My son picked up his motor from the machine shop and we're puttin' it together this weekend. My question is about piston ring spacing. I've always used G.M.'s procedure, which is: if front of motor is 12:00 on piston,top comp.ring gap is at 3:00-lower comp. ring gap is at 9:00,one oil ring gap at 7:30 and the other oil ring gap at 10:30 with the oil spacer gap anywhere between 1:30 and 4:30.
Is there a better way of doing this for Hi-Perf. motors? Where using Keith Black Hyper. pistons with Perfect Circle rings.


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My sons car: 86 Iroc,388ci,Brodix,Victor jr,TPI-700r4,3:73.

 

i've saw that in my manuals but never really followed it very closely. i just make sure the gaps are staggered. it never really seemed logical to me where the gap was, as long as they were stagered more or less like you said. you might want to double check the end gaps on the Kb pistons, they run wider than stock i believe.

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ICON Motorsports

1st & 3rd

 

yeah ive always made sure that they were all staggered and didnt have two close to each other
ive dont alot of motors and never had a problem

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86 camaro:was a v6 car,now its going to be a v-8 5.7l!!
350:cylinders bored .040 over.a little over 9:1 compression(getting a blower some day when im rich lol)line bored.deck is milled a little(was pitted)
trw forged pistons with summit stage 2 polished rods with arp bolts.
194? intake valves(not 2.02( ),pocket ported,gasket matched,and polished ports,old vette intake with new zinc 650 holley

ase certified for a few years,learned alot though

working on freakin NEONS ,cirruses,tauruses,cobras(well` at least they look nice lol)and intrepids all day makes me drink too much
good job security though

im always on the lookout for cheapv-8 t-5,s
and t-56 setups.they must be cheap.i dont care of they need rebuild,as long as they arent totally blown

 

On all the motors I build, I do just about the same as that description. It should work out fine.

ede has a good point; those pistons don't conduct heat away from the top as fast as regular cast or forged ones, that's one of their benefits in that it makes the engine more efficient due to less energy loss, but it also make the top ring especially run much hotter than it would otherwise. That will make it expand more. So it needs a good bit more end gap. I'd suggest something around .028" to avoid it seizing in the bore under high load conditions.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Is the end gap issue something I should worry about also? I'm using GM Hypereutectic pistons (Same material as KB's?). I'll be using Child's and Albert zero gap rings.

As for the staggering, I'll ditto what the other guys have said. Just make sure they are staggered and you'll be fine! I've put several together and had no problems.

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Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand.

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

B9/JP,

Stagger the ring gaps about 120° and try not to have any riding directly over a pistom pin boss. Don't forget to stagger the oil ring rails and expander as directed.

I'm not completely sold on the name "zero-gap" for rings, since technically there is still a gap, but it there is a lap joint for better sealing. You still have to make sure the rings don't dead-end in the bores, but follow the fitting instruction from the manufacturer when in doubt. From what I've seen, there is usually adequate gap designed in for most applications, but checking is always the best idea. I've only seen these installed once, so don't take my word as gospel.

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Later,
Vader
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"No matter how hard you try you can't stop us now..."
Adobe Acrobat Reader 4.0

 

first off i'll say check with the maker and don't go on what i say, but aren't the second ring the "gappless" ring? isn't the top ring the only one you have to increase with hypereutic pistons? i should know this about the hyper pistons, i just put aset in for someone a month ago. i must be getting old.

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ICON Motorsports

1st & 3rd

 

Well ede, they say when you get old, your memory is the second thing you lose... problem is, I forgot what the first one was...

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"So many Mustangs, so little time..."
ICON Motorsports

 

In the set of rings that I picked, the top ring is the "gapless" ring. That is where it would have the most effect. I will contact them about the use with Hypereutectic pistons though.

Vader, If you go with the 120* rule, you would end up with the oil scraper rings in line with compression rings. I usually put the compression rings and the oil expander 120* apart, then the scraper rings somewhere in between. I know that is probably what you were saying, but I usually have to hear it a certain way for things to make sense!



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Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand.

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

Oops, the second is the "gapless" ring. I just looked again.

------------------
Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand.

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

I doubt the GM pistons are the same unless they came from Keith Black (which are cast by Silvolite anyways). The KB pistons have a really high silicon content, more than a typical hypereutectic piston. The top ring is also a little higher than stock.
GM should be able to give you the info, but my guess is that stock ring gap will be ok.

I usually just make sure the gaps arent aligned, but more often than not they tend to line up over time anyway from what I have seen.

 

Ah, you read my message wrong Madmax! I meant that they are the same in that they both have a high silicon content. GM doesn't actually call them hypereutectic, just high silicon. 12371060 is the part number for the kit of 8. As I sai dbefore, I will check with the ring manufacturer to make sure though.



------------------
Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand.

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

O I C

I would contact them then... no point busting off the top of the piston for 5 minutes work and a little research.

 

I'm still trying to figure out the physics of the ring end gap here, as in increasing it with the hypereutectic pistons. If anyone has any technical info that might put my feeble mind at ease..... I fully understand about the fact that if the ring is hotter, it will expand more, but is it enough more that there is a need to worry?

I dunno, just trying to be "Perfect" on my engine! I just want this thing to kick butt!

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Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand.

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

The pistons and rings should come with a sheet that tells you how much ring gap is acceptable for various types of engine applications, as well as piston-to-bore clearance. Marine motors don't like what hot rod motors like, etc, etc. Each piston and set of rings is gonna have it's own slightly different specs because each manufacturer is gonna use slightly different materials, casting processes and designs. Follow their recommendations.

As for rings, just keep 'em staggered and don't put any of the ring gaps on the thrust side of the bore. THat's how I do it, anyway. Doesn't make much difference, the rings slide around in their grooves as soon as the engine starts running anyway.