TGP Guy's and 3400 guys

[Pretty Boy]

Ok so i have a brand new 272H crane cam w/lifters,Complete rebuild kit for (93-95) camaro 3.4 P/R and P&P heads with new locks and springs laying around the house. So my idea was to compare the 2 motors for a back up motor for my fiero just incase .

1st block: TGP 3.1 Will all my parts fit this motor?
2nd block: Camaro 3.4 P/R

I already know that the parts i have work for the camaro due to having had the block and sold it for stupid reason's but back to what i'm getting at.

I was wanting to know COMPARING the 2 are the high compression pistons i can swap in for cheap meaning like putting a set of 3400 pistons in and achieving 10.5.1's?

Aftermarket head and main studs?
IIRC the TGP motor has factory forged piston's?
How easy/hard is it to find a new set of piston's for the TGP motor?

i'm looking for the best bang for the buck for this motor really just wanna play around with it.

[SappySE107]

TGP didnt have forged pistons. I can get forged pistons made by Diamond but thats the cheapest option I am aware of for forged. 3400 pistons won't give you 10.5:1 in any configuration. Bang for the buck, use stock bolts.

[Jonpro03]

Details on the TGP motor:

"Unique rods: these forged versions are unique to the 1989-90 Turbo Grand Prix and 1990 Turbo STE only. Stock 3.1L rod part number is 10078995/12515767, “turbo” 3.1L rod part number is 10070113.

Rod Specs:

Unique construction: C-1037 heat treated steel forging, with SAE 1050 air quenched rod caps.
Weight full assembled: 1.33 lbs

Length Center Line to Center Line: 5.70”

Small end size: .905”

Big end size: 2.474”

Racing Specs per Chevy Power manual: 7,000 rpms possible, but the rest of the rotating mass needs to be tightly balanced for this including a better crank.



Unique crank, started as a heavy duty casting number 981 as seen in the all-wheel drive Chevy Astro, but this one is unique to the 1989-1990 Turbo Grand Prix and Turbo STE, being worked on after starting as a 981 crank! Proof; stock 981 crank part number is 10146900, “turbo” 981 crank part number is 10110549.

Crank Specs:

Material: nodular cast iron

Unique machining: Journals chamfered, with deep rolled fillets that provide residual compressive stresses for added durability

Unique Treating: Ion Nitrided with a hardened depth of .02"-.03" raising surface hardness from 30-35 Rockwell C to 60 Rockwell C.

Weight: 39.5 lbs

Unique Crank dampener, stock 3.1L part #: 14091896, turbo dampener: 10131060



Pistons: Mahle autothermic hypereutectic pistons with reinforcement bar/steel strut to add strength to the top of the piston (which is often left out in aftermarket versions!).

Piston Specs:

Composition importance: 12% silicone

Weight: 365 grams/12.8 ounces

Top compression ring: 1.5 mm

Second ring: 1.5 mm

Lower/oil ring: 4 mm

Compression height: 1.463”

Dish volume: 28 ml

Pin diameter: 22.9950 mm/.9053”"

[Superdave]

Hypereutectic pistons and Forged pistons are totally different.

Compression is going to depend on what heads you have, you said the parts were for a 3.4 camaro so i'm assuming that they are gen1 Irons. Using those with any FWD dished piston will result in around 7:1 compression. You'll need a set from a RWD Iron head 3.1 to get back to around 9:1.

If you use the better aluminum heads then you can get the compression up really high with a few different choices. it all depends on exactly what heads you use. Gen2's have a smaller combustion chamber than Gen3's so you can get more compression out of them.. but you'll lose overall power because they don't flow nearly as well.

[Pretty Boy]

Will i do have 93-95 camaro heads that have been P&P i spent way to much money on them to just let them sit around so i would want to be using them.

What would a set of DOHC 3.4 piston's do for me?

[2.8-350TBI]

my solution would be to slap the 3.4 heads onto the tgp block. that way it is fully supported by iron, and use 3100 pistons for low compression. even if the heads dont flow that well, a turbo and massive amounts of boost will help lol

[Superdave]

Will i do have 93-95 camaro heads that have been P&P i spent way to much money on them to just let them sit around so i would want to be using them.

What would a set of DOHC 3.4 piston's do for me?

even ported your 3.4 heads don't flow as well as stock gen3 aluminum heads, i'd sell them and try to recoup some of your loss.


3.4 DOHC pistons in a 3.4 with iron heads is 9.95:1 with .040 headgaskets

[Pretty Boy]

Well the prob is that i spents $900 on them. yes was not smart and didn't do my research on them. As for 3400 heads on a 3.4 or 3100 i don't wanna do that only cause i want to use my extremely over priced heads that i paid for.

[Superdave]

Holy crap!

oh well then, when you want to pick up another 50-60 HP you know what to do.

So which engine are you building up? If it's the 3.1 then your highest compression option is going to be 8.45:1 with those heads.. With the 3.4 block you can use the DOHC pistons but you better check your piston to valve clearance several times and make sure to use a new timing chain.

[Pretty Boy]

What is the highest compression i can reach with the DOHC piston's in the 3.4? I know of the 3500 top end on the 3.4 like what forced firebird is running would be awesome but i have a complete 3400 that i'm in the process of saving money to build soon will have the LS6 yellow beehive springs for the build. just slowly building a collection of parts for the motor i wanna build it once and that's it.

[Superdave]

I'd be careful with the LS6 yellows, I've personally seen 2 of them break on a cam well below their coil bind.

3.4 block, 3.4 DOHC pistons with 3500 heads is 13.08:1 with .040 headgaskets and 12.2:1 with .060 gaskets assuming a stock bore. With 3400 heads it's 14.16:1 with .040 gaskets and 13.13:1 with .060 gaskets. 9.95:1 is highest with iron heads.

[SappySE107]

Were those the rusty springs off ebay? I have a hard time telling people the LS6 springs are going to break for no apparent reason.

[Superdave]

I don't remember, but that's possible. I know the replacements came directly from GM.

[Mars]

My yellows have been going strong for years @ .510 lift 7000RPM. No issues soo far. Back on topic.....

[Pretty Boy]

Well that LS6 springs will be going on my 34/3500 hybrid build not my 3.4 P/R motor