Timing advance question

[Stephen Carter]

So I've done a small tune up on the truck (87 K5), which included new ICM, Coil, starter, and moroso HEI advance kit. I went to check the timing, found the little timing pointer, but I cannot tell which way it reads lol. I cleaned it, but there are no little numbers that i can see, so How do i read this thing?

 

[ktmoutfront]

Timing a TBI truck, timing is st at 0 with the plug under the brake booster unplugged. No numbers needed. Maybe 2 degrees advanced per some people. But factory spec is 0.

 

[Stephen Carter]

This truck is no longer a TBI, has a standard HEI distributor. The reason i ask, is the mark on the balancer, was at the far end of the scale (towards the passenger side) with my timing light set at 0

 

[ktmoutfront]

I did not catch that. The timing Tab should have been changed also. There should be a zero notch on the tab you have. Has the engine been rebuilt at some time? I have seen guys put blank tabs on for self marking though.

 

[Stephen Carter]

all the notches look the same.
I don't know if its been rebuilt, it might have been at some time, but the history isn't well known to me.

 

[ktmoutfront]

Best thing to do then non is find TDC and mark the tab. Just guess work until then. Is it running bad?

 

[Stephen Carter]

Hard starts when warm. And had a stumble at idle in gear only. So I replaced the icm and coil, and the starter

 

[ktmoutfront]

Hard starts when warm? Cranks hard? Usually means too much advance.

Stumbles at idle can be that or many other issues.

 

[Stephen Carter]

I also replaced the timing weights, to get more timing at cruise. The stock weights were minus bushing and the holes hand elongated.

I just walked out and double checked I do have a deeper notch which I'm guessing is the 0 notch?

Also, on the hard starts, I mean it takes a while to actually start, some times 4 or 5 goes at it for 5-6 seconds at a time. Had instances where it didn't want to start at all

 

[ktmoutfront]

The deeper mark is zero. Start from there. Cranking like that is probably a fuel delivery issue over spark.

What carb are you running? Are you assuming it is a stock engine? Or has it been cammed?

 

[Stephen Carter]

I'm assuming a stock engine.
It has an edelbrock 750 cfm carb on it, but I'm thinking I need to drop down to a 600 cfm

 

[ktmoutfront]

Yep. Over carbed. Is it blowing black smoke out the tail pipe when it stubles and when it cranks long? Or right after it starts?

 

[Stephen Carter]

haven't noticed really, the exhaust dumps under the truck but the other night I think it did when I finally got it to start (which took about 45 minutes and a jump start)

 

[ktmoutfront]

Loaded up. Too much fuel.

 

[dyeager535]

I'm assuming a stock engine.
It has an edelbrock 750 cfm carb on it, but I'm thinking I need to drop down to a 600 cfm

750 what? Double pumper? Vacuum secondary? 750CFM is not too big for a 350. If the primaries are a terrible design, it's a mechanical secondary, or the whole thing is garbage, you'll run into issues. If it's a vacuum secondary, get it tuned right, or, if a piece of junk, replace with something good, like a Q-jet. Good carbs cost a fair chunk of change unfortunately. A 600 will of course work, and probably make it seem like the previous carb was too large, but that's an assumption.

Properly designed and tuned, a large carb will work, and work well. Better than smaller.

Vizard was writing about it 11 years ago, if not sooner: http://www.hotrod.com/how-to/engine/0511phr-carburetor-boosters-tech/

If you want to learn something, read that article. He has a good one on exhaust as well.

 

[Stephen Carter]

750 what? Double pumper? Vacuum secondary? 750CFM is not too big for a 350. If the primaries are a terrible design, it's a mechanical secondary, or the whole thing is garbage, you'll run into issues. If it's a vacuum secondary, get it tuned right, or, if a piece of junk, replace with something good, like a Q-jet. Good carbs cost a fair chunk of change unfortunately. A 600 will of course work, and probably make it seem like the previous carb was too large, but that's an assumption.

Properly designed and tuned, a large carb will work, and work well. Better than smaller.

Vizard was writing about it 11 years ago, if not sooner: http://www.hotrod.com/how-to/engine/0511phr-carburetor-boosters-tech/

If you want to learn something, read that article. He has a good one on exhaust as well.

It's an edelbrock 1407. Do not know if it's vacuum secondaries or mechanical. I think vacuum. Since the metering rods move on springs rated in in/hg.

I just set the timing to 0*-1*. And found out my vacuum advance is bad. But it starts a lot easier now lol I think it was at 12-14*.

 

[Carcinogen]

I just set the timing to 0*-1*. And found out my vacuum advance is bad. But it starts a lot easier now lol I think it was at 12-14*.

0 is for TBI because the ECU controls timing... You will probably want to go back to around 12 base.

That is assuming that your timing marks were correct, always best to double check.

 

[ktmoutfront]

What manifold is on it?

 

[Stephen Carter]

What manifold is on it?

Not sure, 14101074(I think) is stamped on the back towards the distributor

 

[ktmoutfront]

Stock, 4 barrel, mid to late 80s if my memory is correct.