Single or Dual plane intake manifold?
10-10-2003, 06:02 PM
#21
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Location: Spicewood, Texas USA
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Just to throw some more data into the mix. I had a 454 that was built to about 525 HP. Merlin rectangle heads, Crane 731 cam, 750 Holley and Dart intake. It ran really good on top end but I always felt it was too sluggish below 4000 RPM. After running it about 200 hours I switched out to an Edelbrock RPM air gap intake. That thing really came alive on the low end and lost nothing on top end, at least up to 5400 RPM. It also smoothed the idle out. Based on that personal experience I've been using that intake on all of my recreational marine engines. I'm sure the single planes make more power at higher RPMs and in more radical setups though, but if you have to live with it every day at lower speeds it's hard to beat the Edelbrock Air Gap intake.
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1983ScarabIII (08-28-2023), KAAMA (08-27-2023)
10-11-2003, 05:39 PM
#24
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Nothing like the old single plane/dual plane question to start an argument!
bobl: You hit the nail on the head. Single planes do have certain visual appeal though.
Vortech suggests that single planes are better for blowthrough carb applications, I'm not sure why. We require the use of a single plane intake with the Rtech box, but that's because the carb is mounted sideways.
bobl: You hit the nail on the head. Single planes do have certain visual appeal though.
Vortech suggests that single planes are better for blowthrough carb applications, I'm not sure why. We require the use of a single plane intake with the Rtech box, but that's because the carb is mounted sideways.
10-11-2003, 07:01 PM
#26
Well I know that a lot of guys here are strong belivers of the air flow speed created by a dual plane but I have a single on my stock 454 and gained rpm's over the stock cast iorn unit. would I have gained from an aluminum dual? Mabey. I do run a dual on the BBC in my burb but I cut the center divider out. What do you think of that? Rag's
10-12-2003, 12:29 PM
#27
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Not really apples to apples
Went from 509 to 515, decreased quench to 30 thou, went from a air gap dual plane 950 holley to Merlin single plane w 850 demon and performance increased 3500 and up. All with a 741 cam. Merlin iron VR heads, 9.8:1 comp.
I felt w/ the airgap there was too much tq down low, (620@3500) in my 4600lb boat. With a heavy boat I would stick w/ the airgap.
Dan
Went from 509 to 515, decreased quench to 30 thou, went from a air gap dual plane 950 holley to Merlin single plane w 850 demon and performance increased 3500 and up. All with a 741 cam. Merlin iron VR heads, 9.8:1 comp.
I felt w/ the airgap there was too much tq down low, (620@3500) in my 4600lb boat. With a heavy boat I would stick w/ the airgap.
Dan
Last edited by DanB; 10-12-2003 at 12:32 PM.
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KAAMA (08-27-2023)
10-12-2003, 04:35 PM
#28
The way I see it is if you change to a dual plane manifold and it makes more power chances are there's a problem somewhere else. Over cammed or too big intake runners would be my first guess. The short runners on a dual plane are shorter than the short runners on a single plane. An intake manifold is a piece of plumbing to connect the runners to the carb, pretty crude. What makes it worse is trying to keep fuel atomized around the bends. A tunnel ram would be my first choice. Single plane second. my 02
Last edited by JimV; 10-14-2003 at 10:11 AM.
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Rookie (08-27-2023)
10-13-2003, 08:53 AM
#30
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Originally posted by TomR
For a 9:00 to1 502ci, 242/[email protected] dur. .610/.623lft, headers,mildly ported stock heads, 800cfm #9022 Holley. Which would be a better choice for intake, Dart (rectangular or oval port), Brodix, Merlin??
Seems as though I never run under 4500rpm!!
For a 9:00 to1 502ci, 242/[email protected] dur. .610/.623lft, headers,mildly ported stock heads, 800cfm #9022 Holley. Which would be a better choice for intake, Dart (rectangular or oval port), Brodix, Merlin??
Seems as though I never run under 4500rpm!!
Dennis is right, he is over-cammed for it being a 502 cu-in w/ only 9.0:1 compression. Use of this cam should have a minimum of a 540 with 10:1 or a 502 with 10.5:1 compression. I'm thinking a dual plane would help his performance by getting his BSFC numbers up. If it does help it also means he needs to get those cylinder pressures up. Bet that thing has a mean idle though.
Roby
