Crate engine swap advise please?

[73 C10]

I bet my last dollar your just experiencing rattling rockers...

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Could be. This is the first it's been explored. Would that be from a lifter going out. Not pumping up?

That might explain why it seamed to appear later in a trip without changing anything.

 

[350runner]

Ok so i downloaded the instructions and they are talking about crank degrees. Unless you are trying to degree a cam looking at the cam paperwork all manufactures are speaking in crank degrees. Why? Because that's what everyone knows and it prevents any liability issues due to misunderstanding.

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[350runner]

Could be. This is the first it's been explored. Would that be from a lifter going out. Not pumping up?

That might explain why it seamed to appear later in a trip without changing anything.

Yes that is exactly why nothing would of changed. I can't say why it's happening but we've ruled out the timing theory... Did this only start happening after you messed with the timing?

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[73 C10]

Ok so i downloaded the instructions and they are talking about crank degrees. Unless you are trying to degree a cam looking at the cam paperwork all manufactures are speaking in crank degrees. Why? Because that's what everyone knows and it prevents any liability issues due to misunderstanding.

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OK. But, why, when I pull the va by hand pump, when the base is set at 12* on the tab, with the light zeroed, does the light need to be adjusted 20* to line up the TDC mark back up with 12* on the tab.

 

[350runner]

Because the vacuum advance is advancing the timing way to much. Vacuum cans provide anywhere from 8- 20 degrees of timing. This is why I'm always suggesting 8 - 10 degrees limited vacuum advance at the crank. You will notice no difference in performance or mpgs between my. Setup and the one you have chosen. Maybe if you were running a quench engine with aluminum heads and a good cam, but not on a stock or close to engine. Especially in our heavy Chevys.

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[73 C10]

Ok so i downloaded the instructions and they are talking about crank degrees. Unless you are trying to degree a cam looking at the cam paperwork all manufactures are speaking in crank degrees. Why? Because that's what everyone knows and it prevents any liability issues due to misunderstanding.

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This crank cam thing seams to be debatable if I read you and Rich correctly. I am trying to speak two languages I think. I think Rich knows this. I would like to speak one, crank. Rich explained earlier that distributor manufactures may spec in cam degrees. Correct me Rich if I've got that wrong.

Check out #12 in the download. We have not tried this yet.

"12. Test drive and listen for audible noise under load and at part throttle. If spark
knock occurs under load, at full throttle, retard the initial timing as required to
eliminate it. If spark knock occurs at part throttle an adjustment to the vacuum
advance is necessary. This adjustment is made by inserting the Allen wrench into
the vacuum advance canister port and turning it two turns clockwise. Test-drive
the car and repeat the adjustment until the spark knock is eliminated. "

 

[350runner]

1. The crank/ cam debate only exist here.?
2. Trust if you dialed the timing back to 8- 10 degrees btc and removed the vacuum advance you would not even have to worry about step #12

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[73 C10]

Because the vacuum advance is advancing the timing way to much. Vacuum cans provide anywhere from 8- 20 degrees of timing. This is why I'm always suggesting 8 - 10 degrees limited vacuum advance at the crank. You will notice no difference in performance or mpgs between my. Setup and the one you have chosen. Maybe if you were running a quench engine with aluminum heads and a good cam, but not on a stock or close to engine. Especially in our heavy Chevys.

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Well, on a 0-20 scale it was at 11* of va, 'till 3 changes ago. I was at 11* of va the first 5 of 8 changes, since this last problem. Rich thought I should be at 15*of va.

 

[73 C10]

1. The crank/ cam debate only exist here.?
2. Trust if you dialed the timing back to 8- 10 degrees btc and removed the vacuum advance you would not even have to worry about step #12

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Oh, good point. I thought too little could cause it too. And the wrong springs too. Read here.

 

[350runner]

You're thinking to much. Lol just stay away from to much advance.

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[350runner]

Yea the wrong springs can cause it because they cause the mechanical to come way too early at idle and thought the rpm range

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[73 C10]

You're thinking to much. Lol just stay away from to much advance.

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OK. We got it down to 8-10* base, no va, and whatever mechanical. Idle was more labored, bogged taking off rattled when dropping the hammer. Stopped when letting off.

I won't even "think" about the 5" springs and their roll in this.

 

[73 C10]

Oh. I see you said change the springs. I promised Rich I would be doing this next.

 

[350runner]

I'm talking about the centrifugal ignition advance springs in the dizzy.

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[73 C10]

I was talking about step up springs when referring to Rich. I guess you are talking about the springs related to the mechanical. My bad. Step up springs are next.