[393Clevor]

I just got my scales out and started weighing my pistons and rods. The pistons are out by 5 grams. If you were to grind on the piston where would you do it? I have done this before and I took some weight of the wrist pins to match the piston weight. I figured that the pins would be a safe place to grind.

Any thoughts????

 

[67stang]

5 grams ain't enough to worry about. My .002

 

[393Clevor]

Just how fussy do they get when they balance an engine?
I would think the closer you get to 0 tolerance the better. Why not get them to 0?

Also has anyone ever used the rod fixtures for weighing the rod ends? How do they work? I have tried to make a fixture but I can't seem to swing the rods accurately enough to be consistent. If I could find a good picture of a fixture I could fabricate one up.

 

[85mike]

I remove the weight from the bottom of the pads below the pin bore. Easy to do in a lathe. Try Powerhouse Products for a piccy of the fixture. I made a valve spring tester from their piccys.
The machine shop is probably gonna charge you full price to do the balance work, so why bother.

 

[393Clevor]

Well, If I match the rods and pistons before it goes to the shop to be balanced I know that they are done to 0 tolerance. You never know what kind of mood the tech is in when doing the job. His old lady might be cheating on him and his mind is not where it should be (good enough, ship it ) So if I know that the pistons and rods are dead on it will make his job easier and take less time. Might even be cheaper. Around here it's 300.00 to balance a motor. I would feel a lot better knowing the pistons and rods are dead on before it goes to the shop. Plus I like doing this kind of stuff it keeps me out of trouble.

 

[mavman]

I used a 1/2 inch drill bit to drill "dimples" into the bottom of the piston, directly under the head of the piston. I've found that most trw pistons are thicker around the edges, so theres plenty of metal to dimple. 2 dimples=1 gram. Drill just deep enough to make a 1/2" diameter dimple, and no further. I have also found that trw's are notoriously different weights from one piston to another. I weighed the srp's I have now, and they're within 1/2 gram of each other, not to mention 110 grams lighter!

 

[mavman]

by the way, if you get everything weight matched, that $300 you were quoted for balancing would be more like $200, because the machinest will have to do less work.

 

[CantedValve]

V8740 - If your machine shop's quality of work is hinged on whether the machinist's wife is banging the mailman, you need to find a better shop.

 

[67stang]

I did the weight matching on the pistons and the rods on the first 357 that went into my stang. Very time comsuming, but necessary.
The Eagle kit I got last year, was all balanced already, with the internally (mallory metal), crank. I ended up having to cut, (well, the machinist......I watched), had to cut .100" notches in the intake side, and .045" on the exhaust. (pistons). In either case, they went from 5 cc to 9 cc. (not alot). The weight only changed 10 grams. We weighed all the pistons before cutting, and all were within 1 gram of each other. Other than being 10 grams lighter after cutting, they were still within 1 gram of each other.
Talked to 2 different machine shops, (besides the one that's doing my 41

, and all agreed that while perfect would be great, they wouldn't lose sleep over 10 grams. My (and their), .002

_________________

<font size=-1>[ This Message was edited by: drag79stang on 2/18/02 7:57pm ]</font>

 

[393Clevor]

I just got done reweighing the pistons on a triple beam dial-o-gram scale without the pins. I go 2.35 grams difference. KB 116 pistons.

The rods got weighed as a total not the ends and I got a difference of 1.45 Scat I beam rods.

I also found one of the wrist pins clips were in one of the pistons that was 5 grams out. This was done on an old scale that's not so accurate. The triple beam is a lot more sensitive.

 

[85mike]

Don't forget to take 1 set of rings and rod bearings when all the parts go to the chine shop.

 

[393Clevor]

Thanks

 

[horsyhorse]

Maybe I´m crazy and have to much of freetime.
But I borrowed a paintweighter 1/100 grams
and matched my pistons and pins separetly.
After all work it feels good, even if just
a couple of oil stains will screw the grams.

 

[Hottarod]

The closer to dead on it is the better that puppy will run. Any out of balance means vibration and vibration steals back horses. A good balance and blueprint job can get you as much as 25 horse pressures.