Set it where it sounds the best without pinging.
1974 454 ignition timing?
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Intermediate
Joined: Aug 2007
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From: Toronto Ontario
1974 454 ignition timing?
What is the degrees i should be at for my 454 1974 corvette....2, 4, 8 12, 14, 16? I have an hei distributor i recently installed and now my timing says 16 when my mechanic checked it with his gun. Where should it be at?
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Thread Starter
Intermediate
Joined: Aug 2007
Posts: 38
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From: Toronto Ontario
Since i made my first attempt at putting my new HEI distributor in and thought that I had it right with the timing, not realizing that the vaccum advance needs to be set also, my clutch fan has not come on. It used to come on when my temp gauge reached around 195 degrees. The car is also running alot hotter quicker. If I am on the highway cruising at around 70-80 miles it reaches over 200 degrees. Like I said, my mechanic said that with his timing gun he noticed it at 16 degrees and thought that , that may be the problem and asked that i find out if its right or if it should be less to get the car to run cooler. Although I will lose some power, I think.
What are all your thoughts. I am stumped.
What are all your thoughts. I am stumped.
Pro
Joined: Oct 2006
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From: Bryan Texas
When I got my 71 about a week ago, the vacuum advance hose was hooked up to a wrong port on the carb. It was getting full advance at idle and no advance under load. Make sure yours is connected to the correct port. It should have no vacuum at idle.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
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From: Newark DE
If you hook it up to ported vacuum than you will get no vacuum advance at idle and for a number of years that's how the factory set them to run but the ONLY reason for it was because of emissions reasons and most cars run better by switching it over to run off of full manifold vacuum instead.
Under load you will have little to no advance regardless of how it's connected since under load the motor is producing little to no vacuum.
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Pro
Joined: Oct 2006
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From: Bryan Texas
It's easy to check your ports with a vacuum gauge, but can be done with your finger too. At idle, pull the vacuum advance hose from the carb and put your finger on the port, if you feel vacuum, that's manifold vacuum. If you feel no vacuum, rev the engine, if you feel vacuum while reving, that's ported vacuum. That's the one you want to hook your distributor vacuum advance to. On my q-jet, it's on the front left (driver's side) of the carb.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
It's easy to check your ports with a vacuum gauge, but can be done with your finger too. At idle, pull the vacuum advance hose from the carb and put your finger on the port, if you feel vacuum, that's manifold vacuum. If you feel no vacuum, rev the engine, if you feel vacuum while reving, that's ported vacuum. That's the one you want to hook your distributor vacuum advance to. On my q-jet, it's on the front left (driver's side) of the carb.
Ported vacuum was used only for emissions reasons
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From: At my Bar drinking and wrenching in Lafayette Colorado
Burning Brakes
Joined: Aug 2004
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From: Tyler Texas
FYI reminder: Front driver's side nipple is PORTED Vacuum on 67-74 Q Jets. However, front driver's side is full MANIFOLD Vaccum on 75-81 Q-Jets. Easy to give and get wrong information re such unless you know which Q-jet year is applicable.
Ported Vac for vacuum advance was not used after implementation of catalytic converters in 1975 forward. i.e. a 78 vette came with full manifold vac advance.
I had forgotten this difference until I recently saw a post by Lars reminding everyone.
Ported Vac for vacuum advance was not used after implementation of catalytic converters in 1975 forward. i.e. a 78 vette came with full manifold vac advance.
I had forgotten this difference until I recently saw a post by Lars reminding everyone.
