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#25882 09/24/2002 4:06 AM | Joined: Feb 2000 Posts: 12 Junior Member | | Junior Member Joined: Feb 2000 Posts: 12 | My '57 235 starts and runs beautifully until I reach about half throttle. At that point, the power drops off slightly and stays flat until the pedal is on the floor. When I let up to about half throttle, I feel a slight surge. The initial acceleration is fine, it just starts to drop off about half throttle. This problem was noticed after I had done some repairs when trying to fix another problem: rebuilt carb,new vacuum advance(timing set ball to pointer,then octane selector at about 6-8 advanced),new fuel filter(generic type between gas tank and fuel pump. This was similar to but not exactly the same filter used previously),points set correctly (before timing).
Vacuum is 20. My inclination is that it is leaning out under heavier acceleration. Carb is a Rochester B. Accelerator pump is working.I soaked it in cleaner and blew out the passages with compressed air. I wonder if the problem is:
1. the carb
2. fuel filter is more restrictive
than previous one
3. something else
I'll bet one of you guys know. Thanks. | | |
#25883 09/24/2002 8:55 AM | Joined: Feb 2001 Posts: 1,897 Member | | Member Joined: Feb 2001 Posts: 1,897 | Well you may have a problem with the new fuel filter if it is more restrictive.Did you use new rubber lines?
If you have the points set correctly THEN se the timing(by the book),it narrows it down to the fuel going through the carburetor.Possibly dislodged some small spec of crud from one place and it is now lodged elsewhere.
There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!
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#25884 09/24/2002 12:11 PM | Joined: Apr 2002 Posts: 146 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2002 Posts: 146 | Sounds more like a spark advance problem. Check both the mechanical advance and the vacuum advance.
if it dosen't need fixed, break it
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#25885 09/24/2002 6:43 PM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | Check your power valve in the carby too. It richens the mixture when the vacuum drops.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#25886 09/25/2002 12:57 AM | Joined: Feb 2000 Posts: 12 Junior Member | | Junior Member Joined: Feb 2000 Posts: 12 | Well, I replaced the fuel filter with one like I used to use and the problem is still there. The advance is working. The recently rebuilt carb may not be working right. I guess I should tear it down and check that power valve. | | |
#25887 09/25/2002 7:19 AM | Joined: Jun 2001 Posts: 34 Member | | Member Joined: Jun 2001 Posts: 34 | Joe: I was having a power loss problem with my 261 and went through all the steps you list,too. Finally found 2 oil fouled plugs,put in anti-foulers and clean plugs and solved the problem.
Should of checked the plugs first but it was "obvious" to me it was a fuel system problem. So much for my ability to see the obvious! | | |
#25888 09/26/2002 8:38 PM | Joined: Jan 2001 Posts: 230 Shop Shark | | Shop Shark Joined: Jan 2001 Posts: 230 | I often find the power valve piston to have grooves in it that prevent it from freely moving - polish it up and see if that helps and also re-check the timing and leave it after lining up ball & pointer .
-Nate
There is no problem so difficult it cannot be overcome by generous application of brute force & ignorance
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#25889 09/27/2002 5:52 AM | Joined: Feb 2000 Posts: 12 Junior Member | | Junior Member Joined: Feb 2000 Posts: 12 | Thanks for the tip on the power valve. I'll check that. As to the timing, I had been running it ball to pointer with the octane selector at 0. I wonder what most people do with the octane selector. In another post,Mechainiac suggested advanced 6-8. Owners manual says engine should have a slight ping on acceleration. I've never heard that. Octane of gas I run is 87 using (R+M)/2 method. | | |
#25890 09/27/2002 6:19 AM | | Anonymous Unregistered | | Anonymous Unregistered | Kedso is on the right track. Sounds like the vacuum advance is not holding vacuum. I am sure VOLKSWAGEN NATE will analize your problem to death & tell you, you need an engine rebuild.  | | |
#25891 09/28/2002 4:08 PM | Joined: Feb 2000 Posts: 12 Junior Member | | Junior Member Joined: Feb 2000 Posts: 12 | Engine is in good shape, only 30,000 mi. since rebuild. Vacuum advance is new. | | |
#25892 09/29/2002 7:02 AM | Joined: Feb 2000 Posts: 12 Junior Member | | Junior Member Joined: Feb 2000 Posts: 12 | It's fixed! 4onthefloor and Vwnate were on the money. After tearing the carb down again, I noticed the power piston hanging up. The stem was slightly bent, which caused it to bind where it meets up with the ball in the power valve. After straightening the stem, I polished the power piston body with some emery cloth. My 57 stepside has come alive again. Thanks to all for the ideas.  | | |
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