Van

So, I've got an '84 engine apart and an '86 engine apart... And I'm surprised to see difference between the pistons and the connecting rods. Are some better than others? Some forged and some cast? Which should I use on my super-duper, high-zoot (read as: stock) ChumpCar motor?

Also, what is this copper colored area on the piston? (I soda blasted the piston to clean it up.) It looks like a flake or a chip in a coating, but it's super smooth to the touch - doesn't feel wrong.

f1rocks

I try to use forged when possible. But honestly your (and my) chump car engines won't see enough stress to make a significant difference.

Since youre dealing with a big build budget, I'd send the pistons to swain and have them coated for that extra tenth of a horsepower.

Don't forget to shave the head to bump compression as well.

Van

Brent, then I have to weigh-match and balance them!

Actually, I was thinking that if either set of pistons or rods were forged, I could sell those and use the money for some good, hard, all-season tires!

catamax944

I presume the nice bits came out of the '84 ?
The early engines '82 and '83 had forged rods(RARST) and forged crankshaft with extra oiling passages for the rod bearing journals. Strange that yours is an '84 .
I didn't know however that the pistons were also different.
Since you have them it would be a shame not to use them ,also check the crankshaft.

PS: you wont get more than $300 out of all of them. I vote you use them.

StoogeMoe

Yeah, forged vs. cast rods. Use the forged. Check the tolerances of the wrist pin first.

As far as the pistons go, that orange color is mostly the iron coating on the piston to prevent it from being galled against the silicon in the cylinder. You shouldn't have blasted that off. Now you'll have to get them coated or they won't last very long.

Van

The soda blasting is really gentle (and I had the air pressure at like 30psi) and actually had no affect on the orange areas. Seeing it in person, it's really the color of copper - not ironoxide.


Cool - I think I'll use them! (I'll look at the crank when I get a chance.)

Van

Yeah, the early crank is cross-drilled at each rod journal (2 holes for the oil to flow through, as opposed to 1).

Other early and late differences:
-The cylinder walls are 7mm thick on an early engine block and 8mm on a late block
-The late balance shafts have the plastic covers on the counterweights to improve windage (drag through oil to reduce foaming)
-Early engines have a bearing mount in the balance shaft covers; late engines have a secondary bracket that holds the bearing

V2Rocket

Also different coolant sensors.

To add further fuel to the fire, the late style engines (with these features) started in the early 1985 model year. My car was built 12/84 and has a "late" engine as original equipment.

Jeff951NJ

Wow Van.. You got real lucky with where ever you got that early motor.. LOL

T&T Racing

Van,
The RARST rods are forged and were used in the turbo engine. Probably should replace the wrist pin insert bearing on the rod.
Coated rod bearings are important for longevity and initial startup. Swain can coat your rod bearings for the crankshaft end.

vette951s

IIRC, the cross drilled crank and forged rods were used in automatic transmission equipped engines in 1984 models! Definitely use the forged rods if they spec out OK. Those cast rods were used in factory Turbo S engines beginning around December 1988 production and all S2 motors, so using those is not out of the question either.
There were two different piston suppliers, Mahle and KS, and there were subtle differences.
John

T&T Racing

Van,

Another subject. What PCA race class do you run your Jagermeister car? What front A arm bushings are used on the Jagermeister car?

Thanks,
Tom PCA Niagara member

Van

Tom, I run it in SP2 (944 Cup). I have the weltmeister bushings at the subframe, 968 caster blocks and Kokeln adjustable camber plates. See you at Lime Rock?

Will Feather

Glad to see everything worked out Van, and good score on the RARST rods, maybe a late 83' sold as 84.

Throw some pics up of the difference in the cranks for reference!

johntorg

Lots of good information in this thread. I have a few questions:

1. How do I identify the RARST rods is there a specific part number?
2. I will be building a 2.8 Turbo engine for the street. I have a set of Mahle stroker pistons and would like to have them coated (1 skirt is a bit scored). Should I have both the tops and skirts coated? Which coating should I have applied? I have been looking at Swain, does anyone else apply coatings to 944 pistons to run in stock bores?

Answered one of my questions the forged rod seems to have RARST stamped on it (Duh)