Does this vacuum routing look correct?
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Tuned
Joined: Feb 2017
Posts: 324
Likes: 6
From: SoCal
Does this vacuum routing look correct?
I have a 460 in my 65 F100. Looking over my vac lines this is what I have. I normally wouldn't run my brake booster off a t-connect with the trans vac line but this is how it has always been.
Can someone look over this diagram and let me know what you think?
Thanks!
Can someone look over this diagram and let me know what you think?
Thanks!
Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
Yes. That is fine.
BTW - On the front of the carb you will have a "ported" vacuum port and an "open" (i.e. manifold vacuum) port. The ported vacuum only has vacuum on it when the throttle is open some (no vacuum at idle speed).
You need to be sure you are connected to the correct one.
BTW - On the front of the carb you will have a "ported" vacuum port and an "open" (i.e. manifold vacuum) port. The ported vacuum only has vacuum on it when the throttle is open some (no vacuum at idle speed).
You need to be sure you are connected to the correct one.
Thread Starter
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Tuned
Joined: Feb 2017
Posts: 324
Likes: 6
From: SoCal
Yeah I'm aware of that and tried both ports. It didn't seem to make a difference. My 460 has low vac at idle and the truck hesitates off idle when first giving it gas. I am currently trying to solve this issue. The truck idles perfectly and only hesitates off a stop but clears right up quickly. For my truck I would assume running the vac line off the open port is the correct choice but it has always been on the ported port. Either way doesn't seem to make a bit of difference though.
Thanks for the help!
Thanks for the help!
Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
Maybe you need a larger pump shot. I find that the off-the-shelf carbs don't work as well on our heavy truck without increasing pump shot. Is it a Holley carb (if yes, try a larger "accelerator pump cam"?
I should have mentioned above, your distributor should be connected to manifold vacuum (not ported vacuum). Why? Read this (skip to last paragraph if you're in a hurry) http://chevellestuff.net/tech/articl...r_manifold.htm
I should have mentioned above, your distributor should be connected to manifold vacuum (not ported vacuum). Why? Read this (skip to last paragraph if you're in a hurry) http://chevellestuff.net/tech/articl...r_manifold.htm
Last edited by CountryBumkin; Apr 26, 2017 at 07:11 AM. Reason: add link
Thread Starter
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Tuned
Joined: Feb 2017
Posts: 324
Likes: 6
From: SoCal
I have a Edelbrock Performer 750. It is brand new and replaced a Carter that worked flawlessly.
I have read about upgrading the acc. pump and that is something I'm looking at. Also looking at re-jetting as I think the carb is running too lean.
Yeah like I said I have swapped it to the open port but saw no difference. I will switch it back again. I have read that write up as well and looked high and low for that Echlin #VC-1810 advance can with no luck in finding one. I know that will help but Napa nor anyone else sells it any longer. Spent a couple of days trying to track this part down.
I have read about upgrading the acc. pump and that is something I'm looking at. Also looking at re-jetting as I think the carb is running too lean.
Yeah like I said I have swapped it to the open port but saw no difference. I will switch it back again. I have read that write up as well and looked high and low for that Echlin #VC-1810 advance can with no luck in finding one. I know that will help but Napa nor anyone else sells it any longer. Spent a couple of days trying to track this part down.
Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
But I don't think that has anything to do with your problem.
Do you have a long duration cam, like more than 230 degrees duration at .050" valve lift (i.e. low vacuum at idle)?
Thread Starter
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Tuned
Joined: Feb 2017
Posts: 324
Likes: 6
From: SoCal
I'm not sure of the details but I do know the original owner of this truck took the 460 from a 73 Lincoln and in 1999 he had it rebuilt. The paperwork is chicken scratch but I know a hotter cam was installed. The mechanic that handled my fire repair damage informed me that the low vac at idle is caused by the cam.
I have been trying to find that parts equivalent for my ford. Mainly because I want the dist. vac advance to be fully-deployed at 8 hg vacuum. I have been thinking this would help my hesitation. The engine idles smoothly but when I press the gas softly (like a person would normally when leaving a stop) it hesitates. If I romp on the gas pedal there is no hesitation at all and it spins the rear wheels as I accelerate.
I have been trying to find that parts equivalent for my ford. Mainly because I want the dist. vac advance to be fully-deployed at 8 hg vacuum. I have been thinking this would help my hesitation. The engine idles smoothly but when I press the gas softly (like a person would normally when leaving a stop) it hesitates. If I romp on the gas pedal there is no hesitation at all and it spins the rear wheels as I accelerate.
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Lead Driver
Joined: Feb 2002
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From: Greater Austin, Texas
You only need ported vacuum if you cannot get idle speed down correctly using manifold vacuum. If this is not a problem, then use manifold vacuum.
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Thread Starter
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Tuned
Joined: Feb 2017
Posts: 324
Likes: 6
From: SoCal
Solved my problem.
The original owner of this truck removed the mechanical gas pump and placed a plate over the hole. He then installed an electric pump on the frame of the truck. The pump he installed was a 2-4 psi model. I replaced it with a slightly larger 4-5 psi model which did not solve my issue.
So installed a new mechanical pump on the motor and BAM the carb is working great and zero hesitation.
Nice.
The original owner of this truck removed the mechanical gas pump and placed a plate over the hole. He then installed an electric pump on the frame of the truck. The pump he installed was a 2-4 psi model. I replaced it with a slightly larger 4-5 psi model which did not solve my issue.
So installed a new mechanical pump on the motor and BAM the carb is working great and zero hesitation.
Nice.
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