Alternative Dizzy Vaccume Source?
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Elder User
Joined: Mar 2003
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From: S.C.
Alternative Dizzy Vaccume Source?
Hi All,
Been running well ('54 239 Y with 55 merc dizzy\points) but hearing some valve noise\chatter upon acceleration. I installed the pertronics kit and set timing but could see no vaccume advance change with the timing light when I plugged the vaccume line back to dizzy. Apparently there is no vaccume coming from the rear port on the carb (holly Ford script 94).
I have already rebuilt the carb and all else works great, other than tearing down to see if vaccume port is plugged...can I use another source of vaccume (intake) for the dizzy or would it be too much constant vaccume?
I'm thinking it has to be the carb source but I also know alot of you have come up with some interesting solutions.
Thanks for any input!
Ed
Been running well ('54 239 Y with 55 merc dizzy\points) but hearing some valve noise\chatter upon acceleration. I installed the pertronics kit and set timing but could see no vaccume advance change with the timing light when I plugged the vaccume line back to dizzy. Apparently there is no vaccume coming from the rear port on the carb (holly Ford script 94).
I have already rebuilt the carb and all else works great, other than tearing down to see if vaccume port is plugged...can I use another source of vaccume (intake) for the dizzy or would it be too much constant vaccume?
I'm thinking it has to be the carb source but I also know alot of you have come up with some interesting solutions.
Thanks for any input!
Ed
Elder User
Joined: Sep 2002
Posts: 503
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From: Edgewood, NM
You may have already done this, but I would rule out the hose as the culprit first. If you pull the hose off at the carb side and suck on it and hold with your tongue the the dizzy should advance and hold, if not your hose may be bad. Not sure if you can see this with the petronix ignition?
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Elder User
Joined: Mar 2003
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From: S.C.
I'll check the dizzy with a vaccume pull tonight to see if things change, hose is new, carb is old but rebuilt...dizzy came fron so. Cal. shop as rebuilt but I uess you never know. The only tell while driving was the mechanical noise upon acceleration. You can get away with a little more on these old trucks. I rechecked the timing after the pertronics install and it was a little advanced due to install so I adjusted it back to where it should be. I'll check vaccume advance on dizzy, recheck hose and possible the carb tonight....tomorrow I'll readjust the mixture screws on the carb as well. My book calls for apx. 400 rpm's at midle but I like it more around 600 rpm's.
thanks for the input\replies.
Later, Ed
thanks for the input\replies.
Later, Ed
Thread Starter
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Elder User
Joined: Mar 2003
Posts: 929
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From: S.C.
Update......Good To Go!
Went thru the checks, dizzy vaccume held, hose was good, reading up on carb I saw that the vaccume doesnt show at curb idle...only as rpm's increase due to the spark advance control in the carb.
Check with timing light as I increased the rpm's....advance works well.
Re-adjusted the fuel mix screws with throttle at apx. 1100 rpms until a smoother idle was heard and there was no lean drop, then readjusted the curb idle to apx. 575 rpms.....she's sounding better than ever now.....I hope the pertronics holds up well over time....well see.
thanks for the input, Ed
Went thru the checks, dizzy vaccume held, hose was good, reading up on carb I saw that the vaccume doesnt show at curb idle...only as rpm's increase due to the spark advance control in the carb.
Check with timing light as I increased the rpm's....advance works well.
Re-adjusted the fuel mix screws with throttle at apx. 1100 rpms until a smoother idle was heard and there was no lean drop, then readjusted the curb idle to apx. 575 rpms.....she's sounding better than ever now.....I hope the pertronics holds up well over time....well see.
thanks for the input, Ed
