BoostGuy951

I have disassembled my Parts car motor, which is an 86 NA. I've recorded some of the weights from my digital scale.

Here they are, in grams, from Cylinder 1 to cylinder 4, progressively.


Pistons: 551, 559, 557, 558
Pins: 134, 140, 134 ,134
Rods: 831, 831, 828, 830


Now these parts were just removed from the engine, sprayed with simple green, and scrubbed with a cloth. They are not completely spotless, but they have been cleaned in a uniform fashion. Either the Tolerances really are this loose, or this is mostly due to non-uniform wear characteristics. It could also be due to air fuel ratio imbalance caused by the intake manifold. Non uniform a/f ratios would cause different piston temps, causing the pistons to collect deposits at a different rate. This doesnt excuse the rods, though. Curiously, the weight deficient rod (828) is not the #2 rod, which is what I expected, due to the excessive wear on the #2 bearing. Both the bearing and journal of the # 2 rod are discolored to a brown color. I will post again with new weights when these parts soak in the parts washer and are scrubbed to nearly spotless.

Ahmet

When I pulled my 176k mile 944 turbo engine apart (86), after letting the parts sit in the parts washer for two days, cleaning and drying them, the whole assemblies (piston +rod+pin) weighed w/in 1 gram of each other). I did not have excessive wear on any of the components, but I bought the car with no records so it may have been apart before.
Ahmet

NZ951

Interesting findings Boosty. What was the motivation of using the NA engine for parts?

BoostGuy951

Well, I was going to use the NA block as a rebuild core, since my turbo block's walls were pretty scored. Turns out the parts car block is scored as well. I decided to sleeve it and go with a bigger aftermarket piston. So I have a few boxes of NA engine parts with nothing to do with them. Although I think the Rods from it are forged. They have forging marks. Should an NA 86 have forged rods?

westcoastprshe

NA 86 should not have forged rods. It's pretty easy to tell if they were forged based on the shape. Take a picture and half a dozen people can tell you which one it is.

BoostGuy951

I would if I had a digital camera that worked. I've seen alot of forge marks, and these are pretty obvious forge marks to me, but I guess it could be due to some casting procedure I am not used to seeing.

BoostGuy951

Shouldn't someone also be able to tell by the weight?

westcoastprshe

This one is forged:


Compare to yours

BoostGuy951

It looks exactly like that in shape and contour, but it is missing the part numbers from the center beam. It just has the number "85".

westcoastprshe

It doesn't have a part number on it ANYwhere?

BoostGuy951

Not anywhere. WTF?

NZ951

Aftermarket?

westcoastprshe

Yeah, I would be really surprised if that was a factory rod, get a picture and maybe we'll be able to ID it.

BoostGuy951

It says 944 on the cap the same place yours does, and it has the exact same shape and contour. I dont know why anyone would put aftermarket rods in an otherwise stock NA.

BoostGuy951

I have new Rod and wrist pin weights with fully cleaned dry parts.

Pins: 134, 140, 133, 133

Rods: 828, 828, 825, 827

The rods had three grams of grime each. The Pins were mostly unaffected. I will post the piston weights when I finish cleaning them. I am gonna let them soak a little while longer.