Aftermarket cam grinds for 4 valve motors

[MarkRobinson]

Since there's stil quite a bit of racing 928's around, has anyone found any reasonable cam grind for mostly stock 928's yielding decent returns for the dollar? It appears that the cams/intakes & management appear to be the hold-backs on these motors...certainly not the head ports..

Mark

[mark anderson]

Talk to Laurie at Web cam (909) 369-5144

[DK]

Yes I agree.
Based on dyno results from 'marge' at devek, Don H's prelim dyno run, the kelly moss motor, seems there are very strong indications that these motors respond well to short intake runners. GT cams vs. S4 cams in the same motors also show easy hp gains, but not as dramatic as the intake runner change.

Mark A and Joe F have an optimized long-runner design, and that theoretically should give them a flatter torque curve all over, with a slight flattening at the top-end compared to the short-runner. But the short-runner has given up nothing on the long runner in the middle of the band.

These are just my observations of the dyno results, not meant to say anything is wrong with Mark or Joe's config - I can't catch either of those guys, so what do I know...

'79 Euro +/-
'80 SC +/-
www.eaglesledge.com

[Fastest928]

Dean, keep in mind that I made 500 rwhp with a STOCK intake, plenum expander and our B1 cams. Mark and Joe both have some custom cams, all the same "innards as I do" PLUS a super 5K plus carbon fiber short runner intake and still only make 500 rwhp.

Marge made an easy 550...and with Dons intake (which I speced for my engine are my "parts") would have made 600 rwhp.

DEVEK B1 cams ... $1600 per set exchange. The initial 670 hp KM engine had our B1 grind. Dons street "old race engine" and race engine have our cams. My street 6.5 had em, so did "Marge"... Louis has em, as do a few others....

About the best cam grind I have seen... and often copied

BUT, keep in mind that on a stock engine, you will have difficulty idling and will need a SMT6 to control the fuel/timeing at idle.

Marc

[atb]

Marc,

Would the B1 work on A/T stroker? Is the idle "difficulty" just at factory idle speeds so that it can be cleaned up with setting a faster idle?

[GregBBRD]

Having owned my own chassis dyno for over 10 years, the only thing that I have found out for sure is that dynos are good tuning tools.....when doing back to back testing and comparisions. Drawing conclusions from dyno to dyno (even when using the same brand dyno), especially from afar, can be very deceiving.....at best. I've seen many tests (on Porsches) right off the "popular" choice of dyno that read out more rear wheel horsepower than the factory claims for flywheel horsepower......which is, of course, absurd.

People generally want optimistic horsepower readings.....it makes them feel good. Follow some of the threads on this forum about horsepower readings and you will instantly realise that many, if not most, of the horsepower readings are.....to be polite.....overly optimistic. Come on people....if your stock 15 year old car is tested and you have more horsepower at the rear wheels than the factory claimed the car had at the flywheel when it was new.....you might want to consider that test to be......flawed.

People who advertise a product especially like optimistic horsepower readings......there's an infamous company in the Phoenix area that routinely published "dynojet" results that were.....again.....overly optimistic. They realised very early that certain dynos would give them results that looked very good on paper......but the cars never seemed to live up to the claims on the track.

I guess that Mark and Joseph's engines "only make 500 rwhp". I also know that somehow both of those cars will drive right by a GT3RSR on the banking at Fontana.....where horsepower is king. I also know that those RSR's are using 6 active gears and because of the gear ratio limitations in a 928, Mark and Joseph are only using 3 gears. I also know that both Mark and Joseph have been fighting significant clutch failure issues because of torque issues. You see a dual disc "floater" plate ripped right off the rivets, or 3 sets of clutch discs with the friction surface ripped right off....all on the same weekend, and you know that you are seeing some serious torque.

I'm not trying to dispute any of the claims made about horsepower.....I'm just trying to point out that the comparisions made are just a form of "bench" racing and should be taken with a grain of salt. The true test of power is to put two cars side by side and test them on the same day on the same dyno.....or better yet, just run them against each other.......Fontana seems like a good spot for this. I think that would be very interesting....indeed. Any takers?

[Lagavulin]

Originally Posted by GregBBRD

Come on people....if your stock 15 year old car is tested and you have more horsepower at the rear wheels than the factory claimed the car had at the flywheel when it was new.....you might want to consider that test to be......flawed.

I can say that on this board, the 993 board, and the Z06 board, I have not seen any such claims regarding stock engines and overly optimistic rwhp output reported by a dyno-sheet.

Not even once.

[m21sniper]

GregBBRD, i agree 100% with your opinion wrt dynos.

[m21sniper]

Lagavulin: "I can say that on this board, the 993 board, and the Z06 board, I have not seen any such claims regarding stock engines and overly optimistic rwhp output reported by a dyno-sheet.

Not even once."

Read some magazines, it's a quite common charge leveled at dynos. I just saw a writeup saying the exact same things Greg said about two months ago.

I think it was road & track or automobile magazine.

Dynos are wildly overrated IMO. Nothing beats a timeslip.

[Lagavulin]

Originally Posted by m21sniper

Lagavulin: "I can say that on this board, the 993 board, and the Z06 board, I have not seen any such claims regarding stock engines and overly optimistic rwhp output reported by a dyno-sheet.

Not even once."

Read some magazines, it's a quite common charge leveled at dynos. I just saw a writeup saying the exact same things Greg said about two months ago.

GregBBRD comments were made on the Rennlist 928 Forum, not a magazine, and I addressed his view with respect to the 928 and 993 Rennlist Forums, plus threw in the Z06 Forum as well.

I don't care what the magazines say, I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE. Just because a magazine may have 'discovered' some unscrupulous shops doesn't invalidate the rest of the shops that run their dynos correctly.

Dynos are wildly overrated IMO. Nothing beats a timeslip.

'Wildly overrated IMO'?? That's funny! Just curious, have you even dyno'd a car before?

Nonetheless, that's just your opinion, and you're entitled to it; however, I disagree. A timeslip is GREAT stuff, but there's way too many variables from run to run versus a controlled SAE dyno run.

[GregBBRD]

My point was that dynos are a tool that measure something. The information gathered is sometimes useful and sometimes more information is required. You can do a compression test on an engine and gather some information. You can do a leakdown and a compression test and suddenly you know a whole bunch more than you knew with just a compression test. To "hang your hat" on dyno testing engines on dynos separated by hundreds of miles.....well, that's my point.......more testing might be required before any conclusion can be made. Thus, the "bring it on" attitude.

Timeslips are "GREAT stuff".....and when you are dealing with cars and how they perform against each other is what the final story, at the end of the day, is all about. A "contolled SAE dyno run" tells a small part of that story.....not much more.

[mspiegle]

Originally Posted by Lagavulin

GregBBRD comments were made on the Rennlist 928 Forum, not a magazine, and I addressed his view with respect to the 928 and 993 Rennlist Forums, plus threw in the Z06 Forum as well.

I don't care what the magazines say, I've seen many many many dyno sheets from all over the world, and every single stock Z06 dynos between 340-355 at the rear wheels (..DynoJet). EVERY SINGLE ONE. Just because a magazine may have 'discovered' some unscrupulous shops doesn't invalidate the rest of the shops that run their dynos correctly.


'Wildly overrated IMO'?? That's funny! Just curious, have you even dyno'd a car before?

Nonetheless, that's just your opinion, and you're entitled to it; however, I disagree. A timeslip is GREAT stuff, but there's way too many variables from run to run versus a controlled SAE dyno run.

Wow, I gotta agree with Lag on this one. I've trolled lots of forums, and haven't heard about these overly optimistic dynos. Sure, some dyno technologies read DIFFERENTLY (mustang vs dynojet) but they'll still read UNDER the factory hp rating @ the fly. The only time i've seen it "get close" is when you're talking about horribly underrated cars using the LS1 motor. There are also plenty of '03+ cobras that dyno within 10hp of their factory flywheel hp with just a cold air intake.... but that's a completely different story. I'm well acquainted with other forums (bmw e30/e36-m3,chevy,ford) and can say that this is the first time i've heard of "wildly overrated" dynos.

[DK]

Originally Posted by GregBBRD

Having owned my own chassis dyno for over 10 years, the only thing that I have found out for sure is that dynos are good tuning tools.....when doing back to back testing and comparisions. Drawing conclusions from dyno to dyno (even when using the same brand dyno), especially from afar, can be very deceiving.....at best.

Appreciate your feedback here.

My comment was with respect to the overall torque band of the short-runner intake, not wrt hp, I never mentioned hp ratings nor compared them.

But you are basically telling us that the results cannot be compared because dyno operators, atmospheric conditions, and other factors play a role in producing optimistic results. I can buy that. Having thought about it, without seeing the a/f, one can't really say the engine is even tuned, so why make the comparison.

Originally Posted by GregBBRD

I guess that Mark and Joseph's engines "only make 500 rwhp". I also know that somehow both of those cars will drive right by a GT3RSR on the banking at Fontana.....where horsepower is king.

The true test of power is to put two cars side by side and test them on the same day on the same dyno.....or better yet, just run them against each other.......Fontana seems like a good spot for this. I think that would be very interesting....indeed. Any takers?

Of course there are takers - Mark and Joe wouldn't want it any other way I suspect, nor would any other racer out there. No, I don't agree that's 'better yet', I think the same dyno on the same day would be more accurate. Fontana has a large amount of aerodynamic and testosterone factors.

'79 Euro +/-
'80 SC +/-
www.eaglesledge.com

[GregBBRD]

Again, the dyno tool has limited use. The complaint with a Dynojet test is that it doesn't allow an engine to reach "end point" thermal loads......the test is way too short for that. A Dynojet test actually takes less time to accelerate through a given speed than it would take to accomplish the same thing on a road. So, a tuner could crank in a bunch of timing and dump fuel to compensate to get inaccurate results......all the time knowing that the combustion chanber temperature was not ever going to reach an end point in the short time span of the test. Blown fuelers do this every day. They can make insane horsepower for 3-4 seconds, but would be "chunks" if the test lasted for 30 seconds. The people out there running crazy boost with NOX on their "rice rockets" making insane horsepower know this: they can't do it for very long without backing something down before end point thermal equalibrium is reached.

Road racing cars (Porsches fall into this category) are meant to be driven and tested on tracks.....not on dynos. And comparing outputs of different engines, tested on different dynos, on different days, with different calibrations, and with unknown timing and fuel specifications can be a very useless comparision. That's the point I was trying to get across.

[Shane]

Nice info on Dyno's and stuff guys.

Now lets hear some more about aftermarket cam grinds!!