273 carter afb

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MILO

MILO

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When I disconect the vacuum line in the front of the carb the one that gos to the distributor it seems to have full vacuum at idle the same as the one that gos to the choke pull off. Its a carter afb 4v I know the distributor vacuum should rise as the rpms rise. Cant figure what the problem is. The carb is a 1965 273 4v stock carter afb
 
OK I think I now know the problem by doing a little searching. The carb hose that gos to the distributor should not have vacuum at idle is should increase as you accelerate thats why they call it vaccum advance. And it is controled by the carb plates as they open a hole in the bore supplys vacuum. So I guess that my plates arnt closing far enough or one of the blades is bent. So IM going to get a look at it this weekend.
 

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I have seen documentation that shows the vacuum low at idle and then increasing with accelerator and the other way.

I have found that when you set it up with low vacuum at idle and then increasing as you press on the pedal you end up with a stumble on acceleration.

So I am not sure that you have it wrong as it is, how does it run ?
 
Right now it has full vacuum at idle and it runs good with the line unhooked but when you hook it up it runs rough. And I did set the points at specs and checked the dwell and set the timming with the vac line disconnected and plugged I was thinking of just leaving it unconnected but Im going to investigate further this weekend. Pull the carb and check it out at least its fairly easy to work on compared to the new cars.
 
Are you hooked up the correct port on the carb? the dist vacuum advance is the one to the left of the idle mixture screws. If your getting full vacuum at the dist spark advance port then either the idle is set too high (throttle blades open too far) or the one throttle blade is bent as you suspect. If the car has a PCV valve it could be clogged and the idle set to high to compensate. If no PCV system there should be an air bleed plug (9/16 I think) between the idle mixture screws which might be turned in too far. Or the little plug in the base plate under the vacuum advance port came out, you'll have to pull the carb off to check.
 
If your 65 carb is like my 66 carb, there is only one vacuum port for the distributor. It's on the front of the carb and is ported. It produces vacuum off idle. The slots in the venturis that supply the vacuum are below the throttle plates and only produce vacuum when the throttle is opened. The only other port is on the choke side and provides vacuum to the choke pull-off constantly.
For some reason is your idle speed so high that the dist. port has constant vacuum? Otherwise you may need to overhaul your carb. Something isn't right there. Mike
 
Well I had time to take the carb off and check it out I turned the idle screw out a few turns and the primary throttle blades close fine and cover the vacuum ports for the distributor fine. So now I guess that I have to keep the idle turned up because of the cam and that causes the vacuum at the distributor port at idle. With the distributor vacuum line disconnected the engine smooths out but still sounds pretty lumpy at the tailpipe. So I guess its back to the cam change and if that dont work I will take the offenhauser manifold off and find a stock early 273 cast iron 4 bbl manifold.
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Here is the link on the cam

http://www.forabodiesonly.com/mopar/showthread.php?t=159046
 
This is a second thread I started about engine running problem after replacing the camshaft with a stock one I was able to adjust the idle down and now there is no vacuum at idle. And it runs and sounds good so no need to go any further. Soon it will be ready to put away for winter and will be ready for next spring. Thanks for everyones replies. Milo
 
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