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Projects 1956 straight six idles but won’t rev

Discussion in 'The Hokey Ass Message Board' started by CliffF, Oct 9, 2021.

  1. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Hello. I have a 1948 Chevy 3100 with a 1956 straight six. It’s was running fine then all of a sudden died. The truck will start with gas pedal pressed to the floor and idles when pedal
    is released. However, it will not rev when I press the gas pedal and it dies with gas poured down carb. I changed fuel line, spark plugs, rebuilt carb, changed points, changed gas and checked timing. I even tried spraying a touch of starter fluid with it idling and it dies. The pedal linkage to the carb is good. I can’t figure out why when given gas, there is no change in the revs of engine. Any help would be appreciated. Thanks.
     
  2. trollst
    Joined: Jan 27, 2012
    Posts: 2,069

    trollst
    ALLIANCE MEMBER

    Plugged exhaust?
     
    Truck64 likes this.
  3. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    thanks trollst but the exhaust is good.
     
  4. Budget36
    Joined: Nov 29, 2014
    Posts: 7,563

    Budget36
    Member

    If starting fluid won’t light it off, maybe weak spark? Coil or condenser issue maybe?
     

  5. Hook up a vacuum Gauge and see what it tells you

    Vacuum leak

    bad / weak spark

    burnt valve

    carb ? Dirty / worn etc ?
     
    Johnny Gee and Truckdoctor Andy like this.
  6. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,029

    302GMC
    Member
    from Idaho

    Put a good used Delco-Remy condenser in it
     
    Truck64 likes this.
  7. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thanks budget. I did change the spark plugs, points, and condenser. It does start but it won’t rev. I changed the coil about a year ago but perhaps it went bad. Not sure why is will run at idle but not rev if it’s the coil but I’m just learning here.

    Vandenplas, thanks. I did just clean and rebuild the carb. I can see that it adds fuel when the gas pedal
    is pressed but I can’t seem to get it to rev, it dies if too much fuel is added. Maybe it’s a weak spark (bad coil?), would that cause the issue? I haven’t hooked up a vacuum gauge so I will try that. I did pull the valve cover and had one valve stuck closed. I was able to free it up and everything seems to work fine. Not sure how to check for a burnt valve though or what symptoms that would cause. Any thoughts would be greatly appreciated as I have been working on it for the past three weekends and nothing.
     
  8. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thanks 302GMC. I did just put in a new condenser but maybe it’s a bad one. A coil was my next guess but I’m tired of throwing parts at this one so wanted to check in with the experts here to get some thoughts. Would a bad condenser cause the no rev?
     
  9. 52HardTop
    Joined: Jun 21, 2007
    Posts: 970

    52HardTop
    Member

    Is there any fuel spilling from the carb? You said you rebuilt the carb. There might be a chance that the kit you bought was an old kit with rubber parts that are destroyed by the ethanol in the gas. I'm just throwing that out there. It happened to me when I rebuilt two carbs with old kits.
     
  10. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thanks 52. No fuel spilling from the carb. My first carb rebuild so may need to redo, but I was very thorough and everything seemed good. I did the carb first thinking that was it but it didn’t change things. I would think if it was a carb issue, the gas down the carb trick would give me a little rev but still nothing. I could be off on that thought though.
     
  11. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,843

    greybeard360
    Member

    How did you fix a stuck closed valve?
     
  12. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Hey Greybeard, I put a small thin flat screwdriver against the spring and gave a few light taps on the end and the valve popped opened. Didn’t take much force.
     
  13. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,193

    Mr48chev
    Member

    When you rebuilt the carb how did you adjust the float level? Rochester or carter Carb?
    The float level adjusts a tad different on each.

    It may be that you have the float level set way too low and the needle valve won't open enough to fill the fuel bowl.
    Try this first. Take something that you can carefully pour gas into the float bowl vent tube and pour maybe between 1/4 and half a cup of gas into the vent tube. That will fill the float bowl and should let the engine rev up for 20 seconds or as much as a minute or so. Start the engine and see if you can get it to rev up without dying for several seconds or until the bowl runs out of gas. If it won't rev up it could be inside the carb and if you got a kit with several gaskets between the bowl and the top you could even have the wrong gasket if you didn't match the new gasket to the old gasket.

    One more thing to think about, is it getting enough fuel? There is usually a shut off valve under the floor on trucks with seat tanks and that valve may be partially closed. If you take the fuel line off the carb and crank the engine do you get a good shot of gas into a plastic pop bottle held over the end of the line?

    Simple things first always when you are trying to figure something out. Rochester single barrel x_LI.jpg
     
    alanp561 likes this.
  14. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,193

    Mr48chev
    Member

    I'm not going to edit post 13 again but in reference to my comment on more than one gasket for between the top and the bowl. If you use the wrong one it will block off fuel to the main nozzle and possibly the accelerator pump discharge nozzle Single barrel carb kit.jpg
     
    VANDENPLAS likes this.
  15. 57Fury440
    Joined: Nov 2, 2020
    Posts: 39

    57Fury440

    What did the old plugs look like when you took them out? Maybe you have a weak spark. Rebuilding the carb. didn't change anything. Pull the dist. cap and look to see if you are getting a good spark.
     
  16. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,843

    greybeard360
    Member

    Still not understanding this..... If the valve it stuck closed ( in the up position) it would bend a pushrod or break a rocker arm. Are you sure it wasn't stuck open (downward)?

    Either way it wouldn't idle very well. Was it popping thru the exhaust or intake?
     
    Truckdoctor Andy likes this.
  17. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thanks Mr48. I’ll definitely take your advice and post back. It’s a Carter carb. I adjusted the float with a gauge that came with the rebuild kit but it’s basically parallel with the top (when full). I checked the gaskets when I put them back. They looked the same but I saved the old ones and will double check. I’ll also try filling the float bowl like you suggested but when I changed the gas I emptied the tank and kept the line disconnected. The engine idles for a while before finally dying (wanted to ensure all bad gas was out). I’m guessing the float bowl is filling but I will double check. The strange thing is I can see down the carb and move the accelerator arm and I can see gas pump down the carb but there is no rev and the engine just wants to die. It looks like it’s getting gas but there’s no reaction. I’ve also sprayed starter fluid around the whole carb looking for leaks but again no change in engine rev.

    Thanks 57fury. It definitely could be the ignition system. I changed the distributor cap last year and just did the plugs, points, and condenser. The only thing left there is the coil. Each plug is getting spark but not sure if it’s strong enough under pressure. There was a lot of soot on the plugs when I changed them.
     
  18. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Hey Greybeard. Definitely new at this so maybe I am thinking of it wrong. The spring was stuck compressed down. I thought that was closed but maybe that is open. The push rod was off the rocker arm but luckily not bent. I’m guessing once the spring got stuck in the compressed position the push rod slipped out from the rocker arm. I found that because there was exhaust coming out of the carb and the engine would only start with a plug removed. Once the valve was released the engine started with all plugs in and there was no more exhaust out the carb. Again, new to this so please correct me if I am thinking of this wrong.
     
  19. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,843

    greybeard360
    Member

    Makes sense now.... Yes, down is open.

    Sounds like this may have set for a while and old fuel is causing the valves to stick.

    How did you clean the carb? Just spraying with carb spray won't get all of the little passages cleaned out. It also needs air pressure blown thru the passages to make sure they are clear.
     
  20. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thanks for the clarification on the valves Greybeard. I took the carb apart, soaked it for a few hours in the chem dip stuff, used carb cleaner, sprayed out all the ports and used compressed air to ensure all ports were clear. I then put each piece back together checking that they worked as I went (added gas to check the accelerator pump before I put it back together). I was surprised how few components were in this carb but it’s a simple single barrel carb.

    I got the truck with the house. It’s a yard truck used to plow and grade a long dirt driveway. I’ve learned a little each year. I was tuning it up before the winter and that’s when the issues started. It’s been used every year for the last 8 years. Not regularly but I live in Maine so it gets enough action each year.
     
  21. Wanderlust
    Joined: Oct 27, 2019
    Posts: 398

    Wanderlust

    I know you said it’s good but did you verify this, had a bike do the same, cleaned carbs , changed tank , filter, would run but would not accelerate, turned out mice had packed about a pound of canola into exhaust pipe.
     
  22. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,193

    Mr48chev
    Member

    If (or when) you pull the carb off and apart check the float drop along with float level. If the tang that controls the float drop gets bent it may not drop down the right distance to let enough fuel in and just let a tiny dribble in.
    This link shows the correct adjustments for a Carter YF
    Carter YF & YFA Adjustments - Mikes Carburetor Parts (carburetor-blog.com)
     
  23. Tickety Boo
    Joined: Feb 2, 2015
    Posts: 1,441

    Tickety Boo
    Member
    from Wisconsin

    Disconnect the exhaust pipe and see how it runs :rolleyes:
     
  24. Rickybop
    Joined: May 23, 2008
    Posts: 7,454

    Rickybop
    Member
    from Michigan

    I had the same experience with a Chevy straight six that wouldn't rev.
    I had just rebuilt and installed the engine... all new tune up parts. But the carburetor was not good. Rebuilt and reinstalled the carburetor.
    Same symptom. Still would not rev up. Couldn't figure it out.
    Wife came out to check on how I was doing. Not good. She said... Did you change the spark plugs? Silly woman... of course I changed the spark plugs. She said okay well, good luck and went back in the house.
    Standing there wondering what next. Thought about what she said. Whatever... I don't know what else to do anyway. Can't hurt to check the spark plugs again I guess.
    Well what do you know. My brand new spark plugs were already black and fuzzy as could be from running the engine before I rebuilt the carb. Changed them out and the engine ran like butter. Revved like crazy. 500 HP.
    So the obvious question is...
    Have you checked your new spark plugs since you rebuilt the carburetor?
    Good luck.
     
  25. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,556

    oldsman41
    Member

    I know everyone is settled in on the carb but did you make sure the springs in the distributor our good. Just throwing other ideas out there
     
  26. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Thank you everyone for the advice. Had work today so when I get home I’ll check it out. The air coming out of the exhaust pipe is strong, however, living in the woods, I would not be surprised if some critters got in there so I will definitely pull the exhaust to see if it makes a difference. I did pull a plug last night and it was all sooted up. Gonna grab a few on my way home, could be a simple fix. I truly appreciate everyone chiming in. I’ll keep everyone posted.
     
  27. carbking
    Joined: Dec 20, 2008
    Posts: 3,196

    carbking
    Member

    "The engine was running fine, and then it died"

    "It does start, but won't REV"

    If changing the plugs do not solve the issue, try loosening the distributor slightly so that you can manually advance the spark as a test.

    If the distributor does not advance, the engine will not rev regardless of the condition of the carburetor.

    Jon.
     
    Cosmo49 likes this.
  28. CliffF
    Joined: Oct 9, 2021
    Posts: 11

    CliffF

    Hello Everyone. I wanted to provide an update to this one. I went through all the suggestions here and still couldn’t get the engine to rev. I pulled apart the carb one more time and that’s when I finally noticed there was an “extra” piece sitting between the carb and the manifold. Turns out the truck had a governor on it. I pulled it off, cleaned it up, changed the gaskets, and reinstalled but still no rev. I finally changed out the mounting bolts for shorter ones and pulled the governor all together. I turned the key and without hesitation she started right up. Pressed the gas and she revel’s right up. A little adjustment to the carb, and the truck runs better than ever. Such a simple thing, I can’t believe I didn’t figure it out earlier. Maybe someone suffering from the same problem will use my stupidity to easily figure out their issue and get rid of the governor.

    Anyway, thank you everyone for chiming in. I truly appreciate the help and definitely learned tons from all your answers. This is such a great community. Thanks again.
     
    jimmy six, ottoman and Budget36 like this.
  29. KJSR
    Joined: Mar 7, 2008
    Posts: 2,485

    KJSR
    Member
    from Utah
    1. Utah HAMBers

    Glad you figured it out. Were mostly hot rodder's here....stuff like a governor will be removed automatically!
     
    jimmy six, 427 sleeper and Budget36 like this.

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