91CamaroRS305

iTrader: (2)

ok, i am building a high rpm high horse power SBC engine. i know that a forged crank will take more heat and is stronger, but i am planning on having 400+ hp at the rear wheels and want to know if i should go all forged internals. i and going to go with forged pistons cause i want to run a pretty decent shot of nitrous eventually(after the motor is broken in). but do i need a forged crank and rods, or should i take what i got and get it checked out? or should i get one forged and the other not. i have heard from guys i know that i should go all forged, but where i can i get a crank for an 88 block with a one piece rear main seal without selling my soul to the devil. and what degree of forging should i go with cause i see all this 4340 4140 7570 and assorted other numbers. i just need a little direction here so i dont end up toasting my Roc at the track. thanks

92camaro

Go all forged. Get a 4340 forged crank and the H-beam rods. Go with a good forged piston from someone like JE, Ross or CP. Depending on how much nitrous you want to spary will depend if it need to be custom or not. What type of block are you going to use.

ME Leigh

You could go with a cheaper 5140 crank and PM GM rods. That should definitely be good for 400 rwhp or 500 crank.

85TransAm406

iTrader: (1)

4130 would be fine. Avoid H-beam rods if you can, they are pretty heavy compared to I beams. Or a ME suggested should be fine too.

BowtieDriver2

Cranks:
4130 very reliable and reasonably priced. good for 650 or so hp and 7000 rpm.

4340 almost indestructable. more exspensive but worth it if you are on heavy spray.

Eagle and Scat are decent. Lunati is good. Wheeler Motorsports has really good cranks. Their Competition series (4130) is strong and reasonable. The Pro series (4340) is great.

Rods:
I would go with 4340 Eagle SIR "I" beam rods and ARP bolts. Great combo for decent price. And they are much lighter than H beams.

Pistons:
Forged all the way. Just remember to run a loose piston to wall clearance if you are using heavy spray. Brand is mainly preference but cheaper slugs tend to be heavier and weaker in the skirts. So pay attention to what you are buying.

All this is just my personal advice. you have to make the final decisions.

BowtieDriver2

Almost forgot,

you also may want to look into coating the pistons. it will reduce friction and increase your detonation resistance. which is always a good thing with nitrous.

later

cgb

Far be it from me to not agree....

But if you're not going to REGULARLY turn more than say 6500 RPM, why spend all that extra on forged? Most people who push forged either have a big money tree in the backyard, or the first time around they bought the cheapest stuff they could fine..

If you're stock crank is in good shape, have it polished / turned. Have it magged as well to check for cracks.

GM rods work just fine. Have em checked. If they are okay, just add some ARP bolts.

Forged pistons are a good idea for nitrous, just follow the piston maker's advice on clearances. If you get too loose, some setups will give you a nice "Slap" when cold. That can make you almost lose your lunch.


Balance everything as a rotating assembly, and have it balanced at speed.

Invest the money you save in GOOD Quality machine work, and the best harmonic balancer you can afford.

I build a 355 two seasons ago for a local guy at the track. Roller block, factory GM crank, GM rods, ARP fasteners etc. It gets shifted at 6800 RPM since the addition of the monster heads he added last year, and when pulled apart this winter it was in great shape.

In my opinion, the most important things that contribute to an engine's longetivity:

- Machine work...QUALITY work.
- Attention to detail when assembling. Doesn't cost anythign / anymore to do it yourself and do it RIGHT, checking and re-checking ALL Clearances, and not just accepting "within tolerances"...


I have used more than few forged cranks / rotating assemblys...

As for quailty.. Lunati used to be the BEST for the $$$.. since they were bought out by Holley awhile back, I haven't been impressed with their parts.

I've had good luck with Scat. Never used any forged Eagle stuff.

I've used Wheeler a few times, there stuff was good...

BE AWARE, that only ONE TIME have I ever used a "Balanced rotating assembly" that actually did not require further balancing. That's why I don't even pay the extra, I just have it done at my machine shop, that way I know it's right.

For off the shelf pistons, I like TRW / Speed Pro. I've never had problems.

For odd compression ratio's / odd motors / combo's etc, JE is the choice....sometimes the only choice.

There's also Wiseco and Keith Black for pistons.

Rings are an often over-looked part.

Personally I like the Childs-Albert file fit moly rings...they only run about $90, but I've never had a problem. Of course any good ring get for a quality manufacturer will do the job, I just like getting my clearances where I want 'em.

And my pet peeve...people spending all that money on good parts and using crappy bolts / fasteners.


Hope this helps.

BowtieDriver2

I dont think you disagreed. you did a good job of expanding on what else I should have said.

You are completely correct on the machine work and balancing.

To the original post, also take the time to blueprint the build. Not only will it make your life easier in the future, but it will make you pay attention to every detail now. which is what cgb said.

I personally do not care for TRW/Speed Pro. Not that they have failed me, but they have failed a friend of mine. And the set that is in my 400 now (I bought before his broke) are making me nervous because of how much they weigh and the fact that my buddies broke near the pin. Looked like it was just overstressed and gave out. I like Weisco's slugs and C&A rings.

And GM stock rods are good but by the time you do the refinishing work, the new Eagles with good ARP bolts make more sense to me.

f-crazy

iTrader: (-1)

the lunati 4340 crank is rated at 800hp
the lunati PRO mod i beam rod will hande 750
and SRP forged are over 700 aswell....


http://www.sdpc2000.com/cart.asp?act...=1580&pid=8137


that will be my next motor.....