Stall during acceleration

[Silvertip]

Warm up the engine and then shut it off. Now open the throttle fully and look at the secondaries throttle plate. It should still be closed even though the throttle is wide open. Then gently push on the secondary air valve (the plate). It should require just a slight amount of force to open it and it should then spring back lightly. Remember incoming air forces the plate open because of the high vacuum beneath it. Looking at the carb carefully will reveal the spring that does this work. That is adjustable. If it is too tight slamming the throttle means there will be a bog until higher revs are achieved or it may never reach higher rpm because of the engine load trying to work on only two barrels. If the spring is unhooked or set too loose slamming the thottle dumps the secondaries and the engine gets too much fuel and it can cause a backfire or actually put out the fire and you have a stall. If this engine has had a carb replacement that has mechanical secondaries then again, ignore this. My description applies only to AVS (air valve secondaries).

 

[Jfreakman84]

Warm up the engine and then shut it off. Now open the throttle fully and look at the secondaries throttle plate. It should still be closed even though the throttle is wide open. Then gently push on the secondary air valve (the plate). It should require just a slight amount of force to open it and it should then spring back lightly. Remember incoming air forces the plate open because of the high vacuum beneath it. Looking at the carb carefully will reveal the spring that does this work. That is adjustable. If it is too tight slamming the throttle means there will be a bog until higher revs are achieved or it may never reach higher rpm because of the engine load trying to work on only two barrels. If the spring is unhooked or set too loose slamming the thottle dumps the secondaries and the engine gets too much fuel and it can cause a backfire or actually put out the fire and you have a stall. If this engine has had a carb replacement that has mechanical secondaries then again, ignore this. My description applies only to AVS (air valve secondaries).

Thank you. That was very well explained!

 

[nola mike]

sounds to me like the timing is not advancing , use a timing light to check if the mechanical advance is working , it may just need some lube.

No mechanical advance on his engine.

Warm up the engine and then shut it off. Now open the throttle fully and look at the secondaries throttle plate. It should still be closed even though the throttle is wide open. Then gently push on the secondary air valve (the plate). It should require just a slight amount of force to open it and it should then spring back lightly. Remember incoming air forces the plate open because of the high vacuum beneath it. Looking at the carb carefully will reveal the spring that does this work. That is adjustable. If it is too tight slamming the throttle means there will be a bog until higher revs are achieved or it may never reach higher rpm because of the engine load trying to work on only two barrels. If the spring is unhooked or set too loose slamming the thottle dumps the secondaries and the engine gets too much fuel and it can cause a backfire or actually put out the fire and you have a stall. If this engine has had a carb replacement that has mechanical secondaries then again, ignore this. My description applies only to AVS (air valve secondaries).

I think we're talking about a Weber/Edelbrock, in which case the secondaries are weighted, no adjustment

 

[tank1949]

I'll check the accel pump linkages on Monday. Float levels were set when I rebuilt the carb but I guess I can recheck them, which way do I need to go with them? Spark plugs were new, I'll pull some on Monday as well. How do I measure fuel pressure?

Buy a new carb.

 

[Jfreakman84]

Buy a new carb.

Ok...I was told not to in my previous post. Can you expound on why I need to buy a new one, please?

 

[flashback]

With all respect! You may not have the knowledge to rebuild it and would be better served to go new..

 

[Scott06]

Ok...I was told not to in my previous post. Can you expound on why I need to buy a new one, please?

most likely the carb needs another rebuild With a good kit. A lot of folks get rebuilt ones off the web that are problematic And or not set up correctly for the application, hence the recommendation to rebuild yours if its is an unmolested core…

likely you are lean in transition circuit or idle passages. get a good kit best if you can maybe find someone to help who has done it successfully before. Otherwise watch videos for webber or edlebrock 4 bbls learn how they work And go for it. That how we all learn.…

 

[Jfreakman84]

With all respect! You may not have the knowledge to rebuild it and would be better served to go new..

It's already been rebuilt and the boat is running better with the exception of this issue. I was told not to buy new since it would take a lot of adjustment to tune the carb to my motor. I have no wish to spend four or five hundred if it's a simple adjustment.

 

[Jfreakman84]

most likely the carb needs another rebuild With a good kit. A lot of folks get rebuilt ones off the web that are problematic And or not set up correctly for the application, hence the recommendation to rebuild yours if its is an unmolested core…

likely you are lean in transition circuit or idle passages. get a good kit best if you can maybe find someone to help who has done it successfully before. Otherwise watch videos for webber or edlebrock 4 bbls learn how they work And go for it. That how we all learn.…

I got the kit from carb junkys. The guy I spoke to was very knowledgeable and I believe he posts on this forum. As I posted above, I don't have a carb shop around or anyone to learn from apart from youtube, which I watched multiple videos of before I attempted the rebuild and during the rebuild.

 

[Scott06]

I got the kit from carb junkys. The guy I spoke to was very knowledgeable and I believe he posts on this forum. As I posted above, I don't have a carb shop around or anyone to learn from apart from youtube, which I watched multiple videos of before I attempted the rebuild and during the rebuild.

Only a couple thing i can think of
where are your idle mix screws set? I found my edelbrock can idle so lean that when you get into transition circut it stunbled.
if i were you tear it down double check needles and seats are floats arent hanging up. Take out jets and boosters to make sure all passages are clean. I was experimenting with jets on my GTO, went from a 63 to a 61 jet, went way lean, go back in to change jets back and find a piece of airhorn gasket covering one of the jets… for the record i tore that carb down at least ten times by the time i got jetting, idle tube size, and accelerator pump nozzle sizes dialed in ..

 

[nola mike]

Haven't seen it mentioned if you've tried the different adjustments on the accel pump linkage. 3 different holes that adjust the amount of the pump shot

 

[tank1949]

Ok...I was told not to in my previous post. Can you expound on why I need to buy a new one, please?

If you have tried everything recommended and achieved 0 results, it is your only option. I have rebuilt several q-jets and Hollies over my life. If they get internal corrosion or blockages, sometimes it is better to just trash them.