Engine Timing With Vacuum Gauge - Setting Timing For Good

78Delta88

Master Mechanic
Supporting Member
May 23, 2022
406
43
SW Arizona
Psi on compression is good but the 2 that are 10 down could be an issue. Typically you don't see numbers that are all the same all the way across.
 

Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,120
63
On 87 fuel back down initial to 10 to 12
Ported vacuum
Your listening to some that are sending you the wrong way. I've been doing this 40+ years and usually get to fix what the experts screw up
Full on advance by 2500 not 3500
I have base timing set at 12 degrees before top dead cylinder and I added 24 totaling 36° total timing...

I have my vacuum advance canister connected to the ported/timed vacuum port...

I have tested it on the main roads and I have tested it on the highway and it runs great.
 
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Rt Jam

Master Mechanic
Mar 30, 2020
340
63
Ontario Canada
I have base timing at 12°, so I guess I'm going to put 22 at 2500, making total to make it 34 total timing.

Right now I'm adjusting the idle mixture screws using a vacuum gauge. When I'm done with that I'm going to do total timing, reconnect the distributor to ported and take it down the street and back and see how it does.

Should I go ahead and throw in the heavier weights in the distributor since I already put in the lighter springs or should I just use the weights that came with the aftermarket HEI distributor ?
This is hard to answer this. It depends on what your car wants. Major factors are cam shaft and torque converter and drivetrain gearing.

Heavier weights and lighter springs do the same thing. The allow advance from initial to total to happen at less rpm.

Fully tuning a distributor is a deep science. At a minimum you will need to plot a timing graph. Timing vs rpm.
I have base timing at 12°, so I guess I'm going to put 22 at 2500, making total to make it 34 total timing.

Right now I'm adjusting the idle mixture screws using a vacuum gauge. When I'm done with that I'm going to do total timing, reconnect the distributor to ported and take it down the street and back and see how it does.

Should I go ahead and throw in the heavier weights in the distributor since I already put in the lighter springs or should I just use the weights that came with the aftermarket HEI distributor ?

Heavier weights will make the total timing come in before 2500. That is pretty early but nobody knows unless you post the torque converter, gearing and weight of the car.
How are you doing total timing?
 

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