Short block assembly questions...
 

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.:party-smiley-004:

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.

Fixx
 

+1 :drink:

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.

Fixx
 

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 !!!!

rick,the ring gap varies depending on what brand of ring you use.generally on a blown gas engine about .006 gap per inch of bore[4 inch bore=.024 gap.]always follow the recomendation that comes with the rings.i always replace the chain&gears as a set,i like cloyes true roller billet set,as far as oil pump,i like the mellings select.when you buy gm performance parts,you are actuially buying aftermarket parts made for gm,this holds true on app 90 percent of gm perf parts.good luck with your build.

The Devil is in the Details!
 

As an experienced engine builder I will toss in my "of sometimes questionable value "-two cents here.

On assembling short blocks for ENDURANCE marine performance engines, its actually more important to pay very concise attention to the block machining, clearances, fitment ,preparation and cleaning than just talk about the great aftermarket parts for the build. The importance of a straight mainline, square even decks, straight to the mainline boring and concise proper honing and fitting of all the various parts cannot be stressed ENOUGH! Good simple de-burring, setting deck heights, piston to bore clearances, bearing clearances, careful cleaning after machining and prep, etc.,etc.,etc will yield many more hours of trouble free operation.

This is why most good professional engine builders have better success ratios on big horsepower marine ENDURANCE engines than private owner builders on par. Just the equipment, tools, machines and years of experience are very expensive and are required provisions for successful engine builds.

There, now that I got that piece of wisdom off my chest!

Its time to add value to your question.

My experience with supercharged engines, which is not huge, but reasonably successful has led me to start with the right material and type for supercharged engine ring sets. We have had great success with the Total Seal Hellfire ring sets for supercharger use and on your bore size a .028" top ring gap and a .030" second ring gap should be just about right provided the piston set has an accumulator groove over the second ring. If not the second ring gap should probably be opened +.002" or so to make sure pressure does not create ring flutter on the second ring. Make sure the file to fit work is done by someone experienced on a good machine and the corners are properly dressed before assembly and use. DETAILS-DETAILS-DETAILS!
You or your shop should also pay particular attention to the final hone pattern and finish as it will play a huge part in ring seal and life. Your performance ring manufacturer would have the best specs. on their particular ring package

As for a timing set you should definitely make sure your camshaft is properly dialed in a set to its best timing for your use, this is best accomplished with a nice true roller hex-adjust set form Cloyes which has strong CNC billet gears and special chain.

As for an oil pump, the Melling Select 10778C mentioned by others here is definitely the best unit for your use.

Hope my advise is helpful and good luck in your build. Just don't cut the corners for a flawed budget or skip the important details and end up buying your new short block twice!

Best Regards,
Ray @ Raylar

Ray, what do you like about the Hellfire rings?

I was advised against using them by some reputable builders.

I've also seen a lot of debate on the 2nd ring gap. There doesn't seem to be any evidence one way or another and each builder seem's to have their opinions on it.

As for machine work, there's no doubt the equipment is expensive. I don't own any machinery but have an excellent machine shop I farm all my machine work to. At the end of the day my dial bore gauge and torque wrench works as good as anyone else.

I've done work myself and also paid others to do it over the years... It all depends on cash flow....

Hellfire rings.....
 

these rings are supurb for blown applications-IF the proper
cylinder finish is achieved- best with a "plateau" finish ie:finer
than what you would generally use for a standard moly faced
ring set....

:drink: