Is it feasible to metal spray a cam?

[Dwight Southerland]

Bill -

If you are working on the turbo slant 6 project, it might be that the effort ($$ & time) spent trying to put a roller cam and lifters into the motor would not have enough ROI to be worth it. I do not believe that there is enough power to be gained above 6000 rpm or so to warrant the roller setup. The slant 6 valve train is light enough to be controlled with available valve springs at that engine speed. Remember that a flat tappet arrangement has the design characteristic to have much faster off the ramp acceleration and faster ramp action under .150" lifter rise than a roller cam and that is a great benefit to the performance of a boosted engine. I would spend more energy on camshaft profile for a flat tappet cam than get anal about a roller lifter moving the valves. I bet there wouldn't be a 2% difference in power output after five years of thrashing between a flat tappet engine and a roller tappet engine. IMHO

The cylinder head flow is your biggest limitation on that combination.

[Chris Hill]

Originally Posted by dwight southerland

bill -

if you are working on the turbo slant 6 project, it might be that the effort ($$ & time) spent trying to put a roller cam and lifters into the motor would not have enough roi to be worth it. I do not believe that there is enough power to be gained above 6000 rpm or so to warrant the roller setup. The slant 6 valve train is light enough to be controlled with available valve springs at that engine speed. Remember that a flat tappet arrangement has the design characteristic to have much faster off the ramp acceleration and faster ramp action under .150" lifter rise than a roller cam and that is a great benefit to the performance of a boosted engine. I would spend more energy on camshaft profile for a flat tappet cam than get anal about a roller lifter moving the valves. I bet there wouldn't be a 2% difference in power output after five years of thrashing between a flat tappet engine and a roller tappet engine. Imho

the cylinder head flow is your biggest limitation on that combination.

x'2

Very well stated too!

[bill dedman]

Originally Posted by Dwight Southerland

Bill -

If you are working on the turbo slant 6 project, it might be that the effort ($$ & time) spent trying to put a roller cam and lifters into the motor would not have enough ROI to be worth it. I do not believe that there is enough power to be gained above 6000 rpm or so to warrant the roller setup. The slant 6 valve train is light enough to be controlled with available valve springs at that engine speed. Remember that a flat tappet arrangement has the design characteristic to have much faster off the ramp acceleration and faster ramp action under .150" lifter rise than a roller cam and that is a great benefit to the performance of a boosted engine. I would spend more energy on camshaft profile for a flat tappet cam than get anal about a roller lifter moving the valves. I bet there wouldn't be a 2% difference in power output after five years of thrashing between a flat tappet engine and a roller tappet engine. IMHO

The cylinder head flow is your biggest limitation on that combination.

Dwight,
Thanks for that good advice, and just FWIW, I agree with everything you said except...
My motivation toward putting a roller cam in this engine is not for increased power output, but rather, to avoid the jeopardy of cam/lifter failure... nothing else.

These turbo slant six motors (at least the ones I'm familiar with) never see the far side of 5,500 rpm. I am still ignorant about the reason why they don't make power up to 6,000 rpm, but I suspect it's the extremely poor flow characteristics of the head. Even a well-ported head that has the biggest valves available (1.74"/1.5") only flows about 200 intake cfm and 150 exhaust, and that is to feed a 39 cubic inch cylinder, so you can see the problem. They just run out of breath after 5,000 rpm, even with 25 pounds of boost.

Still, they manage to make well over 500 horsepower, even at that low rpm... one such engine I know of (a twin to ours) runs 127 mph in a 2,800-pound car.

That is with a cam with only .484" gross lift, and 220/220 degrees of duration @ .050". That motor runs 28 pounds of boost without incident, on race gas.

The Shell station on West Markham in Litttle Rock, now has an E85 pump, and we're considering using that blend for its anti-detonation properties... but we haven't fired the engine, yet... the jury is still out on that one. We'll have to get a different carb, or this one modified, of course.

Our plan, once the engine is broken in, is to raise the boost level (but, not the rpm) to a higher value (up to maybe 35 pounds?) and see what this infrastructure will accommodate without blowing itself into a basket of scrap iron. LOL!

Because Mopar slant 6s were originally intended to be cast in aluminum (a plan that was scrapped early on, due to casting problems) and their head is so poor (due to the small 3.4" bores, and the small valves it necessitates), forced induction seems to be unusually appropriate for this engine. When the factory abandoned the aluminum block in favor of the cast iron construction, they didn't change the robust-design infrastructure that had been part and parcel of the aluminum block and head design, and as a result, the thing is REALLY strong in terms of stiffness. The crank is forged, and although the 4-main bearing design, is short (and doesn't "whip" like a longer, 7-main bearing crank,) and uses main bearings that are the same size as the mains in a 426 Hemi... sizeable, for a 225 cubic inch engine.

One guy in Australia is making 638 horsepower with his, using a stock exhaust manifold with a turbo flange welded to it(!) His name is Cameron Tilley, and his car (a 4-speed) is on You Tube, if you want to watch...

So, we're just trying to avoid the flat-cam blues.... we don't run much valve spring pressure (125# closed/335# open at .500") so it may not be a problem with enough ZDDP.

Sorry for the long-winded diatribe, and thanks again for the good info/advice!!!

[Dwight Southerland]

If you want to eliminate worries about camshaft-lifter failure, send your cam and lifters to Bud Yancer at Mach Engine Development in Phoenix for treatment.

[bill dedman]

Originally Posted by Dwight Southerland

If you want to eliminate worries about camshaft-lifter failure, send your cam and lifters to Bud Yancer at Mach Engine Development in Phoenix for treatment.

Sounds like a plan! What does he do?

[Bob Pagano]

http://www.machdevelopment.com/page/page/236996.htm

[bill dedman]

Originally Posted by Bob Pagano

http://www.machdevelopment.com/page/page/236996.htm

Well, I talked to them, and I think we can do some bidness; $250 to coat the cam and Lifters with their proprietary coating process. Sounds good!

Thanks a lot!

Appreciate the good info!!!