NOS cylinders in GM Boxes

[BowTieJohn]

I came across 6 cylinders with pistons and rings in GM boxes on Craig's list. Can anyone tell me what they will fit. The number on the boxes are 3869276, GR 0.030. So I'm going to guess they are 0.30 over. I would like to use them on a 63 motor. Any info will help. Thanks

[66vairguy]

I don't have my parts book handy. The GR 0.30 is the GROUP number. All Corvair pistons were std. AFAIK.

DO BEWARE - GM matched piston weights in opposing pairs NOT as a set of six. The NOS pistons (in the cylinders) should have an INK number on top of them for the weight category (not the actual weight, just a group GM cherry picked pistons into).

I learned about this when I picked up set of NOS pistons from a fellows estate. He bought six from the dealer and never used them. Of course there were not enough pairs of the same group weight to match them up (apparently the fellow did not know this and the dealer parts folks didn't either). I was sending them all out to be balanced as a set of six so it wasn't a big deal for me. If you don't want the expense of balancing the pistons, then ask for the piston numbers (if they haven't been cleaned off).

[Scott V]

3869276 = 65-9 std pistons/cyl/rings.

-Scott V.

[BowTieJohn]

3869276 = 65-9 std pistons/cyl/rings.

-Scott V.

So I gather they will not fit my 63...

[BowTieJohn]

I don't have my parts book handy. The GR 0.30 is the GROUP number. All Corvair pistons were std. AFAIK.

DO BEWARE - GM matched piston weights in opposing pairs NOT as a set of six. The NOS pistons (in the cylinders) should have an INK number on top of them for the weight category (not the actual weight, just a group GM cherry picked pistons into).

I learned about this when I picked up set of NOS pistons from a fellows estate. He bought six from the dealer and never used them. Of course there were not enough pairs of the same group weight to match them up (apparently the fellow did not know this and the dealer parts folks didn't either). I was sending them all out to be balanced as a set of six so it wasn't a big deal for me. If you don't want the expense of balancing the pistons, then ask for the piston numbers (if they haven't been cleaned off).

There are 4 12s and 2 11s. So I need to have them balanced?

[cnicol]

"There are 4 12s and 2 11s. So I need to have them balanced?"

Craig replies: No, to get to the level of "factory" balance, just install the "11" pistons opposite each other; such as on cylinder positions 1 & 2.

I will say that "factory" balance isn't particularly "balanced" though. A full, competent, machine shop balance hits all parts (crank, flywheel, rods, pistons, pressure plate) and will yield a smoother engine, especially if it's used with a manual transmission and you expect to race around a little now and then.

[BowTieJohn]

Thanks for the info. As this build is for a friend and has a good budget, I was going to balance the rotating assembly anyway. It is a standard trans and we want it to run smooth. He's building for his daughter to drive, not a show car but it's going to be a complete restore.
I don't know too much about Corvairs. Do they come "matching numbers"? I know it's a big deal on some restorations. The car is a one owner,his father, and has never engine work done on it.
I have a 68 motor that came with the pistons and is supposed to be HiPerf but I don't know what that entails and it doesn't really matter as I'm going through the hole drive train anyway. If numbers matching isn't important than I'll use the 68 block

[Scott V]

So I gather they will not fit my 63...

no. they wont fit.

the 63 heads can be opened up for the 65-9 cyls. but the pistons dont have the right pin height.

-Scott V.

[BowTieJohn]

Thanks thats good to know I'll keep that in mind

[notched]

I have found that a lot of those NOS GM cylinders for 65-69 models are actually 64 cylinders with a sleeve over the top. I have had 3 sets like this and have one set in a car right now. If needed you can remove the sleeve and use them on an early engine IF yours in fact like the ones I have/had. Of course if they have pistons they will not work with the 140/145 shorter stroke crank.

[BowTieJohn]

can I use the 65-9 crank in a early block? I plan on replacing it anyway.

[cnicol]

Yes, with minor clearance-grinding (see "how to hot rod corvairs" book) and a change to a 164 cam (narrower exhaust lobe for rod clearance) and a change of bell housing or a special seal spacer.

[BowTieJohn]

Thank you. Just ordered both the original and the revised addition on ebay. Can't have too much info on hand.

[Jbyenko77]

hi

If you are still looking for 61-3 (EM) NOS piston/ring/cylinder set, I have one set of 6. I would be interested in trading, since I don't have any EM's .


jeff ballard
camarillo, CA