Timing question

[Dazman63]

I‘ve been undoing a lot of work the previous owner did and now I discovered he has the wrong spark plugs in gapped at .039. I ordered new plugs with the correct gap of .044.

I’m also wondering if he installed the distributor the right way. So I timed my 400 to 18 degrees and it seems to run well there. I then cranked the engine over by hand so the rotor lined up with the number one spark plug wire on the distributor. The mark on the harmonic balancer reads 22 degrees.

How can this be? Should it not read 18 degrees?

 

[Tiha]

Really should be using a timing light.

Besides that, 22 degrees might be okay depending on a lot of other things. But if it is a factory stock engine then most likely that would be advanced too far.

 

[Dazman63]

Yes, I did use a timing light. The previous owner had it rebuilt.

 

[Dazman63]

I got home on Friday and Saturday I worked on finding TDC. I rotated the engine and when I got on the compression stroke I kept moving the piston until it stopped moving. It lined up on 3 degrees before TDC. I then rotated the engine in the other direction doing the same thing and noted the position on the balancer. The middle point of both marks was 0 degrees before TDC.

So it looks like the 0 degrees is bang on. I also checked the timing and it’s 17 degrees before TDC.

The odd thing is, now I’ve got the correct spark plugs in there is no vacuum at idle on the carb’s port, whereas before I had about 16 Hg. If I give it some gas the vacuum increases. Any idea why this would change?

 

[Whipsaw]

I have a '93, 351W; in order to set the timing the SPOUT (Spark Out) jumper must be removed. Then use a timing light and sight the harmonic balancer. The ECM will advance or ****** the spark, pulling the SPOUT jumper disables this. The SPOUT is near the left rear of the engine compartment down by the fuse boxes, its just a one end line hanging out down there.

 

[Whipsaw]

While we're talking about setting the timing, what is a good way to highlight the marks on the HB?

 

[L\Bronco]

I got home on Friday and Saturday I worked on finding TDC. I rotated the engine and when I got on the compression stroke I kept moving the piston until it stopped moving. It lined up on 3 degrees before TDC. I then rotated the engine in the other direction doing the same thing and noted the position on the balancer. The middle point of both marks was 0 degrees before TDC.

So it looks like the 0 degrees is bang on. I also checked the timing and it’s 17 degrees before TDC.

The odd thing is, now I’ve got the correct spark plugs in there is no vacuum at idle on the carb’s port, whereas before I had about 16 Hg. If I give it some gas the vacuum increases. Any idea why this would change?

Hey Dazman
If its the small vac port on the front of the carb that goes to the dist, its a ported vac signal for vac advance. It doesnt get a vacuum signal until the throttle is open slightly.
In all of your tuning and repairing you may have been able to slow the base idle down a bit, (this would cut the supply to that port.)
Hope that helps.
Is she good now?
Cheers

 

[Dazman63]

Hey Dazman
If its the small vac port on the front of the carb that goes to the dist, its a ported vac signal for vac advance. It doesnt get a vacuum signal until the throttle is open slightly.
In all of your tuning and repairing you may have been able to slow the base idle down a bit, (this would cut the supply to that port.)
Hope that helps.
Is she good now?
Cheers

It’s running good now, but the vacuum coming out of the carb’s vacuum port, manifold, flickers back and forth rapidly by 1”of Hg.

 

[L\Bronco]

Hook your gauge to the vac tree behind the carb to compare.
If its still erratic, it could indicate an intake valve leaking.
Whats the vacuum value? (Average)

 

[Dazman63]

Hook your gauge to the vac tree behind the carb to compare.
If its still erratic, it could indicate an intake valve leaking.
Whats the vacuum value? (Average)

It’s around 14 and the needle settles out as the rpm’s increase.

 

[L\Bronco]

Are you able to do a compression test or cyl leakage check?
Those were famous for breaking valve springs, if it was on an intake valve it could cause your symptom.
They usually made a ticking noise, but not always.
Could pull the valve covers ad do a visual inspection too.
Hope that helps
Cheers

 

[Dazman63]

When I get home in two weeks I’ll do that. Thanks for the advice.

 

[L\Bronco]

Good luck!
Cheers

 

[Dazman63]

Are you able to do a compression test or cyl leakage check?
Those were famous for breaking valve springs, if it was on an intake valve it could cause your symptom.
They usually made a ticking noise, but not always.
Could pull the valve covers ad do a visual inspection too.
Hope that helps
Cheers

I pulled the valve covers off and all the springs seem fine.

 

[johnnyreb]

Really should be using a timing light.

Besides that, 22 degrees might be okay depending on a lot of other things. But if it is a factory stock engine then most likely that would be advanced too far.

A timing light is good--IF the vehicle does NOT

 

[johnnyreb]

A timing light is good--IF the vehicle does NOT

HAVE ALOT OF MILES ON IT and they are not accurate at that point--because alot of the parts get warn. Then you have to go but ear. If you don,t have a hearing problem. If you do--find someone who has good hearing and knows how to adjust it that way.

 

[Dazman63]

I have a timing light and I purchased a dial back as well.

I’ve got it sent to 15 degrees BTDC and runs nice. I also ordered a tuning kit for my MSD distributor and I’ll have to work on calculating my total timing.

 

[L\Bronco]

Hey Daz
do you know what camshaft you are running? If the overlap is high, you can get a nice lumpy idle, but erratic vacuum at idle comes along with it.
Just a thought.
Cheers

 

[Dazman63]

Hey Daz
do you know what camshaft you are running? If the overlap is high, you can get a nice lumpy idle, but erratic vacuum at idle comes along with it.
Just a thought.
Cheers

Exactly, lumpy idle. It’s a Comp Cams 32-242-4 Extreme.

You might be on to something.

 

[Dazman63]

Using an online calculator my overlap is 48 deg and LSA is 109 degrees