I have decided to use a performer air gap dual plane on another BBC engine that I am building for a friend of mine and he has N2O on board.
Most of the N2O people I have talked to say that that manifold is not a good choice due to poor distribution issues but I have used them with a 1 inch spacer under the plate and seen no issues with a 150 kit. Is this the biggest kit we should try and use with this intake(he has a 250 kit) or are we worried for nothing?

Thanks! graemlins/beers.gif

I have no experience with that intake but what I have heard is 200 is the max on a dual plane intake. I do know that from working on some SBF stuff, after you get past the 200 on a plate system things get a little funky with the plugs as the distribution is not very good on the SBF intakes. Some will run okay while the others are either way lean or I have to pry them out of the hole with a pliers(not good). But I would try sneaking up on the tuneup and see what the plugs look like after a pass. Seems kind of the hard way of doing things when for the same money you can get a single plane and not have the worries. Let me know what happens.

I agree with Flyboys. I would keep it in the 150-200 range MAX for the dual plane. If he really wants to use the 250 pills, then he should bite the bullet and get a single plane.

The distribution problems are real with the dual plane intakes, this doesn't count out the singles either, you will find racers pulling up ring lands and cupping the pistons with out bad plug readings. 250 is a decent shot and one of the biggest improvements you can make is in the ignition box, the MSD 7 has a built in firing timer that will control spark at the plugs to make it more efficent and safe. We have guys running 600 from the hit all season with no problems at the end of the day.

4mula-I thought the ring land/piston failures were from juicing up on cast or hyper pistons that are unable to deal with the increased presure levels. I have not had a failure yet with forged slugs.
All-What about the use of a 1 or 2 inch spacer plate? I would think that would help the distribution out.

Thanks. graemlins/beers.gif

Originally posted by 67johnny:
4mula-I thought the ring land/piston failures were from juicing up on cast or hyper pistons that are unable to deal with the increased presure levels. I have not had a failure yet with forged slugs.
All-What about the use of a 1 or 2 inch spacer plate? I would think that would help the distribution out.

Thanks. graemlins/beers.gif That is partcularly true of those pistons, yet we have had many failures where the ring lands have been pulled so high they hit the heads, and it's still all caused by distribution, the normal symptom of the chevy head design. Plates are notorious for bad distribution under any circumstances. Adding a plenum spacer may only cause the damage to slow down and make the shot just a little less than what you figured because of the time spent in that large plenum. Check your plucgs after each run and let the engine pull you down at the finish instead of cutting it off after the traps. get back fast and read your plugs. The best advice I can give to you beers.