I currently have an Edelbrock RPM dual plane intake manifold I'm running on a 383 small block. My motor runs great! But I'm wondering if it would run better with something else? All I do with this thing is wide open throttle mud drags, I am affraid of single plane intakes though because of all the bad stories I hear about them.

Im running a .509/.528 220/230 cam and 210cc 2.08/1.75 AFR heads, and a 750cfm vaccumm secondary 4150 holley carb, would swapping to another manifold like an RPM air gap make me anymore noticable power over what I have now???? :confused:

you probably wont notice any difference in the rpm and rpm air gap. you might see a few hp on a dyno. but nothing you will feel in the seat of your pants. what bad stories have you heard about single plane intakes???

you probably wont notice any difference in the rpm and rpm air gap. you might see a few hp on a dyno. but nothing you will feel in the seat of your pants. what bad stories have you heard about single plane intakes???


Less power throughout the powerband. I've heard that unless you are running 6K+ all the time, they really dont benifit you any. Am I wrong?

they are for higher RPM use. it really depends on the individual intake. honestly with the 210 AFR's and 2.08 valves your running you might want to look at one. especially if you are only doing mud drags with this truck.

they are for higher RPM use. it really depends on the individual intake. honestly with the 210 AFR's and 2.08 valves your running you might want to look at one. especially if you are only doing mud drags with this truck.


With that small cam though? Sometimes mid-track the motor will pull down to about 3K rpm, that is like at the bottom end of the rated HP range for a single plane isnt it?

yeah. weiands are rated that low. edelbrocks are up around 36-3800. i assume your using an automatic? how much RPM do you loose when you shift?

yeah. weiands are rated that low. edelbrocks are up around 36-3800. i assume your using an automatic? how much RPM do you loose when you shift?



manual, and I dont shift at all, one gear all the way. It will pull down to about 3K mid track though.

just from bogging down? sounds to me like you need to get your rpms up. but i dont know actually. i have NO experience in any kind of mud drags.

rpm and rpm airgap are identical except for the airgap. both dual plane and the runners are identical. the only diff is the airgap MIGHT have a cooler air charge because of the airgap itself. you won't notice a difference. oh and BTW, you have way too much head for that motor.

tell us about the rest of the truck, trans, t-case, rearend ratios, tires etc. what class do you run?

I'd suggest you try a Holley 300-25 Strip Dominator, provided you're running up around 6500 RPM peak or so, and you do not drop below 3000 RPM. If you have room, try a 1" Super Sucker spacer.

You can even try the Super Sucker on the intake you have, first. Another thing you can do is cut your plenum divider down between 5/8" and 3/4", to improve higher RPM power without losing much, if any, below 3500 RPM.

Honestly, your heads are a little on the big side for a 383 (are you sure you have a 1.75 exhaust valve, those heads usually have a 1.6, or 1.625 exhaust valve) unless you have a lot of compression, and turn it up. And the cam is small enough to limit RPM and power as well.

You have something of a mismatch in your engine. Your heads area a bit big for a 383 (383 engines have become too common, and people seem to thing they work for everything) and your cam and intake are too small for your heads. Unless your 383 is a 400 block with a 350 crank (4.125" bore x 3.48" stroke), as opposed to the much more common 350 block and 400 crank. The most common 383 (4.00" bore x 3.75" stroke) is better suited for low RPM performance on the street in a heavy vehicle, or towing.

400 block with 350 crank is a 377 not a 383, completely different motor and application






get a vic jr and it will be more to your taste. if you were running an auto tranny i would say get a 3000-3500 stall converter but .............

Victor Jr for rpm

400 block with 350 crank is a 377 not a 383, completely different motor and application

The actual displacement depends on bore size. A 400 block with a 350 crank can be a 383, with the correct bore size (0.060, as a matter of fact). I've been building them both ways for 20 years. And people commonly call a 400 block with a 350 crank a 383.

The actual displacement depends on bore size. A 400 block with a 350 crank can be a 383, with the correct bore size (0.060, as a matter of fact). I've been building them both ways for 20 years. And people commonly call a 400 block with a 350 crank a 383.

ok, i had never heard of it going that way. thats a lot of over bore but its do able, you didnt mention that in your first post, you even posted it as 4.00 not 4.060, cool though. still a different motor and app.


isnt 350 stoke 3.48 not 3.75? cause you have the strokes listed as the same and 4.125 and 4.00 as the bore but youre calling them both 383's somethings not adding up.

shouldnt it read as 4.125x3.48 and 4.00x3.75 ?

yes. and not that many 400's can be bored out .060 over and last. and in any case a 400 with a 350 crank will not make the same power as a 350 with a 400 crank. two completely different animals. the 350 blocked 383 will make more torque than the 400 blocked 383 which will make more HP.

Holley list 9381 double pumper carb with annular boosters
dart single plane intake
solid roller cam, 260* duration at .050
GOOD springs, valvetrain.
MSD 6al, or 7al2
GOOD clutch, like a crowerglide. *(a cheapo centerforce will do, for a while, till you lose a foot.)
as much compression as you can stuff into it.

The above combination should be good for 550 honest hp before you start tweaking it. expect more if you can tune it correctly.

depending on your combination, a 350 crank in a 400 block will make as much hp as a 400 crank in a 400 block. y ou might have to figure different camshafts and compression into it...It will not however, make as much torque.

generally, people say that a longer stroke crank gives you more torque, which gives you more power. This is true, to a point. the longer stroke gives you more piston speed with less rpm. If you figure out how to get your piston speed to the same as a guy with a longer stroke, you can make the same power. all it takes is RPM.

Piston speed with a 3.48 stroke crank at 6500 rpm =3770 feet per second

Piston speed with a 3.75 stroke crank at 6500 rpm = 4062 feet per second

Piston speed with a 3.48 stroke crank at 8700 rpm = 5046 feet per second.

in my eyes, the more rpm with the shorter stroke crank will make more power because it has more piston speed. but only if you have enough duration at .050 to get the air in there.... and it takes at least 260* at .050 to make that rpm happen.


and just so you guys figure it out how to determine cubic inches of displacement, one of the formulas is bore x bore x stroke x # of cylinders x .7854 .
you can have a 383 with both combinations. theres more than one way to skin a cat,

rpm and rpm airgap are identical except for the airgap. both dual plane and the runners are identical. the only diff is the airgap MIGHT have a cooler air charge because of the airgap itself. you won't notice a difference. oh and BTW, you have way too much head for that motor.




at 12:1 compression? I just got the heads, one piece of the puzzle at a time. I dont have the motor back together yet, just wondered if I should just get a new manifold before I put it back together or just see how it runs with the RPM first.

tell us about the rest of the truck, trans, t-case, rearend ratios, tires etc. what class do you run?



Class I hopefully, if it pulls vacuum when I get it back together, class II is'nt out of the question either if its hopefully fast enough with the cam thats in it now. If it starts winning class I races I'll probably get a different cam that works better and move to class II.

I would go with a victor jr. And it will pull from lower because the RPM range is for a 350. A 383 will lower its operating ranges some. You do have a lot of head, but with your comp it can work. I would invest in a bigger cam, something around .55 lift single pattern cause the exhaust on those heads flows well. If your crank and rods can take it I would try winding it a little tighter with a bigger cam. What is the highest RPM you see in a run and what is the average? I would tune the motor for the average, but with those heads on a built 383 with a good single plane and a bigger cam you could probley get 550hp. The RPM is limiting your HP. Also what size headers are you running? I would run 1 3/4 primaries with a 3" collector and a good X pipe to balance the cylinders. Your motor sounds simular to some of the dirt track motors I have built. With the right tune on race fuel we have put out 600+ hp on the dyno with these, but its at 7200 RPM.

Get the dart. Spend the money on the right parts the first time.

The Dart is probley the best intake you can get. Really good flow with a good runner that isn't huge, but it is pretty big. If you got the money go with the dart. And if you want to run Class I put a cam in it with a wider LSA so you will pull more vacum, but it will raise you actuall comp. What is you cylinder pressure?

I would go with a victor jr. And it will pull from lower because the RPM range is for a 350. A 383 will lower its operating ranges some. You do have a lot of head, but with your comp it can work. I would invest in a bigger cam, something around .55 lift single pattern cause the exhaust on those heads flows well. If your crank and rods can take it I would try winding it a little tighter with a bigger cam. What is the highest RPM you see in a run and what is the average? I would tune the motor for the average, but with those heads on a built 383 with a good single plane and a bigger cam you could probley get 550hp. The RPM is limiting your HP. Also what size headers are you running? I would run 1 3/4 primaries with a 3" collector and a good X pipe to balance the cylinders. Your motor sounds simular to some of the dirt track motors I have built. With the right tune on race fuel we have put out 600+ hp on the dyno with these, but its at 7200 RPM.




I still have 1" and 5/8ths headers, like I said, one part at a time ;) but I do have an x pipe. The cam/springs in it now let it wrap up to right at 7000 wot, thats usually what I take off at. I was hoping with the higher compression would give me just a little more power and mabey not lug down so low mid track. I'm also worried that pulling vacuum at idle (15" requirement) with a single plane might be a problem, but I dont really know what vac it will pull now that I increased the compression :confused: It would pull right at 15" before with 10.5:1, now at 12:1? I guess I'll know in about a week ;)

I still have 1" and 5/8ths headers, like I said, one part at a time ;) but I do have an x pipe. The cam/springs in it now let it wrap up to right at 7000 wot, thats usually what I take off at. I was hoping with the higher compression would give me just a little more power and mabey not lug down so low mid track. I'm also worried that pulling vacuum at idle (15" requirement) with a single plane might be a problem, but I dont really know what vac it will pull now that I increased the compression :confused: It would pull right at 15" before with 10.5:1, now at 12:1? I guess I'll know in about a week ;)

if anything, you should be pulling more vacuum. single plane or dual plane, the intake doesnt matter for vacuum. its the cam timing and valve opening events that do that.

A friend of mine has a 557 inch ford that pulls 22 in/hg at an idle with a solid roller cam. .700 lift, 260-ish duration at .050.

Yea, that cam you got is one thing whats holding you back. You either go hi-end or low end. That cam's great for low end torque but not for the high end band. Sounds like everything else in your rig is great for the high end rmp range. The gear ratio on your axles is also a big drag if that's not optimal for what you're trying to accomplish. I may have missed it, but I didn't see an answer on that on this thread.

I would stick with the RPM over Vic Jr for your combo. When you are in the middle of the track and it lugs down at around 3000rpm you will be down probably 25-30 fptq. You will notice that with heavy mud ladden tires.

I would stick with the RPM over Vic Jr for your combo. When you are in the middle of the track and it lugs down at around 3000rpm you will be down probably 25-30 fptq. You will notice that with heavy mud ladden tires.

honestly, the RPM will make less power and torque than the single plane. its such a restriction on the top end that its not really worth it in the short run. Ask some of the top drag racers and engine builders in the country what they think about dual planes vs single planes... they will tell you that the single plane is worth more ftlbs and hp than a dual plane. not just at the top of the RPM range either. besides, with the right components, you wont be bogging down to 3000 rpm anywhere on the track.

with a matched combination, such as I previously posted, you wont have to worry about having a dual plane. you wont want one. youre not idling on rocks here. as for the tires being mud laden, if you cant clean them out, then you need to gear accordingly.

I just put the top end together for a local racer. He used dart 215cc Iron eagle heads, with 64cc chambers, about 10.7:1 compression, and a cam just a bit bigger than the one being used by the original poster on this thread *(230/236* @.050, ..488/.510 lift). He leaves the line at 6800 on the rev limiter with a 4 speed. on a 200 foot long track with 3.08 gears, 3rd gear(sm465), low range with a np208 transfer case, hes already won 1st place at one venue once this year. and he stays on the rev limiter the whole 200 feet. At the second race, he got a bit trigger happy and jumped the light and disqualified himself. he runs a single plane.

this is a 1986 chevy shortbed half ton with 10 bolt axles... which surprisingly, havent broken yet. for tires, he runs 35x15.50x15 TSL swampers. Awesome tire speed. around 5500 lbs.

Hes going to a th400 to keep from taking his feet off, though, so he will need a 4500 rpm converter to get it moving.

I just ordered a Super Vr.

Guess I'll know for sure soon enough ;)

RESULTS!!


:eek: Eye opening to say the least! I got it put on last night finally. Power increase was unbelieveable and I lost almost no low end. Definately worth it ;) and really woke the motor up.

gooood.


Glad to hear it.