[chiphead]

Well since my 433 stroker project is a bust I'm starting a thread for refreshing my 400. The engine is at the shop now getting checked out. Application is a street/strip 400 on pump gas in a Lemans.

What piston rings do you recommend with Ross pistons in a street/strip motor with a 150 shot? I think it uses the more modern ring pack with .060" compression rings.

What valve guides should I use in 670 heads with a HR cam?

What main bearings with N crank? Stay with the tri-metal 3/4 groove or is there something better? What about the newer aluminum bearings like LS engines use?

What rod bearings with BBC rod journals? tri-metal or aluminum?

What main and rod clearances? I'm thinking .00225" on mains and .002" on rods. That's slightly larger than the recommendation for .00075" per inch of journal diameter.

[gtofreek]

If you use nitrous, you don't want to run Moly rings. You will need either a steel gas nitride top ring, or a Hellfire ring, or some call them heat treated ductile iron ring.

I like the FM 113M main bearings with the 3/4 groove.

ACL makes a really nice performance rod bearing for the BB Chevy rods. That's what I would use.

Those main and rod clearances would work. I would keep those a minimum to be safe.

With the heads you can either have bronze guide liners installed, or full bronze 1/2" guides, whichever your machine shop is setup to do.

[chiphead]

OK so I've done a lot of reading. It appears that the problem with moly and nitrous is that the detonation inherent with nitrous use will fracture the moly off the ring. That appears to be what I've got, the coating is totally gone from the moly top rings that came out of this engine. Engine also shows signs of loss of oil control, which makes detonation worse. Go figure.

Does cylinder bore wear happen faster with a steel nitride top ring? What would be the downside of using a steel nitride top ring with a napier second ring?

Anybody got a torque plate I can borrow? Shop doesn't have one.

[gtofreek]

The thermal shock using nitrous is more the problem with the rings. Steel do not wear teh cylinders bad. They are fine, and definitely use a Napier second ring.

[steve25]

Does the cars fuel system have a near 50% reserve supply / volume wise ?
Even with a 150 shot that is the safe way to go and then with the normal backing down on the timing Moly will stay on Ring faces just fine!

[HWYSTR455]

All the previous 400 spray engines I've done always used the iron (hellfire) rings, and always gapped them on the bigger side. Never had an issue all the way to like a 300 shot.

Leave room for padding and to grow on the ring gaps. Spec the gap at double what you plan to run, it's a good safety margin.

With N2O, the engine is more resistant to det. The cooling effect and burn rate combats det.

As an example, the one iron head 400 I had was about 9.98 static CR, and when not spraying it, it was a struggle to keep it from det. Spray it and I could fully load it and not have even a hint of det.

Use good solenoids, and medical grade N2O. Make sure your fuel system is perfect. Maybe even run a separate fuel system for the N2O fuel sol, like a 1 or 2 gal tank on the core support with it's own pump, regulator, and filter, especially for any shots over 200.

.

[chiphead]

Any concern with the hellfires and bore wear in a street/strip application? What are hellfires made out of? They are a heat treated ductile iron ring?

Is gas nitride the same thing as "chrominum nitride" or is that a modern chrome ring? The ring pack on these pistons is 1/16, 1/16, 3/16. I measured the old rings. I've learned to keep all the old parts until the new engine is built, LOL.

I'm now schooled about nitrous ring gaps. I gapped the plasma moly rings .005" (top), .0055" (second), per inch for "street nitrous" per the speed-pro instructions. On teardown I had a little top ring butting in the DS cylinders. I've learned I need to go at least .006" top and .007" second on whatever I put back in. Basically a little less than the "drag nitrous" recommendations. Likely part of the issue was the block not being honed with a plate.

What was the consensus on the HR lifter ticking issue? What part number HR lifter do I want to use?

Do I want to have the machine shop do the oil galley mod described in that thread?

[chiphead]

Block Prep Questions:

How much does low speed oil pressure drop when drilling the .030" hole in the rear galley plug? Is it the same size plug that is recommended to be installed in the front galley locations?

What is the tap diameter and thread pitch used to tap those two galleys in the front? It's NPT not bolt thread, right?

Do I need to open or modify any of the factory cooling passages in the decks?

Do I need to modify the oiling passages in the lifter bosses for hyd roller lifters?

Anything else I need to do?

[steve25]

A .030" hole drains off no oil pressure.
All three plugs you ask about are 3/8 NPT, but the front plugs can not be standard depth / lenght as they will block off oil feed holes .
To deal with this you can cut Brass plugs shorter and then tap the passages deeper, or order shorter steel plugs from Grainger or the like!
A hardened steel plug used for the rear will be a bitch to drill unless you anneal it first, then you can drill it with a big bit untill you have .050" wall thickness left and then blow thru it with a .030" bit, or you can just use a aluminum plug and make it easy.

[gtofreek]

Yes, you will need to modify the lifter oil feed hole by lowering it 1/4".

[chiphead]

Is that a 3/8-18 NPT tap? What minor diameter hole is required? I've had shops be hesitant to drill and tap those in the past. If this one wont, I'll just do it.

Can I do the lifter boss mod with a dremel and a chainsaw stone? I understand .250" below the current hole, but how wide and deep does the groove need to be? What would be a good way to deburr afterwards?

Wasn't there a mod that involved opening up a deck coolant passage, or was that 389/421 only?

[chiphead]

Good news! Talked to the machine shop yesterday. The engine mags clean, no cracks. Cylinders are straight and will hone out. Forged pistons can be re-used and have .006" piston to wall clearance. Crank is good just needs a polish.

They said I didn't have to use a torque plate for a brush hone job, but I'm going to rent one anyway. They use diamond stones and I'm going to use a gas nitride ring pack.

Should I use standard or low tension oil rings with a napier second ring? Anybody got a PN for the correct set of gas nitride/napier rings for 4.155" bore and 1/16", 3/16" ring lands?

Is it worth having the piston skirts coated by Swain to reduce piston slap?

[chiphead]

So I'm at the point where I really need to pick rod bearings. Should I run the 743P or H bearing on a 400 crank with 2.20" rod journals and eagle rods?

[gtofreek]

If you're going to run it hard, I would get the "H" bearings. If it is an aftermarket crank, you need the "H" bearings. If it's just a street engine then the "P" bearings are fine, but since you are putting in BB Chevy rods, it sounds like you're planning on running it hard, so I would run the "H" bearings.

[Blued and Painted]

machine shop doesn't think torque plate is needed cause he does not have one. Don't know where the wives tail was started that pontiacs don't need plate honing because of head bolt placement.
All those super duper hard rings will have a hard time sealing an old bore.
How can a standard size race piston correctly fit a cleaned up old bore?
Sound like this guy really doesn't want to mess with a pontiac block. Pay the man and find another machine shop.
Just my opinion.

[chiphead]

Thanks for the answer on the rod bearings!! It's a nodular 3.75" stroke that was turned to 2.20" for a wider choice of rod bearings.

I rented a torque plate and had it drop shipped to them. They used it and shipped it back. Easy peezy, lemon squeezy. Honed it with diamond stones for nitrous rings. Equivalent to about 250-280 grit is what the guy said.

Next up: What nitrous Rings? Hellfires, or Total Seal AP steel rings, or Perfect Circle/Mahle Firepower?

I apologize for asking the same ring question a few times. I've tried to do my own research and the net is full (and I mean full) of guys that claim the hellfires wore the stock iron block out in 5-10K miles, or wouldn't seal.