Help With Idle
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Junior User
Joined: Apr 2021
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Here is a link to the truck running after installing the new carb and working out some issues. Let me know if everything sounds okay.
If you plan on buying one of these reman carbs or anything cheaper than $100, buy a matching rebuild kit for it just in case. After installing it, gas leaked from the accelerator pump almost immediately. Thankfully I had a spare from the old carb that was brand new. I was able to swap it in while it was still in the truck and so far, it has worked great. The idle screws were both out 3 turns. I set them at 1 1/2 turns which is where they are in the video. The gaskets were also low quality but seem to be working. I may replace them at some point. Maybe when I get rid of the egr (it's plugged off right now).
The only problem I seem to be having is the ported vacuum. I have the idle set at 700 rpm right now. I had the timing set at 12 degrees advance. I had the vac advance plugged off but when I attached it, the timing when to 15 degrees which means some vacuum is getting to the port at idle. I've tried to drop the idle with no change. I went as low as 550 rpm. Is this normal? It's only 3 extra degrees. I've got the timing backed down to 9 degrees (12 with the vac advance).
Let me know if everything sounds okay. I appreciate it! Thanks again!
Edit: I should also add that I sprayed EVERYWHERE with carb cleaner and didn't find any leaks! If I sprayed it into the top of the carb while running, it kind of bogged a bit. Is that a sign of running rich or normal? Thanks!
Last edited by 1965 F250 390; Apr 26, 2021 at 10:37 PM.
Tuned
Joined: May 2014
Posts: 311
Likes: 30
From: MD
Hey congrats! I always find projects much more enjoyable when they are drivable. More issues? fine as long as I can also putter around in the thing.
Timing:
I personally would set the timing of your dizzy so that all in mechanical is ~34degrees as that to me is a safe start point for just about any motor. So if you know the dizzy adds in 22 degrees total mechanical advance when 'all in' I'd set initial timing without the dashpot hooked up to 12 degrees. Now because you are using a dizzy curved for egr cooling the cylinders you may want to be less aggressive. The 9 degrees you have right now is likely fine to use as a start point since you can always adjust it later. I may be wrong but I seem to vaguely recall that the emissions dizzy on the 351w I used to have added a whopping 28degrees of mechanical which meant I would usually put in 6-8 degrees at idle.
WRT the ported vacuum. I'd expect the vacuum to drop off to zero with you having tried dropping the rpm to 550. There are divergent thoughts on the importance of using ported vs manifold vacuum for your dashpot. To really dive in to that I leave it up to youI will state three things:
Hope that helps.
Timing:
I personally would set the timing of your dizzy so that all in mechanical is ~34degrees as that to me is a safe start point for just about any motor. So if you know the dizzy adds in 22 degrees total mechanical advance when 'all in' I'd set initial timing without the dashpot hooked up to 12 degrees. Now because you are using a dizzy curved for egr cooling the cylinders you may want to be less aggressive. The 9 degrees you have right now is likely fine to use as a start point since you can always adjust it later. I may be wrong but I seem to vaguely recall that the emissions dizzy on the 351w I used to have added a whopping 28degrees of mechanical which meant I would usually put in 6-8 degrees at idle.
WRT the ported vacuum. I'd expect the vacuum to drop off to zero with you having tried dropping the rpm to 550. There are divergent thoughts on the importance of using ported vs manifold vacuum for your dashpot. To really dive in to that I leave it up to youI will state three things:
- I tend to run ported
- The ONLY difference between ported and manifold is at idle. under all other conditions it is the same
- Running manifold can cause a lumpy idle IF your motor doesnt have steady vacuum at idle
Hope that helps.
Thread Starter
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Junior User
Joined: Apr 2021
Posts: 78
Likes: 0
Hey congrats! I always find projects much more enjoyable when they are drivable. More issues? fine as long as I can also putter around in the thing.
Timing:
I personally would set the timing of your dizzy so that all in mechanical is ~34degrees as that to me is a safe start point for just about any motor. So if you know the dizzy adds in 22 degrees total mechanical advance when 'all in' I'd set initial timing without the dashpot hooked up to 12 degrees. Now because you are using a dizzy curved for egr cooling the cylinders you may want to be less aggressive. The 9 degrees you have right now is likely fine to use as a start point since you can always adjust it later. I may be wrong but I seem to vaguely recall that the emissions dizzy on the 351w I used to have added a whopping 28degrees of mechanical which meant I would usually put in 6-8 degrees at idle.
WRT the ported vacuum. I'd expect the vacuum to drop off to zero with you having tried dropping the rpm to 550. There are divergent thoughts on the importance of using ported vs manifold vacuum for your dashpot. To really dive in to that I leave it up to youI will state three things:
Hope that helps.
Timing:
I personally would set the timing of your dizzy so that all in mechanical is ~34degrees as that to me is a safe start point for just about any motor. So if you know the dizzy adds in 22 degrees total mechanical advance when 'all in' I'd set initial timing without the dashpot hooked up to 12 degrees. Now because you are using a dizzy curved for egr cooling the cylinders you may want to be less aggressive. The 9 degrees you have right now is likely fine to use as a start point since you can always adjust it later. I may be wrong but I seem to vaguely recall that the emissions dizzy on the 351w I used to have added a whopping 28degrees of mechanical which meant I would usually put in 6-8 degrees at idle.
WRT the ported vacuum. I'd expect the vacuum to drop off to zero with you having tried dropping the rpm to 550. There are divergent thoughts on the importance of using ported vs manifold vacuum for your dashpot. To really dive in to that I leave it up to youI will state three things:
- I tend to run ported
- The ONLY difference between ported and manifold is at idle. under all other conditions it is the same
- Running manifold can cause a lumpy idle IF your motor doesnt have steady vacuum at idle
Hope that helps.
Looks like the mechanical arm in use says 18L. It does have a sleeve around the post so maybe it's more like 16 or so. Still, that's 32 degrees advance right? I'm thinking I should just flip it to the 13L side so it's down to 26 degrees. That should take care of the egr curve I think? Please let me know if I'm headed in the wrong direction. Thanks!
Edit: The vac advance is hooked up to the ported "nipple" on the passenger side of the carb, just infront of the choke.
Edit: The vac advance is hooked up to the ported "nipple" on the passenger side of the carb, just infront of the choke.
Last edited by 1965 F250 390; Apr 27, 2021 at 08:09 PM.
Thread Starter
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Junior User
Joined: Apr 2021
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Tuned
Joined: May 2014
Posts: 311
Likes: 30
From: MD
Looks like the mechanical arm in use says 18L. It does have a sleeve around the post so maybe it's more like 16 or so. Still, that's 32 degrees advance right? I'm thinking I should just flip it to the 13L side so it's down to 26 degrees. That should take care of the egr curve I think? Please let me know if I'm headed in the wrong direction. Thanks!
Edit: The vac advance is hooked up to the ported "nipple" on the passenger side of the carb, just infront of the choke.
Edit: The vac advance is hooked up to the ported "nipple" on the passenger side of the carb, just infront of the choke.
Here is some more details on what all is involved if you need it.
The Ultimate Duraspark Distributor Timing Guide. (foureyedpride.com)
Thread Starter
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Junior User
Joined: Apr 2021
Posts: 78
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I agree. I would flip it to use the 13L and then set my idle timing to ~8 degrees. Adjusting from there.
Here is some more details on what all is involved if you need it.
The Ultimate Duraspark Distributor Timing Guide. (foureyedpride.com)
Here is some more details on what all is involved if you need it.
The Ultimate Duraspark Distributor Timing Guide. (foureyedpride.com)
Cargo Master
Joined: Dec 2015
Posts: 2,549
Likes: 331
From: Harned, Ky
Haven't read through the entire thread but I notices a couple of things you need to look at and possibly correct.
(1) the pct should not be connected to a vacuum tree in the manifold, this will cause a lean condition on the cylinders that intake runner goes to, the pct needs to be connected to a large vacuum port on the carb or carb spacer.
(2) You engine still has the aluminum ear spacer, that's bad! Those spacers are known to burn out on the bottom side and sometimes blowout on the right side.
You need to pull that spacer off and check it's condition on the bottom. Best is the tap the ear port in the intake for a pipe plug, install a pipe plug and grind it off smooth with the carb mounting surface, then purchase a standard carb spacer to go under your carb thus eliminating the ear system.
A recent poster had this same issue not long ago, my nephew is dealing with a burnt out spacer on his 83 F-150 with a 351W
(1) the pct should not be connected to a vacuum tree in the manifold, this will cause a lean condition on the cylinders that intake runner goes to, the pct needs to be connected to a large vacuum port on the carb or carb spacer.
(2) You engine still has the aluminum ear spacer, that's bad! Those spacers are known to burn out on the bottom side and sometimes blowout on the right side.
You need to pull that spacer off and check it's condition on the bottom. Best is the tap the ear port in the intake for a pipe plug, install a pipe plug and grind it off smooth with the carb mounting surface, then purchase a standard carb spacer to go under your carb thus eliminating the ear system.
A recent poster had this same issue not long ago, my nephew is dealing with a burnt out spacer on his 83 F-150 with a 351W
Thread Starter
|
Junior User
Joined: Apr 2021
Posts: 78
Likes: 0
Haven't read through the entire thread but I notices a couple of things you need to look at and possibly correct.
(1) the pct should not be connected to a vacuum tree in the manifold, this will cause a lean condition on the cylinders that intake runner goes to, the pct needs to be connected to a large vacuum port on the carb or carb spacer.
(2) You engine still has the aluminum ear spacer, that's bad! Those spacers are known to burn out on the bottom side and sometimes blowout on the right side.
You need to pull that spacer off and check it's condition on the bottom. Best is the tap the ear port in the intake for a pipe plug, install a pipe plug and grind it off smooth with the carb mounting surface, then purchase a standard carb spacer to go under your carb thus eliminating the ear system.
A recent poster had this same issue not long ago, my nephew is dealing with a burnt out spacer on his 83 F-150 with a 351W
(1) the pct should not be connected to a vacuum tree in the manifold, this will cause a lean condition on the cylinders that intake runner goes to, the pct needs to be connected to a large vacuum port on the carb or carb spacer.
(2) You engine still has the aluminum ear spacer, that's bad! Those spacers are known to burn out on the bottom side and sometimes blowout on the right side.
You need to pull that spacer off and check it's condition on the bottom. Best is the tap the ear port in the intake for a pipe plug, install a pipe plug and grind it off smooth with the carb mounting surface, then purchase a standard carb spacer to go under your carb thus eliminating the ear system.
A recent poster had this same issue not long ago, my nephew is dealing with a burnt out spacer on his 83 F-150 with a 351W
(1) I will re-route it to the pcv port on the back of the carb. Thanks for pointing that out.
(2) When I had it off, the bottom was still intact as far as I could tell. I can see how it could blow being so close to the edge like they have it. I am planning on buying a regular spacer and plugging the egr "hole" on the intake, so that should be taken care of pretty soon. I'll be sure to stay away from aluminum. Thanks again!
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