ptuomov

What indicated that the engine is/was undercammed?

Carl Fausett

We found that the water brake was able to snuff the engine too easily starting at about 6000 RPM. Now, its a 1500 BHP water brake - so it could always snuff the motor - but we were not able to accelerate against it like we should have. We tried several different cam timing changes and even one cam phasing change, but the engine labored to produce torque in the higher revs, while it did very well in the low revs. EGT's were high, so we know we are wasting some power out the exhaust. We are going to increase the LSA and lift, and go back at it.

Marti

Strosek Ultra

The cams are made but not run yet. They include the adjustable intake cam feature I have designed. The last cam is very hot and intended for a high speed 7L stroker having individual throttle bodies.
Åke

Bigfoot928

Good luck with the cam mods. I tried to do that years ago and ended up with broken cams The factory cams are very brittle. but those don't look factory.... huge lobes~!

V2Rocket

that's putting a lot of faith in a collar clamp?

could you drill/tap some holes in the cam indexed to a few degree positions? so youd remove a screw, rotate the teeth portion to the next desired degree setting and re-tighten the screw there?

ptuomov

Bigfoot928

I ended up with broken cams when we tried years ago.... keep experimenting we all learn from it.

ptuomov

Rob Edwards

Forgot to follow up on this, I measured the GTS cams out of my '93 a while back. The 1st 4 rows are the specs from the factory books, the lower two are my measures of used S4 and GTS cams. I think the GTS LSA is closer to 114 degrees.

ptuomov

Thank you, this is useful. It makes all the sense in the world that GTS has 114 degree lobe separation angle and both intake and exhaust duration and lift right in between S4 and GT/S3 lobes.

Strosek Ultra

The clamp holds the chain gear very hard, no way it can slip. The gear is made of steel and much stronger than the cast iron gear on the stock cams. The drawback with this design is that I have to cut down the lobes at one half of the camshaft in order to get the adjustable chain gear on. Later the lobes will be welded and ground to the profile desired. I use WEB Cams for the making of the cams. They have plenty of profiles to choose from. In this case I have put on profiles we used to have on highly modified 2V motorcycle engines like Kawasaki 900/1000 and Suzuki 1000 back in the 70´s and 80´s. The cams are mechanical design and will be run on lightweight 37mm solid motorcycle bucket lifters.
Åke

Strosek Ultra

Adjustable valve timing is a must for a serious high performance engine build. The are more ways to do it. Here some photos of adjustable 944 cams designed by David Finch at Raetech and used by Michael Mount. It is a two-piece design bolted together with the chain gear. Note the heavy duty cam girdles and the fat lobes.
Åke

Strosek Ultra

Yes Rob, we have discussed this earlier. It looks like the factory specs for the GTS cams are incorrect. Here is the lift diagram I made for the GTS intake cam.
Åke

ptuomov