What rpm can you safely run at for a race engine?

[GT2 Gordon]

I spun a rod bearing ?? I race a 3.4L Camaro engine in SCCA GT2 Fiero. After just two 30min races the rod bearing spun and broke the con rod. Lots of damage.
Before I invest again in more parts what kind of rpm can these engines take for racing. I was using a 7000rpm limiter.
The crank is cross drilled, con rods are 4340 H beam, pistons are forged ROSS. High vol oil pump. Data acq showed oil pressure was at 70PSI with no issues. Main bearings with upr grooved. Block trued, all arp bolts. 2 of the other rod bearing showed signs of lack of oil.

Just wondering if these bottom ends can take 7000rpm in racing conditions? If so is there anything else I should be doing?

thanks
Gordon

[1988GTU]

That oil pressure # is irrelevant if it's cavitating. Lower the pressure to 45-60 range and either try a larger capacity oil pan or sump configuration with a proper oil cooler. It should be okay upto 7000, but really that motor is not doing you any good that high up in the RPM's. You would be best with a 3400/3500.

Is your limiter bouncing off 7K all the time or is it just peak 7K for a couple seconds and you stay well below the limiter?

[Superdave]

run a Gen 3 block instead, priority main oiling will help you out in those higher RPM's.

[GT2 Gordon]

I road race it so I'm between 5000 and 7000 all the time.
I do run a large oil cooler and oil thermostat.
I run a race cam ( 310 dur, .525 lift) with a custom intake that is engineered for high flow and hig revs. Full ported heads. The engine pulls very nicly to 7000rpm making very good power compared to the other cars.
Cavitating is a good point. I was doing the 10psi/1000 rpm approach. How can you tell if your oil pump is cavitating?

[bob442]

Let's see this machine!

[pocket-rocket]

I wouldn't want to run grooved bearings on anything high RPM. It gives a smaller cross section for the oil film which with the same RPM/load will increase the pressure over the area vs a non grooved bearing. You have the right idea with the cross drilled crank, though.

[Jonpro03]

Let's see this machine!

This

[trewyn15]

This

x3! lol

[1988GTU]

Cavitating is a good point. I was doing the 10psi/1000 rpm approach. How can you tell if your oil pump is cavitating?

Quick test that can be of help is to: Put a see-through hose that is able to take the abuse, inline to the oil pressure sending unit and spin it up to the target pressure. If you see pockets of air bubbles flowing thru, then you are not getting lubrication.

[Superdave]

I road race it so I'm between 5000 and 7000 all the time.
I do run a large oil cooler and oil thermostat.
I run a race cam ( 310 dur, .525 lift) with a custom intake that is engineered for high flow and hig revs. Full ported heads. The engine pulls very nicly to 7000rpm making very good power compared to the other cars.
Cavitating is a good point. I was doing the 10psi/1000 rpm approach. How can you tell if your oil pump is cavitating?

similar operating RPM range to mine, similar cam as well. Mine's all for drag racing though. In for pics, i'd like to see this thing.


if the pump cavitates you'll see the pressure drop, it would have to be a digital gauge/sensor, an analog one wouldn't react fast enough. IIRC mine hits a little over 60 PSI at 7K, i run 15w40 Royal Purple.

[geoffinbc]

Go back to a standard volume pump. At sustained high RPM you can suck the sump dry and introduce air into the oil system.

Another thing you may be over looking is the clearances you are running. Tight street clearances are not good for racing engines. Opening up the clearances a bit and using a heavier oil would be a safer approach.

[GT2 Gordon]

Super Dave,
Did the 3500 FWD block bolt right up to a T5 trans in your Camaro? What about the starter? Are you using the front drive block? Since my engine is toast I guess I should go this direction.

In terms of oil pressure - The clearences are race spec and I run racing 20W-50. I also run a accusump incase the pick up is uncovered in a coarner. I run a AIM dash with a data logger. I sample oil pressure with a MTS sensor 10 times a second. There was never an issue with oil pressure.

Other questions for Dave and others
GM suggests using the cast iron heads for off road competition? Are the 3500 alum heads good for extended racing?

Thanks for all the help

[Superdave]

Right now i'm using a built 700R4 with the gen 3 3500 engine, however yes the V6 T5 fits perfect. The only problem is that the starter on the FWD blocks is on the drivers side. You'll need to find either a dual pocket V6 T5 bellhousing (i think Betterthanyou knows the exact years) or what i'm planning is a newer WC T5 from a 2000 ish 3.8 Camaro. It should have the starter pocket on the correct side. That bellhousing might interchange with the older T5's as well.

the aluminum heads will make way more power than the irons could dream of and you should have no problem with extended racing. Just use quality gaskets and ARP studs. There are even MLS gaskets available.

There are other benefits to the FWD blocks like overall strength, cross-bolted main caps, better oiling, set up for roller cams stock and the 3500's have oil squirters under the 5&6 pistons to keep them cooler.

[neophile_17]

I've got a 3400 in my street Fiero and it will get swapped into the race car for next season. The starter is on the correct side for the Fiero transmission. The 3400 worked great for the HPDE day I did in September before I blew the heater core (1 hour total track time). Loosing the weight of the iron heads balanced the car better than I could have hoped for. I'm running the 3400 stock for now so I kept the red-line at 6000. In my series the 60V6 is considered one of the more reliable engines and that's mostly Al head motors.

~sam

[geoffinbc]

Well I am not sure what "racing specs" are but if any of the bearing clearances are too tight when the crank flexes and the block distorts you will get metal on metal contact. That could very well have been your killer. Also look at the main cap and rod cap interface surfaces and see if there is galling that would indicate cap walk.

If you want to beef things up then the FWD 3X00 block with forged crank is a better way to go.

You can get a couple bellhousings with a drivers side starter. The Chevy 2.2L in and S-10 and the 3800 in the Camaro both should work. There was a pic floating around the internet with all the different small metric pattern bellhousings.