'65 327/365 hp timing problems

[William Dillon]

Hello,
After having my distributor rebuilt, installing a new correct vacuum advance canister, new cap, wires, plugs and and new Pertronix ignition, I'm still having a problem with getting my timing curve up to specs. With the vacuum advance plugged and WOT timing @34*, the initial timing is right around 6* (too low to idle properly). If I advance the initial timing to 12* (where it is supposed to run), then WOT advances to over 45*! (way too much - the engine won't rev). I tried different weights and springs and a new bushing on the shaft pin - but it still advances too far. Any suggestions? Is there a way I can limit the amount of advance it is putting in?

Bill

[Loren L.]

Does it have the correct balancer? *NM*

[Duke W.]

Re: '65 327/365 hp timing problems

Is it a correct dist. for the engine?

If so it should provide 24 crankshaft degrees at 2350 engine revs. Have you verified that the centrifugal stops advancing by 2500.

Also, with this aggressive curve, the advance starts at about 700, so the engine must be below this speed to set initial timing, and it will barely run below 700, so it is best to set the total WOT timing by revving it to 2500 with the vacuum can disconnected and setting the timing at about 36.

Then reconnect the vacuum can and check the total idle timing at about 900 and it should be near 30 degrees.

Also, 327s have the timing tap spot welded to the timing cover. Later SBs had a separate tap that was secured with a couple of the timing cover bolts. If you install the later bolt-on tap without the later balancer or correctly relocating the OE balancer notch, your timing measurements will be off at least ten degrees.

This is somewhat related to Loren's comment about checking the balancer ring for slippage. Either slippage or the wrong timing tab/balancer combination will result in inaccurate timing measurements.

Duke

Duke

[William Dillon]

Re: Does it have the correct balancer?

It has the correct balancer and timing cover, but I don't think the distributor is correct because it has no tag on it. Can the distributor that I have be set up to the original's specs or should I fork out the money and buy a fully adjustable MSD unit?

[Duke W.]

Re: Does it have the correct balancer?

You will be far better off correcting the current distributor. You can start by characterizing the current centrifugal and vacuum advance curves to understand what needs to be done. This is relatively easy to do with a Mighty Vac and a dial back timing light.

The best way to correct any deficiencies in vintage Corvettes with only a very few exceptions is to bring the subject system back to OE specification rather than trying to re-engineer it with aftermarket hotrod parts.

Duke