020 off the tops of the pistons, and run 3.4 iron-head headgaskets.....

any suggestions?

[ForcedFirebird]

3500 heads and Camaro pistons give you 11.5:1 with 3500 head gaskets. That's how mine is getting built - and then I'm going to add a couple of pounds of boost to it to see what happens. Then 3400 pistons are going in and big boost is comming.

[ezrollin]

Will those be stock 3400 pistons,cast ?

[ForcedFirebird]

Will those be stock 3400 pistons,cast ?

Yes. I'm not putting a ton of money into the 3.4 shortblock when I know a full 3500 will take it's place when I can afford a tubular k member.

[johnnymossville]

I am using these pistons:

http://store.summitracing.com/partdetail.asp?part=STL%2DH800P&autoview=sku

They are 3.4 iron head pistons and are hypereutectic pistons made with 16% more silicon which makes them much stonger than stock. They will give you 11.5:1 cr with 3500 head gaskets just as Forced has said. They will handle nitrous or boost with no problem. N/A all the way! By the way the pistons that you listed were stock 3400 pistons and 3500 heads will drop your cr to around 8.8:1, not good for N/A performance.

[johnnymossville]

If you used your 3400 heads the pistons that you listed the cr would be like 9.54:1 and a .020 overbore might raise it about .1 or.15. The pistons that I lisred would give you around 12.9 or so with your 3400 heads, way to much for a DD. We are kind of limited on piston selection to change our cr unless we buy some forged pistons for big bucks.

[ezrollin]

"3400 pistons and 3500 heads will drop your cr to around 8.8:1, not good for N/A performance" but great for boost !

[ForcedFirebird]

"3400 pistons and 3500 heads will drop your cr to around 8.8:1, not good for N/A performance" but great for boost !

9.1:1 with 3500 head gaskets .

[RedBird]

So those pistons, +.020 overbore, should give me 9.5-9.6:1ish compression..... Now, say if i were too, oh, shave .020 off the tops of the pistons, so i could run camaro HG's, that should put me at a fairly decent DD comp. ratio, no?

[ForcedFirebird]

So those pistons, +.020 overbore, should give me 9.5-9.6:1ish compression..... Now, say if i were too, oh, shave .020 off the tops of the pistons, so i could run camaro HG's, that should put me at a fairly decent DD comp. ratio, no?

Not enough meat on the Camaro pistons to enlarge the dish. Camamro pistons and 3500 heads gives you 11.5:1.

[RedBird]

i dont think you understand what i'm saying. Also, i'm tired of hearing about 3500 parts, I'm not using any i already have a set of Fully ported 3400 heads. Might use an upper at some point, but that's it....

3400 pistons pop out of the deck .020. What i'm saying is shave that much off the top, so they come flush, giving me enough room to safely use thinner head gaskets to increase CR. If the pistons i listed are the same shape as stock 3400 pistons, then it's just .020 off the outer rim, since the dish is more than .020 deep

[ForcedFirebird]

You can open up the chambers a little and use 3.4 pistons. I haven't looked real close at the 3400 pistons to see if they can be safely milled. Form what I have seen, the ring lands are already slightly brittle.

How much compression do you want?

[Superdave]

I just sandblasted a 3400 piston clean to verify, Should be no problem shaving .020" off the top.

http://www.3500z.com/Gallery/main.php?g2_itemId=883

Damon, i've still got those extras if you want to have one shaved we can CC the dish.


and trust me, his heads will flow more than enough.

From some quick measurements shaving .020" off the top will result in a dish volume of around 26.5cc from the stock 27cc.. with the use of .040" Iron head gaskets it appears to bring the SCR up to 10:1.


Iron head guys, do your pistons pop out of the deck at all?