ksmitty

How do I set the timing on a 1970 olds 350 that has been rebuilt and they put a performance cam in it if I do not know the specs on the cam. And it has a MSD ignition system with HEI distributor.

don71

You'll need arond 35-36* of total timing. Your initial timing could be from 14-20degrees..depends on your set up. A dial back timing light helps here.

You might need to take advantage of a distributor re-curve..and maybe an adjustable vacum advance. If the car starts and shuts off correctly under most conditons, your pretty close. Whats it like when your driving under load?

Tell us a little more details about your set up. This info is pretty generic.

ksmitty

its in a 1987 cutlass 442, with a 200 4R trans, 2500 stall converter 373 gear in the rear end. # 6 heads with roller rockers. not sure if any machine work done on the heads. eddlebrock performer rpm intake manifold and eddlebrock #1407 750 cfm carb. Heddman headers with flowmaster super 40 mufflers. I wish I knew more about what was in the engine but I bought it complete and running. so why tear apart a good running motor. Most of the time it starts decent but every once in a while it does not. I have not worked on cars for over 20 years but getting back into it with my 19 year old son and could use all the help I can get. When you say total timing are you saying with the vacuum advance hooked up to the carb? And with out it hooked up between 14 and 20 degrees? under load something does not seem right

oldcutlass

No, with vacuum adv. disconnected, your curb idle timing a (initial) should be around 10-14 deg's btdc. Your total mechanical timing is checked at around 34-3600 rpm with adv. disconnected and should be 34-36 deg's btdc. Your total timing with vacuum adv connected @3400-3600 rpm, is initial + mechanical + vacuum = 50-60 degrees btdc.

Most just get away with adjusting initial timing to 10-14 btdc or as much as they can get without pinging. The rest generally falls into place.

I hope this helps!

ksmitty

OK i believe I have the timing close it starts ok and no pinging. Under load I feel like it has a slight miss or something. What should the spark plug gap be? I think the AC delco plugs I put in were gapped at 60. Is that to much and possible the problem. What will happen if your gap is to wide? I have new and good wires, new MSD cap, rotor. And the MSD ignition box is the 6AL model. Not sure why else the slight miss and sometimes a slight hesitation.

oldcutlass

Depending on spark plug it can be from .045-.080. The size of the gap changes the amount of voltage it takes to jump the gap when it fires. The slight miss may be a carb adjustment.

Is your vacuum advance connected to ported or manifold vacuum?

ksmitty

Ported

oldcutlass

I Would adjust my carb and ensure my choke was working correctly.

ksmitty

My choke is disconected for now. Have not wired it yet I thought where it was an option on that carb I didn't need it.#ome people tell me its too big, some say its fine I don't know who to believe. I do know on eddlebrocks web site with that intake manifold that's the carb they recomend.

svnt442

Use the plugs recommended for the 70 and gap them to .045. That is what I have found to be best. If you get the plugs for the HEI engines the gap is HUGE @ .080 and you can't close it down that easily.

Aceshigh

I recently went through this with my Aunt's boyfriend on that engine Kevin.

The initial timing IIRC was 16 btdc and we ran it up to 32 something.....I forget.
Used one of those dial timing lights to figure it out.

I think you should do the carb adjustments we talked about first.
Have you hooked up the air fuel mixture gauge to determine proper metering rods yet ??
I never noticed any misfiring at all.

Starter heat soak will be an issue in the summer if you don't put a shield over
the starter if it's very close to the headers.

ksmitty

Did not do the wide band tuner as its to much money and when the guys did the exhaust they cut off the part of the flange that the o2 sensor goes in. We have to take a break from it because of money was going in faster than we were making it. Also still have posi to put in and trans issues. Not torn up but not shifting correct in automatic