proper timing for a 350

[pumper578]

I have a 1971 C10 and i have a slight issue possibly with my timing and i can not find what the actual timing is supposed to be, i have heard 5, 8, 10. can anyone tell me what it is supposed to be, i think timing is my issue, when i press the gas it wants to sputter a little and then go, but after that it is fine until i come to a stop and have to start from a stop and it does the same thing, it is also dieseling out, (after i shut the off the ignition it wants to try to keep on running, not all the time though). Any help would be appreciated.


Tjon

[sd-slider]

I don't have the specs....but....

I had a similar issue on my 66 Skylark and it turned out to be the Vacuum Advance...replaced it and timed per the specs and now she runs great!

[kwmech]

I set everything at 6 btc. except for the computor controlled stuff.

[cooters]

the sputter sounds like a lousy eccelerator pump in the carb. The dieseling could be the idle to high.

[truckdude239]

Originally Posted by cooters

the sputter sounds like a lousy eccelerator pump in the carb. The dieseling could be the idle to high.

[cstanley]

mine does the exact same thing on all accounts. i'm watching...

[72hotrod]

Cooters is on to something. When the throttle plates are set too open,you can diesel, and you don't get enrichment from the idle transition slot, so you stumble. This usually happens when you have a weak idle from bad timing, idle mixture too far out, or vacuum leaks and you just try to idle up with the idle speed screw. Check if that is the case and correct that by closing the plate enough to hide the last 1/3 to 1/4 of the transition slot (just barely open), crank it up and keep it running until the choke is off, it's warmed up, and kick off the high idle. Set the timing, and use a vacuum gauge to set the mixture evenly on both sides to highest vacuum reading. You might have to increase the timing a bit, to get it right. Just remember to try for the strongest idle with the least throttle. If you have a big cam, you might have a problem doing this with your carb. But that's another story.

[franko72]

where do you attach the vac gauge when adjusting both sides?

[72hotrod]

Tee off the distributor vacuum hose, hose off of unused carb nipple, maybe use the modulator nipple on back of intake manifold. Just be sure it's manifold vacuum, not ported.

[Billla]

there are a million threads on this - a little searching in the engine forum will tell you everything you need. Generally, steps are:

1. Verify TDC. Don't skip this step.
2. Set initial timing to 12 degrees BTDC.
3. Install an advance curve kit - including the limit bushing and install the lightest set of springs. I like the Mr. Gasket kit:
http://store.summitracing.com/partde...G&autoview=sku
4. Set timing to achieve 32-36 degrees total advance at 3000 RPM using either an advance-capable timing light or timing tape. I like the MSD set because it covers all sizes, but if you know the size any tape will do - you can even make your own.
http://store.summitracing.com/partde...5&autoview=sku
5. Do some full-throttle runs, leaving the vacuum advance plugged; if there is any pinging, move to the next stiffest set of springs.
6. Whatever initial timing is required to get 32-36 total is fine as long as it's less than 16 degrees.

This is going to get you within a hair of perfect every time. Assumption is no other engine issues (carb jetted WAY wrong, vacuum leaks, etc.) Next step if you want the best possible fuel milage is to install an adjustable vacuum advance can; I like the Accel unit. The instructions for the Accel unit are perfect
http://store.summitracing.com/partde...5&autoview=sku

I always get the timing right before looking for carb or other problems.

Hope this helps.

[Billla]

Originally Posted by franko72

where do you attach the vac gauge when adjusting both sides?

Any manifold vacuum source.

[Billla]

Bog on initial acceleration AND run-on is almost always a sign of incorrect timing. Not that it can't be something else...but IMHO it's the first thing to get right.

[dmec]

has this problem been fixed yet? have a friend with the same problem. looking for an answer

[GREASEMONKEY72]

Billla to the rescue

ive got mine set at 10* from 8 because of the heat, would going up to 12* improve it do you think?

[cooters]

when the balancers are usually out a few degrees anyway, just play with the distributer a few degrees at a time and see what happens. Every motor has a sweetspot that works best for it

[hyarbour]

I had that problem a while back and couldn't figure it out. It turns out the advance weights were hanging up. If your distributor is really old get a rebuilt unit and an advance kit to tune it in.

[Billla]

Originally Posted by cooters

Every motor has a sweetspot that works best for it

For an SBC, that's 34-36 degrees total advance before 3000 RPM.

[Billla]

Originally Posted by GREASEMONKEY72

would going up to 12* improve it do you think?

Again, initial timing is worked back from total mechanical - i.e., set total mechanical and use whatever initial is timing. If it's over 14-16 degrees, then there's a problem with the curve.

[Billla]

Originally Posted by hyarbour

I had that problem a while back and couldn't figure it out. It turns out the advance weights were hanging up. If your distributor is really old get a rebuilt unit and an advance kit to tune it in.

I ran into this for the first time myself recently. It was a Mr. Gasket kit with adhesive goo on the weights which the installer didn't remove.