exhaust problems still....

Ok, so after getting everything put back together last summer, (head job, valve adjustment, botched exhaust, ignition system, timing, etc....), I had a problem with the front pipe on the jeep glowing, (I could see it through the hole in the floor where the pedals come through),I cannot tell how far back it glows, or if the manifold is glowing because it will only do it under load, (I have tried just running the engine at a high rpm with the hook open and it wont do it), I assumed that it was just the botched up, restrictive "emergency" exhaust job I had done. Well, after I remove the restrictive exhaust, it still glows. Its only visible at night, so I guess its not glowing all that brightly, but it still concerns me. I have heard all of these warnings about burning up exhaust valves, but I don't know how to tell if I have a problem with that or not. I know that running lean can cause excessive exhaust heat, but it does not appear to be running too lean. It only glows at 2500 rpm and above. I'm going to double check the timing again, to make sure it didn't "self adjust". Other than the glowing pipe, it has been running great, even peppy at times. Any ideas on what I might be missing here? Anything else I could check? (I also looked at the plugs, and they look fine, a little black around the edges, but otherwise clean and normal looking). If I'm running too lean, should I look into a bigger jet for the carb? Or maybe just screw the mixture screw out more? I have also entertained the notion that maybe its normal for an f-head exhaust to glow a little at high rpm's, can anyone verify for or against this?
Any help would be great.

 

What do the plugs look like? Where is the glow ... at the manifold or actual exhaust pipe (you said 'front pipe', not sure what you mean) ?

 

my dumptruck does it, but only when running the snot out of it, would be checking the valve adjustment and timing to start off with

 

I guess mostly what "Patrick" said...but the plugs are very clean. maybe a bit too clean come to think about it. I will try running it a little richer. if my valves were suffering, I would have some kind of symptom, right? Oh, and I really can only see it glowing through the hole in the floor due to the fact that it will only do it under load. I will be double checking my timing, and I wonder if maybe I need to advance it a bit beyond spec? It makes sense to me that if the timing is too retarded then the fuel would still be combusting as the exhaust valves open, thus heating the exhaust. But I do have the ait series vacuum advance distributor, which I would think would actually advance the timing a little excessively if anything, especially at high rpm's, any thoughts?(i spent the better part of three days adjusting the valves with all of the varied methods that people/books gave me to do,so I am pretty confident that they are still good, you could probably find all of my posts about it if you look hard enough)

 

If your valves are properly adjusted, Initial timing not over 10 degrees with vacuum plugged and the carb has metering rod and main jet within design intent I would not loose any sleep over being able to see a faint dull red glow under load at night.

The Vacuum advance on the distributor will not be applying any advance under load anytime the manifold vacuum drops to around 6hg to 8hg or less ( depending on unit calibration ), your vacuum unit is ok and is not contributing factor if initial timing is within spec.

It is not abnormal to see a faint red glow under load at night somewhere within the first few feet of pipe from the manifold, Especially if there is a sharp direction change close to the manifold. Its more evident on some engines than others. In our case with the F-Head it may be inherent of the 1 5/8 pipe to manifest this, This does not necessarily mean that its inefficient or dangerous.

The F-Head has larger intake valves than the L-Head so therefore digests more fuel air charge and produces a little more power ( and heat ). The early exhaust system was carried over from the L-Head without any changes. The 1 5/8 pipe may be right at its maximum flow limit with the F-Head.

What would be interesting is for other members that are interested to observe this on their own rigs and see if others show the same tendency with 1 5/8 pipe or if those with 1 3/4 pipe or larger dont do this.

My rig has been down for part of the winter replacing Seals, overhauling the T-Case, and replacing the Transmission. When I am back on the road here in about 2 weeks I will make it a point to observe mine, I to have a cobbled up PO exhaust that has some serious dents in it that no doubt restrict flow to some degree, I will let you know what mine does as You have me interested in this.

All of the above is my humble opinion of course and subject to member review and comments

 

Thanks alot. I did go ahead and richen up the idle mixture a bit due to the plugs being a little cleaner than I usually like, (look brand new after a few months of driving), I also advanced the timing a couple of degrees, just in case. After the installation of the new exhaust, (Thrush turbo muffler and 2"tail pipe), and the aforementioned changes, the first test drive seemed promising. Almost drives like a "normal" vehicle, (accept for the fact that it tops out at about 50 mph). I will see if the glow has changed any when I drive home tonight. And I always did wonder if it was somewhat normal, due to the fact that I have had no aperrant ill effects with it happening. I am however very anxious to see if others have the same thing going on. I know that its not common place to be able to look through your floorboards while your driving down the road, and part of me almost wonders if this is a commonplace thing on other vehicles as well. anyway, keep us posted,
(and by the way Brian; Thanks for all the help with the carb over the summer. It has run beautifully since you helped me out.)

 

You are most welcome, Anytime I will post back how my exhaust acts.

If you dont mind me asking, How did you " richen up " the fuel/air mixture a little? Did you have a slightly smaller Metering Rod ?

Opps, misread your post, you specifically said Idle Mixture.....never mind (-:

 

UPDATE: ok, so after advancing the timing a bit, initial drives were very promising. No one told me that this thing was supposed to be able to actually accelerate and drive up hills......The exhaust only barely glows a deep barely noticeable red, (whereas before it was a bright orange), and when I finally got a timing light on it, I am only now, (with the vacuum advance hooked up, it was single digits outside when I checked it, so I was in a hurry), at 5* btdc. So it appears that it had moved itself (probably my fault) to somewhere between 0* and 2* btdc, thus glowing exhaust and sluggish performance. Now I only have one question: With the vacuum advance hooked up, what should the final timing advance be? I know that for the IAY series distributor it says 15* final advance, but mine goes pretty far beyond that....anyone else running this distributor that may know how far it should advance?

 

The vacuum unit should pull on an additional 12 to 15 degrees when fully activated. The port on the carb for the vacuum connection is located so there is no vacuum applied at idle. When you crack the throttle plate just above idle this port is exposed and vacuum is applied to the unit.

With engine at idle and initial advance set at 5 degrees and the timing light hooked up pull the vacuum line and suck on it while watching the timing marks, It should advance to between 15 and 20 degrees.

The full mechanical advance limit is a separate issue, If your vacuum unit works as noted above you should be good to go. Under heavy load ( low manifold vacuum ) the vacuum unit does not function and the mechanical takes over.

 

ahhh, I see. With the timing light on and the vacuum advance hooked up, it advances at least a good 15 degrees before it stops, at 2,xxx rpm, maybe close to 3,000, (I have a cheap timing light that does not show rpm on it). Also, I went ahead and adjusted the distributor another 2 degrees or so advanced, (I can only see the timing light at night, I'm actually returning it today to get a better unit), which leads me to my last question: If I had pre ignition, "ping", I would be able to hear it over all the other clicks and thuds and knocks that the engine normally makes right? Or is it something subtle I really have to listen for? I took the jeep up some pretty steep hills and ran it hard up them, didn't notice anything out of the ordinary. I just want to make sure that if it were to happen, I would know what to look for.

 

Sounds like you are on it. Timing and Mixture. If you still end up with a little glow, that is probably Ok. I also have seen exhaust glow near the manifold if they have been pulling hard. I doubt that many of us have bothered looking at the hot exhaust at night. Maybe they all glow a little.

 

Ping ( spark knock from over-advance ) can be inaudible in low compression engines, what you will notice first is a loss of power under load.

With the F-Head you should not have to worry about any ping issues provided the initial mechanical advance is not more than 10 degrees and the mechanical advance itself ( reluctor, springs and flyweights ) are not broken or excessively worn.

With the initial advance set to 5 degrees and the specs stating that you should have 15 degrees of mechanical advance you should read 20 degrees with the mechanical advance fully thrown in, So at ( for checking purposes ) say 3000 rpm you should read 20 degrees advance with the vacuum unit disconnected.

With vacuum unit connected you should read around 35 to 40 degrees total advance at 3000 rpm.

 

sounds about right. I think when I get the time I will mark more timing degrees on the timing cover for more accurate reference, but right now it seems to be about right, and there is no loss of power under load. Thanks alot.