belgiumbarry

that is correct.... my new BMW650 needs oil change after 30k km , as 20k miles !
Must be that synthetic oils keep it that long in modern engines... ? I think so as they give warranty for 5 years...

PS the car is now just 1 year old and i have 23k km... in the hole year they just added 1 litre oil after the break in period , a message i got on the computer.

IcemanG17

Doc brings up some very good points.......there is quite a variance in dyno's of the same build in different shops...& add different weather and it gets larger....

So then whats the easiest way to see which stroker produces the most verifiable data....

Doc Browns motors
Anderson: whose numerous race wins against GT3RSR's speak for itself
Rob (928SS): I've gone for a "ride" in this beast

Devek motors
White Car: 211mph in 1999 speaks for itself
Tim Dey: 208mph, over 200mph 6+ times
Louie: I've driven this one, and even at 8000ft it had power

Todd (greenbay)
Kibort: Almost a overall victory in SCCA, except the alt died.... :>(
Todd: 7.4L monster....still not done :>(

Of course devek motors do not exist anymore.....so Doc Brown is it....& I've also been to his shop and seen his work 1st hand.... very impressive...& its safe to say he builds more strokers in 1 year then probably anyone else has ever built

Any way you look at it, internal engine work costs serious money.....boost is cheaper since you can "bolt" it on and your done.....

RicerSchnitzzle

Interesting that manufacturers recommend frequent changes and even recommend a brand of oil in most manuals (kick back?), yet the manufactures that include the oil changes for the first 3 years (BMW) go 20K? When it's their dime the truth comes out.

Bill Ball

Out where? I mean this is always a fair question, but when I read this yesterday I wondered what direct relevance this had to the current question and 928s. I'm sure you can tweak the settings on any dyno and create fake results, but I can't recall any results in this group that were that suspicious looking, at least in the high direction. For example, my results on the dyno at DEVEK were always lower than expected or, at least than I had hoped, but I believe they were right.

Louie928

Hi,
Welcome back. I'll try to offer some of my observations. I don't think Marc at Devek did anything greatly different than anyone else building a stroker. He did concentrate on some aspects of the build and maybe that made a cumulative difference. He tried to get cylinder/piston leakage as low as possible. He was fanatic about keeping the cylinder as round as possible during the boring process. He used a thick deck plate bolted on in place of the cyl head while the block was bored. He mentioned at one time that it was important to circulate hot water through the block while it was being bored too. He was meticulous on clearances during the build. He had a certain spec for the torque it took to turn the bare crank in the block with the bearings in place. If it took too much torque to turn the crank, he disassembled it and found where the binding was happening. He told me once that he had special intake valve seats made for the 968 intake valves. Something about the stock 968 seats wasn't right. It was just little things like that. How much of this really happened and how much was planned for the next build, I don't know. I'm sure Greg B knows all this and does it with his builds.

The stroker motors will make very good torque below 4000 rpm with stock 928 components. To get above 400 rwhp, you need to extend the good torque higher in the RPM range. You have to increase the breathing capability at higher RPMs. The stock intake can stay. For passing CA smog you have to stick with it anyway. You will need to use 968/944S2 intake valves and touch up the ports for better flow to take advantage of the larger valves. Not a huge port size increase, but more re-contouring the shape. You may get to 400+ rwhp using GT cams. I'd suggest using the cams Jim Morton developed for Dennis Kao's engine. Use 944S2 valve springs or a bit stiffer. The stock springs won't keep the lifter in contact with the cam. If you can find a set of Devek L2 headers use those. Otherwise 928 Int'l had some equal length headers that should work well. They are intended for track use and will take some modification to fit nicely on a street driven car. When choosing headers, consider that some headers don't permit the clutch housing to come off with the headers in place. Behind the headers, use a couple of the modern free flowing cats. Some have a grid of 100 cells per sq in and flow a lot better than the more normal 400 cells per sq in. Then go to a X crossover. The size could be either 2.5" or 3" OD tubing. The 2.5" might be a little small and the 3" might be a little big. Experiment. Remember that with larger pipe size, it's harder to muffle it. I use 4 mufflers on my car with 3" pipe and it's still loud.

If you can find a GTS 5 spd with a bad engine, it may make a good platform. The GTS 5 spd transmission is stronger than any that came before it. GTS tranny's are really scarce and expensive by themselves. The GTS also had a tranny cooler so that mod would already be done.

Vilhuer

What valve spring installation lenghts people have used with 944S2 springs? AFAIK '87-95 928 use 35.5-36.0mm intake and 34.5-35.0mm exhaust mounting lenghts while 944S, 944S2 and 968 all use 38.0-38.5mm and 37.0-37.5mm. I presume this is done to allow longer valve movement for higher lift cams.

However there is difference between lower valve spring washer used in '87+ 928 and other heads. 928 version is 3mm thicker. Which part combination is used with 944S2 valve springs and modified high lift 928 cams?

968 valve springs appear to be much softer than 944S2 and 928 32V springs but they are also much longer. Softer at least when not installed. 944S2 springs are much stronger than 928 springs while they have same free lenght. Its bit difficult to say how they behave when installed without measuring it. Would need to measure them when compressed to installation lenght. Unless someone already has this info?

'87+ 928, 944S, 944S2 and 968 all seem to share same valve installation wear limit of 44.4mm on intake and 43.4mm on exhaust side so there is no difference how far valve extends above spring mounting surface. Presumably also distance from cam base lobe to valve mounting surface is same in all variants?

nsantolick

Just curious; has anyone stroked AND supercharged/turbocharged a 928? What about rebuilds with lower compression pistons with turbos, similar to factory turbos?


P.s. - Car still isn't done. Passed the 2 month mark at the current shop last Wednesday, BUT, it's imminent. Probably next week. Of course, I'm going away and the weather lately would prohibit me from picking it up anyway. Oh well.

P.s.s. - If I was to do it again, I'd seriously consider some cryogenic suspension for a couple of months... lol (This really has been torture...)

IcemanG17

There is one boosted stroker..."Big Bird" has is 6.0L of vortech boosted fun...over 600hp too

GregBBRD

Ryan:

We are currently running Torco in almost everything. Brad Penn (essentially still making the old "Kendall" oils) makes an nice product, but has to come from the East Coast.

GregBBRD

I use "good old horsepower" numbers...like those used in the late '60s/early '70s. Somewhere along the line, the magazines started "inflating" horsepower numbers. It has now gotten to the point that if you can't assemble a stone stock 350 Chevy engine that makes over 450 horsepower, you shouldn't be able to buy tools at Sears.

Some of the horsepower claims out there are just silly, even on this forum. I've got a friend, here in town, that has a very trick 100,000 engine dyno with all the bells and whistles. We were talking about 911 Turbo engines one day and he said, "I've put literally dozens of 500 horsepower engines on my dyno to tune and I'll tell you one thing...I've never seen a real one, yet. However, as soon as they leave my door, they suddenly make way over 500 horsepower. It's simply amazing how much more power they make on the way to the truck, outside."

He'll also tell you that he does what he calls "hero" pulls all the time. Crank in the timing, crank up the boost, dump in fuel, and get a quick pull. "You can get away with almost anything, for a few seconds." Will that engine live in real life making power that way....not a chance.

I just think that, when someone is looking for ideas on different engine combinations, they need to know that not all apples are apples and not all oranges are oranges. Flash readings and "hero" runs are not real stuff. I'm telling you, I can make my dyno read 75 more horsepower than the vehicle is making, without touching the internal calibration. Pull up the power, overshoot load, and suddenly, you will see very high numbers....as the engine slows down. That's the "infamous" deaccelerating horsepower number. Really easy to do, on both a Mustang and a Dynojet.

That is all my comment had to do with this thread.

Louie928

Errka,
I didn't use Porsche springs. I took some data on S4 springs as well as 968 springs and found this.
The S4 springs had 43 lbs seated pressure and 140 lbs when opened 11mm. The 968 springs had 51 lbs seated pressure and 187 lbs when opened 11mm. The problem I didn't like with the 968 springs was that they had 0.055" coil spacing when open. Maybe that close coil spacing is satisfactory, but seemed tight to me. Valve springs go through some strange harmonic vibrations as they open and close at speed and I didn't want any chance of coil contact.
The springs I used had larger diameter wire and fewer turns. I set the seated pressure to 64 lbs and that gave me an 11mm lift open pressure of 207 lbs. I set the installed height for 35mm +0.3/-0.0 on the intake side and 35.5mm +/- 0.3mm on the exhaust side. I had both spring perch/spacers from the S3 as well as the S4. I also had 0.5mm and 1.0mm shims to get to the installed height I wanted using various combinations. Marc Thomas had also ground the perches starting with the S3 thick ones and having them ground to the exact thickness he wanted.

Here is a pic of the S4/GT springs on the right and the ones I used on the left.

https://rennlist.com/forums/attachme...1&d=1229823932

mark kibort

Thats one of the reasons the dyno jet is pretty solid in the results area. (as long as you can see the dynograph afterwards to see that the peak HP number is not just noise at the end of the run)

Sure, you can pump up values by conversion factors, but that is usually listed (SAE vs Actual). Pretty hard to fake the acceleration of the drum over a WOT pull. It either does it or it doesnt. Mustang dynos and engine dynos can use more tricks.

Andersons for example back when the intake was put on, got 485rwhp peak. however it was all noise at the end near 7000rpm. it really was around 475rwhp when you looked at the curve. now, his and Joes are well over 500rwhp in the smooth section of the peak hp curve.

mk

mark kibort

Dont forget Randy's stroker here in Santa Clara. 420rwhp with devek bottom end stroker, level II headers and 968 valves with GT cams, no other mods. fuel shark tuned from 385 to 420rwhp. basically, the same motor as mine, but a more restrictive exhaust, engine accesories and the bigger valve heads (no much port work at all)

mk

Vilhuer

Thank you Louis very much for the comment. It explains a lot.

Since modded S3 cams I have have just 10.5 and 9.5mm lift and engine is goind to be limited to stock GTS 6600 rpm I'm hoping using 944S2 springs on intake and 968 springs on exhaust side will be enough. Thinking about using stock installation height for both. At least they should be better than S4-GTS setup and they are designed for 11mm lift.

John Veninger

Just another data point. I used 944S2 springs with S3 lower washers. Don't recall the valve seat pressure, but it was much higher than 51lbs.