tuning Holley
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From: Atlanta
tuning Holley
I have a flathead and a 4bbl holley. I have started the task of tuning my Carburetor and have been looking at several online references but I have not been able to tell where I should hook up the vacuum gauge. I found one reference that suggested the intake manifold but I really don't have a place to hook it to the manifold.(It is an offenhauser manifold) I have a place on the throttle plate and when I hook that up I get about 15" Hg. When I go to adjust the mixture screws I see no real change in vacuum by either tightening or loosening until I get it almost all the way tightened then the engine starts to slow. Is this normal?
Fleet Owner
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From: NM
The Holley instructions show you:
http://www.holley.com/data/Products/...8108-2rev2.pdf
Did you go to a different distributor too?
http://www.holley.com/data/Products/...8108-2rev2.pdf
Did you go to a different distributor too?
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From: Atlanta
I used the full manifold vacuum port as the instructions suggest. I have not tried another carb. I don't have another one. This is the one I got with the truck but I have rebuilt it.
What started this effort was that I got the truck started and sitting in the driveway it revs very nicely. When I tried to drive it down the street It was very jerky. I never managed to get the clutch all the way out without the engine dying.
What started this effort was that I got the truck started and sitting in the driveway it revs very nicely. When I tried to drive it down the street It was very jerky. I never managed to get the clutch all the way out without the engine dying.
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From: Atlanta
The way it was set up when I bought it was with the dist connected to the Timed spark Vacuum source on the dist. I guess I am not sure if it is the stock distributor(Can you tell from the photo below). I did notice what might be a problem. This is my distributor from the top:
If I compare it to the illustration on Van Pelt It would appear that my #1 on the dist is connected to the #5 cylinder:
Would it even run if it was one cylinder off?
If I compare it to the illustration on Van Pelt It would appear that my #1 on the dist is connected to the #5 cylinder:
Would it even run if it was one cylinder off?
Fleet Owner
Joined: Jul 2004
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From: NM
I mentioned in another thread that there are two plug wiring diagrams out there; Van Pelts is 180 compared to the more common one. Either will work, just set the crank so the bump on the pulley aligns with the pointer; the rotor should be pointing to #1 plug wire or #6.
You have the stock Load-A-Crapic distributor. It uses a unique vacuum signal that combines ported vacuum with manifold vacuum (and connecting the two together won't work). Nothing but the stock style carb will work properly with LoadAMatic. If you connect to the ported vacuum port on the carb, you will essentially get something similar to centrifugal advance (advance with RPM), if you connect to the manifold connection you will get better economy. But neither will be the complete picture. Try each one and see which works best. In the long run, you'd be best off with a "Bubba's" distributor, or an MSD, both of which have mechanical centrifugal advance and separate vacuum advance. It makes a HUGE difference!
"Bubbatronics" Electronic Flathead Distributor
PS -- I assume you are already 12v?
You have the stock Load-A-Crapic distributor. It uses a unique vacuum signal that combines ported vacuum with manifold vacuum (and connecting the two together won't work). Nothing but the stock style carb will work properly with LoadAMatic. If you connect to the ported vacuum port on the carb, you will essentially get something similar to centrifugal advance (advance with RPM), if you connect to the manifold connection you will get better economy. But neither will be the complete picture. Try each one and see which works best. In the long run, you'd be best off with a "Bubba's" distributor, or an MSD, both of which have mechanical centrifugal advance and separate vacuum advance. It makes a HUGE difference!
"Bubbatronics" Electronic Flathead Distributor
PS -- I assume you are already 12v?
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From: Atlanta
It is 12V. I was hoping another big purchase would not be in the cards until I can drive the truck. Would this explain the severe hesitation or can the load-o-matic be made to work for the time being?
Thanks again for all the help ALBUQ F-1
Thanks again for all the help ALBUQ F-1
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From: Atlanta
I am in the process of looking for the other wiring diagram but no luck so far. This is that I have. When I put the timing light at "A" I do not see a timing mark with any setting on the timing light. If I set for "B" and turn the light to before "0" I can see the mark but not get to it.
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From: NM
Not sure what you mean by "setting it to A" (or B), I assume you mean clipping the pickup onto that wire? You should be clipping it to "C" or "B", and with the vacuum line disconnected, the dial set to zero, the bump on the crank pulley should align with the pointer. Loosen the distributor clamp and turn the body of the distributor until they do line up. It sounds like you are set too retarded.
Nothing wrong with the wiring you've got.
Nothing wrong with the wiring you've got.
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From: Atlanta
That is good to hear. I tried both of the positions you indicate and my mark is close but not on the arrow. I'll have to adjust the distributor. Then my timing light stopped blinking so I'll have to sort that out first.
I am still not sure why it is stumbling but I certainly understand my engine more than I did this morning.
Thank You for all the help,
I am still not sure why it is stumbling but I certainly understand my engine more than I did this morning.
Thank You for all the help,
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Joined: Nov 2006
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From: Fallon,NV & Bainbridge OH
You should not see much change in vacuum reading with the idle mixture screws, at least with a standard vacuum/pressure gauge. As far as drive ability it sounds like an accelerator pump adjustment issue. 9 out of 10 times accelerator pump adjustment is off and it is an easy fix.
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