Jump to content

Marvel carburetor


Recommended Posts

That’s where I’m at.ran good before I changed float,which was sinking and overflowing.  That was the only change, and now it runs so poorly I can’t drive it??

Link to post
Share on other sites

It has been removed and plugged. Odd thing is, I can run the car in the garage from idle to 45 mph (per rpm), and it is not too bad, slight miss, but when I take it on the road, it immediately goes bad and I am not sure I will get back. Have put my timing lite on each plug wire to view firing and none miss a beat, so I’m sure it is not elec. your thoughts?

jim

Link to post
Share on other sites

As the car was running well before you replaced the float.  Sounds like the new float is working too well and restricting  flow of fuel at the higher rev,s.  Allowing enough fuel at the lower rev,s but not enough when your out on the road

Link to post
Share on other sites

There is no tube. It is plugged at both ends. The car ran fine until  I replaced the float. Took the carb apart again to make sure all 6 jets are open. Checked plug firing again with my timing lite and found that 3&8 are. Not firing consistently. Question the plug wires although they look new. They are however carbon fiber. Ordered a new set of copper ones .should get them mon or tues and will see if it makes any diff.

 

Link to post
Share on other sites
2 hours ago, Rod Wise said:

As the car was running well before you replaced the float.  Sounds like the new float is working too well and restricting  flow of fuel at the higher rev,s.  Allowing enough fuel at the lower rev,s but not enough when your out on the road

Can run it at high rpm in the garage and it does not run out of fuel

Link to post
Share on other sites

Rod- can run it at high rpm in the garage and it doesn’t run out of fuel. Since there is some miss at all speeds I am wondering know if it could be electric.  Will see after new plug wires installed.

Link to post
Share on other sites
16 hours ago, Stamm said:

There is no tube. It is plugged at both ends.

I was not asking about the horizontal tubes.  I am asking about the vertical tube inside the heat riser above the carb.

Link to post
Share on other sites

Good thought. The modification was done when I bought the car, so never checked. I had it repaired on the last 32 I restored a few years back, as it was bad. I know it can be a problem. Will check it out, thanks.

Link to post
Share on other sites

Thinking about this further, as long as the opening to the exhaust pipe is sealed, the condition of he tube you are referring to shouldn’t matter, should it?

Link to post
Share on other sites

If the heat riser tubes are leaking, the area around the center tubes acts like a vacuum tank and does not allow responsiveness to needed vacuum changes as the throttle goes through any changes. On Marvel carbs, the jets are affected by vacuum changes.  

 

Bob Engle

Link to post
Share on other sites

One positive thing about this adventure, I have become extremely efficient at removing a carb! The tubes have been replaced and look like new. I somehow have to determine ,for sure, is it carb or elec. the timing lite on each plug wire at one time indicated they were all firing perfect. The next time i did it, no 3 was not consistent, and 8 wasn’t firing at all. Changed plugs with the same result. So thought maybe it was the carbon fiber wires and ordered new copper ones. Waiting.  remember it ran ok for the last 3 years, until I changed the float. It misses and runs poorly at all rpm’s, so I am thinking elec?. The dist cap looks new. Thanks for all the advice

jim

Link to post
Share on other sites

You can also check for vacuum leaks by spraying starting fluid or WD40 on the intake manifold connections with the engine running.  If it speeds up, you found a leak.  Good luck,

Link to post
Share on other sites

Hi Stamm,  

Great advice given so far, have you taken off the float bowl cover to see exactly where the fuel level is? is your float arm straight, have you examined the rubber on your metering pin? is your float binding against the bowl wall? does it run with the float cover off? sometimes the cover may bind the float arm if its set too high.  have you checked the fuel intake screen? glass bead it if you havent done so. If it ran fine and the only thats changed is a different float, then dont mess with ignition timing, have you checked your fuel source, electric/mechanical pump output? will it run with choke pulled? I scribed a line like Bob recommended  and was very accurate to spec factory setting on my series 90/ fuel level and float level are 2 different things.  As for ignition, I dumped the points and installed the petronix electronic, works great. I have broken the code on how to make a marvel run as originally installed, took awhile!!!

PM me if I can be of more help. 

Link to post
Share on other sites

Well, this situation gets more interesting as I keep checking. Got the new copper plug wires and installed them. No improvement! But as I put my timing lite on each plug wire to check firing, I again notice 3 is not steady and 8 not at all, as before? As I am fussing with the wires I notice sometimes 8 will fire. As I keep fussing around I find that if I push on the dist towards the block, it fires just fine. There must be something wrong in the dist. Take off the cap for a closer inspection, see nothing wrong. However i notice that the points rub has stopped EXACTLY ON A HIGH POINT. something sometimes difficult to get to happen. So I thought since I have the perfect opportunity, why not check the points. They were a sloppy 20. Tightened them up to a tight 20. Seeing  nothing wrong, I put the cap back on and started the car. All plugs now firing perfect, and when pushing on the dist, it makes no difference. Conclusion- the small amount of wear in the shaft allowed me to push the points closer so they were able to close and allow the coil to function. Wires 3 & 8 are on the side of the cap away from the block, so this made since to me. As luck would have it, I was the victim of a perfect storm. That happened at the same time the float failed. So now I have new plugs, wires and coil, that I didn’t need.

Anyway, it now runs much better, not too bad up to about 40, then it hesitates some. Pulling out the choke helps some. Will keep playing with the carb adjustment. FYI, it is a 50 series cabriolet. With the right carb, it ought to run as good as my 8 cyl packards. Smooth. If I have to flip the intake for a down draft, anybody with any experience doing this? What carb did you use to facilitate hooking up the linkage? 
my thanks to all who tried to help

jim

 

 

Link to post
Share on other sites

Jim, 

       Glad that you found the major part of the problem.  Also consider looking for stray sparks at night around your plug wires.  Your Marvel is similar to my 1925 model so consider looking at the condition of the air valve and the venturi operation in the carburetor.  I also ran into issues with a little rust or trash that got into the air valve piston and was keeping the air valve from moving.   Attached is a link.     Hugh

 

https://forums.aaca.org/topic/322950-1927-buick-carb-removal/

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...