refresh on 435 hp timing

[Jay Hastings]

today I put the cv 1810 vac. advance on the 67 and hooked it up to the
choke pull off and set the timing at 10* seems to run great and the exhaust doesn't smell rich. I can't remember what I was told to set the timing at.
thanks jay

[Duke W.]

Re: refresh on 435 hp timing

According to the engine tune-up specs I have from Corvette News Vol 10 No. 2 the '67 L-71 centrifugal curve is as follows.

0 @ 900
30 @ 3800

The initial timing is specified as 5 degrees with no range. Five degrees initial with 30 centrifugal seems a little short on total WOT timing for a SHP big block, so I would go as high as ten initial if it doesn't detonate.

Idle speed is listed as 750, and with ten degrees initial your timing light should show 26 total with the vacuum can connected and 10 without. If you are not satisfied with the idle quality at this speed feel free to set it higher, but be careful checking initial at 900 or above as this is the point where the centrifugal starts.

I assume you verified that the L-71 has OEM ported vacuum advance, which is why you switched the signal line to the choke vacuum break to get full manifold vacuum to the vacuum can at idle.

Also, what is your idle speed/vacuum with the new setup. What fuel blend are you running, and are you getting any detonation.

Duke

[Jay Hastings]

Re: refresh on 435 hp timing

Duke,

in the beginning of winter I had a chat with some people on the board and they told me to change the vac. and connect to the choke pulloff for the
manifold vacuum and change the timing to I think about 10-12*. I knew the car
should time at 5-8*, and it seems that it was about 5* more. so I figured
about 10* should be ok. I lost my notes on the setting of the timing i was told.

One of the people i was chatting with told me he had did this and his car ran great. I didn't get a chance to drive the car yet so I dont know how it is going to run. I am getting the car out thursday after work for a friday night cruse and a show on sat. so I am going to test and ajust the timing thursday.
I usually run chevron 92 10 gal with about 1.5-2 gal of 110 race fuel
I do know something is better for the first time sincewe got the car (1982)
I didnt have to slip the clutch to turn off the car.
thanks, jay