1965 Holley 3849804 Vac. Problem

[Berndt U.]

Hello from Berlin Germany, I just have a Problem with a Stock Holley Carb. on a 1965 327 . The vacuum port to rum to the Distributor has full vacuum at all time the engine running .

I think that is not correct. This carb. has only 1 Vac. port on the right side just above the idle mixture screws . And no port on the throttle Body like newer Holley carburetors.

If you have any Idea so please let me know

So I need a advise to fix this problem.

Thanks Berndt

Holley 3849804
List 2818-1
0619

[Gene M.]

Re: 1965 Holley 3849804 Vac. Problem

No, it’s correct with full vacuum.

[Duke W.]

Re: 1965 Holley 3849804 Vac. Problem

"Ported" vacuum advance is an emission control strategy. By retarding idle advance to well below optimum, EGT increases, which helps burn HC and CO, especially with air injection into the manifolds.

There were a few exceptions to this in the pre-emission era including the '63 FI engine, who knows why, but Chevrolet corrected this by implementing full time vacuum advance in the ...380 unit that began installation early in the '64 model year.

You didn't mention the OE engine configuration or whether it's modified, but you should check that the installed VAC meets the Two-Inch Rule.

Duke

[Berndt U.]

Re: 1965 Holley 3849804 Vac. Problem

OK Thanks but it does not make sense to me. If we want to set the ignition correctly, then we only have the rev.curve for the early ignition. Then we have 32 degrees at 3000 rpm and 18 degrees at idle. Does it make sense to have so much early ignition in idle?
For testing purposes I have a edelbrock carburetor mounted and with it the engine runs very well, but you can not leave it that way.
So what the correct ignitor setup for this engine 327/365 ?

[Leif A.]

Re: 1965 Holley 3849804 Vac. Problem

Berndt,
Are you getting the 18* at idle with the vacuum line removed and plugged from the VAC?

[Duke W.]

Re: 1965 Holley 3849804 Vac. Problem

OK Thanks but it does not make sense to me. If we want to set the ignition correctly, then we only have the rev.curve for the early ignition. Then we have 32 degrees at 3000 rpm and 18 degrees at idle. Does it make sense to have so much early ignition in idle?
For testing purposes I have a edelbrock carburetor mounted and with it the engine runs very well, but you can not leave it that way.
So what the correct ignitor setup for this engine 327/365 ?

Download my tuning seminar - easy Web search - duke Williams corvette san diego - to learn how to set up the spark advance map for any engine.

A couple of tidbits - total idle advance should be in the range of low 20s to low 30s and the higher the valve overlap, the more advance needed, so the 365 HP engine, assuming an OE equivalent camshaft needs to be at the upper end of this range.

The best spark advance map for the 365/375 HP engines is OE as specified in your service manual and AMA specs. The only thing you should do is set total WOT advance as high in the 36-40 range as the engine will tolerate without detonation.

Idle behavior should be close to 10" manifold vacuum at 900 in neutral. If not, it's likely not an OE equivalant 30-30 cam.

Also see this nearby thread.

https://www.forums.ncrs.org/showthre...111#post830111

Duke