zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-16-23 09:14 AM - Post#2864211
Hoping someone might have some insight here. My L31 crate engine only has a couple thousand miles on it. I've carefully gone through the edelbrock carb. Adjusting the idle mixture I'm only getting 4 inHg (steady). Has an off idle stumble and smells rich but seems to have power when past the stumble. Brake boosters been replaced. I've sprayed carb cleaner everywhere with no change in idle. Next time I'm under the hood I'll verify initial timing but it should be 10-12.
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 Shepherd
Valued Contributor
Posts: 3186
Loc: Lake George, NY
Reg: 11-11-15
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11-16-23 09:55 AM - Post#2864212
In response to zepplinc20
Without a giant cam or a big vacuum leak, never seen that low at idle. When did this start, timing checked with dist vac disconnected, gage known to be accurate?
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 Magnetocheck
"2nd Year" Silver Supporting Member
Posts: 300
Age: 69
Loc: Charlotte, NC, USA
Reg: 09-05-22
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11-16-23 10:09 AM - Post#2864214
In response to Shepherd
Agree with Shepherd. Never heard of vac that low with any kind of street cam at normal RPM. . Check the vac can for a leak. BTW, What is your idle RPM?
Bob
'65 Impala SS 396 Convertible |
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-16-23 11:11 AM - Post#2864217
In response to Shepherd
I've been thinking the same thing, I'm going to acquire another gauge just to verify. This project truck has been sitting a few years. It started after having issues with the carb getting clogged I believe. Eventually found the pickup strainer was the issue. Never seemed to run right after. I also recently replaced the plugs which looked fouled.
Edited by zepplinc20 on 11-16-23 11:15 AM. Reason for edit: No reason given.
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-16-23 11:11 AM - Post#2864218
In response to Magnetocheck
800 rpm
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-17-23 05:02 PM - Post#2864250
In response to Shepherd
Found the problem
https://imgur.com/g2T5lMb
https://imgur.com/a/7OUiCQj
https://imgur.com/a/RhWnoaW
https://imgur.com/a/5TDX8VC
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Magnetocheck
"2nd Year" Silver Supporting Member
Posts: 300
Age: 69
Loc: Charlotte, NC, USA
Reg: 09-05-22
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 11-17-23 06:09 PM - Post#2864251
In response to zepplinc20
Way to go!
Bob
'65 Impala SS 396 Convertible |
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65_Impala
Very Senior Member
Posts: 4991
Reg: 12-29-02
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11-18-23 09:12 PM - Post#2864266
In response to zepplinc20
Care to share what it was?
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-18-23 11:48 PM - Post#2864268
In response to 65_Impala
It's in the videos I linked. Crane cams 99600 adjustable vacuum advance had a leak. Reinstalled a regular vacuum advance I had laying around.
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-21-23 11:18 AM - Post#2864328
In response to Magnetocheck
Well turns out that wasn't THE vacuum leak. The vacuum advance was bad but it's still not fixing the problem. I had the carb dialed in nicely, but as soon as I started driving it around the problem returned. First the idle was rough and low, so I bumped it up. When I shut it off it dieseled. Then I made a trip to the parts store and it was idling at 1500 rpms. I noticed it was running decent when the choke was on. Last night when I parked it I readjusted the idle mixture screws and got a huge rpm increase when I turned the driver side out. I then tried to lower the idle back down but the idle screw isn't even touching the linkage and it's idling at 1000 rpms. So clearly more work is to be done.
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Magnetocheck
"2nd Year" Silver Supporting Member
Posts: 300
Age: 69
Loc: Charlotte, NC, USA
Reg: 09-05-22
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11-21-23 12:07 PM - Post#2864330
In response to zepplinc20
Take a look at the fast idle cam/choke set up on the other side of the carb Maybe it is messed up holding the throttle plates open. Bad spring, bent linkage, something?
Bob
'65 Impala SS 396 Convertible |
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Shepherd
Valued Contributor
Posts: 3186
Loc: Lake George, NY
Reg: 11-11-15
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11-21-23 01:20 PM - Post#2864334
In response to Magnetocheck
Make sure the secondaries in the carb are not partially open.
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zepplinc20
Newbie
Posts: 11
Reg: 04-02-07
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11-21-23 05:29 PM - Post#2864339
In response to Shepherd
So today I addressed the pcv which hadn't been eliminated. It had the original type with 2 outlets, one to carb and the other to the vapor canister. I replaced it with a new one outlet to carb and new hose. I dialed my idle mixture back in with tach and vacuum gauge. It seems to be back to running pretty well. What little driving I was able to do things seem promising. Even the off-idle stumble that it had is 70% gone. Fingers crossed the problem is solved and I can move on to carb calibration and dist recurve. I guess it was throwing me for a loop that it wasn't an external leak detectable with carb cleaner.
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