[Travis Q]

Here's what I would do, for whatever that's worth.

Give the block a good deburr. No need for anything terribly fancy, just clean up any flash and sharp stuff that could be a starting point for cracks, especially around the main webs.

I would give the block an extra little bit of piston to wall clearance. Call the piston mfg, and tell them what you're doing with it. A lot depends on what alloy the pistons are made of.

The piston ring end gaps need to be a little bit looser than a naturally aspirated engine. How much looser depends on your ring choice. What's the bore size? What piston ring pack is the piston set up for?

At this power level, bearing clearances should be close to whatever you would run with a NA engine.

I wouldn't worry too much about a block fill.

Good fasteners are always a good investment. I prefer head studs, regardless of power level, but if you can't swing that, at least use a good head bolt and main bolt.

500 hp should be no problem at all. At 10-12 psi, I would not be surprised at all with 600 hp or more.

[Squidward]

Thanks, Travis.

I want to use the stock windage tray. ARP makes main studs, with 200K yield strength, but no worky with windage tray. Milodon makes studs rated for 190k, but says it works with windage tray. Any big deal in the 10k difference?

I'll have to call Probe. They included specs that got looser as one stepped up from their street level pistons to their race pistons, but never had any setup differences for boost.

Concerning rings: Anything to stay away from? I've read in some threads where some people said "Stay away from moly", but I'm not sure if they were playing in a "bigger sandbox" than I will be playing in.

Thanks again!

[Squidward]

I checked with Probe's website and found some ring gap info. It had a formula for gap based on bore size. They also suggested adding .005 to those numbers for boosted apps.

Suggested piston clearances was .0025 minimum to .0065 max. They said minimum was OK for NO street motor, but go looser for boosted or race apps.

I guess I have to figure out how loose to go. .0040, maybe?

[Travis Q]

I wouldn't be at all afraid of the Milodon studs, I have not used them, but they are bound to be a great improvement over a stock bolt.

I would think .004-.005 would work just fine on piston clearance.

I have used a moly ring in some pretty high power stuff. I really wouldn't be afraid of it at all; a fair bit of the negative stuff you hear about moly comes from the early versions of the rings that had some issues. Then it gets repeated/regurgitated forever. Is it a 1/16" ring or a 5/64" ring? You definitely want to stay away from the stainless and tool steel rings, they are pretty hard on the cylinder bores.

I'm no engine builder, but hope this helps anyway.

[screamingchief]

Squid,the moly ring talk you mention is most likely in reference to the nitrous guys.

Anything over say 175 to 200 hp shot and it's not @ all uncommon for them to find it'll knock the moly coating off the face of the ring,and then you tend to lose ring seal,and oil + nitrous = very bad things.

Boost & nitrous do indeed share some traits,but from my understanding that is'nt one of them,nitrous applications often have a very high/quick initial "shock" to the engine in terms of cylinder pressure,and that can be hard on things like moly rings & headgaskets and such,where-as boost tends to be applied in a more "linear" fashion.

Though like a nitrous engine,I'd probably still shy away from low tension oil rings for an application like this.

One other thing I'd mention here is this,if you plan to use the Cometic headgaskets,be sure the machinist understands and can supply a proper RA finish to the decks & heads for those gaskets,as they have some specific recommendations for those MLS gaskets.

Good luck with this!

Bret P.

[Squidward]

Originally Posted by Travis Q

I wouldn't be at all afraid of the Milodon studs, I have not used them, but they are bound to be a great improvement over a stock bolt.

I would think .004-.005 would work just fine on piston clearance.

I have used a moly ring in some pretty high power stuff. I really wouldn't be afraid of it at all; a fair bit of the negative stuff you hear about moly comes from the early versions of the rings that had some issues. Then it gets repeated/regurgitated forever. Is it a 1/16" ring or a 5/64" ring? You definitely want to stay away from the stainless and tool steel rings, they are pretty hard on the cylinder bores.

I'm no engine builder, but hope this helps anyway.

I measured the ring lands, and came up with something like 1/16, 1/16, and 3/16.

I talked with the shop, and they were leaning toward .005-.006, but I told them that I didn't want to go straight for the upper end of the recommended clearance. I wanted .004-.005.

Does anyone have a brand and product line they would recommend?

And Bret - I haven't yet thought about head gaskets. I know that 350 options are limited, so I guess I have to look into that. I appreciate the heads up since I would hate to haul an engine back to the shop for putting the right finish on the deck.

[screamingchief]

As of now,the only decent/functional 350 headgasket choices are the Cometics,and the Innovative Seal (formerly ROL IIRC).

There have been some discussion about that in the street forum not too long ago,a search should bring up those threads.

All the other headgaskets are made for the larger bore engines,and thus have too much "dead space" around the top of the bores.

One of the main reasons some of us are looking at the 350 for a boost appl. is because the smaller bores should allow for slightly more headgasket material between the bores which hopefully may add some % of strength to a known weak spot in the larger bore applications,this would be especially important with regards to the center cylinders with the siamesed exhaust ports (3-5 & 4-6) as that's where pontiac headgaskets are most likely to fail.

HTH

Bret P.

[Squidward]

OK, thanks. I looked at the Cometic. Just over a bill - definitely not your run of the mill "Mr. Gasket" stuff.

I've searched for Total Seal rings, with 3.915 bore and 1/16-1/16-3/16 rings. Found a couple of places. Is it better to get something a tiny bit bigger and file back to the proper gap, or does ordering the exact size usually get ya in the ballpark with just a little bit of tweaking needed?