camaroracerlt1

Hey, I am building a 7000 rpm lt1 (LE3 heads, GM 847 cam, ported intake, 58mm TB etc.) and am thinking about using the stock bottom end. My shortblock is an all stock 4 bolt main real LT4 with about 30,000 miles on it. Will this hold up to my projected 7000 rpm redline reliably. I plan dragstrip and roadcourse use so it may see high rpms for 30 minutes at a time on occasions. Should I just reuse the short block as it is or should I upgrade while its apart. I was thinking of doing just arp rod bolts and a high volume oil pump. Also I have heard of people using increased bearing clearance and thicker oil to prevent spinning rod bearings. Anyone do this here? If so do you use special bearings or turn the rod journals on the crank? If I have the rotating assembly balanced can I just neutral balance the flywheel or does it need to be replaced? Any suggestions would be appriciated. Thanks.

seawolf06

I think I'd worry more about the stock opti with those kinds of RPM, but you might as well get some better parts while it's apart.

If you're doing the road racing thing, get an aftermarket pan and HV pump with a cooler.

Not sure about the bearings, but there are some threads in the advanced forum, so check there.

rmackintosh

I run my car in SCCA.....road race only.....no longer a street car. Up until this year, I ran the stock bottom end with Ai heads/cam combo....it was fine.....rather strong actually. 400+ RWHP. Reliable.

SS RRR

If you're planning on using a HV oil pump then by no means should you use the stock oil pan especially for road racing. Plenty of expensive testimony on here about that.

SStrokerAce

Yeah, a few things here....

Get a road race pan, like a Canton 242T and you don't need a high volume pump just a high pressure one. Even then if you are using R compound tires I would still do more to make sure there was oil in the pan, namely a accusump.

Don't reuse the stock rods with just rod bolts. It's better to start off with new rods with good bolts and bushed pins anyways.

Bret

rmackintosh

I agree with both those statements. I used the Canton pan from day one with a COMPLETE stock 112,000 mile "mule" motor the first season...with a Melling High Volume pump. Accusumps are great, but I have never used one, and never had an oiling issue.

I DID however reuse the stock rods and pistons in conjunction with a GM ZZ9 forged crank (because it was CHEAP!) and we just took that set up apart after 2 seasons of hard road racing....looks beautiful. It wouldn't be my preference, but it can be done for road racing at least up to 400 RWHP. The machine shop did rework the stock rods when rebuilt, and used ARP hardware however.

Mike96z

Id put atleast a forged crank and leave the PM rods and pistons. You will need to get the LTCC setup, coil pack per cylinder to run 7k efficiently, the opti will hold but may misfire occasionally or more. The LTCC will be coil pack per cylinder and the opti is just used for telling which cylinder to spark.

SStrokerAce

Depends on the RPM.... if I was seeing 7000rpm all day long I would rather have stronger rods, espeically with a heavy piston attached to it.

Bret

rmackintosh

My machine shop had the same opinion when I did it 2 years ago.

I did it for cost. Not a problem now, as the new completely new, all forged 383 comes out of the machine shop on Monday!

SStrokerAce

Yeah I understand. I just ran some numbers on a cast crank 355 build. If you lower the mass of the parts (I think I was down to under 1400g bobweight from 1850g) and slowed the peak piston speed with a longer rod you can get the same lbs of Force on the crank at 7000rpm that you would at 6000rpm the OEM stuff is intened to last to.

Bret

Z-RATED94

Nice bit of free info right there.

RAT454

I would be inclined to go with aftermarket h beam rods and then use lighter forged pistons with low drag rings. Higher capacity baffled pan and std volume OP but with higher pressure. have the crank turned (or at the very least have the grinder check that it is straight, and chuck it up on the machine and use the arnold gauge to see for yourself that there is not taper and that the journal is actually round and consistent) The goal is to have round and consistent journals with no tapper..be sure that your crank grinder does not get into the journal radiuses with the grinding wheel. I prefer lighter high quality synthetic oil with tighter clearances. What ever you do get it professionally balanced by an experienced balancer, torque your rods using the rod stretch method. (again just my preference)... Invest in good bolts/studs and use high quality gaskets...be sure the cooling system is capable of handling the load (clean/unconstructive radiator).

Not sure what the general consciences is concerning the type of balancers,

Just my thoughts...