Aspkiller

You are absolutely right, but they will last even longer if you shift them at 3K. And, if the drivers of those happy little cars try pulling 1+gs in really big sweepers, sooner or later something really BAD will happen.

Also, we are talking about engines that produce 700+ crank hp NA. Not 500-550 crank hp. All the engine builders that have established a solid racing reputation have extensively modified the LS7s race engines they build (Katech Mast etc.) in order to keep them from having oiling problems, vibrating connecting rod problems, collapsed lifter problems, broken spring problems, etc. Granted, these problems won't happen when you don't wind the car above 6,500 or keep in constantly above 5,000 in a race mode.

As to the temps allowed for the LS7 production motors; what's going on there. Couldn't believe some of the temps guys were reaching in their stock Z06s. Oil going up to 290-300. I would be in a state of panic if I saw anything above 235.

dprantl

The first time I worked on a C4 vette, I almost had a heart attack. I quickly learned that coolant temps of ~220 deg F were normal during idle! I guess those engines are just designed to run at significantly higher temperatures than most other cars that I'm used to.

Dan
'91 928GT S/C 475hp/460lb.ft

Aspkiller

Maybe they are, but my brand of common sense tell me that metal, especially the aluminum kind, expands and contracts with added or subtracted heat. Minimizing that function has to be better once the oil being used reaches its optimum operating temperature. If someone thinks I wrong, they're going to have to bring some serious documentation to convince me.

ubercooper

With a dry sump and mild supercharger kit, LS7s will easily push 650+ crank hp all day without issues... thats the beauty of having a massive V8, you dont have to be banging it around at high RPMs all day because you have ungodly amounts of torque to pull you out of the corners. Unless you are on a straight there is no need to be upwards of 6000 revs with these motors

dprantl

And... this is exactly the case with the 928 engine as well. I would consider 10 psi mild, and that produces just over 500rwhp on a 32 valve 928 engine.

Dan
'91 928GT S/C 475hp/460lb.ft

IcemanG17

Larry
INTERESTING

The 928 Estate makes at best 270hp and 320ftlbs (at the crank)...has NO oil cooler at all....I saw temps of about 275F when I was pushing the car hard this weekend.....about 240F when I was cruising..... if you are only seeing 235F oil temps then your engine is running VERY well..many Z06's see water temps near 230F.....

BTW the Estate is now 69.5 hours strong on the $300 engine....no indication of any engine problem at all....I should have oil analysis in a week or two for a firm answer.....

I am anxious to get back on track with my new wheels and Pirelli slicks....I am optimisitic I can shave some real time with this combo.....maybe 2:02 on the bypass at Thunderhill

Aspkiller

Hello Brian-

What I have come to understand is that the progress we make in recording lower times has far more to do with what we have learned about racing & driving and far less to do with the improvements we have made to our race cars.

In my case, the car I drive is more than capable of turning a sub 1:50 over the top at TH. The reason it doesn't is my fear of going off and my basic lack of driving skill and experience. Hopefully, there will come a day when my driving abilities exceed my cars abilities. At that point in time, racing should become really interesting. Hopefully also, is that I'm still racing when that day arrives.

Stan.Shaw@Excell.Net

I wandered into this thread, and saw this post.
The hybrid motors were @300rwhp.

I blew up motors rather than changing rod bearings, but I would speculate some motor problems were related to the unprofessionally building of mine.

John Veninger ran a similar build before building his stroker motor. As JV seems to be quite meticulous about his motor work, his experience would be of better value.

At one time David Lloyd's, John Veninger and my cars had many similarities including the "hybrid" motors. They were fun but were effectively momentum cars as the chassis were much more capable than the motors, so they were also frustrating.

mark kibort

Then there are my motors and race cars, not only driven by me, but scot as well. all, min of 290rwhp and the highest 372rwhp, running within 8% of any supercup GT3 on slicks. This is over 11 years of all out racing, with only some slight cut backs this past season.
All the blown 928 engines ive witnessed have been dooomed by the start, or were run without oil .

slate blue

Daniel standard rod bearings are unacceptable for racing period. Way too soft, the other issue is to examine the bearings for wear in terms of contact patch which relates to egocentricity. There is a lot to consider when it comes to bearings.

mark kibort

15 years of racing multiple 928's would disagre with this statement.

however, if you start going out of the designed capability envelope, you will have issues , as with any mechnical design. anderson and fan still use stock bearings. (i think) . 520rwhp and 1:30 at laguna is real pumped up race speeds! even for a platform that is 25 years old!
1:36.1 is not bad for my rig, and lap after lap around 1:37 for hours a season, with only 372 rwhp and big DOTs.

mark kibort

1:50 would be a huge feat for you car. keep in mind, the winning transam car (GT1 vet) from last year (frank emmit now owns) puts out near 1000hp, darrel anderson in his white mustang beast which is a handling monster, and near the same weight at near 550rwhp, is in the 1:51s. you would have a long way to go to get 1:50 at t-hill with the hill.. the first half of the track, some great handlng cars might be able to hang until you were able to stretch its legs. with the mustang vs the transam vet, it was cat and mouse. the vet would leave the mustang in the straights and the mustang would run up its tail in the turns. your 928 wouldnt be anwhere near these cars handling wise, but it could with some tuning ad testing. get that camber back to 2 degrees. up front! trust me! or, you will figure it out when you start pushig it harder in to the 1:50s. Now, laguna is a different story. certainly with 200more hp, if the handling was good, 1:30s would be possible.

there is a huge difference in cars that can run 1:55 and those can run 1:50s and its not really about hp at that point. Cup cars run the 1:48 to 1:50s because they are handling monsters!(and have good power too)

When can we see your car . it is amazing . I dont mean to take anything away from it. sequential transmssion?? are you kidding me???? awesome!

slate blue

And they change their bearings regulary, high rpm race engines need different bearings, if you don't you need them you don't have a race engine or use it like it is a race engine. Many have blown them up with bearing material stuck over the big end journal. I would think you have different bearings in your stroker also so I don't see how that applies.

mark kibort

I race the car, so its a race engine. the holbet car was in 120 races, and beat very stout, very expesive machines with real "race engiens" and never had a bearing issue. you are right that if high rpm is requred and its not always in all race engines, you need special bearings. special bearings would be needed like special cranks, rods or pistons for engines that produce a lot more power than their original design. we are fortunate that a 928 engine needs very little to be a race engine and be used in a race car. I dont think the stroker use any kind of special bearings. the holbert engine didnt need special bearings, and raced against the porsches, vets , mustangs and camaros, many of which had very epensive race engines, yet they still blew up. for some reason, mine never did, after 8 seasons, no problems at all . It was an ongoing joke with andreson and me at the pro races, that we felt guilty that we didnt even jack up our cars after the race sessions, or after a race sometimes before the next race.
tell all they guys ive been racing this year that i dont even have a race engine, and you might make them feel bad.

danglerb

Regarding bearings is it "racing" or detonation that makes hardness an issue?