602 crate pistons - "Old" vs "New" version - engine builder ?

[swaybar]

So the GM circle track crate motor manual says that the old version 602 and the new version 602 should perform the same. The new version has a piston/pin combo that weighs about 70 grams per cylinder lighter than the old version. I had a newer version factory sealed 602 that ran very well. Replaced it with a freshened "old" version and can't seem to get the same lap times any more. To me, I'm thinking that the newer version 602 with the lighter pistons may have a fairly significant edge over the older one.

Can any of you engine guys with 602 experience offer an opinion on that?

[apr28]

Might have your compression checked. From what I have found out 602 crates can vary on their compression. So far I found the range can be 8-8 up to 9-4. They advertise as being 9-1. I'm wanting to get a crate next spring so if the new version is better than the old I would like to know also.

[swaybar]

Have had compression checked on both motors with the "whistler" device. The newer version motor which is still sealed from the factory checked 9.4. The rebuilt one checks 9.2. Leak-down test on both motors is good.

I've done a lot of research on this topic in the past few days. From what I can tell, you are better off buying a new post-2010 produced motor than having an older one rebuilt. The newer (lighter) pistons that GM is claiming to be using in the newer version motors are next to impossible to get from any source at a reasonable price, so builders would most likely use the much heavier slugs from the older version that are much cheaper and readily available from various sources.

[brad hibbard]

Have had compression checked on both motors with the "whistler" device. The newer version motor which is still sealed from the factory checked 9.4. The rebuilt one checks 9.2. Leak-down test on both motors is good.

I've done a lot of research on this topic in the past few days. From what I can tell, you are better off buying a new post-2010 produced motor than having an older one rebuilt. The newer (lighter) pistons that GM is claiming to be using in the newer version motors are next to impossible to get from any source at a reasonable price, so builders would most likely use the much heavier slugs from the older version that are much cheaper and readily available from various sources.

Swaybar,
the piston price is exactly the same when buying pistons from GM-- are you insinuating that rebuilders would use aftermarket pistons?

anyway--- you asked for my opinion on this in another thread so i will just jump in here

because of the price of the 602 rebuild parts we have only ever rebuilt 2---so my data base is very small and i don't have much to compare to

as an engine builder---when I hear lighter---I think better----BUT GM has alot of eggs in this basket and they explained the situation very well in the tech manual.
one thing you did not point out was that they changed crankshafts as well to accommodate the piston change and that the wrist pin is heavier

I am an apples to apples guy and at the end of the day i have to go with what GM has printed because I don't have any data to support otherwise

we have dynoed alot of 602's but not on a heads up test-----we did just recently dyno a new 602 on the same day as a new 604 and it fell 50HP short just like it is suppose to

I don't have a solid answer for you----but I believe GM did their best to keep it equal

I will still take a new RR tire and a driver with a good attitude over a few HP any day---LOL

Brad

https://www.race-1.com

[HCR#16]

From what I saw the new 602 has a coated piston, little better ring pack, and changed the rod a good bit.

Just from what I have saw in the two engines I would buy the newer 602

[swaybar]

Brad, thanks for the reply. I'm not suggesting anything in particular about rebuilders using aftermarket pistons. Although from what I can tell, this would definitely be an option in the older 602 because they are so readily available. See if this makes sense:

From what I have been able to tell in looking at the technical manual and from doing lots of research, the old 602, part #88958602 used piston #12514101. That piston is available from any number of sources for a reasonable price but, according to the technical manual, weighs 598 grams plus 144 grams for the pin.

The "new" 602, part #19258602 uses piston #88894280. I can't find that piston available anywhere for less than about $80 each with the average price being around $125 each. According to the manual, that piston weighs 512 grams with a 159 gram pin. The piston also has coated skirts. That's a 71 gram difference in pin/piston combo between the old and new motors. I know GM says that the two motors perform closely on the dyno and you have even verified that yourself. But we all know that we don't race on the dyno stand. My question really is just this - shouldn't a rotating assembly that is 568 grams (over a pound) lighter than another have an advantage on the track? Sure seems to me like it would.

Here's a side question - why are the 88894280 pistons so expensive and hard to come by?

Thanks again

Swaybar,
the piston price is exactly the same when buying pistons from GM-- are you insinuating that rebuilders would use aftermarket pistons?

anyway--- you asked for my opinion on this in another thread so i will just jump in here

because of the price of the 602 rebuild parts we have only ever rebuilt 2---so my data base is very small and i don't have much to compare to

as an engine builder---when I hear lighter---I think better----BUT GM has alot of eggs in this basket and they explained the situation very well in the tech manual.
one thing you did not point out was that they changed crankshafts as well to accommodate the piston change and that the wrist pin is heavier

I am an apples to apples guy and at the end of the day i have to go with what GM has printed because I don't have any data to support otherwise

we have dynoed alot of 602's but not on a heads up test-----we did just recently dyno a new 602 on the same day as a new 604 and it fell 50HP short just like it is suppose to

I don't have a solid answer for you----but I believe GM did their best to keep it equal

I will still take a new RR tire and a driver with a good attitude over a few HP any day---LOL

Brad
www.race-1.com