Crate engine swap advise please?

[73 C10]

Doesn't work like that... You still need a tdc mark on your balancer.

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I have one. It lines up with the 0* on the tab.

I don't trust the tab to tell me anything but 0 now that I have an adjustable light.

 

[rich weyand]

Let me help you find your Way...
If you can't read the timing off the balancer due to not having a timing Mark how do you know where your timing actually is? I suggest finding tdc and marking your balancer https://youtu.be/xg6eAWWvrPA

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^^^ This.

I don't like that your tab and the delay timing light disagree. There's something goofy in all this.

Here's my recommendation, reviewing all of the above:

1) Find TDC and get an accurate set of marks on the timing wheel and polish up the tab so you can see WTF your timing really is.

2) Limit the vac advance to 12 to 15 degrees. 20 is too much. That may be the whole trouble, because it will knock when you get on it until the vac advance responds by backing off.

3) Set base timing for now to 8 degrees (ONCE YOU KNOW YOU HAVE AN ACCURATE READING).

4) Get the A/FR meter and set the needles/jets for cruise and power circuits first, then adjust the idle mixture. You should have something like 13 idle, 14.5 cruise, 13.5 power, 12.5 secondaries.

5) Now go back and set the base timing higher 2 degrees at a time, testing for knock each time. When/if you get to 16* BTDC base timing, stop there.

BTW, detonation (pre-ignition, knocking) sounds like you are shaking a 1# coffee can with a 1/4" steel ball bearing in it.

The reason our recommendations are all over the map is a lack of instrumentation: no reliable timing measurement, no A/FR readings.

You give us those, and MO and I will agree on everything.

 

[73 C10]

^^^ This.

I don't like that your tab and the delay timing light disagree. There's something goofy in all this.

I don't like it either. I've tried to use light #'s only.

Here's my recommendation, reviewing all of the above:

1) Find TDC and get an accurate set of marks on the timing wheel and polish up the tab so you can see WTF your timing really is.

The one mark is visible, and the tab is polished.

2) Limit the vac advance to 12 to 15 degrees. 20 is too much. That may be the whole trouble, because it will knock when you get on it until the vac advance responds by backing off.

I will, but we've been there. Was most recently at 11. I know it not 15. I'm working on it.

3) Set base timing for now to 8 degrees (ONCE YOU KNOW YOU HAVE AN ACCURATE READING).

This has never been done, but has been suggested. OK. Will do.

4) Get the A/FR meter and set the needles/jets for cruise and power circuits first, then adjust the idle mixture. You should have something like 13 idle, 14.5 cruise, 13.5 power, 12.5 secondaries.

This will take a few days.

5) Now go back and set the base timing higher 2 degrees at a time, testing for knock each time. When/if you get to 16* BTDC base timing, stop there.

BTW, detonation (pre-ignition, knocking) sounds like you are shaking a 1# coffee can with a 1/4" steel ball bearing in it.

This sounds like a clatter, a rookie would think it might be valve rocker noise.

The reason our recommendations are all over the map is a lack of instrumentation: no reliable timing measurement, no A/FR readings.

I thought I just spent $100 on a light to get a reliable timing reading. Very frustrating.

You give us those, and MO and I will agree on everything.

I'll get the meter. And in the mean time I'll try 8* base and 15* va.

 

[350runner]

I have one. It lines up with the 0* on the tab.

I don't trust the tab to tell me anything but 0 now that I have an adjustable light.

Earlier you said...

It looked to be at ~15* of va on the crank. I set the base to 12-13 BTDC. It's hard for me to read the deg. Because I have not figured out how to mark my balancer sutch that a mark is ever on the tab. My tab goes from -12 - 10. -16* is off the tab so it's a bit of a guess

So you can see why i and others say what we say.

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[73 C10]

What's wrong with measuring va by setting the light and plugging and/or unplugging the vacuum and measuring the delta from base, when below the RPM mechanical starts contributing, and with enough vacuum to pull full advance?

 

[350runner]

Even idling the mechanical advance should not be I play. It should start no sooner then 300 rpm above idle.

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[73 C10]

Earlier you said...

It looked to be at ~15* of va on the crank. I set the base to 12-13 BTDC. It's hard for me to read the deg. Because I have not figured out how to mark my balancer sutch that a mark is ever on the tab. My tab goes from -12 - 10. -16* is off the tab so it's a bit of a guess

So you can see why i and others say what we say.

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Yes. I see you are quoting post 182.

You can see that I was sure of my base setting of 12-13. And was unsure of the va by saying that va was about 15 (~15*).
I then tried to explain why I was unsure about the 15.

You and the others must have missed post 196, where I said I bought a adjustable timing light. My TDC mark has never been a problem.

I verified my TDC mark on the balancer lines up with 0 on the tab, while at actual TDC quite some time ago, in a previous thread regarding this truck.

I would need another mark, a incremented balancer, or timing tape to read anything greater then 12 on the tab with a plain light.

 

[73 C10]

Even idling the mechanical advance should not be I play. It should start no sooner then 300 rpm above idle.

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Yes. We agree on this. Mechanical advance does not kick in 'till ~900. So like I asked, what would be wrong with measuring va if below this point. Mechanical would not be contributing, therefor not skew the va #.

 

[350runner]

Ok if you want to measure vacuum advance while idling. With the engine on, vacuum advance unplugged, and at idle set the timing to zero. Next plug connect the vacuum advance. What does it read?

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[73 C10]

Yes. We agree on this. Mechanical advance does not kick in 'till ~900. So like I asked, what would be wrong with measuring va if below this point. Mechanical would not be contributing, therefor not skew the va #.

I asked this question because of what MadOgre said in post 217.

 

[73 C10]

Ok if you want to measure vacuum advance while idling. With the engine on, vacuum advance unplugged, and at idle set the timing to zero. Next plug connect the vacuum advance. What does it read?

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Like I've been saying. If base is set to whatever, lets say 12*, with the vac un plugged at idle, and i zerod the light, plugged in the vac, and adjusted the light to bring the TDC mark on the balancer to 0 on the tab, the result is 20*.

 

[rich weyand]

Yes. We agree on this. Mechanical advance does not kick in 'till ~900. So like I asked, what would be wrong with measuring va if below this point. Mechanical would not be contributing, therefor not skew the va #.

Yes, that's right.

Another issue is that the vacuum advance may come in too soon, keeping you advanced after it should have dropped out.

Stock is something like the AR23: "5-7 7.5 @ 11-12.5", which is:

Advance starts coming in at 5-7" Hg, and maxes out at 7.5* (camshaft degrees -- 15 crankshaft degrees) at 11" to 12.5" Hg.

 

[350runner]

Like I've been saying. If base is set to whatever, lets say 12*, with the vac un plugged at idle, and i zerod the light, plugged in the vac, and adjusted the light to bring the TDC mark on the balancer to 0 on the tab, the result is 20*.

Try limiting it to 8- 10 and see what that does.

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[rich weyand]

Like I've been saying. If base is set to whatever, lets say 12*, with the vac un plugged at idle, and i zerod the light, plugged in the vac, and adjusted the light to bring the TDC mark on the balancer to 0 on the tab, the result is 20*.

OK, so that is not 20 degrees of vacuum advance. That is 8 degrees of vacuum advance, which is probably too little.

The following are "terms of art", and what we assume you mean when you use them.

"Base timing" is what you read at idle when the VA is unplugged.

"Vacuum advance" is what you read at idle with the VA plugged in MINUS the base timing. That is, it is the amount of advance the VA unit ADDS to base.

"Total timing" is the timing you get from 3000-5000 rpm with the throttle wide open. That is base + mechanical. So-called because race engines don't have vacuum advance, because the throttle is pretty much always open and it's just another thing to break. Also, if the VA breaks on a race engine and goes into advance when under full throttle load, the heads are going through the hood.

"Mechanical Advance" is what you read at 3000 rpm with the VA unplugged MINUS the base timing. That is, the amount of advance the mechanical advance unit ADDS to base.

 

[rich weyand]

Like I've been saying. If base is set to whatever, lets say 12*, with the vac un plugged at idle, and i zerod the light, plugged in the vac, and adjusted the light to bring the TDC mark on the balancer to 0 on the tab, the result is 20*.

OK, so I re-read this and maybe you are reading the difference. I don't know what light you are using.

If you are reading the difference, that is too much VA.