high impact

iTrader: (5)

I am preparing to assemble my forged bottom end ls1 with 6398x3903 wiseco pistons, callies 6.125 rods and stock crank. The block has been honed to fit the pistons and according to the machinist everything is ready for assembly.

My first question, what are the best rings to use for nitrous and boost with these pistons? I plan to hit it with a 200-300 shot for a couple years then swap out heads and boost it later. I am reading a lot on here about total seal and wiseco gfx rings. It appears I need a steel top ring.

My second question is, what are the best ring gaps for my intended use? I am finding some conflicting information. My machinist is telling me to gap top .022 and second .016 but I am seeing on the boards recommendations top .019 and second .021. There seems to be quite a contrast between recommendations.

One last thing, how do I figure out static compression ratio? My pistons mock up .003-.004 under the deck and the machinist took .010 off my 241 heads. Is there a formula I can use to determine compression ratio and how much can we safely mill these heads?

Thanks!!!

A.R. Shale Targa

iTrader: (2)

I milled my heads .030" but I'm still using the factory flat-tops and a small cam. Plenty on here have milled .050-.060 in non boost, fly cut applications.
In your situation I'm guessing with 3cc valve reliefs and GM gaskets you're probably only at 9.8:1 but a .040" Cometic could get that up to 10.2ish.
I'd run the Speed Pro Hell Fire ring set for the spray now and boost later.
You'll definitely want to run more gap on the secondary ring to reduce inter-ring pressure which causes flutter and unseats the primary ring tension sooner in the power stroke. This is one reason why dry sump engines and wet sump drag engines with air pumps benefit so much from reducing crankcase pressure which promotes better ring-seal.
If you are serious about spraying a 300 shot then I'd put the primary gap at .024" and the secondary at .026". You'll sacrifice just a few ponies on NA with them on the loose side but you'll wreck a bunch of **** if they're on the tight side.

high impact

iTrader: (5)

Yes 3cc valve reliefs and was planning on cometic. I thought factory pistons are much deeper in the hole, Like .020 - .030? So I was assuming I gained compression as compared to my factory pistons. Isn't 10 to 1 factory? I want at least 11.5 to 1 so I will find another machinist if I need to. Yes, I am serious about spraying 300 but of course conditional with good tuning and I will start out spraying 100 first and step up as my tuning allows. I am also spraying on a progressive.

I thought the ring gaps didn't sound correct. My machinist is very well known around here for many years of reliable engine building and fantastic work but he obviously doesn't have the LS engine experience he claims. He has too many old school engines in the winners to even count so I know his work is top notch.

high impact

iTrader: (5)

Dang. Found a compression calculator and it appears I need to mill to at least 60cc to get up to 11.0 to 1

high impact

iTrader: (5)

Best I can tell with his cam at 10.5 static compression I end up very close to dynamic compression of 9.19 and 190 psi cranking compression. Is that good or can a little more and still run 93 octane with a decent amount of timing?

A.R. Shale Targa

iTrader: (2)

Factory pistons are zero CCs (no reliefs) and usually out of the hole .006-.008" to make
the compression 10.19. Your pistons have 3CC and are now down .010" from stock and
although you've milled your heads .010" the combustion chamber shape is still less than
the bore diameter so yoy lost comp.

high impact

iTrader: (5)

As I have stated my Wiseco pistons measure .003-.004. My machinist claims factory pistons are deeper in the hole. I don't disbelieve you, I am just recieving conflicting information, he may not know as much as claimed about ls engines, I brought my assembly to him completely torn down and I never measured where my deck height was before. If what you are telling me is true I need the blocked decked unless my dynamic compression is good. I figured that dynamic with my static at 10.4. What would I have to have my deck and heads milled down to reach my goals? Thanks for your help!

conan

iTrader: (5)

My total seal rings are gapped to .021 top ring on .023 second ring on my boosted 383ci.

high impact

iTrader: (5)

Here's the direction I think I am heading. I want to boost in a few years and plan to drop compression with a ls9 head gasket and 317 heads later. For now I will mill another .030-.040 off the 241 heads if I can get away with that much shaved and still fit my 102 intake. I will leave the pistons where they are instead of zero decking the block since it will hurt me down the road for boost. I will also run the thin cometic head gaskets. Where does that put my compression for my build now and then later when I switch to the 72 cc heads?

That's what I will do if the compression will work with my G5x3 cam now. I do plan to swap cam, heads and intake when I boost in a few years.

I also found the ring gap chart from wiseco and they show .005 for top ring x bore size and .0055 for second ring. That puts me at .019 and .021. I think I will run the bigger gaps like you recommend - it seems larger gaps aren't hurting anyone but too small a gap kills engines.

Does this seem like a solid approach? Thanks for dealing with my rookie questions!!!

conan

iTrader: (5)

This is just my opinion but I would get a set of 5.3L heads and leave them un-milled. You want the decks to be as thick as possible with that much go gas, and compression. The thinner the deck of the head, the better chance you have of lifting the heads on hard pulls.

What kind of budget are you working with for heads ?

The 706 heads have a 61cc combustion chamber as they sit. If your $$$ allows you get get them P/P and bigger valves to help them flow a bit better.

I get 10.8:1 compression with the 61cc heads, .040 / 3.910 cometic gaskets. That with a 200+ shot will be enough to get in trouble.

trw427ssrs

Here's what Total Seal recommends.

...................................Fuel........... .....Top Ring.............Second Ring
Nitrous 150HP-350HP....Gas, Alky, E85....Bore X .0065"........Bore x .0065"

Oil Ring
Min .015"

Which is .025 top and .025 second.

high impact

iTrader: (5)

Already committed to my current heads until I boost. Now I just to determine how much to mill for a compression ratio that works well. I guess if I cut back on compression a little for n/a I may be able to keep a little timing in the tune and make up for that little loss of compression on the juice. I wish my machinist would have said something sooner, I told him I wanted a minimum of 11.0 to 11.5 to 1 compression and he said, not a problem. ;-/

high impact

iTrader: (5)

After some additional research the machinist and I both determined .024 top ring gap and .030 second ring gap to be nitrous and boost friendly. We are currently figuring out how much more to mill heads (if we should) and if there is a thinner head gasket then the cometic .045. As stated above I am already committed on the heads, the valve job with undercut valves is already completed as well as a port and polish.

I have found cometic produces a 3.910 stainless steel head gasket in .027 compressed thickness. That gains me another .013 with no more milling. But will that gasket cause any sealing issues? My machinist is going to cc the heads to see exactly where we are at since the multi-angle valve job pushed the valves into the combustion chamber decreasing the chamber volume.

If I am figuring correctly; 3.905 bore, 3.622 stroke, 64.5 combustion chamber, 3.0 valve relief, 3.910 bore .027 thick gasket at .003 piston deck height should put me right at 10.69 to 1. That would work if it is correct.

Almost there!