Amatuer carb and tuning help!!!!

[quagmire]

Hi all! I finally got my Challenger running and am in the process of breaking it in and tuning it and I have a few problems.  I am new to carburetors, and have no experience until now with tuning them (and I suck at it.)  I am running an Edelbrock 800cfm Thunder AVS unit, and can't seem to get it dialed in.  I know, Holleys are better but I didn't know that when I bought it years ago and being a soon to be college grad in 3 weeks I cant afford another one for quite some time so I am kinda stuck for now. 
At idle (950 RPM) only it seems like it runs a lot rougher than it should.  I have tried setting the idle mixture screws, and it has helped a little but not too much.  I have checked for vacuum leaks and adjusted the timing to where it seems happiest but it still shakes quite a bit, especially in gear.  Another issue I have is when the fast idle is set it seems to slowly increase in RPM up to 2300 from 1500 after a few minutes of run time.  I have adjusted the choke but it didn't do anything.  Also, while tuning the off idle circuits I can't seem to get this carb to run rich.  Every time I jet it up I have pulled the plugs and they still look too lean.  The ground strap is light gray and the porcelain is chalk white.  I am about to jet it as rich as possible according to the fuel map that came in the instructions but I seriously doubt it will be enough.  The car just doesn't pull like it should, but I haven't really taken it over 4500 RPM yet either.  My engine combo is a 408 stroker small block with Edelbrock Performer RPM heads and cam, Air Gap intake, Dynomax ceramic headers and 2.5" dual exhaust with H-pipe, and an MSD Pro Billet Ready to Run distributor with a Blaster 3 coil.  I have the timing set to 17* initial and 38* total all in by 2400 RPM.  I am running vacuum advance too.  Plug gap is set to .045".  Behind it is a built 904 and an 8 3/4 with 3.91 gears and a Powertrax locker.  Any help will be mucho appreciated! - Dan

[dodge freak 2]

I don't know. I tried one and could not get the idle speed under 1200.
It ran good wide open but if I was like in 2nd or 3rd gear and floored it-I have a manual valve body in my "auto" trans-it stink. Did not have much power at all. Those primary's are big...should have gotten a 650.

Thing that got me is my holley 750 dp had more power at the same low rpm's.

Its going on E-bay this spring I believe.

[quagmire]

Mine will idle as low as I set it, it's just the motor gets pissy when I try to set it lower than 950 RPM.  I figured with it being a stroker the cam would actually be a bit undersized and idle pretty smooth and low.  It seems okay at low engine load and cruise, but when I get on it doesn't have the get up and go that it should.

[dodge freak 2]

Well I was lucky enough to have a good running Holley carb on before I switch over. I think the motor may have had too much advance at idle speed. I put a heavier spring in the dist. but only had one, it did not seem to help and my gas mileage wasn't any better so I gave up.

Your motor should idle good. If you had not have it running good with a diff. carb, it could be something other than a carb. The intake could be leaking...that cause many problems.

Your spark plug wire or wires might be bad. Timing could be off.

All that needs to be OK before the motor will run good, no matter what carb you have on.

Wish I could be more help.

[dodge freak 2]

Double check that each spark plug wire is were it should be. Crossing just 2 wires will make the motor shake bad-don't ask how I know.

My 800 was lean too, I drill the front jets out to .120 and still seem lean. But I was using a single plane intake. Those 800 like a dual plane intake, I believe. My motor was not shaking, just felt weak at low rpms. Did sound cool running though the gears. If I had no Holley I might have thought it was normal. Sure the 650 would have been better at lower speeds, thats why I got a 600, wasn't going to spend $200+ dollars thou on another eddy till I sell this one.

Then again, if I get a dual plane for it, the 800 might work out good.

[quagmire]

Plugs and wires are all new and routed properly, I set the timing to 17* initial and it didn't seem to like anything lower than that.  I checked for vacuum leaks and didn't find any.  It isn't a constant shaking, it is more intermittent.  Almost like it misses every now and then.  At idle in park the manifold vacuum sits around 11" and fluctuates up to 15" every once in a while, I will be doing a compression test later today but I don't think it is a mechanical problem since it doesn't seem to have a constant miss or shake.  I still don't understand why this carb always seems to be lean no matter how much I jet it up. 

[Chryco Psycho]

you need to increase the jetting size ,this requires removing the top of the car to get at them , most Eddy carbs are adjusted too lean from the factory , make sure you check the float level settings while you have the top off as well

[HP2]

Go to the Edelbrock web site and down load the technical manual on your carb. That will help immensly with details of operation and tuning. The AVS operates a little bit differently that your previous holley, so you want to understand the idle, off idle, power and cruise circuit functions before yous start tweaking everything. The great thing about the AFB/AVS carbs is you can adjust the WOT fuel curve independently of the part throttle cruise settings using differing combos of jets, rods and step up springs.

[quagmire]

Yeah, I am currently using the largest jets and smallest metering rods for the carb and it still too lean.  The floats are set properly too, I think I may have to drill out the jets to get it where it needs to be.  I read the tech manual and I think I understand it all, it just seems like no matter what I've done it still is lean.  I don't mind if the cruise is slightly lean that is probably better anyways, but the power mode is more or less what I am worried about.  I'd be pretty upset if I melted one of my new pistons.

[dodge freak 2]

You might want to E-bay it and get a plain Holley 750 3110.

I am going mess around with mine again come spring time but lucky have other carbs to put on if I can't work things out.

You need a good running carb. Holley themselfs sells carbs on E-bay, Holley Performance is their name. Carbs are customer returns, not worn out rebuilts. You get enough $$ for your carb to get a Holley 3110 from them, or close to it.

[dodge freak 2]

Holley Street Avenger series are great too, lately they had a bunch on it. Min price it goes for is $190 plus cheap shipping, they don't rip you off like some sellers.

[MEK-Dangerfield]

Just throwing this out there. I have a new Holley 800. It has no choke plate, and the choke housing has been milled away, so it HAS to flow more than 800CFM. I sent it out and had it powder-coated red, just for some bling. It ran like a scalded rat on my car(less than 100 miles), but I just didn't like going without a choke up here in the North. Those 5 minute warm-ups aren't for me.  I'll let it go cheaper than what I paid. Just PM me.


  Mike

[HP2]

BTW, you are running pure gasoline and not racing gas or some ethanol blend (10% or so) are you? Gas additives and mixtures all change the way you read plug colors.

[quagmire]

I believe it has been getting pure 93 octane with no ethanol.  I did a compression test today BTW, every cylinder had had 150 psi except for #7 with 130psi.  The throttle was opened and all plugs were pulled, but the engine was not fully warmed up.  I let it cool down for awhile before I pulled the plugs.  Oil didn't do much on number 7, so I guess it's time to pop off a valve cover.  Even 150psi seems low to me, but I don't know if it is a normal reading with a performance cam.   This motor should only have slightly less than 10:1 compression.  I think I will also start saving up for a new carb too. 

[quagmire]

I've been reading up on here and checking out features, but I still am not sure what carb to buy.  I was thinking about a 750cfm 4160 or a Proform 750cfm carb which I think is based on the double pumper design.  This car will be 90% street, so gas mileage while crappy would still be nice to have.  I've read that the double pumper is also a gas guzzling carb.  Also, do they make complete kits to tune Holley carbs?  Most of the kits I've seen only contain one kind of part, and I could spend hundreds buying all of those kits to tune everything.  Finally, is the 150psi compression numbers low for this engine?  Thanks again for all your help!