'65 timing troubles

[William Dillon]

Hello, I just had the distributor rebuilt for my '65 327/365 hp. What are the timing specs for this engine? I heard that total timing should not exceed 34 deg but at what rpm is this measured at? I set the initial timing at 12 deg and the car seems to run well, but the total is approaching 40 deg when I rev the motor(I don't have a tach on my timing light). Is the total measured with the vac advance plugged or unplugged? Thanks.

Bill

[Wayne K.]

Re: '65 timing troubles

Bill,

Plug the the vac and when you see no more advance ( should be between 4000 & 5000 rpm ) that should be your total and it should be around 38 deg. If your not getting any detonation your probably good where your at if checked as described.

Wayne

[Duke W.]

Re: '65 timing troubles

There are at least three "total timing" numbers you can measure, with the initial timing set in the recommended 10-14 range. Also, since the centrifugal curve starts at about 700 you need to reduce the engine speed to less than 700 where the engine will just barely run. An alternative is to set the total WOT timing at the below spec at over 2350 RPM. Both these checks are done with the vacuum can disconnected.

Total idle timing (vacuum can connected) - initial plus total vacuum, 26-30
Total WOT timing (disconnect vacuum can to simulate WOT) - 34-38 degrees.
Total cruise timing (vacuum can connected) - 50-54 degrees at over 2350)

The specifications for you centrifugal and vacuum advance are in the '65 Shop Manual Supplement and the '65 Corvette GM Restoration Package.

Duke

[Duke W.]

Re: '65 timing troubles

'65 SHP/FI centrifugal is all in at 2350. With the vacuum can disconnected the timing should not advance above 2350.

Duke

[William Dillon]

Re: '65 timing troubles

Thanks for the info guys, I'll set it to these specs and let you no how its running.
Bill

[George J.]

Re: '65 timing troubles - Be Careful

Bill,

though Duke is correct about all the advance being "in" at 2350 for the SHP, this is the factory spec. I have been told that the weights that accomplish this advance curve are almost impossible to find. Your distributor may have weights that don't develop full advance until later. You don't want to find out that there is another 10 to 15 degrees of advance left. Run the engine up to the point where the advance is steady and then time it.

George

[Duke W.]

Re: '65 timing troubles - Be Careful

Corvette engines have a wide variety of ignition advance maps, and it was common for them to be modified. Before starting any distributor work one should have the specs for the centrifugal and vacuum advacne curves. These are in the appropriate service manual and the free restoration package available from GM Customer Service.

With specs in hand one should test to see if the distributor is to OE spec, and if not, one should characterize the curve. The maximum centrifugal should be reached when the timing stops advancing, but as a final check I usually briefly bring revs up to near the redline to make sure it does not overadvance.

Duke

[William Dillon]

Re: '65 timing troubles - Be Careful

If I can't accomplish the factory spec advance curve with the weights I have, how about a weight and spring kit - such as the one Moroso sells?

Bill

[Patrick H.]

Re: '65 timing troubles - Be Careful

Good luck if you try it. I bought the kit and played with it, without success. I ended up having another NCRS member (Bill Clupper) check and/or recurve four distributors for me in the past year or so (3 Corvette and 1 Cutlass). It was well worth it for me, as I now know exactly how each one is curved, and if they were out of spec I know each one is back where it should be or where I wanted it.

Much easier than getting frustrated with the very few options for adjustment I had when using my own few springs and weights here in the garage.

Patrick

[Eugene B.]

Re: In the old days ...

Gents,
In the old days (late 60's-70's) we used to take distributors to a auto electric shop that had a machine that the distributor was placed in and the advance curve ploted versus RPM.

It was easy to change springs, vacuum advances, etc. to get the curve you wanted without performing the operation under a "shade tree".

Don't know if speed shops still do this, but I'm sure someone does.

Good luck,
Gene

[Joe C.]

The Good Old "Sun Machine"

I know someone who has one, and there are still lots out there. But the technology is now obsolete, what with today's computer programmable (PCM) engine controls.

Joe

[Patrick H.]

Re: In the old days ...

Gene,

Bill Clupper has one. No one around here does - the machines are all gone. It was easier to ship a batch than drive 60 miles each way twice to have my distributors done "locally."

Patrick

[Mike M.]

Re: In the old days ...

Pat et al: i too have a sun dist machine that anyone can come and use on the cuff.mike

[Art A.]

Re: In the old days ...

Mike, Do you have a manual for it? I know someone with a sun machine and needs a manual.

Art

[James F.]

Re: In the old days ... Art

Art,
Have your friend contact: Rmasters3@Insightbb.com
Contacted them this morning. They (say) they have a manual for mine. Regards,