Well.... my effort to stimulate discussion with the quote on rod length didn't generate much traffic, so let's try one on engine coatings.

A sidebar in Chevy High Performance magazine, by Darin Morgan, Reher-Morrison's R&D cylinder head specialist.

 

I would think the first question is to quantify what is considered to be an inefficient engine. When compared to a Pro Stock engine I would think that most lightly modified or even some H/C motors would be considered inefficient when compared. How efficient are most common cam or even H/C selections that eople run, i.e. Hot Cam, CC306, LE1, etc?

 

Good point I think a lot depends on his definition of efficient.
The other thing is most of us expect to put some street miles on and how do the coatings holdup to that use?

 

I'm sure his definition of efficient equals SUPER EFFICIENT!

 

I'm sure it is Are we talking volumetric efficiency or thermal efficiency or do they go hand in hand? If thermal efficiency, I'm sure that a car that runs iron heads with a lower compression would benefit more from coatings as compared to an aluminum headed motor of a proportional compression ratio just because of heat retention, right?

 

And what about these coated bearings? I mean, are they something you would use in your average street motor? Would they be worth the extra $$$ in something like the average 355 build? (stock crank, better rods, forged pistons) Or are they something for a higher-end more "race-only" setup?

 

ulakovic22,

I believe you're wrong about the iron head motors. I would tend to think that they are more inclined to thermal efficiency because of their heat retention. It's a basic abidactic principle. I'm sure one of the more knowledgeable members will correct me if i'm wrong.

My $.02

Jeremy

 

When Darrin talks about the efficency I think he is talking about a lot of things. It's odd but there are things that go on in the intake ports and exhaust ports that will change how much timing a motor needs. The less timing the better, but that is also relative to the stroke and rod length. A F1 motor can take well over 50° at idle, but it's not because of the inefficentcy of the chamber/piston design, it's that there's no stroke in there.

Say if you are running a setup like we commonly run here, the coatings are going to help it more than a Pro Stock motor. Now a old Smog headed setup would benefit even more than a LT setup, since the LT has better chambers, and better thermal properties. Or take something like a Cleveland setup, those things have caverns for ports, bad exhaust ports, bad chambers (even on a 4V 302 head) and compare that to a Yates head which is basically a modern version. The old Cleveland will gain more from coatings.

As for bearing coatings, they are worth it on about anything. If you ever go light on oil, starve the pickup or have a bearing spin they will definately save you money or a motor. Do some digging on coated bearings and a guy called Keith Dorton and see what you come up with. FWIW If I have the time and the budget to coat the bearings in a motor, it's done.

Bret

 

Jeremy, yes the cast IRON is better but most of the time the chambers are so bad it doesn't help. A new Vortec head would be much better than a smog head, but not as good as a SB2.2 head.

Bret

 

Think a Pro-Stocker is SUPER EFFICIENT around town? Or would it barely run?

I used coated bearings this time because I needed a few 10 thousandths to get my clearances where I wanted them. The shop that machined my block said that they get engines back to freshen up with coated bearings where the bearings look like they did when they put them in there. That's the kind of thing I like to hear. I didn't coat my pistons, but they came with some kind of coating already on the tops and a Grafal anti-friction coating on the sides. I think the key to coatings in general, is that the parts are prepped correctly and the coatings are applied right and the heat involved doesn't queer the part. We were experimenting with magnesuim pistons at work with a special coating on them and they seemed to work pretty good without galling. yeah, I guess you could say I am a believer in coatings.

 

It depends on your definition of efficiency. In a motor I would say efficiency is how much of the gasoline you burn is turned into HP at the crank.

 

If it's race engine, "efficiency" is BMEP (torque per cubic inch), especially at power peak rpm. If you are in an "economy race" like yesterday's (6/25) Cup road race, BSFC becomes as important as BMEP, and perhaps more so. Rumor says Terry Labonte's engine might have had a slightly smaller carb than max allowed. He sure "made gas" the last 55 laps finishing 3rd behind faster, more powerful cars.

 

Don't you go knocking the 4v Cleveland motors, I'll take some offense...I think LR might too.

 

Nah, with a lot of brazing and epoxy those heads are worth something!

Bret