Edelbrock Choke adjustment

[ceejayjay]

Hi

Recently bought a Sumo RV8. Very happy with it. One issue foxing me ( I'm an enthusiastci mug! ) is getting to grips with my Edelbrock performer carb.

Its definitely running rich - cleasr its throat on longer runs, but in town it soots up plugs. From cold the choke kicks ins fien but then as it gets to operating temp its as if the choke is still open. Plugs sooty, exhaust black etc. On restarting it belches out black soot, and then clears its throat.

I know the engine is fine, Oil Pressure bang on 35psi at 2500 etc and my old man always told me the permanent bluey-white smoke was when matters were serious, but its a pain in traffic as the 800 tickover get lumpier and lumpier, and its not that economical I guess. Revs hard through to high 5000's without a problem, but misfires for awhile until the plugs clear.

Thing is! - downloaded the Edelbrock manual, but it makes no sense to me. Don't want to twiddle away and make it worse.

Please help a thickie.

PS Bought it from Hallmark and can say I am very happy with it. I knew there were mixed reviews on them and Sovereign but I found Paul and Mike straighforward, honest and helpful
Cheers
Chris

[wilf]

Chris - no straightforward answer I am afraid.

You need to establish some things:

1: Is the choke operating correctly (personally I believe you could take it off completely and eliminate one source of problems).

2: Is the basic setting of your carburettor correct (air/fuel mixture) - that can only really be set up on a rolling road.

3: Are there any other issues to be dealt with, like incorrectly adjusted accelerator pump, wrong float level, excess fuel pressure etc.

4: Sounds like your tickover mixture is too rich, or your plugs too cold a heat range.

If you are not sure how to tackle these things, I would suggest you take the car to an experienced engineer like Cheng at Thunder cars, or 7 indulgence etc. and get it properly set up. Tinkering can make things a lot worse.

Whereabouts are you in the country? Scratch that question - I just saw - Edinburgh - anyone know of some good V8 engineers up there?

[dinosoar]

Sounds like idle mixture to me. Your idle speed is a tad low for a rover. I would set it at 900rpm.
I agree that you don't need the choke. A few pumps from the accelerator pump should do for startup
It is easy to set the idle fuel mixture by following the manual.
It give a step by step procedure and is best done with a tacho on a multimeter so you can observe rev changes as you adjust the screws.


HTH

Andy

[ceejayjay]

:thumb: Thanks guys, helpful advice and good to hear there's nothing ghastly wrong. Will look to take off choke. There is a very good specialist up here so I may do as you suggest and get an expert to do it.

Even I can set the idle higher - thanks
Cheers

[craigh]

what cfm rating is the carb? its been discussed on the forum a few times that it may not be jetted correctly for your application

[Sidecarbod]

Originally Posted by ceejayjay

Hi

Recently bought a Sumo RV8. Very happy with it. One issue foxing me ( I'm an enthusiastci mug! ) is getting to grips with my Edelbrock performer carb.

Its definitely running rich - cleasr its throat on longer runs, but in town it soots up plugs. From cold the choke kicks ins fien but then as it gets to operating temp its as if the choke is still open. Plugs sooty, exhaust black etc. On restarting it belches out black soot, and then clears its throat.

I know the engine is fine, Oil Pressure bang on 35psi at 2500 etc and my old man always told me the permanent bluey-white smoke was when matters were serious, but its a pain in traffic as the 800 tickover get lumpier and lumpier, and its not that economical I guess. Revs hard through to high 5000's without a problem, but misfires for awhile until the plugs clear.

Thing is! - downloaded the Edelbrock manual, but it makes no sense to me. Don't want to twiddle away and make it worse.

Please help a thickie.

PS Bought it from Hallmark and can say I am very happy with it. I knew there were mixed reviews on them and Sovereign but I found Paul and Mike straighforward, honest and helpful
Cheers
Chris

Hi Chris,

I was in the same boat as you not that long ago, my RV8 was over fueling and I'd never worked on an Edelbrock carb. I also looked at the manual, in my opinion its rubbish and has at least one error in the charts.

V8 Developments gave me some help over the phone, armed with that I bought a calibration kit from Real Steel and had a go at setting the carb up myself, (Any tuning shop that you go to will probably want you to buy a kit before turning up so you might as well have a go anyway).

You need to be very careful when removing the top off the carb as the gasket is very delicate, remove the air filter stud to avoid breaking the gasket, also watch out for the
clips for the choke and accelerator pump rods...they are microscopic!!

I agree with Wilf, you should either wire the choke open or remove it all together. I actually removed the choke plates but set it up to give a fast tickover when the choke knob is pulled (you need a single strand stiff choke cable if you are going to do this).

You also need some torx drivers to get the top off the carb.

Basically the choke has two modes of operation, cruise and power, the needles control the mixture strength along with the fuel jets, the needle springs control when the carb goes from the cruise mode onto the power step (the stiffer the spring the sooner this happens).

Using the following method you can compare different jet and needle combinations.

Take the two needle sizes (i.e 65x52) and subtract them from the jet size (i.e 86), all the sizes are in thousands of an inch 86-65=21, 86-52=34. These two numbers are the size of the hole that the fuel can flow through, the larger number is the power step, the smaller is the cruise mode (The example that I used is what is supplied as standard with the 500 CFM carb). This setup is bad for a standard motor as it will over fuel and cause bore wash.

I found that you do not have to change the size of the holes much to make a big difference to the mixture strength (The plugs will show the change after a few miles).

I also tried 83 jets and 65x52 needles, ie 18, 31, it was as flat as a fart on cruise but OK on the step!

My motor is tuned but the following is the setup that I run with, 86 jets 67x55 needles, which is 19 cruise, 31 power mode. The pump rod is on the middle hole, the needle springs are orange (which is standard), the pilot screws are 2 3/4 turns out, which seems like a lot but it doesn't pick up quick enough if I lean them off too much (might have to turn them in 3/4 at MOT time!) The secondary jets are 94 which is standard.

It takes 5 minutes to change the needles (or rods as they are sometimes called) and it takes 15 minutes to change the jets.

I know other people have said don't mess with it and get it set up on a rolling road but IMHO if you make a note of all the settings that you have now then give it a go, whats the worsed that can happen? If you cock it all up just put it back to standard.

Check your float height before you do anything as mine were out.

When you get you kit draw up a table that gives all the combinations that you can try, remember to include the standard jet 86, and standard rods 65x55 with all the combinations. (I even bought a rod from another kit 65x52 to give me a bit more scope).


Its dead easy....give it a go!

cheers,

Pete.

[Sidecarbod]

I noticed that mentioned bad fuel comsumption.....mine was also bad, I reckon 15mpg, after doing the carb I get about 20 to 25mpg, the saving soon pays for the 45 quid that the calibration kit cost.

[craigh]

id agree with the suggestions,buy a calibration kit first and then take it for a set up,ive tried fine tuning 2 edelbrocks and found myself messing around for hours

[Sidecarbod]

Originally Posted by craigh

id agree with the suggestions,buy a calibration kit first and then take it for a set up,ive tried fine tuning 2 edelbrocks and found myself messing around for hours

I never said that it was a quick thing to do!!! I was messing about with mine for days!!
but I hope that you agree that its not difficult.

I've had another thought about the pilot screws (which I reckon is where the immediate problem is unless its the pump over pressurizing the carb or duff float valves etc).
Before my motor had the stage three heads fitted the screws needed to be about 1 3/4 to 2 turns out, the heads effected the tickover mixture quite a bit. If your motor is more or less standard these settings maybe nearer the mark.

The way I checked was to do the following, (not very scientific but it works).

Warm the motor up with the srews set at 2 turns then gradually turn them in until you hear the revs drop slightly (the revs might even pick up before dropping, this is OK, it just the motor telling you it wants a leaner mixture) open the screws 1/2 a turn from where the revs start to drop.
Stop the motor and wind each screw fully home making a note of how many turns they were open. Wind them back out that amount.

Take the car for a drive and from a reasonable speed take your foot off the gas and allow the engine to slow the car down to maybe 30 mph, then feed in a very small amount of throttle, if the engine hesitates for a fraction of a second or does not respond at all until you press the throttle more its running lean, open each screw 1/4 of a turn and try again. Keep repeating the test opening the screws until it picks up properly. Don't press the thottle too quickly or the accelerator pump will dump a load of fuel into the manifold which will spoil the test. Basically you just need to get rid of any hesitation and not go any richer than that. (After a while you can even feel the difference with 1/8 of a turn on each screw).

Once you've got that sorted your car will run OK but heed my words with regards to the standard setup over fueling your RV8, it will damage the bores if you leave it long enough.

let us know how you get on!

Cheers,

Pete.

[TINKA]

Before you dive in too far just try changing the needles first I took my RV8 to a rolling road and this was all he needed to change and chatting to him whilst he was doing it he told me he virtually never has to change the jets as most results can be obtained from the supplied needles in the kit.