Getting close to assembing my 525SC short block...Once I get everything back from machine shop...

1. JE .030 over pistons...What should the ring gap be for the top & second ring for a blown engine (5 - 7 lbs boost). Should I buy the .030 rings & gap them accordingly, or go for the .040 & gap accordingly?

2. It is a Gen VI block...the timing chain was tight, but I do plan on replacing it. I noticed it was a GM performance tru roller set-up, & that particular one is still available. Should I simply order a new GM chain (the gears look perfect), or opt for aftermarket, maybe Cloyes?

3. Oil pump will also be replaced...Same question as above...GM, or aftermarket, maybe Milidon HV?

Thanks for any input...

I DONT MEEN TO SOUND RUDE,BUT THE QUESTIONS YOU ARE ASKING MAKES ME BELEIVE ENGINE ASSEMBLY IS NOT FOR YOU,HAVE SOMEONE ASSEMBLE THE ENGINE WHO HAS EXPERIANCE WITH MARINE ENGINES.IN THE LONG RUN,YOUL BE GLAD YOU DID.

No, acutally I have plenty of experience building engines (street rods). Just not in the supercharged, & I've noticed that the recommended ring gaps for a blown engine range between builders. I also realize that the boost makes a difference. So, I was just looking for a little insight on this.
In addition, if the .030 rings will come close to what I need, then I'm good, but with the rings being availble for a "file to fit", or just opting for .040, maybe that would be a better approach.
As for the GM vs. aftermarket...I'm just looking for opinions. I've usually went aftermarket, but I've noticed that GM performance is used quite a bit with Mercruiser built motors, so it was just a question regarding the comparsion.
Thanks for the input.

+1

their is way to much going on in that engine to just throw it together and have it last..gap less rings work best for boosted applications,always replace the timing chain and anyone under $100.00 is a piece of junk..true roller billit is what you want..The oil pump you want to use is a melling part # mel.10778c and make sure you use the correct pick up tube and set the correct distance to the bottom of the pan then weld the pick up to the pump..

Just curious what the difference is between the Mellings 10778c and the M77HV

The 77 is a standard High Volume, the 78 is the HV with the shafts that extend thru the bottom case. I used the 78 on my last build.

As far as rings go.... I went 28 on the top and 26 on the bottom which was pretty close to what the ring manufacturer suggested.... 580 cu in, blown with about 7 psi boost.

As far as the timing chain goes, I would opt for the Cloyes Billet.

Personally, I don't like the gapless rings.... I had them in my last set of engines and opted not to use them again..... Very little blow-by at idle but it would pop the dipstick under boost.. With the standard rings I have the opposite effect and I'd rather have the blow by at idle than pop the dipstick or have positive crank-case pressure.

what he said,also its cnc machined,has a manganese phosphate coating,the pressure relief spring hole is threaded and tapped and plugged instead of just a roll pin holding the spring in and i think it has billet steel gears instead of cast gears and the main shaft has a guide that keeps the main shaft from wobbling..also has anti-cavitation gooves in the body and cover.

Do it yourself. You'll kick yourself in the ass if you hand it over to Joe Blow's performance engines only to pull it back out in 10 hours.

Hold both of those oil pumps in your hands and you'll know. Angels sing when you look at one, the other... nothing

Thats priceless !!!!