2k Cobra

Good point!

Builder should have advised OP of the great "Racetrack Ready" oiling system..

C5 Hardtop

What tires were you running and was the course direction CCW?

Dirty Howie

What tires?


DH

AzDave47

I can't find the link now, but there was very detailed oil pressure logging at Buttonwillow which is a flat track and it was clear in any high G left turn with the 8Qt system that oil pressure would drop in a major way at approximately 4 seconds of the high G's. None of the data was logged on a NASCAR banked oval. It is a left turn issue because of where the dry sump suction picks up the oil in the sump. In right turns the G's help feed the suction.

It is an issue at many tracks for unmodified 2006-08 Z's, most likely when they run sticky tires, but now even some of the street tires can pull 1.2 G's in "flat" turns.

phipp85

That's enough to cause problems especially if they were sustained 1.2G's, even on a flat track. Other things about the track layout to consider as well, like heavy braking before said left hander.

Unreal

I found it. Even then, it was a dip in oil pressure, not a complete loss. Guy didn't lose a motor.

This sounds like a case of a hurt motor being put to bed by being beat on at the track. Either way it sucks, and maybe it was the insufficent stock system that led to failure. The C6Z, just like the C7Z is not a track ready car.

Michael_D

Scat rods and Manley pistons..... Reeks of a "budget" build. I've use Scat cranks and rods before, just not in anything serious. Manley is not know for their pistons either. These two things make me wonder what else was used for this "bullet proof" engine, as well as the machining, blue printing, assembling.....

Unreal

Another local guy had that shop do an engine. It came apart rather quickly and "budget" doesn't even begin to describe it. All sorts of 1/2 *** stuff and hacks. While the oil pressure thing "may" have effected it, the extremely poor track record of that shop would be where I would look at first.

olddragger

Wait--you had a cruising rpm/temp oil pressure of 35psi? That's very low for a stock engine---don't know the clearances etc your builder used---but just for reference at 1600rpm oil temps at 190f my oil pressure is about 52psi with 0w/40 oil. And my engine has 72000K miles on it.
Like unreal said engine may have already been hurt?

Unreal

As for people saying the "builder" should have know to tell the person to upgrade, I don't agree. If you take a block to a machine shop, and have them put a motor together, a random machine shop is suppose to know what other parts of a car are suppose to be upgraded? A machine shop assembling a motor isn't a race shop, or a corvette shop. Now if it was a high performance shop that did it, I agree, but a random machine shop, no way they should know what needs to be done to every car. That is the risk and trade off you take using a machine shop instead of a performance/race shop.

Michael_D

Your generalization is most likely going to offend an entire profession of "automotive machinists". Ever hear of the "School of Automotive Machinists", aka S.A.M. ?

As I am a milwrite, with decades of experience, machining and building hundreds of engines over my lifespan, I would rather take my engine to a machine shop that specializes in engine work, than a damn tooner/bolt on performance shop that doesn't know fckall about engine building.

Now if a performance shop actually specializes in engine machining, and assembly, or even complete assembly - different story. Not as many of these around.

Unreal

True, but how is a machine shop suppose to know about corvette racing? Are they expected to keep up with all the different models and limitations?

I wouldn't ask a tooner shop how to measure bore taper, and I wouldn't ask a machine shop what size oil tank a corvette needs.

Yes I rather have a machine shop that specializes in engine work, but I wouldn't depend on them to tell me all the parts the car needs to road race it. They build the motor, the person building the car puts the rest together.

If you pay a machine shop to assembly a motor, where is the line on what they should recommend or provide? Do they have to suggest a new fuel pump to ensure it gets enough fuel? Injector size? Tune it? Cooling system upgrades?

Michael_D

Valid points. I am not disagreeing with them.

Normally, there would be a business relationship between the machine shop and the shop installing the engine. It's incredibly expensive to be proficient in all aspects of making **** go fast.

It's the shops that bolt crap onto oem short blocks that concern me the most.

Regardless, I feel for the guy who started this thread. He has been screwed.

HOXXOH

I made the comment to check with the builder, since the builder was not known, nor did the current owner have the engine built.
When buying a modded car, you generally have expectations that the mods were appropriate for the intended use. Maybe the OP should have checked with the builder prior to his purchase, but that doesn't mean the current problem wouldn't exist.

I'm not a professional builder, but I've built several engines, including NHRA/AHRA record holders, and instructed automotive machine shops to do what I want done. The only failure I've ever had in the 57 years since my first engine build, was caused by a mis-marked bearing. So my point is that it doesn't require a high performance shop to build an engine, nor is failure the result of using an everyday machine shop.

C5 Hardtop

Don't be so modest. You are a professional. Congratulations on your NHRA and AHRA achivements

carlvr

The course was CW. Tires are 275 Section RE71R snd shaved 355 P Zero Corsa System rears. The RE71Rs got up to temp quickly and held on very very well for those 5 laps I got out of the car. The P Zero also worked well especially in the last few laps

C5 Hardtop

The CW rotation of your track puts T1 at a slower speed so it is less of a 'big sweeper' type of corner.

If you look at ThunderHills map linked here for example, taking T2E traveling CCW is known to cause oil starvation issues on track tires (R compound).

carlvr

Just spoke to Larrys.. Got some more info.. The car went in there 2 years ago with a spun bearing so they did a budget build on customers request. Budget meaning adequate for N.A. application with a cam. They told me that indeed the rods are budget rods but adequate for what he was trying to do. They told they are aware of the importance of upgrading oiling system for track use and the original owners intent was just 1/4 mile and street use. They have no Idea why this could have happened and want to look at the engine to see if they can pin point. They said that the same owner had the engine worked on in Texas for some reason after they had it. I know the cam was swapped out for a smaller one, probably right around that time. Also when I got the car the tune in was absolute ****. I had Nick tune it maybe a month or two after I got this car. Even still they may not be able to tell why the there was such a lack of oil pressure and oil starvation. One thing I will be doing 100% is upgrading the tank and oil pump and most likely the cooling system. Though I don't buy that this happened because the car got hot for one second, I am also not comfortable with temps going that high so quickly..

Now I have to decide where the engine goes for a rebuild. I am a bit more comfortable with Larrys now that I have spoken to them and as my options in Tucson are very limited but not 100%.
I would love any suggestions for or from any builders out there.. I really don't want to do this more than once and I'm not a millionaire

Thanks again for all the help

2k Cobra

That and turn 2 at Laguna..

One of our members did data logging on those tracks with a larger oil tank and got very short drops of pressure on those turns.

olddragger

open up the learning book brother.
Building a dual purpose engine is not that easy....depending on the level of performance you want of course.
An oem engine (with fixed heads) with a proper tune, a few mods--better oil supply, headers, better cooling ( oil and coolant),and intake is a very bad *** start for road course work. Especially if you are not running r compounds and a roll cage. This car is seriously fast as is and can get you in trouble in the blink of an eye.
The above engine--keeping it cool, maintaining it correctly and keeping the rpms below 7K ( it is HPDE--right?) should give you a fair amount of longevity for track and street.