JRUTS

I have a 65 Vette with a 327 cid 365 hp engine. The engine has Z28 heads and presently
has AC 44 spark plugs. Looking to see if there is a suggested replacement plug number.
Engine is running rich.

MikeM

Use AC 45 or 45S or equivalent in another brand.

Fix the rich or no plug will work.

JRUTS

Mike,
Thanks for the AC 45 and 45 S.
Regarding the engine running rich: I also posted the below question on the Holley carb setup maybe you can comment.
I have a 327 cid 365 Hp Corvette engine. It has Z28 heads and has a Holly carb. with dual floats it has stamped on the
car:b LIST 3246 and the number 3885067-EE The engine is running rich and wondering if any of you have any idea what
size carb. metering jets it should have in each fuel bowl...
I've adjusted the floats so fuel is just below the site plugs not sure if lowering this would help lean out the fuel.

Thanks for any suggestions..

MikeM

I'll defer to the carburetor experts here.

There are other reasons for running rich besides what you mention.

gbvette62

If I had to guess, I'd say that it sounds to me like you may have too much carb. The 3885067 Holley was originally used on 396/375 Chevelle's and 427/425 full size Chevrolets, and I think it's 780 CFM. The 65 327/365 used a 585 CFM Holley 2818.

GTOguy

Need more information. What camshaft? What's the timing set to? How do you know it is rich, and if so, how rich is it? Black smoke rich? What's the manifold vacuum at idle?

MikeM

I ran 780 Holleys on 327's and 350's for years and many miles with no problem, good gas mileage, and good performance. I don't believe that's an issue in itself.

#72 primary jets
#76 secondary jets
6.5 power valves
Wood screw in the vacuum secondary linkage to open them instead of vacuum demand.
Tube exhaust headers.

Powershift

Z/28 used about 780 CFM carb as I recall. This is only 302 cubic inches (although 7500 RPM possible in tuned form).

Larry

Powershift

Suggest OP tune idle with a vacuum gage for maximum vacuum. Then look for evidence of either a blown power valve or gas leaking into engine from/thru closed secondary circuit. This is the problem on my 327/350 HP car, and I know it needs a carb rebuild. (I have three rebuild kits but little energy to do the rebuild at this time.........but I will do it soon Car still runs great, but idle is rich )

Check choke function at hot conditions (choke completely open) and also check primary and secondary jets vs factory jet settings in Service Manual or use MikeM info.

Larry

Robert61

The easiest way to clean up a rich idle, if everything else in the carb is good, is to open the rear throttle plates and close the front. There is a small Allen screw on the right side on the bottom that you adjust this with. You have to remove the carb to access it. By opening it you allow air only into the engine no fuel. Then as you close off the front you begin to lean it down. If something else is wrong i.e. someone has messed with the idle feed restrictors or idle air bleeds, or a bad power valve that's another issue.

Frankie the Fink

I'll just say, carb issues notwithstanding, a 44 heat range plug is awfully cold for modern driving - in my cars a 45 was just about right and I could have gone to a 46 (if you can find them)... I split the difference and went with the NGK-B4 in recent years which crosses over to both the AC 45 and 46 plug ranges. Best spark plug I've ever installed.