Started reading the post and felt it was somewhat interesting. It drew me in only to dump on me in the last paragraph. I don't have problems with Corvettes but the post is a ruse. Funny how the mention of Corvette is like catnip around here.

 

Worth noting that about 30% of cats do not respond to catnip...... it is an inherited trait.

 

The other day there was an early '90's C4 corvette at my brother's place for some work. That was the first time I ever sat in one, and boy did it feel like a POS compared to my '91 GT. Oh, and only 245hp out of a 5.7 liter V8 at that time, really? I think I'll keep my 928, thanks.

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

 

Sorry, I didn't mean to be offensive.

I think most of us have been automotive masochistics, I certainly have been, and I'm going to try to expand on this starting with my own major mistakes as a way of explanation, in another post to follow,as ther aqre lessons that it would be better not to have to repeat on your own nickle.

I will say, now, that in general, doing something because you're a passionate fan as opposed to making a cold blooded rational decision tends to be expensive and lead to heartburn, whether Porsches or Chevies or whatever. Kind of like any other emotional relationship

And no, I don't "love" Corvettes and have no intention of ever having another one, but sometimes the late model ones do make sense for cost effective zooming around, assuming that's what you want and you make some realtively monr and not very expensive fixes. I didn't say they were 100% stock. This obviously doesn't work if you want to run PCA events, but I don't like most 911 drivers anyway. As one of my friends who makes his living working on 911s says, "The cars are OK, it's the drivers I find wearing". You guys seem much nicer, so I'm doubly sorry I offended some. Like I said, expanded explanation coming.

I think 928s are fine, it's just helpful to be realistic about the limitations of anyting, and everything has it's own set of limitations. On a 928, the stock oil system certainly seems to be one of them, and that's a very importan one. If, however, you're a true believer that thinks they're wonderful, without fault, and superior to everything else, we're probably not going to be able to communicate.

So the point is, if you're determined to run a 928 hard, and good on you if you are, then in my opinion spend the money for a bulletproof oil system (which may include a properly Chevy drilled crank unfortunately) and assemble the engine with the right clearances to work correctly with that oil system. And make sure the water cooling is up to the task too. Then, if you stay away from detonation and stay within the structural limits of the components, your engine (any engine) should be fine and live a long and happy life.

And no, a dry sump isn't cheap, and unless you have a pre-existing set up to copy there will be some work, but it's a lot cheaper, and a lot less work, than building engines. I like building engines and have the stuff to do it correctly as painlessly as possible, and I'd still rather avoid it since my goal is to get seat time on the track, not work on the car, if at all possible. And let's face it, you're going to get to work on the car plenty anyway, one way or another, if you get time on the track.

There are apparently some people here who have made their 928 wet sumps work, and I commend you on that. Crank scrapers are a given these days for Chevies and just about anything else, as are windage trays/screens, and these are still good with a dry sump, and the only thing better than lowering the oil away from the rotating assembly is getting it out altogether, so these are all good ideas. In my opinion, though, you're still playing Russian roulette with your engine, just with fewer rounds in the gun. The odds are against you, and the sure cure is a properly functioning (big if) dry sump. I do stand behind that. As I said, the surest way to have an uniterrupted supply of clean, cool, unaerated oil is with a properly functioning dry sump, with in general a tank with 3+ gallons of oil. Two gallons is generally just not enough, and this is a "Some's good, more's better, and too much is just enough" kind of thing. You don't want to ever, ever, ever run it dry. Ever. Period. If three gallons isn't enough you already have a new inspection window in the block, or will shortly. At this point an oil pressure kill switch is a good idea, plumbe to the most critical point, or several even, and one of the new solid state oillevel sensors in the bottom of the tank hooked to a great big red light is also a very good idea.

Nothng original here, just good proven answers from lot of people for the problems many of you seem to be having. I really am trying to help, cause I read all 36 pages of the thread. I was puzzled by the mythology and magical theorizing of some. What are the clearances with Glyco bearings? Find out. Is Amsoil the only solution? You have an underlying problem and you're crutching it. (By the way, all oil floats on water. The density is significantly less, motor oil is just more viscous at room temperature than water. Although that's not true at temperature - some people don't know hot oil is as thin as water.)

Accusmps are still great for pre-oiling.

Having said that, the M1A and M1B An Am cars all used wet sumps, Olds, Chevy, or even Ford, and lived pretty well, but they had high capacity elaborate pans with wings and trap doors. On the M6s after a while and on the M8s from the start they finally went to dry sumps, because, despite the complexity and cost, the overall reliability was better. And the older cars got retrofitted.

Another good example is from "The Unfair Advantage" by Donahue. The wet sump Camaros lived OK, then they blew up several dozen AMCs after they switched until the Stupid Car Club of America finally admitted that they weren't really "holding the high cost of racing" by prohibiting dry sumps. At this oint everyone put them on everything, including the Chevies. The Chevy wet sump was on the "maginally acceptable" side of the line, the AMC engine witha wet sump, for whatever reason, was on the "unaceptable" side, and the dry sump cured it.

Racings always expensive, it's just more expensive and less expensive.


"How much money does racing take? - - - - - - - - - - - - - - All of it."

So, just as with these examples, if you're not popping engines you don't necesarily have to have a dry sump, but it's still the ultimate, and guararnteed-if-done-right, fix.

I hope this all helps so there isn't another 36 page thread about oil system problems and broken engines. I hope I've made amends and am forgiven. And I hope you enjoy reading about why racing a Triumph Spitfire is really high on the masochism scale, unfortunately for me, although at 1400 lbs it was great fun to drive, swing axles and all. Education is never cheap.

David Merritt

 

David,
107 race days, much of it is on video on my youtube area. this was a completely unmodified engine. no oil cooler, scraper, fancy breathers, etc. nothing, nada, all stock. now, you say lucky, well, that was for near 8 years of all out racing. not just going to the track every once in a while, but pushing the limits of the engine and car for 8 years with only a process to follow . (oil changes, oil level, warm up procedure, driving style, etc) . well, some will say "lucky" . well, I dont really believe in luck. If i was "lucky" some idiot wouldnt have crashed into me at Sears taking the car away from me! But, still, the stock engine lasted and was disassembled and looked perfect, even after 8 years of racing! then the stroker was put in. it has a chevy drilled stroker crank. still no oiling modifications externally. no accusump, no ext coolers, no scrapers, screens, breathers, all stock stock stock. why still another 3 seasons of racing and still NO problems?? oil comes back perfect from analysis? magic??? Hmmm, I guess it is magic! maybe it is the anti foaming of the amsoil. its tough stable viscosity control at high racing temps of near 260F, maybe its my warm up procedure of making sure my engine oil is at 180F before I ever push the throttle in anger, maybe its the gear selection and rpm levels through critical turns, (not too high for sensless rpm, not too low to be protective and lose pressure, Just right! )
I dont know. But what i do know, if you dont believe in luck, and understand what I am doing with the car, then you will understand that there are many other factors involved in failures of engines. Porsche go it right. and its not just me. anyone following my process also has sucess. I didnt invent it, i have followed those others that have been sucessful running our cars, starting with Mark Anderson.
Ive pulled and taken apart enough motors and my sucess has not been limited to just two motors of mine. Ive had 4 motors and supported 4 others that have been beaten on the track with no issues.

Now, go reinvent the wheel, experiement to your heart's content, but im not going to take chances with un proven stuff that seems to cause more issues than it solves. Ive seen , heard and experienced more issues with breathersystems, crank scrapers/screens as well as accusumps , than i care to count or remember. I just shake my head. As Greg Brown always says, "Why". "What problem are you trying to solve, and dont you think porsche did some research before their design? "

anyway, you are right. it certainly is not perfect, but for racing and racing how most of the engines perform best (i.e. 6500rpm and lower, not by choice but by engine curve performance), the 928 is better than any engine I have ever seen or heard. The chassis is not far behind, and probably even better in its design, in stock, unmodified form. Like I said, you go to Laguna Seca, and see what kind of hardware it takes to run a 1:36.1 . then , look at my car that is 25 years old, original bushings everywhere, NOTHING modified, but headers and a bolt on suspension and a standard cage a highschool kid would have on his autoX car. See if you can imagine any car in the world that can keep up, even 15 years newer with the same mods!!! (and still be driven to and from the track for over 10 years.)

Run good synthetic oil, keep the level full, warm up the car before you beat on it, and use rpm at the track for best performance and you will break the code of problems most have been having.

You tell me if im running the car easy!
http://www.youtube.com/watch?v=xYbFe..._order&list=UL

 

Yep, from what I hear that is correct.

 

David, thanks for coming back constructively. Don't mind Mark - there are plenty of counter examples of engine failures and metal in oil on 928's that are tracked.

Current belief is Mark's driving style contributes greatly to his engine longevity - he's certainly not slow, anything but, however he also thinks hard and long about wheel torque, gear selection and optimum shift points, and his shift points are more rigidly in the peak power parts of the engine curve.

My personal suspicion is that he's actually not hitting as high peak rpm's in corners under G-loading as others, because he's actually thought about how hard he wants the car to pull on exit and is in the correct gear already to be at the start of the peak-power rpm range, rather than the end, so he doesn't lose time/places having to shift as soon.

Anyway.. back to sumps and oiling

edit: The 928 oil pump has a deaeration circuit for removing entrained air from the pressure side - I'm now wondering whether the pump's delivery volume overpowers that circuit under high rpm's when the pickup is exposed during high-G corners. It would also be interesting to see which vehicular-side of the pump internals the air circuit is, as it may explain why the problem is worse turning one way than the other.

 

Has Mark ever mentioned the little Buddha belly he rubs everytime he sits in his car?

 

Oh - just to tie this in with another informative (and combative - like all internet discussions) thread on oiling, which includes video of the inside of the valve covers, as well as discussions on the oil pump and deaeration circuit:

https://rennlist.com/forums/928-foru...n-youtube.html

Another with pics of the oil pump internals:

https://rennlist.com/forums/928-foru...mp-thread.html

 

No buddah, but any exposed wood in my house, including my forehead has knock marks!!

Thanks Hilton! now, im no expert here, and I shouldnt be coming across as one, but we do all have our guesses of what the problem is. obviously, there is a problem, but other kinds of engines have it too. Its really a matter of if ours are worse than others. I would bet that it is, to a certain extent. tigher tollerances, more sensitivity to the issues, who knows. But, i will say, I have had some great experiences racing with the unmodified engine. maybe it is some of those things you complement me with . I dont know, I hope so. But, in the end, there are some smart people trying to find a way to reduce the risk.
carry on!
Mark

 

A lot of us are current or former Corvette owners.

I had no issues with his post.

 

His performance is certainly impressive. As has been said "Lap times don't lie". However he's doing it, and in addition to the techniques things you mentioned (any feedback on that?) he may also be exceptionally smooth, which is easier on everything and wouldn't throw the oil around as much either.

Still an impressive performance. I have no doubt that a stock engine driven within stock parameters, especially the RPM limit, and with good oil, which Amsoil certainly is, and with stock clearances, very important cause everything's working together as designed, could do this with no extra enhancements. I wasn't aware of Amsoil's exceptional anti-foaming characteristics, which I believe, but we deal with that by trying to avoid needing it. Still, if you're working with (and succeeding in his case) a wet sump system, and I still maintain that any wet sump system is marginal at best, that's a good thing to be able to bring to bear. It also appears that without the Amsoil, you may be exceeding the capacity of the stock system, which does indicate you're on the ragged edge. I used to get to spend time at the Shell R & D lab here in Houston and hang out in the tribology department complete with their row of dynos. There's nothing accidental about what any major manufacturer puts in their oil, whether it's right for your application is another matter.

Porsche's engineers are very good about designing to a set of requirements, that's their job. If it's supposed to be a 300 HP 6500 RPM engine with at least some concession to cost, and you want to make it a 400 HP 7000RPM engine because the basic heads will flow the air and you can spin it higher, well, you're on your own at that point, they weren't including those requirements in their design. And if you revere Porsche engineers ( I don't, I think they're good but not magic), you have to ask why virtually every falt six they've built has a simple dry sump system. Cooling (it's really an oil cooled engine, look at the oil radiator in the nose of a 917 the size of a water radiator in most cars) and control. Wth a flat motor you wind up with all the oil in one head or the other in the corners with a wet sump, ask me how I know. You can get a turbo Corvair to make 300 HP for a little while at least, but you can't keep the oil out of the valve covers with a wet sump, I promise you.

So if you need to cool the oil and control it, Porsche thinks a dry sump is worth spending the money on, otherwise they wouldn't do it. It's not a marketing foo-foo thing like the faux drilled rotors for the customers (which race cars these days do not have). A 928, especially stock, may not need the oil cooling or oil control, but at some point you cross that threshold if you hop it up. Again, I'm trying to give you the engineering analysis. And you know, for instance, it made the engineers crazy to have the stylists make them compromise the pan depth, you know the engineers knew better, it became a requirement they had to overcome, not a choice of theirs.

David Merritt

 

wet sumps and high G's are never a good combo......just look at how most wet sump oil pans are designed...they are DEEP...at least 7" deep....the 928 oil pan is about the worst possible combo for a wet sump....shallow and WIDE....not good at all for high G turns.....

Accusumps help...and dry sumps are ideal.....but come with complexity and cost....

Kibort has had great success with stock oilling systems....many many others have blown engines with stock and modified oiling systems..... I tried the stock system and blew two engines.....I seem to have found a relatively inexpensive solution in the OB pan with 3/8th spacer......35 hours and counting on this setup..... While I DO NOT think this is the best solution....it seems to slow down bearing wear to an acceptable level....only a drysump would do that

 

http://www.aardemasohc.net/index_files/Page846.htm

I'm not saying this is a good idea, the tranaxle probably wouldn't like it at all, but I guess once you sue the rat motor big block you could use the C5 C6 transaxle. These heads on a 9 liter motor - and the oiling systems are available - might be able to terrify the 911 guys till they threw you out.

I obviously like sleepers.

And then there's my favorite 928:
http://www.vodcars.com/post/544/artz...ed-porsche-928
with one of these engines, big fun.

David Merritt

 

David, I do think we (I) am running marginally, but for how I use the car, and the RPM range I see, i think its adaquate, proved by not only the raced 3-4 engines Ive had, and the speed at which they all ran around the track, but the others Ive helped do the same thing.
I dont think the porsche engineers are gods, but do agree that they have designed the platform reasonably well. for some reason, when i do run lesser oils, the first thing I see is very low and marginal oil pressure at high oil temps. (even moderate oil temps) with amsoil, this doesnt happen. in fact, i see near 5bar at just over 1700rpm with amsoil, and we see this on no less than 6 engines we have run vs the "other" oils. I think the anti foaming, and viscosity stabilization at high temps (over 180 to 260F) is key as well. but that is just my experience and opinion.
keep in mind, these brillant engineers also designed the 2 valve pistons with an offset that was right for one bank of the engine, but dead wrong for the other side. I was able improve on this design with the help and education of Greg Brown to optimize this error in engineering. (by reversing the piston direction on one bank when cutting new 2 valve cuts on those 4 valve pistons)