midman

Rebuiding a 1931 90 Series Engine

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The covers on the regulators are prone to rust through from water eddy currents.  I would suggest plating the inside or epoxy coating the inside.  

The oil pressure through the unit should be much higher than the water pressure.  Oil in the radiator would be  the indicator of a leak.

 

Bob Engle

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So the car is running but I am struggling to get a good idle and under load I need to choke the engine to keep from backfiring through the carb.

I double checked my timing, valve adjustment, and tried setting the carb. I can make it worse but I can’t make it better. As soon as I think I have a good idle it starts stumbling and wandering again.

I’m done today but I’m thinking of two areas to check.

1. A vacuum leak on the intake side.

2. My distributor shaft has some play in it so I’m going to try to get to the bottom of that though I don’t know that it could be causing my issue.

 

I was having this problem with the car before I rebuilt it so it is frustrating, but at least I don’t have the rod knock any more.

 

Any other thought or ideas out there?

 

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The problems I have encountered with my 29 are similar to yours. Yes check intake gaskets , I doubt it as thorough as your work appears. I would totally verify condition of the heat riser tubes . A tiny hole in a heat tube  can cause erratic engine operation.  The next will be distributor bushing, advance mechanism and contact points condition. My updraft Marvel still likes to run with the choke slightly closed at times. I have no real explanation as to why other than venturi mechanism not being consistent in operation or main jet becoming partially clogged from being parked too long. The venturi in mine has been replaced and was operating flawlessly last time my carb was off, but that was years ago.

Edited by raydurr (see edit history)

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While a long time ago, my '31 liked to have a bit of choke. I fiddled with it a lot and finally just lived with it.  Today I wouldnt tolerate that.

 

When I got the car running after full restoration, It wouldnt run over about 5 mph. Drove me crazy. I was just sure I had a fuel starvation problem. Finally I noticed the the condenser was not on the distributor (outside on the dual point). It was amazing how adding the condenser made it run.  Actually, I was surprised that it ran at all.

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“I won't offer you candy from a windowless van but perhaps I can entice you to the dark side. 

 

Yea, I’ve been thinking about that.

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What's the spark plug color?  That will tell you rich or lean condition.  Marvel carbs are notorious for warpage on the diecast Air valves.  there are some old threads about checking the clearances on these air valves.

 

Bob Engle

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Chuck:

Before I reattach the head and accessories to my engine I am rebuilding my spare Marvel carb.

 My carbs venturi block was warped and the center had at least a 1/16" bulge. After much redressing with a file to get it flat and fitting the tail clearance it is to factory spec (.009-.017clearance).DSCF7001.thumb.JPG.08999daa72f148fe811f8adadb550f3a.JPG I have it at this moment .010.

DSCF7002.thumb.JPG.7d3bc235df1f8db10996572075827a44.JPG

I used the Marvel book from BOB-s as my reference. On my original carb there was no tail clearance and dashpot vane was open about 1/8". (also someone had previously installed the venturi block upside down) I had done that one also as the vane contour was warped to the bore and took a LOT of fitting. When I pulled the carb off for the engine rebuild, I found that I will have to re do some of the tail clearance fitting again. That darn die cast grew again in just 2 years!

 Best of luck.

Larry

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Rebuilt the Marvel........again. The venturi are good. Tweeked the timing a little more. It’s running better. Still have to choke it slightly under load, but better.  I’m still chasing a vacuum leak I think but I can run it up and down the road. I’ll check the plugs in the next couple of days and see how they look. 

 

Thanks for all the suggestions. I’ll  let you know when I figure it out.

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The engine is really starting to run well as she starts to break in. The timing and carb are good now though I hate that Marvel leak at shut down.

 

I am getting vapor lock during my last two break in runs though. It’s hot out here but not crazy hot. I think the 1932’s had a shield to help with this so I might fabricate one.

Any other ideas out there other than shielding or wrapping the fuel line.

 

Other than that she’s coming along

 

Chuck

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To remedy the vapor lock , the first thing that I would do is completely block exhaust from going thru the heat riser,  if you have not done so already. You can temporarily wrap the fuel lines and fuel pump with heavy aluminum foil to see if that helps. If that helps there are  proper wraps that would help keep the fuel lines cooler. A heat shield for the carb and fuel pump would have to help this tremendously. Different fuels are also affected by heat differently.  Good luck.

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Well I’ve decided to do two things this weekend. Take the loop out of the copper fuel line and add a switched fuel pump. The pump is mostly for starting the car after it sits more than a couple of weeks but it might help with the vapor lock too if I notice it. I’ll only run the pump at initial start for the most part. I hate grinding away when first starting.

 

i had already blocked off the exhaust heat exchanger.

 

I’ll report back.

 

Chuck

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I will need to be doing the same on my 37. I had it out for 4 days before all the rain. We drove it for our regular errands. Starts up right away without a problem every day and after all the short drives.  Let it sit for a week and it will take forever to start. I would bring a small container of gas, remove the side plug on the carb and fill it runs out the hole. Give it a squirt of gas down the throat of the carb, hit the starter and it fires right up and idles ....for about 5-10 seconds, then it quits.  The fuel in the carb is gone and it is still waiting for delivery from the fuel pump. 

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