6.5L rebuild adventure finally begins
08-30-2008, 07:07 PM
#61
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Hmm, this could be interesting, but I am going to bet on Louie being right on this 
Not sure why you think 2 valves are better than 4 though, seems clear to me that essentially all new motor development in the past 20 years has found value in more valves than 2. I wouldn't think they are doing it to increase the cost without return.
By the way 928s don't use carbs.
Not sure why you think 2 valves are better than 4 though, seems clear to me that essentially all new motor development in the past 20 years has found value in more valves than 2. I wouldn't think they are doing it to increase the cost without return.
By the way 928s don't use carbs.
08-30-2008, 07:20 PM
#62
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The valve sizes and the camshaft would have to be seriously bigger for a 16 valve head to produce near 500rwhp. Since huge valves and big camshafts hurt low rpm air velocity, these items aren't always the best thing for other than race engines.
One of the things that the 928 engine does very well, is the ability to make "boat loads" of low rpm torque. Since there are many factors that limit the 928's ability to make high rpm horsepower (oiling and intake system come to mind) it is probably better to try and "amplify" the stock engine's qualities....which is our goal when we build a stroker engine.
Certainly, it should be possible to redesign the 928 engine to work really well with 16 valve heads, aggressive camshafts, and a large four barrel carburator on a custom intake system. Combine this with a 6.5 liter stroked and bored bottom end and you will have an extremely potent $30,000 2 valve engine than looks, runs, and sounds remarkably like a $5,000 "crate" Chevy engine.
One of the things that the 928 engine does very well, is the ability to make "boat loads" of low rpm torque. Since there are many factors that limit the 928's ability to make high rpm horsepower (oiling and intake system come to mind) it is probably better to try and "amplify" the stock engine's qualities....which is our goal when we build a stroker engine.
Certainly, it should be possible to redesign the 928 engine to work really well with 16 valve heads, aggressive camshafts, and a large four barrel carburator on a custom intake system. Combine this with a 6.5 liter stroked and bored bottom end and you will have an extremely potent $30,000 2 valve engine than looks, runs, and sounds remarkably like a $5,000 "crate" Chevy engine.
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
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Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
08-30-2008, 07:28 PM
#63
Three Wheelin'
I'm not talking about motors that everyday street cars run to meet epa standards. Go to a drag strip and look at 95% of the cars running. If you want to make a reliable motor that make good HP 16v is the way to go. Less moving parts. You not only have lift but duration as well. Good luck on your project but imho I would look for some decent euro spec heads.
08-30-2008, 08:13 PM
#64
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One of the "problems" with building such a motor, is that it is hard to do it part way to add on later.
For example, I always think of boring but not stroking. This would "save" the cost of a crank and the heads/cams/intake would probably be up to the task, but you "only" get to a 5.4L motor (from 5.0L) and the expected result is not enough for the cost. If you decide you want the crank later, you need a different set of rods, so an expensive "throw-a-way" for the later upgrade at @$1.5k
You could build a stroker shortblock and save $5k by not doing the heads and intake, but again you may only get to that @350rwhp result and still have spent $10k. Of course the later upgrade doesn't have you throwing away parts, except gaskets, etc.
The other often overlooked value of a stroker motor is that it is a rebuilt motor. The "standard" supercharged motor is not rebuilt. Of course in this topic's case, the candidate motor has only 28k miles on it, so probably didn't need to be rebuilt anyways and 928 motors don't necessarily need any work just because they have many miles on them.
Living in emission states definitely raises the value of building a stroker motor vs. having to de-install a SC periodically, otherwise for the street SCs seem like a great idea.
Personally I am still waiting for SC 928s to be proven on the track in race conditions. I believe Carl F. is planning on racing his soon.
For example, I always think of boring but not stroking. This would "save" the cost of a crank and the heads/cams/intake would probably be up to the task, but you "only" get to a 5.4L motor (from 5.0L) and the expected result is not enough for the cost. If you decide you want the crank later, you need a different set of rods, so an expensive "throw-a-way" for the later upgrade at @$1.5k
You could build a stroker shortblock and save $5k by not doing the heads and intake, but again you may only get to that @350rwhp result and still have spent $10k. Of course the later upgrade doesn't have you throwing away parts, except gaskets, etc.
The other often overlooked value of a stroker motor is that it is a rebuilt motor. The "standard" supercharged motor is not rebuilt. Of course in this topic's case, the candidate motor has only 28k miles on it, so probably didn't need to be rebuilt anyways and 928 motors don't necessarily need any work just because they have many miles on them.
Living in emission states definitely raises the value of building a stroker motor vs. having to de-install a SC periodically, otherwise for the street SCs seem like a great idea.
Personally I am still waiting for SC 928s to be proven on the track in race conditions. I believe Carl F. is planning on racing his soon.
08-30-2008, 09:31 PM
#65
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The 2v-vs-4v argument really comes down to simple math. There is simply more valve area available for a given combustion chamber size with 4 valves than with only 2. You have only to look at the highest-output NA engines to see that they all are 4 or even 5 valves per cyl.. At max valve size, a 4V engine will flow more than 2V., its as simple as that....you could even look at the "import" drag engines for comparison- the NA Hondas are making more HP/cu.in than any 2V available...no disrespect intended, just a fact.
08-31-2008, 11:20 PM
#66
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> Chips from your heads fly, this coming Monday. Yeah, I know it's a holiday, but the porting thing takes a whole bunch of concentration and non-interruped time. (Tough to get during the week.)
Sweet! Labor day flying aluminum chips!
Sweet! Labor day flying aluminum chips!
09-01-2008, 12:26 AM
#67
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I presume you understand there is a big difference between DE and racing with respect to the demands put on the motor. I have something like 50 days of DE and 20 days of race experience, and know my experience may be different from others. Most of my DE days are in the top run group or with the instructors, so there is the opportunity to drive a car as hard as can be done at a DE. Yet, because DEs are controlled, passing is restrained in a number of ways and certainly the cars are farther apart. The end result is that there is less overall stress on the car and motor (not to mention the driver).
I am not "dissing" SC cars, nor am I saying they can't be as fast or faster. But I have yet to see an SC 928 road raced consistently and reliably. Of course there is always a level of probability that it is happening but I don't know about it.
I am definitely anxious to see an SC 928 get out there, mix it up, and do well
Last edited by Stan.Shaw@Excell.Net; 09-22-2008 at 01:43 PM.
09-01-2008, 01:47 AM
#68
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TECHNICALLY, The cam ramp and total lift is MORE limited in the 2V setup as it exists than in the 4V. If you were to remove the bearing size issue in the 2V, then maybe, at least, it would be cheaper (no cam toothed gears in the middle).
The 2V heads are limited in port size and shape, as well as valve size by the combustion chamber size, as well as the castings.
The 4V heads are also limited, but at a much higher value. More work can be made on them.
.... at least I think so...
The 2V heads are limited in port size and shape, as well as valve size by the combustion chamber size, as well as the castings.
The 4V heads are also limited, but at a much higher value. More work can be made on them.
.... at least I think so...
The 2v-vs-4v argument really comes down to simple math. There is simply more valve area available for a given combustion chamber size with 4 valves than with only 2. You have only to look at the highest-output NA engines to see that they all are 4 or even 5 valves per cyl.. At max valve size, a 4V engine will flow more than 2V., its as simple as that....you could even look at the "import" drag engines for comparison- the NA Hondas are making more HP/cu.in than any 2V available...no disrespect intended, just a fact.
Comparing 16V engines to 32V engines is more than just saying "because it has more valves it will make more power." Cam dims, port CFM's/design, fuel systems, intakes, exhaust systems.....all of this comes into play, but is unfairly used (or not used) when discussing the apples and oranges argument.
I suspect that if all things were equal, the 32V would just be more headache due to the (number of) parts issue alone.
(no offense to anyone---just an opinion)
--Russ
09-01-2008, 09:26 AM
#69
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Hi Rick,
I presume you understand there is a big difference between DE and racing with respect to the demands put on the motor. I have something like 50 days of DE and 20 days of race experience, and know my experience may be difference from others. Most of my DE days are in the top run group or with the instructors, so there is the opportunity to drive a car as hard as can be done at a DE. Yet, because DEs are controlled, passing is restrained in a number of ways and certainly the cars are farther apart. The end result is that there is less overall stress on the car and motor (not to mention the driver).
I am not "dissing" SC cars, nor am I saying they can't be as fast or faster. But I have yet to see a 928 road raced consistently and reliably. Of course there is always a level of probability that it is happening but I don't know about it.
I am definitely anxious to see an SC 928 get out there, mix it up, and do well
I presume you understand there is a big difference between DE and racing with respect to the demands put on the motor. I have something like 50 days of DE and 20 days of race experience, and know my experience may be difference from others. Most of my DE days are in the top run group or with the instructors, so there is the opportunity to drive a car as hard as can be done at a DE. Yet, because DEs are controlled, passing is restrained in a number of ways and certainly the cars are farther apart. The end result is that there is less overall stress on the car and motor (not to mention the driver).
I am not "dissing" SC cars, nor am I saying they can't be as fast or faster. But I have yet to see a 928 road raced consistently and reliably. Of course there is always a level of probability that it is happening but I don't know about it.
I am definitely anxious to see an SC 928 get out there, mix it up, and do well
Like you I am not aware of any SC cars racing, outside of Open Road Racing. That's why I posted Ken's DE video, it's the closest example i could think of.
09-22-2008, 01:36 PM
#70
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09-22-2008, 03:09 PM
#71
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I was trying to search for some typical track times but only found this:
2007 Panoz DP01 Champ Car Test 1:06.280
[2007 IRL Dallara Helio Pole] 1:06.8375
Zytek 04S 1:11.333
Lola EX257/AER 1:12.431
Audi R8 1:12.935
Chevrolet Corvette C6-R 1:18.033
Porsche 911 GT3 RSR 1:22.663
Toyota MR2 1:52
Porsche 944 spec 1:43.0 (Pro configuration)
Porsche 944 Cup 1:41.9 (Pro configuration)
Spec Miata ?:??
Dodge Viper ?:??
Spec Focus 1:47 (Club Course)
Porsche 911 1:45
11-26-2008, 04:30 PM
#73
Road Warrior
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3 valve heads rock. ford makes a pretty cool head on a 5.4L that can put out 500ft lbs ctq and 445 chp w/only a 6psi twinscrew on top of a stockish bottom end. iirc, the best we've seen on a 928 6psi motor was about 380 rwhp/350 rwtq. oops. this is a pcar site. sorry. didn't mean to start any trouble. hahaa
12-17-2008, 09:53 PM
#75
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Funny, i seemed to remember a stock 928 engine with stock 4 valve heads putting out 445 chp with only fuel changes and a reprofiled stock 85 cam. Oh, did i mention it was a 5 liter too! Imagine what this 928 motor could do with some added mods besides just a cam reprofile. Oh yeah, did i forget to say that it didnt have a blower either? 
mk
Oh yeah, did i forget to say that it didnt have a blower either? mk
3 valve heads rock. ford makes a pretty cool head on a 5.4L that can put out 500ft lbs ctq and 445 chp w/only a 6psi twinscrew on top of a stockish bottom end. iirc, the best we've seen on a 928 6psi motor was about 380 rwhp/350 rwtq. oops. this is a pcar site. sorry. didn't mean to start any trouble. hahaa