stock crank and rods/billet mains

[Renato Velati]

I'm pulling the motor out of my 23,000 mile gn and doing a buildup over the winter. I'm going to use the stock crank, should I nitride and cryo it? Whats the difference between the two. I was told that nitriding it does'nt help for strenght but for wear, and is cryo for strenght then? And as for the rods, putting in ARP rod bolts, what else can be done to strenghten the rod itself, shotpeening? What about wrist pins? Also going to main studs and billet mains, are the center two sufficient, or front and middle two, or all four? Going with either diamond or je forged pistons, any preference? I'm looking at high tens and after doing some research it seems I should be ok with this buildup. Thanks for any input.

 

[coach]

I am doing the same sorta thing with an 18000 mile car. Take out the original engine and build a seperate motor. Leave your numbers matching set-up alone.
As for cryo, it is a deep freeze to relieve stress from heat-treating. I am not sure that factory cranks are heat treated.

Coach

 

[GNDriven]

Assuming mild budget, Many guys running the stock crank into the tens. My research suggested it was good for 500Hp at flywheel, or some 10.80s.

Personal experience advise is to really consider who does machine work and assembly. A miss line bore on those billet caps and it could cost you a block.
I went to a forged crank after the stock one was cut on twice, for poor machine and assemble practices.

What RPM are you going to shift at?

 

[Renato Velati]

Shift point will be 5400 to 5600 rpm's with 28".

 

[GNDriven]

Don't oversize the cam shaft.

Are the heads ported? ok if not, A smaller cam will fill the cylinder better at low rpm. This makes for a funner street car with a low boost rpm theshold.

I drove a friend's stock block with a 61 compressor wheel and It was a blast. Low end torque was so responsive. I miss that.

Also stick to that rpm, do not overload the drivetrain. I do not know your knowledge/experience level, but 3 month ride 9 months broke and repair cycles are the worst.

What turbo?

 

[Renato Velati]

Most likely goin with a TE62, and will be porting the stock iron heads.

 

[turbofabricator]

In my personal experience, the stock crank is good to over 650 hp. (detonation will kill a $2800 billet crank) I also prefere a girdle over steel caps. To me, it really strengthens the whole bottom end. I've seen broken blocks with steel caps, but have yet to see a broken block with a girdle. With caps, you have to line BORE and then hone, with a girdle, you only need a hone, saving more material, and also reduces the timing chain issues. The only down side to a girdle is potential oil leaks and the added weight. If your goals are just high tens, stick with stock bottom end, and a light weight piston. I have used both JE and Diamond, with my preference being diamond, these days. I like Diamonds reverse dome vs. JE's standard dish. But, both are great pistons. Tune up is the most important aspect of engine longevity. Supressing detonation is the single most important aspect to an engine staying together. (besides getting the machine work right to begin with.) If bomb proof is your goal, buy a forged crank, K1 rods and good pistons from a board vendor, and do it right the first time. Oh ya......a Girdle, too. I've always used RJC girdles, but there are Chinese knock-offs available. Your choice.

 

[Renato Velati]

I'm also considering the girdle over the billet caps. I can see in photos how the girdle ties everything together. If I do go with the girdle I might have the stock main caps cryoed.

 

[turbofabricator]

I'm also considering the girdle over the billet caps. I can see in photos how the girdle ties everything together. If I do go with the girdle I might have the stock main caps cryoed.

If you are paying to have it "cryoed", it is a waste of money in my opinion. Cast iron is just that.......cast, with losts of imperfections. I've never been a big cryro supporter. If you can get it done for free....go for it. Then have the block done, too, while you are at it.

 

[charlief1]

Doing a cryo treatment re-aligns the grain structure of the metal to make it more stable. The main purpose in an engine is that it ties the grain structure together better and reduces the tendacy of distortion. DO NOT cryo until all the machine work is done because the machine processes will change the block or whatever you do. Not cheap but for longevity it helps. Great for brake componants to reduce warpage.

 

[GNDriven]

What price structure is involved in cryo treatments?

 

[Renato Velati]

Have'nt gotten a price yet. Going to try and find out this week.