Edelbrock carb problems

[Neil O]

Hi all, I have an Edelbrock 6oocfm carb on a Chevy 350. Th problem is that it starts and runs fine on tick over, also when on the loud pedal it works well, but when I'm just tickling along on a level throttle it spits and farts and judders.x( This is most noticable in 1st, 2nd and 3rd, and causes the slack in the diff to slap about.
When I had it emissions tested, we set to 3.3, since then I've wound the mixture screws out 1/4 turn ( on Repower's suggestion) no difference at all. I think there may be a 'gap' between the idle jet and the primary settings, causing a range where there is no fuel. When the engine was revved to 1500 rpm, the emissions dropped to next to nothing, but at 2000 rpm were healthy again. Even stood still and revving at 1500 rpm you can tell it's not right.
Is anyone aware of any tweeks I can do to iron out this problem?
Cheers,
Neil.:tu

[maxGD059]

Hmm Neil, fine tuning can be a bit of a pain can't it! Do you have the very useful Edelbrock manual? It comes with the carby & has a wealth of info in it. It sounds as though you need to change a rod that richens up the 'cruise mode', but looking at the reference Chart for your carb there are just loads of possible corrective options. You can get a calibration kit but after a while the fiddling just gets tedious. Mine is very close to being set up correctly but eventually I'm sure I'll end up on a rolling road to sort it correctly.
The other option is to email Edelbrock directly. They offer a very good helpline & replied in 48hrs when I tried them. You can find their site from any search engine as I did (but have now lost their address!)
Best of luck

Richard
(Hillclimb convert)

[Shaney23]

Hi Neil,

edelbrock@edelbrock.com

Shane

GD 351W

[graham]

Had exactly the same problem on my Holley on same manifold and engine. More fuel was required. Went up two jet sizes, up one size on power valve, went back 2 degrees on dizzy and went back to stock springs in dizzy as I think I also had two much advance.

Runs great now even though rolling road will be better. Fuel economy now crap (Great - must have been to lean before)

Graham

[Keith Wild]

Hi Neil,

I had exactly the same problem at the weekend and it was my own doing! We had planned a fairly long trip and in order to improve on fuel economy I fitted "weaker" metering rods in the carb and spent 300 miles with the car running like a pig.

Halfway through the trip I returned to the original rods and even went slightly richer and the car ran like a dream.

Real Steel do a calibration it for the carb which comes with a very useful book and numerous jets, springs, rods and stuff. Bit minty but worthwhile

Sod the fuel consumption

Keith

[roger]

Hi
Had exactly the same problem with an edelbrock on a RV8. I think the gap you mention is caused by crap in system.
Tried changing springs rods etc.-no difference so bought new gasket set stripped carb. blew out all ports/jets with airline,problem cured. Very easy to work on-gasket set about £7.50.
roger

[Neil O]

Thanks guys, I'll try the cleaning bit 1st, as the engine (carb included) is coming out in 2 weeks to be swapped for another Chevy, this time 360 bhp! I'd like to cure the problem prior to passing it on to the next guy.
I will keep you posted as to the results.
Thanks again,
Neil.

[Neil O]

Hi all, here is the update.
Took off carb, stripped cleaned blown out with airline etc.
Made no difference whatsoever!!
On further inspection I noticed a very small amount of oil around the base of the dizzy, yep it was loose!!
I then revved the engine to the problem range (about 1500 rpm), then set the timing so that it wasn't lumpy and rough (by ear).
Tightened clamp and set of for a test drive, brilliant!!
I will be checking the timing to see what I've ended up with, but it drives really well now.
Moral of the story?
Look under your nose first!!
Cheers
Neil.

[SimonP]

Neil,
Mine is the same. I've yet to start tweaking as I need to get the crank endfloat sorted first. (Going down to Repower Thursday)

My guess is that there's a bit too much vac advance. Because of the cam timing, there's not much idle vacuum, but the slight increase in revs soon creates a lot of vacuum and is probably putting too much advance on at light throttle. As I understand it, on "stock" engines, the "timed" vacuum port is used for the advance can (ie no vac advance until part throttle) but these tuned setups tend to require vacuum advance at idle too, so use the "manifold" vacuum port.

I don't think it's the carb that requires adjustment (on mine, at least) as the CO emissions were 3.5% at idle, 3.3% at 2000rpm which is more-or-less right.

I set mine up to 15deg BTDC vac off/plugged as Brian recommended and have checked it after some mileage - it hasn't drifted.

Simon.

[Neil O]

Hi all, I went out at the weekend and bought a timing light, checked the timing as I had set it 'by ear'. Timing was showing 8d btdc, so not far off the 10-12d that Repower say is correct. Out of interest I reset to 12d and it ran like a bag of shit at 1500ish rpm. I have now reset it again to 8d and it seems fine. If I was really looking for any problems I would say that the top end power is slightly down, but not by much so I'll leave it as it is now. It's a much smoother drive now.

Cheers,
Neil.