Empi 32/36 DFEV - Too Rich?

[WBPDX]

I have:

1979 Spider
- Stock pistons, cams, head
- 78 1800 manifold with all ports plugged except vac advance and brake booster
- EGR system bypassed\unused
- 4-2-1 header
- Brand new Empi 32/36 from Mark Allison, with the 20mm spacer. Empi chrome air cleaner.

I have done:
- All new gaskets, set valves, etc. as part of head gasket replacement.
- New NGK plugs, recent wires\cap\rotor
- Checked compression after rebuild, also have constantly checked cam\crank timing at every stage. Static timed distributor to be pointing at #4 for TDC.
- Adjusted timing, set to approx 10 deg
- Adjusted idle down to the 900rpm range

Car starts and idles great. I take it out on the street and drive-ability is not good at all. Every time I jump on the gas or try to take it past about 2,500rpm I am getting a poof of grey smoke out the tailpipe, sometimes backfiring out the carb, and the car is bogging down badly.

I come back to the garage, check for vac leaks and find none, then I make sure the vac advancer is working (it looks new.) It is. I start playing with the mix screw a little bit. I make small changes and can't hear much of a difference; but when I turn the screw in about 2 turns, there is a marked difference. At 2.5 turns in from the stock setting, it is running much smoother. Anything further in and there is another drastic change for the worse.

I take the car out again and it is slightly better. Still, definitely grey smoke (rich) coming out the tail pipe on hard acceleration attempts. I do my best throttle-chop so I can read the plugs.




What I find is very black plugs. They were not oily (I know what that looks like from lots of thumper motorcycles with bad rings...) but just as sooty as I can imagine!

I am hoping someone will tell me A) If this is normal for a stock Empi, and B) What jetting I should be using, and WHERE to get those jets as quickly as possible!

If it is not normal I would appreciate advice! The backfiring seems odd; is it possible to install the distributor 180-off? As a starting point, I static timed the rotor to be pointing at #4 when the engine is at TDC.

[manoa matt]

"when I turn the screw in about 2 turns, there is a marked difference. At 2.5 turns in from the stock setting, it is running much smoother. Anything further in and there is another drastic change for the worse."

The setting of mixture screws is in terms of: how many turns out from fully seated. Turn the screw until you feel it bottom out and seat lightly in the carb body, then turn it out about 2 turns and see how it runs. If you need to turn the mixture screw 3 turns out or 1 turn out, then you need different jets. This will help: http://www.piercemanifolds.com/category_s/313.htm

What is the specification on the NGK plugs? You may need a hotter plug to burn off the carbon deposits.

I'd buy some Champion RN9YC type plugs and try and set it up according to the setup best lean idle adjustment.

[WBPDX]

Thanks; I realize that settings are normally described in terms of "from bottomed out." I just didn't bother checking what that setting was. I will check...

[So Cal Mark]

is the choke opening fully? Usually those carbs are on the slightly lean side for a 2L. Backfiring through the carb indicates a lean condition. Are you sure the ignition timing is set at 10?
I keep jets in stock, and they are the same jets the Webers use.

[WBPDX]

I was expecting white plugs based on the backfiring through the carb as well... I was kind of shocked to see how sooty they were.

I will check the choke operation and timing (again.)

[majicwrench]

THe idle mix screw does not play much of a part in hard accel, so I would not worry too much about it at this point. But do set it to where engine idles the best.
I would bet that the carb comes jetted close enough to work well right out of the box, so I would be suspicious of other things.

[WBPDX]

I agree with the comments - After sleeping on it, I think it is choke or timing... I won't know until I get back in the garage tonight.

Timing because I remember the paint I used 'ran' a little bit down the pulley and made it hard to tell exactly where the notch was. I may have misread it, but it would only be about 5-10 degrees off.

Choke because while I was installing the spacer, I just set the carb off to the side. Perhaps something got pushed into the wrong position or is hanging up on the new throttle linkage? Or, maybe I am not letting things get warm enough? I would think if the temp gauge is reading 190, things are plenty warm though...

Thanks for the help! I am looking forward to getting this resolved. I need to pass a basic tailpipe emissions test with the car next week. I am prepared to put a new cat on it if that is what it takes, but I need to be in the ballpark to start with...

[So Cal Mark]

10 degrees off on the ignition timing is alot

[WBPDX]

EDIT: Barking up wrong tree... Bad evidence.

[majicwrench]

While the fact that your timing light is not consistant on 1 & 2 is interesting, it may well only be that. If spark was coming and going, engine would be missing terribly
Pull #1 wire and put an old plug in it and rest it against the head. Start engine. Will now miss on #1, but should run OK on three cyl. SHould be able to watch spark, zap zap zap.
Try same on #2, then why not #3.

Do not think it "obvious" that you have an ignition problem till you have some proof.
Keith

[WBPDX]

I just ran out and performed this test, and of course everything was fine.

It was then that I realized I was not paying attention to the orientation of my timing light's lead. I won't do that again! When the proper way around, everything is great. When backwards, it produces the weird results I was seeing before.

It does still stumble slightly at idle. Removing the plug wires on my previously-suspect cylinders makes a major difference in the idle quality; not the minor difference I previously remembered.

So, to recap; still have sooty black plugs, backfires out the carb when under load and trying to somewhat-quickly accelerate. When not under load, it revs up freely with no issue. Slightly rough idle; you can see it missing occasionally. Timing is correct, and vac-advance does work. Choke is operating correctly.

I think maybe it is time to check more in-depth for vac leaks?
Electric fuel pump that has been added on? (I have no idea if it was good before I started this project; the furthest I drove the car was around the block 3x before tearing into it.)

I would suspect valves, but I Just did a warm compression check on 1,2 and 3 and all seemed well.

[So Cal Mark]

if you have a vacuum leak, it will not idle smoothly. How old is the gas in it? From what you describe, it sounds lean on acceleration. Were the plugs sooted up from the previous carb? Is there much blowby from the crankcase hose? What condition is the air filter?

[WBPDX]

if you have a vacuum leak, it will not idle smoothly. How old is the gas in it? From what you describe, it sounds lean on acceleration. Were the plugs sooted up from the previous carb? Is there much blowby from the crankcase hose? What condition is the air filter?

Some of the gas is of an indeterminate age; probably 6 months, a few gallons of it is 3 months old, and I pumped out about a gallon and replaced it with a gallon of fresh gas (Tank was half full.) I also checked and made sure there was no junk in the gas making it to the carb. While letting the electric pump pump out some gas, I noticed it was quite quickly filling a 1/4 gallon container, so I assume the pump is okay too?

Plugs were oily under the previous carb (bad\missing valve stem seals, fixed now,) not really sooty. These are brand new plugs, although I can't say at what point they got sooty. I should probably throughly clean them and recheck, or buy another set I guess...

I don't think there is any significant oil blowing by. Before I had the hose mounted to the air cleaner, you could see a bit of vapor coming out the hose when it gets hot, but that was about it.

The air filter is your Empi chrome unit. Is it running lean because of the open filter? Seems like an obvious thing I didn't think about...

[txspider]

A friend just installed one of these carbs on a customer's car and was having issues also - the problem was solved when he dismantled the New carb and found one of the internal gaskets was split causing a vacuum leak - hope this helps.
Mike in Houston

[WBPDX]

A friend just installed one of these carbs on a customer's car and was having issues also - the problem was solved when he dismantled the New carb and found one of the internal gaskets was split causing a vacuum leak - hope this helps.
Mike in Houston

If that is the problem, I will probably throw this carb through a window.