My 69 runs alot better with 16 degrees of initial timing. It starts fine and does not detonate. I have a new GM dampner and my dist is a points type, which I recently got back from the machine shop. (mechanical advance 36 total)

I was instructed to set it at 12 but if I do, I have to set the idle speed on the carb, and the blades of the carb is out of the idle circuit. Runs bad and pops through the carb if you jab the throttle.
Any idea's?

If it runs good at 16* then leave it there. You haven't mentioned if you use a vacuum advance and how it's hooked up? If you are running at 16* with it hooked up, what is it when disconnected? If it is disconnected at 16*, I would hook up the vacuum advance to a ported source (above the throttle plates) rather than base source (below the throttle plates) Just for fuel economy and driveability reasons.
Jim

If you adjust the idle mixture screws instead of the idle screw you should have no problem getting you engine to idle at 12 degs of initial. I'd think that if you really have the throttle blades open beyond the idle ckt you would have some run on when you shut off the engine. Maybe the accl pump is out of adjustment and setting the initial timing higher is masking the problem.

There's not really anything wrong with running 16 initial unless you have too much total advance and that could cause pinging (detonation) at WOT which isn't good. Your dist has 24 degrees of mechanical advance built into it based on the 12 initial and 36 total (36 - 12 = 24) That's total minus initial equals mechanical. Take your 24 mechanical and add 16 initial and you can see you should have 40 degs of total advance. 36-38 total is good for the avg 350 and most stroked 350's like 32-34. Gas quality and gearing will play on this too.

Thanks for the info.
The dist. was a vacuum advance type, but the guy reworked it and capped off the port. I have to wonder if its in the dist.? The carb is a holley DP and the engine is a 406 with dart 215 iron eagles.
I will be upgrading to a msd in the future. The engine runs fine the way it is now 16 degrees. Also seems to run cooler too.
Jason

You can try this and see if it helps. It is cheap, quick, and easy.

Pull the carb off the intake. Turn the secondary stop screw "in" 1/2 turn and reinstall. The secondary stop screw is only accessable from the underside of the base plate.

Reset the carb mixture/idle speed to the best idle. The idea is to let a little more air into the idle on the secondary side of the carb and that allows you to close down the primary throttle blades a bit in an effort to get more "transition" effect out of the idle transfer slots. I had the same issue myself and was able to just about tune it out this way. My car would either hesitate or pop out the carb at "tip-in" before I did that. I originaly thought it was the accelerator pump but trying to use that to fill the hole was not the best solution. The car is currently in paint jail so further improvements will have to wait.

-Mark.

16 initial doesn't surprise me at all. are you running a decent sized cam? but as djd said, you do need to worry about your total timing. the best ticket is get the initial around what you have, and have the total at about 34. 406's are kind of sensitive to detonation, so be careful. mine has a fair sized cam, but i have a msd pro billet, so you can easily tailor your curve. i run 18 initial and 34 total, btw. get a dial back timing light, or if the balancer is degreed, just a plain 'ol light will work. but do make sure. good luck hope that helps.

68rs406,
My cam spec's are 250 on the int 259 exh @ .050
lobe sparation 108. solid flat tappet.
I will check the total with a dial back timing light. Also getting an msd soon.
Thanks
Jason

then i'm really not surprised. my cam is 250 @ .050, straight pattern, and a 108 lsa., .610 lift at the valve. this is however a solid roller, and they tend to seem slightly milder at idle. i'd leave it at 16, even 18 if it starts and runs ok, and do what you can to get the total around 34. this is roughly where mine is for best performance/drivability. mine to be exact is 18 initial, 34 total, all in by about 2600rpm. the msd distrubutors are worth every dime just for the tunability of the curve, imo. you should be able to get it to run pretty darn good, mine is street driven a ton, and has real decent manners, as far as i'm concerned. that motor should scream, good luck with it graemlins/thumbsup.gif

Originally posted by 69RS:
Thanks for the info.
The dist. was a vacuum advance type, but the guy reworked it and capped off the port. I have to wonder if its in the dist.?
Jason If you're running a street engine without a properly-calibrated vacuum advance, you're giving up a lot; centrifugal-only is a "race" setup, not a street setup, and makes no sense. Have you mapped your centrifugal curve? Do you know when it starts, how much you have, and when it's "all in"? graemlins/thumbsup.gif

With that big of a cam, you could easily be idling out of the transition circuit. I am less familiar with roller cams but it seems to me a very good chance your idle transition slots are fully exposed. If you make no changes and pull the carb off and check the slots, you will probably see too much of the slot showing. Try the secondary stop screw adjustment first as that is an easy mod. Holley recomends drilling holes in the butterflys when running big cams but the stop screw does about the same thing only it is less "permanant".

-Mark.

although i can only speak from what i've done with my solid roller 406, your flat tappet should react fairly close anyway. my cam specs are very similar to yours, so similar results should be doable. mine idles fine, in the transfer circuit. this is with a demon 750 dp. i just found that fairly large cammed 406's (which yours is), like as much initial as you can get away with (which is what yours seems to be telling you). i would set your timing where the motor likes to be, then adjust the idle air bleeds (4 corner or whatever yours has) to about 1 1/2 turns. then fire it up, and adjust the idle screws (equally) to the lowest reasonable setting. this should baseline you and keep you in the transfer circuit, as long as all other issues are good, like no vacuum leaks. my cars demon should be similar to your holley as far as baseline settings, but if anyone reading this has similar set ups with a holley, please by all means correct me if i'm off. my car idles in gear about 850 rpm, and about 950-1000 in neutral btw. and i must say that in this situation, i feel vacuum advance is unnecessary. i know johnz is very knowledgeable in this area, and don't contest that at all. but i tuned mine with vacuum advance initially, and got it right. but on my combo it was a huge pia, since a large cam just doesn't seem to like it. after i switched to my msd pro billet, no vac advance, it showed no adverse effects whatsoever, and it was much easier to tune and make adjustments. vac advance has its place, but in what most would call a radical cammed street/strip motor, i just don't see it needed. but then again my roots are in drag racing. just my .02, hope it helps graemlins/thumbsup.gif

It seems the 406 does indeed like the timing and have not experienced any problems. I just got the engine in and havent had the chance to drive and see if detonation will occur.(need to put the inner springs in)
I was just surprized about the initial and had to ask about it. I am still trying to work the bugs out. I will check the secondary stop srew, thanks a bunch for the help.
This is my first big cam and dont plan on driving it everyday. Like I said I will be getting an MSD dist and 6AL in the future, just wanted to hear it run and get my blood pumping.

Jason