My 65 BB after coming off choke idles around 900 rpm. Temperature gets to 210 or so and holds fine. Periodically the idle suddenly drops below 500 and then down to 0. It usually restarts with one touch of the key and idles fine again at 900. This happens every other traffic light or so. Got it home and pulled the plugs.. They all look fine. Anyone shed some light on this?
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Re: Idle Drops Off to the Sound of Silence
it is probably caused by a change in the fuel flow in the idle circut. this could be cause by the reformulated gas that they use in the summer months in the usa. it has a tendency to boil and cause air bubbles in the fuel when it gets hot. you could try tweeking the idle/air adjustment screws on each side of the metering block.try turning them out about 1/2 turn, if this does not give any results try putting them back in the 1/2 turn and then go a additional 1/2 turn in. the best cure for this is blocking the heat riser crossover in the intake manifold, but you loose the use of your choke. i did this to all my alum intake corvettes but i never had to drive them in cold weather. if you live in a warm/hot climate you will not have trouble without a choke. -
Re: Idle Drops Off to the Sound of Silence
Checked the two adjustment screws one was out 1 3/4 turns, the other almost three turns. Having both at two turns resulted in the best idle. So far it seems to be idling fine (850rpm). I used a diagnostic tach to check the rpm. What book would be best source to provide all the tuneup specs for the 65 396? I hooked a vacuum gauge to the distributor to carb hose and got a steady 13 to 14 reading. The timing seems way advanced at idle and the dwell was 24. Are there adjustmets with the TI system?Comment
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Re: Idle Drops Off to the Sound of Silence
if you have the TI ignition there should be no way to check the dwell. the timing should be 10 degrees at 800 rpm. the best way to set the timing is to use the power time method, check for 36/38 degrees at max advance at about 4500 rpm.Comment
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Don't forget...
to disconnect and plug the vacuum advance hose when checking timing!
DukeComment
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Re: Don't forget...
What is a good vacuum source to use when tuning?
ChrisComment
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Re: Don't forget... Uh Oh...
Duke is saying that the correct initial timing is set by: disconnecting the vacuum line to the distributor vacuum advance mechanism, and pluging the rubber hose that is still connected to the engine. To check the vacuum advance: reconnect the line to the distributor advance and note the amount of change in the timing (using a timing light). Every once in a while, we all get in a hurry and forget to disconnect the hose when setting the initial advance. - DaveComment
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Re: Don't forget... Uh Oh...
Many of the Holley manuals suggest using a vacuum gauge to optimally adjust the carb settings. I was wondering what vasuum port to use to accomplish this. It would seem that the only vacuum hose on the carb that could be used is the one going back to the distributor.
ChrisComment
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Re: Don't forget... Uh Oh...
Chris --- You could use the hole with the pipe plug, in the intake plenum, behind the carb, if it's not already taken by the power brake hose. Actually, the vac port in the metering block of the # 3124 is direct to the intake, so it should give good readings, but I'd make up a replacement rubber advance line to the distrib, with a tee off to the gauge. You want to adjust idle with the vac advance activated.Comment
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That's the ticket!
Just get a 1/8" tee and a one inch piece of 1/8" vaccum hose. Then disonnect either end of the distributor vac. hose, splice in the tee temporarily, and connect your vacuum gage to the third port on the tee.
To check if the vacuum can holds vacuum connect about a two foot section of 1/8" rubber tubing to the can, draw a vacuum on it, then fold over the hose. Wait about ten to fifteen seconds, release the hose and listen for air rushing in. You can also draw the vacuum - enough to deploy the advance a bit, and check with a timing light to see if the advance holds while the tubing is folded over.
DukeComment
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