Which Forged Pistons To Go With.

[osmar614]

Just looking for advice on which forged pistons to go with for my factory spec 302. The block is remanufactured and has about 3000 miles on it. It's a 9:1 compression and has a Flat tappet mild rv cam. I am planning on adding nitrous in the near future and want to make sure the internals can withstand it. Iv looked on all the usual sites but I don't fully understand the specs of the pistons because all of the aftermarket ones are usually .030 bored over and higher but I don't want to bore my engine at all. I have all the basic mods like complete exhaust, carb, intake, msd dizzy and 6al. I know I should have had the pistons installed before dropping the engine in but I didn't think of going with Nitrous till recently. Any suggestions are welcome and greatly appreciated thanks FEP guys and gals.

[Ethyl Cat]

Find some OEM forged units if you are only looking at a 100 shot or so. They will be fine. Put a good ring set in it and adjust the ring gap accordingly.

Learn about tuning that stuff BEFORE you get too far into it so you do not blow it sky high (forged pistons or not!).

DO NOT go with a "nitrous grind" cam. They are a waste of time with small amounts of juice. Get the best NA cam and spray it! Otherwise you have given up HP and torque off the bottle you did not have to.

I have 6-7 laying of those pistons around I would get rid of cheap.

There are actually NOS std bores floating around out there too.

Good luck!

Steve

[bwguardian]

What year model engine combination do you have? It appears that it may be a pre 85 given you say flat tappet cam...but it is confusing that you state it is about 9.0 to 1 compression ratio, unless the heads and/or engine deck were milled, given factory was 8.4 to 1 compression ratio. The motor will have to come apart anyways and I would install some good rod bolts if you did not already as that is the weak link in these engines...unless you get into high horsepower, then the blocks split!

[bwguardian]

Oh, and by the way...the clearances for cast versus forged slugs will be different to. So it might not be as easy a swap as you think. You need to mic everything and see where you are starting from.

[osmar614]

i purchased the motor here in dallas from city motor supply, and thats what was noted down on the compression for my engine since then i have misplaced the information on the engine. They told me it was factory spec heads, block, rockers, pistons only thing different was an RV cam. I am only looking to install the nitrous no other Force Induction since i am carburated. Im not wanting to get into the high horespower numbers just a 75 - 150 at the strip on weekends. will the forged internals be necessary for this amount of nitrous?

[PaceFever79]

i purchased the motor here in dallas from city motor supply, and thats what was noted down on the compression for my engine since then i have misplaced the information on the engine. They told me it was factory spec heads, block, rockers, pistons only thing different was an RV cam. I am only looking to install the nitrous no other Force Induction since i am carburated. Im not wanting to get into the high horespower numbers just a 75 - 150 at the strip on weekends. will the forged internals be necessary for this amount of nitrous?

Forged internals no, forged pistons, yes!

[PaceFever79]

You could maybe do a 75 shot, but it is easy to crack cast pistons.

Long story short, use forged pistons for nitrous.

[osmar614]

Alright so now which pistons should i go with, pistons from a forged block (late 80's - 92) or aftermarket brand? all the aftermarket ones i have seen are .030 .040 .060 over. but i am not bored over so how do i figure out which ones i need? sorry for the newbie questions?

[PaceFever79]

The stock 87/92 HO forged TRW pistons are fine.

[gmatt]

Myself, I would be checking the bore on that block BEFORE buying pistons since it was 're-manufactured'.

[osmar614]

thanks guys. ill check the bore just to be on the safe side

[306gt]

thanks guys. ill check the bore just to be on the safe side

Get a cheap pair of 0"-6" dial calipers and measure the bore for a quick reference. Standard size bore will be 4.000" A quick check with the dial calipers will give you a quick measurment that you can use. If it is a remanned motor chances are it will be either 4.020"-4.030" - 4.040" oversize as most rebuilders bore them anyways. The quick reference will get you in the ball park But an actual Micrometer and a dial bore gauge will be needed to determine the actual size of the cylinder and the actual size of the pistons to determine the piston to wall clearance. The TRW factory forged pistons would work well for what you want to do but they are heavy (alot heavier then the cast pistons) and might require you to re-balance the rotating assembly.