Won’t rev up

Scottio57

Scottio57

Senior Member
Won’t rev up

I tried to see if this was covered already but I couldn’t find it so please excuse me if it was already covered. 1930 sport coupe, all stock except B head and overdrive. Recent valve adjustment, spark plugs, point adjustment, and carb clean all to spec. In service manual. I got this car in January after my Dad passed. It has always run great but today I kind of pushed it a little. I noticed in high gear, without OD, it will run great up to about fifty mph. Light throttle, full throttle it’s all good up to fifty. After about fifty two mph it stops accelerating and if I push the throttle it stumbles and backfires. At this point I tried a little choke, thinking it was a lean condition, no change. I turned the GAV, no change. Moved the spark to full advance, no change. Full retarded stopped accelerating as it should. If I use OD it will give me about another ten mph and then does the same thing. So it seems to be RPM related, richining the fuel doesn’t help, changing the spark doesn’t help, opening the throttle makes it worse. Is fifty two all I’m going to get out of this engine. Am I floating the valves or the points ? Has anybody run into this. Any suggestions will be appreciated.
 
Re: Won’t rev up

I think your on the right track with thinking it's fuel related. When you reinstalled the carburetor, did you make sure the fuel line NOT in to far? The fuel tank cap may not be venting properly, my 31 would go past 50-55, I pulled over and put the cap in my pocket. It then would run 65-70 , ended up bending the cap ears down so when the cap is turned tight it's a little loose, repoped 30-31 caps are Notorious for not venting well.
 
Re: Won’t rev up

I think Big Hammer is on the right track.

First thing, easy thing, open/loosen the fuel cap and try it. It sounds like a classic plugged cap vent.

If not that then make sure the fuel line extends only about 1/16" or so past the ferrule where it goes into the carburetor.

While the fuel line is off check to make sure there is a good steady long flow.
 
Re: Won’t rev up

Big hammer said:
I think your on the right track with thinking it's fuel related. When you reinstalled the carburetor, did you make sure the fuel line NOT in to far? The fuel tank cap may not be venting properly, my 31 would go past 50-55, I pulled over and put the cap in my pocket. It then would run 65-70 , ended up bending the cap ears down so when the cap is turned tight it's a little loose, repoped 30-31 caps are Notorious for not venting well.
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:eek::eek::eek: My opinion is Big Hammer probably should have left the cap on!:) Have you checked for a manifold leak? How about a carb=to=manifold leak?
 
Re: Won’t rev up

Scott, you have received some good suggestions. Here's one more, check the distributor points spring and assure that the spring is strong. I had one that would only run 40 and then had symptoms similar to yours.
 
Re: Won’t rev up

Being the choke did not help, it could be the spring on the points. I think it is a ignition problem.
 
Re: Won’t rev up

On my way outside to start working on it. I will start with pulling off the gas cap and then go onto the carb. Hey Big hammer. Do you really take your car up to 70 mph without an OD? I would be afraid of it flying apart.
 
Re: Won’t rev up

Scottio57 said:
On my way outside to start working on it. I will start with pulling off the gas cap and then go onto the carb. Hey Big hammer. Do you really take your car up to 70 mph without an OD? I would be afraid of it flying apart.
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Yes I had it up to almost 70, no OD, 3.78 rear, only once had to see if it could, it did thats enough for me :-)
 
Re: Won’t rev up

Chuck Sea/Tac said:
Do you have a fuel filter of any kind?
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Winner!!!!!! Removed gas cap, no change. Removed carb raised float level a tad and cleaned all passages, no change, although it did have a little more gitty up. While I was at it I checked fuel flow and there was more gas coming out than the engine can drink even at full power. Checked point gap, cleaned points, cap, rotor, no change. Removed in-line 5 micron fuel filter problem solved. Thanks very much to all of you.
 
Re: Won’t rev up

Glad its fixed. Surprised at the fuel filter. I always use one, but, I guess not that fine.
 
Re: Won’t rev up

Pat; I don't really understand it either. I felt there was sufficient fuel flow with the filter in line but that was the only change that made a difference. It must have to do with fuel pressure, gravity feed, I guess. I cant explain it, just glad it works. I have one on my T also but so far it hasn't given me any problems. I'm a motorcycle mechanic and we use these all the time. I'm still stunned that hammer drove his car to 70 mph. I would never do that. Even 55 seems a little high. I'm more comfortable around 50 mph.
 
Re: Won’t rev up

Scottio57 said:
Pat; I don't really understand it either. I felt there was sufficient fuel flow with the filter in line but that was the only change that made a difference. It must have to do with fuel pressure, gravity feed, I guess. I cant explain it, just glad it works. I have one on my T also but so far it hasn't given me any problems. I'm a motorcycle mechanic and we use these all the time. I'm still stunned that hammer drove his car to 70 mph. I would never do that. Even 55 seems a little high. I'm more comfortable around 50 mph.
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Whatever anyone says, I believe these are cars for the roads of the day. These monsters are 'comfortable' at 40-45 mph and I'm in no hurry when in one. yes they'll go 50-55 but they are too 'busy' for me.

I use in-line filters in about everything without issues. But I don't use fancy fine micron ones.
 
Re: Won’t rev up

Nice to see it when the original post gets back with information about what it took to resolve his problem. That way we all benefit.
 
Re: Won’t rev up

Patrick L. said:
Whatever anyone says, I believe these are cars for the roads of the day. These monsters are 'comfortable' at 40-45 mph and I'm in no hurry when in one. yes they'll go 50-55 but they are too 'busy' for me.

I use in-line filters in about everything without issues. But I don't use fancy fine micron ones.
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Absolutely. I drive my A often as well as my T and I live in the city. Not ever in a hurry. Normally 45 or so in the A and 35 in the T. If traffic gets to heavy I use the side streets. Always a blast for me and the folks that enjoy seeing it putt down the road. :)
 
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