jimbr

Howdy,

Well, I have "finished" the complete top end upgrade of my motor (see details in photo/signature below). It is awesome, but not quite tuned correct yet.

I hooked up a vacuum gauge and kept advancing the timing for max vacuum. It appears to be timed at about 25 degrees advanced. I'm wondering if the cam is installed at non-zero (set at 4 degrees). I have never had the timing chain cover off and don't know the exact cam specs (clearly not stock though).

Worked on setting the carb a bit. It is much faster car now, which is great.
But it was just toooooo loud :D with open headers, so I left it alone until today...I just got the headers connected to the exhaust pipes today so now it is reasonable to think while it is running (and the neighbors are happier too). It is close, but has some hesitation - I think Ihave carb tweaking to do.

Can people comment on their timing settings? I know a pit crew dude for a modified and they ran that car at 36 degrees (and no vaccumd advance) but that was a 5500-6500rpm running circletrack thing (ugly too).

Thanks,
Jim

PatsLs1vette

i have 15 initial and a total of 38 degrees and it runs fine for me.. i know what ya mean about the circle track guys..im one of them....i keep them locked at 36 degrees..or 38 depends on the track.while i was waiting for my msd dist. to come i had to use one of them for a bit..very tough to start and 11.1 motor locked out at 38 degrees when hot. :mad errr errr err errr errr


[Modified by pats406nitrovette, 7:16 PM 1/11/2002]


[Modified by pats406nitrovette, 7:17 PM 1/11/2002]

Vetterodder

Unless your mechanical advance has been greatly reduced from stock, 25º initial is likely giving you way too much total. Once you go beyond 36-38º total you start giving up a lot of power at the top end, even though it may feel stronger at low rpm. In most cases, an engine will make it's best power at certain total advance and more or less than what is optimum will result in less power than it would make otherwise. If the hesitation you mentioned is occuring above 2500 rpm, it may due to being over-advanced. The proper way to set timing is with a timing light, not with a vacuum guage. That's why they have those little marks on the front of the engine :)

Z-man

Agree w/Vetterodder - I'd start at about 10-11 at idle, no vacuum advance. Use a timing light. Most guys end up with 35-38 advance max. Use the vacuum gauge to analyze problems...

:cool:

Good luck...

jimbr

Hmmm. When I set the timing to about 12 degrees, it had a lot less power than it does at 25 degrees....although I'v got a new carb to tune in as well.

Curious, if the cam gears have the cam timing at 4 degrees instead of zero, would the timing shift also? Same amount? More?

I am going to a dyno soon - wonder what the added cost is for them to adjust the carb and timing or if that is usually included....

Jim

Captain Morgan

Hmm, are you setting it at 12 with the vacuum hose off the vac advance unit and plugged? Best thing to do is get an adjustable timing light and use it to see what your total mechanical is set to, should probably be 34-36 all in by 2500 RPM, again with hose off and plugged. With hose on, you should be around 50 total.

Not sure as to how the cam would change things for your timing.

The dyno shop would probably charge you extra to set up timing and carb. I had mine done in Utah and it was $230. It's normally $100 for two pulls there but I also wanted the dist. recurved and the carb re-jetted. Gained 18 HP at the wheels. Of course, now I'm in Indiana and changed exhaust so I may need to re-jet again. :rolleyes:

Anyway, do a search for topics posted by Lars, probably in the Archive section and see if you can find something about the timing paper.

A C

What balancer are you running? Is it the old one that came off the car to begin with? If so, your inertia ring may have slipped, throwing off your timing mark. This has happened to me twice. I would go to time it with the light and the mark would be way off.....like up under the water pump.

AC

jimbr

Well, lots of ideas. I have timed with out the vaccum line on.... all with the headers screaming at me. Tomorrow, I'll run the set of ideas and check if the damper has moved....that should be a royal pain and require some mirrors.....

Until tomorrow....

Jim