hey guys. i just thought i would post a few questions on here to see if i maybe someone has had my problem and knows the solution. i was running a holley 390. i had it running pretty well, but heard great things about the edelbrock 500. so last week i bolted one on. right out of the box, the thing idled great and ran well. my problem is. when i step on it from a stop. it cuts out and if i hold the gas down it will just die. the other problem is when i go from wot to light throttle i start getting poping. i got steping on it bog a little better by adjusting the pump shot and a rod. richening up the power mode. but still not great. i made a bunch of rod/jet changes according to the edelbrock manual with little to no effect on the problem areas. so i went to an extreme. i jetted it lean. still had the problems, but at least. my plugs changed color. then i jettet it rich. and my plugs turned completely black. this may sound wierd. but it made me feel good to do something to the carb and get a result that i could see. haha. so now all my plugs are probably fouled and i should get new ones. when i got home today i put the carb back to stock settings and drove it around. if i just put around its fine, but still has the original problems. the plugs cleaned up a bit, but i will still get new ones. i guess the next thing to do would be a wideband gauge. its just kind of frustating i guess. i could have spent the money from this carb on a wideband and just dialed in the holley. but i thought the edelbrock would be more street friendly since i have been doin 500 mile roadtrips. here are my build specs.
225 bored .060 over
clifford headers
offenhauser intake
edelbrock 500 avs
stock head
12* initial timing
i know i need to up the compression, hopefully i can get that done soon. i just hate to have the car down when weather is good.

thanks for any help

-aaron-

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it's not only good. it's good enough.

Well now my build is almost same same as yours with exception of Clifford intake and what I do know is...Until we do some head work it's still to durn much carb.I tried the Holley route and finally did the 'out of the box' Eddy and it runs just fine,sort of. I went to orange springs(I think)and just left it alone after that,it stumbles at higher RPMs but I don't do any WOTs except on the rare passing situation.I've got a super6 setup to replace it with and a motor in the shop to be 'built' that will take the 4bbl,just to busy(lazy)to get back at it.Until then if I drive it kinda normal it runs fine and the NGKs have been in for over a year and doing fine so best I can say is,drive it sedately till you build more motor

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83 B-150 slant 6,4 speed. 79 B-300 360 pathfinder 4x4. 74 W-300 318 4x4 git-r-done 80 B-100 sl6,4speed

slantscamp,

This carburetor is just too big for a stock (no head work, or warmed up cam) slant. You are not getting enough vacuum signal off idle, in other words not enough air flow at low rpm to atomize the fuel sufficiently creating a lean condition & bog.

I have a 390 Holley and understand your tuning frustrations, but that carburetor is a bit too big for my application with a ported and shaved head, race cam as well. But I march on with it because it looks cool, sounds cool, and it is mounted in a summer toy that dose nothing more than absorb car wax. If I had any sense, I would dump both 390 & high rpm cam for a torque grind, and a nice two barrel, loose the duals and head banger turbo mufflers and most likely pick up five more mpg, more usable power at highway speeds… But why??? Might as well paint that car beige and slap a Toyota badge on its nose while I’m at it…

From what I have gathered from reading about this stuff from Josh, both on this site, and other places, the higher the air velocity through the venturi, the easer it is to tune a carburetor. There are several was to accomplish this if you can think of your engine as an air pump. Larger valves, higher compression, more displacement, and a different cam, and a higher red line will enable an engine to pump more air per unit of time... CFM

What you did was make a bigger hole with that 500, than your 390 had, so air velocity dropped across the full rpm range in comparison.

This is why the super six two barrel configuration works so well. It is a smaller carburetor that better matches air flow requirements of a stock 225 cu inch engine at red line.

Now if you had a slant that could crank to 8000 rpm & idled at 2000 rpm, that 500 cfm unit would be just the ticket. Maybe a 600…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I have never seen the Offy intake for a slant but assume the runners all come together into a open type plenum and allow each cylinder to "see" the entire carb. What is needed is a dual plane type intake where each cyl can only draw from one half of the carb (one primary and one secondary). This effectively makes your 500 edel a 250 cfm carb which should be about right for the slant.

the offenhauser has the 4 holes on the intake. but i guess that just means i will have to look into doing this spare head i have laying around.

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it's not only good. it's good enough.

Adjust the secondary spring on the AVS to keep the secondary closed longer. For starters, adjust them for the latest opening possible. That should help quite a bit.

Once you get more compression in it, you should be able to relax that adjustment a bit.

CJ

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Part of Tyrde-Browne Racing

thanks guys. so i have been reading up on here about milling the head. it looks like its better to deck the block more than milling the head. but my motor is in the car with a fresh build and i dont want to pull it. i have a spare head. and im trying to have as little downtime as possible. i figure i can pull my current head, measure how far down the piston is. then throw it back together so i can still attend carshows and cruises. then have the new head milled accrdingly. sooo. heres the big question. what can i accomplish by just milling the head? i know this depends on how far the pistons are down the hole. but also, what cam would i benefit from more. when i originally built my car, i put in a comp cam. good for 800-4500 rpm. its nice for cruising around. but i have been going to the track and pretty much floor it everywhere i go. i dont want to cruise anymore. i want to match the cam to whatever compression ratio i can achieve. oh and i figured larger valves and porting would also be a good idea since we are doing the head anyway.

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it's not only good. it's good enough.

I have one of these on my 225. Current build:

8.75cr
Ported big valve head
Dutra Duals to a Y pipe with 2.5" exhaust dumping by the rear axle.
Offy manifold
1" spacer
Erson cam
10* initial, 30* total
3.55 gears
15" of vacuum at idle.

This carb is perfect out of the box with good throttle response and WOT. I am very happy with this carb.

The only problem is a slight surge around 1200 rpm. swapping metering springs and doing the mixture rod shuffle hasn't fix that problem yet. I most likely will need go off the chart to fix the problem, I have downloaded several spreed sheets that have all the combinations of jets/rods available. Using the Edelbrock charts, 2 steps richer fixes the problem, but runs rich overall, one step dosen't, so somewhere in between is the magic combination.

What metering springs are you using? Go stiffer.

Earlier tip in of the enrichment circuit. Generally, the base jetting will be the ticket. Sounds like a lean surge, but not across the entire operating range. Look to enrichment for that.

If that still doesn't do it, see if you can find Fopar's listing of jets rods and springs. You might need to change the step for enrichment, but not the cruise diameter. He has a lot of the combinations.

CJ:

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Part of Tyrde-Browne Racing

After I reassembled the engine, and took it for a drive, the surge had gone away. It runs quite nicely now.

The avs is a close as you can get to a spread bore while still using the standard Holley bolt pattern. The primaries are roughly the same size as the BBD, with the added advantage of not being worn out and calibrated for today's blends of fuels.

Since there is a problem with the Holley 390 and a similar problem with the Edelbrock, the problem may not be with the carbs, but with the surrounding sub systems.