Block 3970010...70s block timing ????

[ellisjay2]

I'm about to re pull and drop distributor and set static timing again on 70s block I've put in my truck. I completed this months ago and drove it back and forth few times, it's sat still mostly last few months from being busy. I only have short tube headers as of now. I originally set crank timing between 10 -12° btdc.....started up fine, (used engine) but now you can hear some ping popping on idle, lacks some power driving. I learned these year blocks required 4, 8, and 10° btdc. I don't know if engine has cam or not...sounds like it....person I got it from isn't around anymore. So I'm thinking reset everything and see what difference I get......

[Dead Parrot]

The emissions tuning sticker might have said 4~8*, but that was to detune the motor so the air pump could burn off stuff in the exhaust manifold. Cleaner emissions but at the cost of power and fuel mileage. Your 10~12 initial is normally a good starting point.

A stock or mostly stock 350 usually wants 12~14 if not more of initial timing. While you have the distributor out, make sure the mechanical advance is working and not sticking. From experience, an intermittent sticking mechanical can cause you to alternate between too slow an idle(when unstuck) and hard to start hot(stuck full advance).

Also check the vacuum advance. The vacuum pot will fail after several years.

[GSP7]

Make sure it has the correct timing tap for the harmonic balancer type. I have a 1973 .....010 block in my '81 k20. I had to get a different balancer and timing tap than the '81 style

https://www.summitracing.com/parts/r...4aAkkKEALw_wcB

[Corts60]

Just some quick reference notes: popping through the carb= not enough timing. Pinging under load or popping through exhaust= too much timing.

[ellisjay2]

So I tried to 4° initial timing and we dropped distributor set the oil shaft at 11 and 5 o'clock lined everything up got the rotor pointing at number one cylinder... Distributor cap terminal number one lines up with rotor.... But engine just turned over no crank....... Redid everything again moved it to 12° before tdc... We drop distributor and fired right up.... But advancing and retarding couldn't get good idle.... After shutting off and recranking but tell me the difference of too much time and or too much retardation.... Problem is I'm doing this without the timing light which I will have tomorrow.... I think I'm going to go a little past 12° and probably catch somewhere between 13....14...btdc.

[Corts60]

I think having the timing light will help you solve your issue. Let us know how it goes.

[GSP7]

Problem is I'm doing this without the timing light

buy a timing light

[KQQL IT]

If it has a HEI Distributor and the cap fairly straight its close.

[Corts60]

Originally Posted by KQQL IT

If it has a HEI Distributor and the cap fairly straight its close.

That all depends on what position the distributor was dropped in last, so I wouldn’t rely on that too much.

[KQQL IT]

One tooth ahead the vacuum advance hits the intake, one behind the vacuum advance is pointing at the firewall.
If the timing tab isn't present or wrong that'll get you close enough.