anyone know of any 12 bolt intakes dual plane for merlin rect. port heads?? i can only find single plane intakes and we're worried about idle rpm. engines wont like idleing under 1500 with a single plane. any input would greatly help.

They will idle OK with a single plane, it depends on all the other factors that are more important. Franly, depending on the cam and displacement of the engine, I would be more worried about the Merlin heads being to big to give you any throttle response or torque.

Depending on your displacement, The old GM dual plane that came on the carbed 502's is a pretty nice intake. I have had a lot of luck with them and judging from the amount of engines that I see from the premium builders with them installed. I would say that there are others that would agree.

I will try and find a part number.

Good luck with your build.

thank's. they had the 16 bolt performer rpm on them before but we just saw that they cut off a part of the ports with the gasket's you need to use. they had a great hole shot and midrange before. going to dyno this week we refreshend them and added more cam. my engine builder is worried about ide quality below 1500rpm with a single plane intake. they are 468's

You should be using an oval port head anyway.

No reason to use a square on such a little engine unless it is blown or NOS, or 650lif cam or something outrageous like that.

Switch to the oval merlins and an air gap intake and watch the majic numbers go way up.

Good luck with your build and share some numbers with us.

thank's i will let you know hopefully in a week or 2. i allready had the heads on last time we did them and there fine so we reused them. we just noticed yesterday the intake's. merlin used to make a 12 bolt dual plane intake but no longer does.

my dart works fine on a merlin head 509 622lift 114 lobe center. idles at 700 to 800 in nu, 600 in gear

It's because it has a big cam.

Can I ask what kind of carb you are using?

4150 flange or dominator

how long can you idle for? we have alot of no-wake zones here on the chain and my builder say's they won't like idleing at 900-1000 rpm with single plane intake on the rect.port heads. this is giving me a headache....or an ulcer. he say's he's seen it enough on the dyno's that the rect.ports don't like idleing at 1000rpm for long with big cams they will load up , snrot, cough, you get my drift. i gotta go with what he think's, i think.

This is what I just bolted to my merlin heads. It use to be a popular choice in B-class when it was restricted to dual-plane intakes. Using an oval port intake on the rectangle port heads might also keep the air velocities up and make a little more TQ also this dual plane will pull power in the higher RPM's.

http://www.holley.com/8018.asp
http://www.holley.com/8019.asp

that's what i just got , the rect. port. did you bolt on a oval port man. to rect. heads?? i had perf.rpms on them but there looking nasty now and they weren't realy right any way.(16 bolt patern) they work but cut off the ports a little.