Edelbrock Air Gap on Magnum 318 Problems

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SheSaid said:
I agree with the others, I doubt there is a problem with your intake. The pro you talked to must not have much experience with small block Mopar. If the Air Gap is only good for 380 ci strokers then about half the 340's at the Mopar Nats must be using the wrong intake. They work really well. I am trying to rebuild a 340 now and trying to find a used Eddie Air Gap is thin pickings. People really like them and never take them off their car.
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I got all the bits I'll need to make it work if it's possible...LOL I have way too much money in this carb setup.
 
Because it's a stick car, it's going to be much more sensitive to problems because the convertor isn't helping take the "edge" off any tuning issues. IMO, the 650HP is too much for the current combination. Maybe a little more gear would help it, but my impression is with the clutch engaged there's just not enough airflow at low speed. So you can mess with the accelerator pump circuits and power valves to try and get the stumble out. Or try a smaller carb. Regardless of the eventual carb choice (or EFI), some tuning is necessary.
 
this:
Ignition is stock Mopar electronic tuned to run 16 degrees initial timing and then 31 degrees at idle with vacuum hooked duirectly to the intake manifold. Timing past 3k rpm is set to max out at 34 degrees using a timing plate from FBO.
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i know someone who is using a summit distributor/orange box package. similar issue. once engine is all warmed up it stalls when coming to a stop sign (auto trans).

i highly recommend using the mopar kit (dist + orange box) which is $200, cheap as far as upgrades go... less problems. and the vacuum advance works properly, so when you are at idle it runs, and when you step on it the vacuum advance releases properly, but still gives you an extra 14 degrees of advance or so at idle.

if the vacuum lines are not attached properly, or a hose is leaking, or the distributor is a cheapy, your advance will be way retarded at idle. it's gonna stumble when you step on it.

this doesnt matter so much for race-only cars, because you will have the rpms up. on a street car you need the vacuum advance working properly, because you are not going to keep your rpms up at every stopsign.

also holley carbs have a specific port for distributor advance. i'm not sure about the 650 HP model that you have, but i think it does have a "timed spark port". your vacuum hose from the dist should be attached there
 
I think lookin at the intake is way over thinking. Sounds like a lean condition right off the base of the pump travel. There's nothing magical goin on, IMO. It's just a normal malfunction I'm sure will be easily overcome with the right repair.
 
try red pump cams then and dont forget to adjust the accelerator lever bolt to .015 gap between lever and bolt @wide open,full depression.


make sure u have the right power valve as well, like 2'' below what vacuum at idle is w/manual trans.

what was stock jetting, 67 primary?
 
SheSaid said:
I agree with the others, I doubt there is a problem with your intake. The pro you talked to must not have much experience with small block Mopar. If the Air Gap is only good for 380 ci strokers then about half the 340's at the Mopar Nats must be using the wrong intake. They work really well. I am trying to rebuild a 340 now and trying to find a used Eddie Air Gap is thin pickings. People really like them and never take them off their car.
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Lol...expert advise blames the air gap intake huh? Edelbrock musta got it wrong..geez. Theres only about a billion of those intakes in use today on 318's..

Forget the intake. Either fuel or timing,or both...
 
1wild&crazyguy said:
try red pump cams then and dont forget to adjust the accelerator lever bolt to .015 gap between lever and bolt @wide open,full depression.


make sure u have the right power valve as well, like 2'' below what vacuum at idle is w/manual trans.

what was stock jetting, 67 primary?
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Stock primary jetting was 69 with 75 secondary. I should have the pmp tuning kit this week. I'm hoping to get it running right so I can drive it some this summer.

I installed a new detroit locker last winter and I need to introduce it to the local Chevy guys.
 
needsaresto said:
Lol...expert advise blames the air gap intake huh? Edelbrock musta got it wrong..geez. Theres only about a billion of those intakes in use today on 318's..

Forget the intake. Either fuel or timing,or both...
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Thank you, I'm thinking his expert advice is a little too expert for me. Then again, we'll see when I get all the different nozzles and cams.
 
StrokerScamp said:
I think lookin at the intake is way over thinking. Sounds like a lean condition right off the base of the pump travel. There's nothing magical goin on, IMO. It's just a normal malfunction I'm sure will be easily overcome with the right repair.
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Thanks for the encouragement, I have been so frustrated with this setup. I'll work on it until it beats me and then leave it be for a month or so. I'm determined to get it working smoothly. I love driving this thing.
 
Are we talking about giving it light throttle off idle or light cruise, or mashing the pedal to the floor from idle or light cruise? Which situation does the bog you're describing take place?



kennygene said:
I have changed the squirters but I think I went too big since I only had one bigger in my cabinet. I may order a squirter tuning kit and see if I can get it to work better. I tried a 1 inch four hole spacer which was supposed to help with my problem - (velocity) but it didn't seem to help which points me back to the squirters or/and pump cam.
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What makes you think you went too big? Did it run differently? How was it different? Having too much of a shot (unless it's way too much) will usually just make it seem a little lazy, but won't jerk or bog like if it's lean.


As for pump cams, this graph should help you understand how each cam performs.

Holley20PumCams.gif
 
Its not the intake. If so why dose MOPAR use Magnum heads 94-01 on 318 and 360 there the same head! Even the same intake just the 318 gets a little less fuel but both the same so bet the carb is the problem to much fuel.......
 
..a heated plenum vaporizes the pump squirt and without it you may be making a temporary lean condition even leaner.
..many will disagree but i'm not convinced the airgap style intake is the best intake for a street application.
 
Make sure your accelerator pump from the primaries as immediately squirting fuel. If this adjustment is not correct you will lean it out from a split second or two until it does pump fuel out. It's an easy check even with out the engine running, grab the throttle lever look down into the carbs primaries and slowly move it like you would if you were driving. the tiniest move you should see gas immediately! if not you need to adjust the pump set screw "usually by reversing the nut" and try again. You can do this with engine running as well and make adjustments to it that way you can tell if it is improving or not. If this doe not make any improvements you might want to look and the accel/pump cam the actuates the accel pump. I have found for street use the ones that came on the carb from Holley work the best only change this out if you are running big cams and such. Hopefully this makes sense.
 
ir3333 said:
..a heated plenum vaporizes the pump squirt and without it you may be making a temporary lean condition even leaner.
..many will disagree but i'm not convinced the airgap style intake is the best intake for a street application.
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This makes no sence. The air gap intake does not heat the intake charge,in fact it does the opposite and cools the intake charge for more power. The stock intake has a heated plenum to warm the intake charge and increase fuel economy.
 
..a heated plenum vaporizes the pump squirt and " without it " (airgap) you may be making a lean condition even leaner.
the air will reach the cylinders quicker than the liquid i.e. temporary lean (lambda)
 
Another day and still no time... I'm planning to do more roof shingles tomorrow evening and Wednesday as well. I'll follow up on this thread as soon as I get it figured out. All parts are here, I just need time.
 
I know it's been a while but I finally got around to changing the pump cam last night. I'll be testing it this evening.
I'll try to keep this thread updated a little better from now on.
 
Wow, 6 months later! lol I understand what happens with the cars when you're building a house though. Time flies!

I'm actually experiencing a similar issue with a Holley 600 DP carb on a 340 with a Holley Strip Dominator Intake (Similar to your M1) and a 4-speed. I'm definitely interested in what you do to cure the stumble.

A 650 on a 318 is definitely a lot of carb, but tuning can always be done. Good luck!

-Mike
 
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