Brent97Z28

I'm looking to change out my stock heads/cam. Since the stock bottom end has 2 bolt main caps, what is the hp and rpm limit? Would it be worth it to have the caps splayed?

Thanks,
Brent

urbaNHunter44

I'm not sure what the weakest link of our bottom end is, so i'll let someone else reply, however many people have had no problems running 410ish rwhp spinning to 6500 rpm on the stock short block, some have sprayed their setups and spun to 7k and lived..

generally it's accepted that it's revs that kill these motors, and 6500 is the max "safe" limit, at least from what i've read.

1997blackz28

it's pretty hit or miss. some last for quite a while spinning to 6500+ some do not. it depends on the shape and the maintenance up keep of the engine.

on a side note i don't think there are too many stock block cars spinning to 7000 rpm with any longevity or reliability.

95ttoplt1

About 10hp and 100rpm before parts fly all over the road or the main spins. Unfortunatly there is only one way to find these limits.

I spin mine to 7k daily and make about 350rwhp. What your will hold only you know.

96capricemgr

Rod bearings seem to be the weak link.
Don't get upset about the 2 bolt mains they work better than most give them credit for. Yes the LT1 is similar to gen 1s but not everything you know about those can be applied here.

At about 60-65K I put a ZZ4 cam in my motor ran it like that till 95K or so, then did the AI package which put me up somewhere near 400rwhp and put 6-7K miles on that before a rod bearing went. Now keep in mind by that time it was over 100K miles total and had been modified for more than 40K miles of that.
I really kick myself for not putting fresh bearings in it when I did the AI heads and cam last spring, IMO if I had I would not have spun the tod bearing in september. Current engine is a 40K mile stock shortblock I managed to find.

mdacton

The bottom end is pretty tough......I spun mine 7k+ and only problems I ever had was bearings.....I tear it down once a year to inspect it and the brgs are always shot but everything else is in great shape

lefty

Is there a way to access the bottom end without removing the engine?

James Montigny

I'm not saying there's a magic safe number to stay under, but if
you're pushing 500rwhp or spinning beyond 6500, you stand a good chance
of breaking something (spun bearings, connecting rods, etc ...)

Those parts were made for a car pushing 250-275rwhp

Having said that, there are people who've flirted with those numbers and
been ok for many passes and others who've had stuff break before they ever
reach 400rwhp.

To be safe, a forged assembly is the way to go if you plan on pushing either
higher RPM or big HP numbers. It's a big investment and it opens a lot of
doors for future mods.

crazydavez28

dynamite.

i'm pretty sure with an a4 you can get the oil pan off with motor in car you'll have to take the through bolts out of the mounts and jack up the motor.

on my m6 we had to jack up the motor AND lower the k-member real PITA but it's possible

2QUIK6

Yep I did mine the same way, jacked up motor about 3-4", put a piece of wood 2x4 in between the mounts to keep it safely up, and then loosened but do not remove the K-member bolts, back then out about 3/4" or so so they still have enough threads to hold and that give you another 3/4" of so clearence.
Here's a pic of mine showing how much clearence you have after doing the above.

Was a snap to get the pan off and on.

Critter

crank is good for pretty much anything you want to throw at it. replace it rod bolts with some arp's and you should be golden.