Got A Question For You Guys With 406 SB
 

I have a 406 sb 268h comp cam, and I'm haveing trouble timeing it the way my chevy buddy says to time it. I have alot of low end his way. Not what I wont. So I started playing with it the way I would one of my old Mopars. I pluged the vacume for the HEI and started advancing it. I found my power about 1/2 inch off the timeing scale . The scale is a bunch of vvvV marks and I have it at ( l vvvV ) if this makes sence. It finely started running like a raped ape, is this normal. I would like to find out what other 406 owners have theirs set at and wat they have to do to get theirs running right. Matt

Maybe this will help


http://www.73-87.com/7387garage/driv...timing101s.htm

Not helpfull Thanks any way. Matt

Not a 406 owner but it's still a sbc. Just a couple of questions...
So you power timing it instead.
At what rpm are you flashing the light on it, to get the 1/2" off the tab? That's if you are going by the tab. Is the harmonic balancer degreed/indexed or at least have timing tape? Is there an advance kit in the distributor with an adjustable vacuum advance?

Im timeing it at idol 700 or 800 RPMs with a light no timeing tape, no diel on the light, just stock marks and no tack. I have a curve kit and a adjustable vacume advance. The harmonic is not spun. At the last mark on the tab, and vacume hooked up it has lots of low end. my friend says ported vacume, I say manifold vacume. So I pluged it off. Turned the dist. till it started running like it should, then checked it with the light. 1/2 inch off the tab. Took it for a drive, now I need new tires. Burned the rubber right off.

you should have the dist vac advance to ported vacuum. at idle it sounds like you have it at like 25 or so degrees. thats too much. Does it grunt when you try to start it? you should get a timing light with an advance dial so you can see how much you have in timing. check the total advance, time it at 3000 and idle, write the two numbers down and subtract, thats your total advance. Example: at 3000 its 32 deg.
at idle its 22 deg. Thats 10 deg of total advance, with the vacuum advance hose off.
To get the idle timing lower without sacrificing total advance youre gonna have to recurve the dist. widen the advance curve. My 406 race engine has 38 deg total advance at 3000. its a crank trigger set up so its locked out but my msd retard module helps when It cranks the timing is retarded 20 deg.
That 268 cam is awesome! I had it in a 355 and I set up the dist to have 12-15 deg total advance, set the idle timing at 15-17 deg at 800 RPM and depending on the gas I ran 27-32 deg at 3000.

Thanks that helps alot. Now my ported vacume on the carb is pulling some vuc, at idol. Not like manifold vac just a little I haven't put a gauge on it yet but is it suposed to pull vac at idol. Maybe this is the problem?. Matt

Well Bluejimmy basically basically said it. As long as it starts hot & cold, I wouldn't TOO much. Well exceot the vacuum advance. However, I would at least throw some timing tape on it. Coat it with a little clear nail polish, around the edges and it should last a little longer. This way you can everything correct and can use for future reference. You might have to fool it with again for the planned head swap and header install.

That's why I asked about the distributor. Like how did you set up the vacuum advance and what springs were tried first? Here's another link that should help you out, one way or the other. They do a good jog explaining, instead of someone else retyping it. Damon doesn't frequent here, but Mike does.
http://www.73-87.com/7387garage/drivetrain/hei.htm

Well I found part of my problem. I dont practice what I preach. After writing that bit on Holleys you would think I was an expert. Well ( Not ). Ported Vacume on my carb was pulling vacume at idol. It's not suposed to do that!. Primary butter flys were open to much, and it was running at 700 to 800 RPMs. Pull a vacume line and the engine speeds up ( to rich ) Im take'n care of that problem tomarrow, then it's on to the HEI and getting the curve right. I want to thank every one for there help. Matt