After I rebuilt the Holley vaporizer carburetor in my 26/27 there has been a vibration in the motor that wasn't there before. I also hear a popping in the manifold. Motor seems to run hotter. I have checked that all cylinders are firing and reset the timing. My question would be "What would cause that popping in the manifold"? I should have left well enough alone but it needed a new float so I purchased all the brass that they sold for it.
Sounds like running lean. Could just be mixture adjustment, but maybe a gasket leak too.
Larry, popping in the intake manifold could be caused by a couple of things. As Hal said, a very lean mixture is one. A leaking intake valve is another and spark on a cylinder at the wrong time is another possibility.
Based on the description of the problem occurring right after work on the vaporizer, I am also thinking that a lean condition is the most likely source of the problem you are having.
If you can't solve the problem by adjusting the carb, and it runs rough at idle or two cylinders that share an intake port are found to be weak when shorted out, you may want to take a close look at your manifold to head connections. A vacuum leak at this point would cause those two cylinders to run lean, while the other two are rich. To test for this, you can hold a piece of hose to one ear and check for a hissing noise with the other end at the intake to head connections. You can also spray a small amount of carb cleaner (or other volatile spray) at these connection points and see if the engine smooths out and the RPM increases. When doing this test, try to make sure you are not sucking the vapors in the intake though.
Hope this is some help.
Thanks guys. I did notice that it cleaned up a bit when I opened the gas but when I went around to the carb side I could still hear some popping. I also noticed yesterday when I had to take the generator off and had to move the carb out of the way a little to make room that there was some dark fuel in the upper chamber (intake) hole above the heat plate. Not a lot but didn't notice any there when I removed the carb for repair. I will do that vacuum leak test tomorrow.
I checked for vacuum leaks and everything seems to be ok. I used more gas for the carb and that seems to have made the difference. I took the T out for a short drive around the yard and back and forth and ended up having to hold the gas adjusting rod in the open position because the vibrations were making it close after a bit. This would start the popping and backfire so that pretty much answered the question. Thanks for your help.
I'm not very familiar with vaporizers, but surely they have a nut similar to the NH that can be snugged up to hold the needle in place. Not too tight or you can't adjust it, but tight enough to keep it from moving on its own.
Thanks Hal. I will have a look see. Maybe I am missing something. I'll post that later.
A small propane torch works well for checking leaks-----without lighting turn the propane on and pass it over suspected areas---the engine will speed up if they are leaking.
Good idea Paul. I will try that.
Hal in response to your idea. I checked the old needle support and there was nothing on that one either. Maybe someone knows how it is done? To me if you put a nut on the needle (which has to turn), wouldn't it come loose each time you opened the gas! I see that the vendors sell a anti rattle rubber that mounts in the hole on the dash and you pass the gas rod through it. Maybe that gives enough friction to keep the rod from turning on its own.
I found a tiny O Ring that just fit into the brass rod support and when I inserted the needle it produced enough friction to hold it from turning. Another thing. I didn't purchase a new needle so maybe the threads on each are made in such a way as to be snug to turn and are matched that way?
Just out of curiosity, Larry, what kind of Timer are you running. I had a similar problem around Christmas with a vaporizer and it would pop through the carb. I blamed valves, ethanol gas, coils, etc, until I finally stumbled onto the actual cause. Now it runs great.
As it turns out it was firing on 2 cylinders at once. One was firing on the compression stroke, the other was firing when the intake was open, thus popping through the intake.
Hi Bill. You ask a question that I don't really know the answer. I felt around the timer for some lettering but couldn't find any. I found some pictures of timers on google and the first one on the page was a Ford True Fire. Mine looks exactly like that from the outside and I am sure it is a roller type.
What fixed your problem? Cleaning and lube, different timer? I am new to this so I don't know. All I know is that it has a vibration and yet fires on all cylinders. I am going to look at the timer tomorrow and clean it although it shouldn't be dirty having not more than three hours on it since the motor was done.
My timer had a deposit of carbon dust in it that settled to about 3/8" or more thick in the bottom. When running I believe that the dust was being tossed around by the revolving carbon brush. This tossing, I believe, was causing the consistent multiple firing, because the carbon dust is conductive, as you know.
In regards to the problem of the fuel adjustment changing because of engine vibration, your vaporizer should have the same needle design as the late NH's. There are two pads that are suppose to rub slightly on the brass needle nut to keep it from moving on it own. To adjust them tighter so that the needle stays were you left it, back out the needle so that the pads are just above the brass nut and squeeze them together with a pliers a little. The idea is to get them to drag enough to keep it from moving on its own but not so much that you can't easily adjust the mixture from the drivers seat.
Hope this is helpful.
Ahhhh! That's what that is for! Yes, I do have them and now they will serve their purpose. Thanks for that Tod!
You are welcome Larry. Glad I could be of some help.
Told you I didn't know much about vaporizers.
Yep, what Tod said. The earlier NH's that I am more familiar with have a special nut that is split and the more you tighten it the more it wedges against the smooth part of the needle and kinda cinches down on it.
The more I am running this thing (the model T) the more I am learning. Lots of stuff to learn. I now have to check out the forum for info on how the timer works. I took the timer off today and it was clean except for a few drops of oil. I did notice that the roller was sticky both in the spring elbow and the roller with signs that the roller was dragging as it went around. I found another in the parts can that was in better shape and lubed it up and installed it and put some oil in. It was reluctant to start and really ran the crap. I couldn't get it to run proper with the various settings so shut the key and it backfired. Scared the hell out of the cat! I guess he thought it was game over for him! Looks like I am going to have to invest in a proper timer!
I have been reading about the various timers and looks like they can be a problem. I came across a post that mentioned truing up the inside of the timer with a wooden block and a dremmel tool. Does anyone recall that post? I did a number of searches for it but came up empty. The inside of my roller timer is a little bumpy so thought I would try to true it up. Any other advice (to do with the timer) would be appreciated.
You could try one of these timers https://www.modeltford.com/item/3221ANCO.aspx You do need to set the timing when changing timer type. These tools help to bend the timer rod https://www.modeltford.com/item/3534TL.aspx Full retard is 15 degrees after TDC.
Thanks for those links John. I will definitely be making an order.
I guess we have pretty much fixed the popping in the manifold problem that I had. In the end it was just that I didn't open the gas rod enough and that was causing it to run lean and thus the popping. Before I overhauled the vaporizer I didn't have to open the gas more than 1/4 to 1/2 turn. The seat must have been worn badly. After the new parts I still opened it up only a little so there was the problem. Thanks to all that posted some help.
To prevent going off topic I will start another thread. Look for TRUING UP THE INSIDE OF A ROLLER TIMER.