Re: 1967 327/350 holley questions
...or check the plug heat range to ensure that it is equivalent to AC heat range "5".
The PO didn't know what he was doing and the OP is new to the vintage Corvette game, so he needs to do some simple ignition system checks before moving on to the carb.
That's what I'd do, but after dealing with sixties vintage small blocks for 50 years what do I know.![Wink](https://www.forums.ncrs.org/core/images/smilies/wink.png)
In the last few months I analyzed two '65s - a 365 and 350 HP. The 365 HP spark advance map was OE, and I don't recommend changing it other than bumping total WOT advance to the 38-40 degree range if it will tolerate that level without detonation. We did a complete blueprint/overhaul on the 350 HP distributor and remapped the spark advance with a different VAC and centrifugal springs as documented in the December thread.
Both engines appeared to have the correct OE cams based on idle manifold vacuum readings, and both have the correct OE carburetor, which is the same for both engines.
I found that the 350 HP engine idled best with the idle mixture screws out one turn from the seat, which is the initial recommended setting in the '65 Corvette Shop Manual Supplement idle/speed mixture adjustment proceedure, but the 365 HP idled best at 1.5 turns out, which makes sense. The higher overlap 30-30 cam yields much higher exhaust gas dilution at idle than the L-79 cam, so the 365 HP engine needs a richer idle mixture.
I always start with simple things first - verify that the plugs are the correct heat range based on what we long term users have found works best - NOT what's in the owner's manual or a spark plug catalog, verify that the spark advance map is somewhere in a reasonable ballpark, and go through the idle speed/mixture adjustment procedure.
If the above doesn't yield good performance and driveability without fouling plugs, then you have to dig deeper.
Duke
...or check the plug heat range to ensure that it is equivalent to AC heat range "5".
The PO didn't know what he was doing and the OP is new to the vintage Corvette game, so he needs to do some simple ignition system checks before moving on to the carb.
That's what I'd do, but after dealing with sixties vintage small blocks for 50 years what do I know.
![Wink](https://www.forums.ncrs.org/core/images/smilies/wink.png)
In the last few months I analyzed two '65s - a 365 and 350 HP. The 365 HP spark advance map was OE, and I don't recommend changing it other than bumping total WOT advance to the 38-40 degree range if it will tolerate that level without detonation. We did a complete blueprint/overhaul on the 350 HP distributor and remapped the spark advance with a different VAC and centrifugal springs as documented in the December thread.
Both engines appeared to have the correct OE cams based on idle manifold vacuum readings, and both have the correct OE carburetor, which is the same for both engines.
I found that the 350 HP engine idled best with the idle mixture screws out one turn from the seat, which is the initial recommended setting in the '65 Corvette Shop Manual Supplement idle/speed mixture adjustment proceedure, but the 365 HP idled best at 1.5 turns out, which makes sense. The higher overlap 30-30 cam yields much higher exhaust gas dilution at idle than the L-79 cam, so the 365 HP engine needs a richer idle mixture.
I always start with simple things first - verify that the plugs are the correct heat range based on what we long term users have found works best - NOT what's in the owner's manual or a spark plug catalog, verify that the spark advance map is somewhere in a reasonable ballpark, and go through the idle speed/mixture adjustment procedure.
If the above doesn't yield good performance and driveability without fouling plugs, then you have to dig deeper.
Duke
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