My pal Doc down the road bought my 83 d-150 that I drove all of 20 times.

We have the timing and idle mixture good and all tue-up parts are new.

He has done loads of stuff to the truck to make it nice and fixed a lot of the worn out running gear.

I rebult the carb and replaced the intake/exhaust gasket and got it to run well with the exception of cold weather hard starting because it was lean then and it also had a "flat spot" (motorcycle term) in the throttle at a certain midrange rpm. I used the thing for moving and a few dump runs and then sold it to him.

He took the carb off and cleaned it out again and found a small intake leak at the carb base gasket and he thought the float level was off and he adjusted it. I know I set it right because I used the cardboard ruler in the kit. BTW it's a one barrel.

He has a few complaints about it's performance. He says it tops off at about 55 and that it should do 75 easily. I have to agree. He also got a new exhaust pipe and muffler. It is all black from carbon in the pipe from relatively little driving.

The A.I.R. system is curently disconnected for "diagnostic purposes" and the EGR is not hooked up also for "diagnostic purposes". I believe these should affect it NONE AT ALL in this regard.

We have about 17.5 inches at idle and it seems smooth with about 9 deg.

The darn mixture screw needs to ba backed out really far, I think about 3.5 turns to get good vacuum and idle. I think it has just been worn out from cranking down too hard.

This carb has been rebuilt more than once I believe before I did it. I did not drill anything but it is a fair possibility that someone has.

No, he's not a real doctor, if he was he could have an '05. He's just Doc. Help us out if you can please. Request information that I may have omitted as well please.

I dont get it. You say it's "lean" but youre getting black carbon in the exhaust, which is usually a rich condition. Is your truck puffing blue? Do you have any comp test numbers? Maybe your valves are tight....

I wouldn't rule out a carb, but would consider that better news than a head/ring job...

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Well, specifically, I said lean when cold. And starting would only have to do with the idle circuit, not the main circuit.

Compression is very good, I forget numbers but I did test about 6 months ago and I was surprised how high.

No blue smoke, that would be obvious engine mechanical prob.

Also please note that lean when cold was mentioned when I owned the truck before he did the carb again. It was prob lean just from choke not tight enough. The "lean" was correct but not an important point.

The pipe has black carbon in it now for sure.

Hmm, valves...

very true, and uncommonly bright of you to say so. If your compression is very good then valves are probably not the culprit. Overfueling would be my guess. Incorrectly jetted/adjusted maybe? Unresolved choke issues? Is it a Holley or a Carter?

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Does the engine get good spark advance?
Use a timing light and look at the timiming mark while you rev the engine. The mark should "jump" with lots of advance when you crack-open the throttle. Does the distributor have a vacuum advance pod?
DD

It's a Holley 1945.

I suppose overtightened valves could affect it at high rpms if they didn't have enough lash although I think these ones are hydraulic. I remember from my motorcycle days that you needed enough lash for high rpms, heck with what they sound like at idle basically. Better a tiny tick at idle than a burnt valve at speed. I don't think valves in this case, but it is a good thing to keep in mind.

Ok, vacuum advance: there is none. The electronics are on the air cleaner for some strange reason. Maybe they last longer if they get jiggled all the time as they must up there.

Mechanical advance is a good place to start looking along with possibly buying factory jets. I wonder if a jet kit is available for this carb.

Here's my battle plan:

1. Check mechanical advance first with timing light and then open dist if necessary to ensure free movement. Does this setup use any kind of electronic advance? I wonder how I find the spec for total timing at what rpm is adviseable.

2. If that's to no avail then I want to get the float level set correctly again, I believe I had it right and Doc used to rebuild airplane carbs and he changed it from where I had it set but he did it by eye.

3. Find/replace jets with smaller size.

4. Look at any further suggestions from you guys and incorporate them as well.

BTW, Doc thought it was clogged cat, reasonable guess, didn't sound like it to me. He took it down to muffler shop and they said didn't seem clogged.

I think we are on the right track here with fuel and ignition.

There's nothing in these carbs that just altogether fails and needs total replacement is there? The only really strange thing at idle on this is that the mixture screw needs to be backed out so far to get proper mixture. I don't know if the mixture screw on this carb controls gas or air (both types DO exist in Holleys). If it controls gas, which I think it does, then a vacuum leak could account for this although unlikely. As I said before I think it MAY be from previous rebuilders overtightening this mixture screw and it is no longer tapered properly.

Oh, I just thought of one more thing, I know that I put the little ball back in the carb under the brass hexagonal "weight". Doc swears it wasn't there when he took it apart as he dumped everything into a bowl and he never found the ball. I KNOW I put the ball in there. I found him a slightly smaller ball from a craftsman ratchet to replace it with, BBs dont fit. I just called my local carb shop and they said that this ball is only a check ball for the accel pump.

I should also clarify my subject title to be "Doc thinks he has to replace the whole darn carb to fix this problem, I think not."

Any replies appreciated, sorry for the long and rambling post but I just woke up and decided to spew all my thoughts onto my keyboard.

-ultra

If you have a Spark Control Computer on the side of your air filter housing, then you have what we lovingly call a "Lean Burn" computer.

With the lean burn computer, you need to set the timing to the factory specification. (this could be why you can't get going faster than 55)

The lean burn system should actually work better with a functioning EGR, if everything else is functioning properly.

If you are in a state that has emissions requirements, you might want to get a service manual and start testing and restoring the lean burn system to it's proper operation. Otherwise, if you want to continue to remove factory emissions equipment, I suggest you remove to lean burn completely and convert to the standard electronic ignition which was used prior to 1980 on slant sixes.

I agree that you may be experiencing some choke adjustment problems with the cold lean condition.

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1980 Aspen 225 super six

Wow, yet another suggestion.

I would like to see if mallory unilite distributor is avail for this vehicle if we go the way of ignition swap.

Ok, gonna go hook up the egr and possibly change timing from 9 to 12, Doc had it at 2 because it pinged at 12.

I will do a bunch of stuff and let you know what the results are.

I don't propose that the egr will fix any noticable problem at this stage. Let me offer some answers to previous questions

1) The distributor will not have any mechanical advance mechanism. The computer controls advance. The advance curve is based on vacuum (there should be a hose going to the computer) , engine temp, O2 sensor readings, and maybe some other sensors, but I don't recall what they are.
A service manual or the emissions sticker under the hood should give you RPM and timing spec.

2) Yep, get the float set correctly. Has the fuel filter been changed? A pump or filter problem could appear to be float or lean jet related

3) I don't understand smaller jets? I must have missed something.

been there and done that.

Vacuum leaks cause big issues with these motors. It would be good to be sure they are fixed before getting into other problems.

Here is a link to some lean burn conversion stuff that might be interesting
http://www.slantsix.org/articles/leanbu ... rticle.htm

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1980 Aspen 225 super six

It sounds like the lean burn computer is in 'limp' mode. I would reconnect all the disconnected emissions devices, disconnect the battery to reset the computer, and see if performance changes. I need to double check, but I believe spec'd timing for lean burn comps is TDC (Emissions decal under hood will show correct base timing, if still present).

-S/6

Most (or all?) of those slant 6 trucks with ESA have base timing of 12º for manual transmission, and 16º for automatic transmission. This is true for 1986 and 1987 model years. I don't have a book to look up specs for early 80's slant trucks.

Yep craig, it's 12 deg btdc and a manual and we have it set to about 9 right now because of pinging. There is no o2 sensor, vacuum hose does go to the carb-top puter, rev the engine up and the timing hits 20 for about 1/4 second and then goes about 12 deg relatively steady. Strange advance behavior.

The Doc man and slant6ram believe there is no mechanical advance in this dist and I cant see one either unless it is under the pickup plate. The rotor doesn't really spring back and forth which either means there is no mech advance or it is rusted solid.

We are going to get some carbon melter and rev end blast it in soon but we both drank too much to drive today to go get it so we figured we'd play with hot spinning engines, wires and vacuum hoses instead.

re. slant6ram's post, the egr could help the pinging/run-on that was happening before by reducing combustion temps but decarbonizing the combustion chambers could do the same. We hooked it up for good measure for now but I agree that it has nothing to do with the actual problem we are experiencing. Apparently upon further conversation the float level was not adjusted much, just a hair. I stopped in at guaranteed carburetor today in Largo, FL (they ship all over the world) and the parts guy there said the enrichment circuit on 1945s is notorious for sticking and holding the metering rod down. We think that is good as we both checked it but it is something to check if we get nowhere with the rest of the stuff. He wants me to check the jet with a thousandths drill bit kit and he can provide smaller ones if needed. slant6ram, I think on of the previous rebuilders may have drilled the jet. That's why I mention it. The guy at the carb shop says that the float being off the amount it MAY be off won't affect driveability as much as Doc is experiencing.

I think this engine should have a lot more than 12 to 14 deg total advance. I think this is an excellent starting point.

How do I check if it's in limp mode? can you on-off-on the key 3 times on this chrysler to check? I should prob check not ask but it's down the street and it's raining and I melt in the rain. Prob not important anyway as I wish to replace the ignition.

Would I be in violation of any board policies if I were to solicit sale of ignition system that is NOT a lean burn type? If there is not policy against this then I am doing so now, I want a dif ignition system for this truck, cheap as possible but we will spend what we need to.

Doc just got rid of a truck that had a nice little weber on it. The truck was towed away and he let that $439 carb go to the j-yard with it, darn. That would have solved/ruled out some problems easy. We could have rigged up a base adapter I am sure. I am gonna try to get it back.

Does anyone have/know where to get any stuff for sale for this?

Indeed you are correct Craig (according to my Chilton's at least ). I don't know what I was thinking about.

I am hesistant to say w/o my manual near me now, but when in limp mode, I was under the impression the lean burn computer provides NO spark advance. Can you confirm this Craig? This sounds remarkably similar to NPU1's problem.

Holleys don't have metering rods, Carters do. Does yur truck still have the catalytic convertor on it? I have an 82 with lean burn and it runs great. I don't know why they call it Lean Burn because this thing burns the hell out of gas.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

http://www.carburetorfactory.com/evindex.html

Go to this site jeb and tell me that the holley 1945 doesn't have a metering rod. Show me the power valve. It has one or the other, right? That is what runs the enrichment.

Doc had a local exhaust shop "temporarliy" remove the cat for "diagnostic purposes" yesterday without my knowledge, (truly). It actually had a bunch of broken chunks in it. It helped a bit he said but not very much.

Super6 and Craig, if you know much about limp mode and weak advance, please tell, please.

I hope I don't seem too fickle but dadgum if I do, I think this may be largely a timing advance problem with the new info I have. Shouldn't it have a lot more than 12 to 14 total advance? Go time your slant6 and let me know if you would please gentlemen.

I will be going to KY and CT from FL for a few weeks and leaving poor helpless old-fart Doc on his own for that time (he'll get a kick out of that when he reads this print-out) so info in the next few days is best but ANY info WILL be put to use eventually. If I just disappear please understand and I will respond to all posts eventually.

Maybe I can get that darn Doc to buy a non-cellular phone line or cable modem so he can post here himself, lol...

BTW, he recently got hit in a small 1982 nissan (I think nissan) pickup truck and rolled about 3 times by a lady in a new honda who blew a light down here in lovely but congested Pinellas county. His truck was wasted and the old fart came out with only scratches. He negotiated with the insurance company patiently for weeks, got nowhere and finally lawyered up. Both parties insurance companies were state f*** (my ins company too) and still they wanted to make it hard for him. They lose, he got a lawyer now. All of the neighbors are completely amazed, his little truck was twisted and smashed and he crawled out the passenger window after going for the ride of his life and walked away just a tiny bit worse-for-wear. His tools were spread out over the entire road as his truck cap/topper blew off. He got only $250 from State f*** for those. Just thought you might like a small anecdote.


You guys are all great thanks for the very fast and helpful posts!


-ultra