I have a LT1 block laying around I want to turn into a nitrous motor that can handle a 250 shot safely, put down 360-370RWHP NA, be 100% streetable, and use stock LT1 head castings.

What route do you guys think I should go, and what parts would you get?

 

I am buying an LE3/355 as we speak. Its a nitrous motor even though I wont be spraying it for a while. The builder said it could handle a 200+ shot without a problem whatsoever. The internals are totally forged with Probe nitrous pistons to complete the package. N/A HP will be in the 410-430 range at the wheels according to Lloyd's website.

So I guess this would be something you could consider... just make sure the internals are done right and you can spray the **** out of it.

 

I want to be able to spray a 250 NX with the ocasional 300.

Is a 4 bolt main a must?

 

Not sure if it is a must - however the LT1 block I have being built is indeed a 4-bolt (vette motor). Better safe than sorry.

The engine builder said if he kept this he was going to go as high as a 300shot, again, I am no nitrous expert...but FWIW, forged internals, 4-bolt mains are something I'd look for when spraying as high as you want to go.

 

Talk to your piston manufacture and tell him what you plan to run nitrous wise and tell him/her what pistons you have, they may want you to set alittle more piston to wall clearence for all that added heat from the nitrous that will make the piston expand more. I ran into that issue with my setup, I think we ewre going to do .004" piston to wall clearence, as per the spec sheet. I called JE and told them what I plan to do now and in the future, and he said to shoot it to .006-.007 to be safe. Just see what they say with that regard, cant hurt.

 

If you plan to run that much nitrous, get "nitrous" pistons. They'll have a thicker crown, the ring pack will be dropped down to thicken the top land and get the rings farther away from the combustion. You may want upper oilers. Dropping the ring pack may entail ring rails, depending on rod length. Your ring end gap and p-t-w clearance have to reflect the increased temperatures, as mentioned above. I would agree that 4-bolt mains are a good idea on an engine approaching 700 flywheel HP. A straight factory 4-bolt (with upgraded caps) or a splayed 4-bolt conversion will work.

 

^^said very well^^

fyi: my motor has Probe Nitrous pistons, again something to look into when considering a nitrous-build

 

I've got a parts list on my "Mods" link. Spraying 300HP on a 500HP NA motor. But the crank and rods are probably overkill, because they were selected to stand up to 1,000HP.

 

What cubic should I go for? Some say stay 350, others say 355, and yet others say 381.

 

Don't scrimp on the rods either if you plan to hit it with one stage that big. Get decent rods and upgrade the bolts...or at least make sure they are up to your needs.

Another thing to look at is a nitrous cam. Spec one out or purchase one that best serves your purpose. You'll want some good exhaust duration and a higher numeric LSA (Edit from Overlap) than a NA cam. Someone will probably come in here and argue this idea, but it is the tried and true concept with ntirous cams. The larger the shot, the more will get sucked out the exhaust when both valves are open.

You also need to consider head gaskets and bolts vs. studs. Big shots can be rough on head gaskets. Too much timing can pop a head gasket with ease. There are many options for head gaskets, find one that best suits your needs as some are hard to seal (copper) and others are easier to pop.

Head bolts vs. head studs are another thing to consider. If you run studs it's not a fun job to switch gaskets because pulling the heads in the car is no easy task if at all possible. Bolts won't hold as well as studs though.

 

You have a real nice setup.

What did your shortblock cost you to build?

My plans were to leave the line with a 125 shot, then bring in another 125 shot higher in the RPM band.

 

Depends on how much you want to spend. Obviously a 381 or 383 is gonna be a lot more money than a 350 or 355.

 

Which has the best aftermarket? I'm looking for the best price/performance ratio.

 

Did you really mean to say that? Higher overlap means you lose more nitrous out the exhaust valve before it closes. You want a higher numeric lobe separation angle to reduce the overlap, and reduce the nitrous loss.

 

That's what I get for not re-reading my posts. I meant LSA not overlap.