Crate engine swap advise please?

[350runner]

Good deal

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[73 C10]

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

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Someone once said put the silver and blue springs in the centrifugal. Not recently. I think that's more of a fine tuning thing right? Stock are in there now.

 

[350runner]

Yea that's right the silver and blue springs will put you in a good place in bringing the centrifugal advance in between after idle and 3500. Heavy vehicles like trucks will see a better gain when the centrifugal is brought in a little later and ends a little later due to the load presented on the engine.

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[350runner]

The centrifugal advance springs are of your least concern at this point. If your rockers were chatty b4 your timing trial and error then find that issue so that you can hear and detonation when you imply Richs timing method.

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Edit....

 

[rich weyand]

You can see the centrifugal advance kick in on the timing light if you have someone slowly rev the engine higher just sitting there in Park. It should be all in before 3000.

I wouldn't mess with the mechanical. Part of the problem is you have too many available adjustments as it is. I have the stock distributor with (I think) the (not adjustable) AR23 vacuum advance can and I have never touched the vacuum advance. That's the one that is 15 crankshaft degrees, per that timing write-up about 100 posts back.

 

[73 C10]

I put the 9" springs back in.

I found base time to be 8* on the tab at 550 RPM with the va plugged. And with the light zeroed I need to adjust the light 8-9* to line the TDC mark up with 0* on the tab. Only 1* different. That looks good to me so far.

I hooked up a hand pump. Now with 8* of base, light zeroed, pumped to >= 18", it takes 22 degrees on the light to get back to base.

Just say'n for reference weather your trusting this or not.

Anyway, like I said the 8* BTDC on the tab as asked, and 9" springs.

Took it out like before, same route, bad bog like not getting fuel, va plugged. It had gas. I put some in to make sure.

I hooked up the va half way, other then the idle coming up, still bogged.

Next. One change. You guys tell me. I'm hearing set the va to 15* of advance. Down from the 22*. Just that change or what?

I need to check my connections to the distributor like power, ground, signal. I've messed with the cap so much already f'n with the spiral limiter on the va. I'm just waiting for one of them to pop off next. I'm guessing I might get a good exhaust pop.

Anyway, next?

 

[73 C10]

You can see the centrifugal advance kick in on the timing light if you have someone slowly rev the engine higher just sitting there in Park. It should be all in before 3000.

I wouldn't mess with the mechanical. Part of the problem is you have too many available adjustments as it is. I have the stock distributor with (I think) the (not adjustable) AR23 vacuum advance can and I have never touched the vacuum advance. That's the one that is 15 crankshaft degrees, per that timing write-up about 100 posts back.

When base was 8* BTDC @ 550 RPM, va plugged, light zeroed, I found that if I set the light for 21* and reved to 3000 RPM, that TDC mark ended back up a 8* BTDC. So if the light is working that should be the mechanical, 21*. 8* + 21* = 29* BTDC with no va. If I've been following this should be closer to 34* witch is why base should be more like 13*. 13* + 21* = 34* no va.

And 15* of va, down from 22*.

Rod, I know. One thing at a time, If your right we'll end up back there.

How am I doing?

 

[rich weyand]

When base was 8* BTDC @ 550 RPM, va plugged, light zeroed, I found that if I set the light for 21* and reved to 3000 RPM, that TDC mark ended back up a 8* BTDC. So if the light is working that should be the mechanical, 21*. 8* + 21* = 29* BTDC with no va. If I've been following this should be closer to 34* witch is why base should be more like 13*. 13* + 21* = 34* no va.

And 15* of va, down from 22*.

Rod, I know. One thing at a time, If your right we'll end up back there.

How am I doing?

Yup, now you got it. Exactly correct, except I would say the sweet spot is 36* for a Chevy V8, which is why I like 16+20 (or with 21 mechanical, 15+21) to get 36.

Limit the VA to somewhere in the 12-15 range. Stock is, I think, 15.

The bog now is in your mixture, I think. Get that meter first though, or your just spinning your wheels trying to find the right setup.

Meanwhile, keep the base timing where it is until you get the mixture set up. You have to do that first before you advance base timing that much.

 

[73 C10]

Yup, now you got it. Exactly correct, except I would say the sweet spot is 36* for a Chevy V8, which is why I like 16+20 (or with 21 mechanical, 15+21) to get 36.

Limit the VA to somewhere in the 12-15 range. Stock is, I think, 15.

The bog now is in your mixture, I think. Get that meter first though, or your just spinning your wheels trying to find the right setup.

Meanwhile, keep the base timing where it is until you get the mixture set up. You have to do that first before you advance base timing that much.

OK.

I see in my Haynes book that for a '73 350, base timing is 8* for manual, and 12* for auto.

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Why did base timing go up from 4* for manual, and 8* for auto for a couple years in '73-'74?

Doesn't it have something to do with the HEI, va and emissions.

Anyway, it says my base should be 12*. So why do you guys want me retarded?

 

[73 C10]

Also, if you don't mind me asking, why were the R45TS plugs run in '71 at .035", but not again 'till '76 but gapped to .045"?

I assume the gap difference was because of the HEI coming in somewhere in between those years.

Whats the T and TS designate?

Is the 45 hotter then the 44?

If so, way did GM run a cooler plug a few years?

It looks like tried something in '75. Huge gap .060" R44TX, but didn't stick with it.

 

[350runner]

Since we were trying tip figure out your rattling problem it's best to start low with the timing. We all still need too know if this rattling issue was prevalent before you messed with the timing.

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[73 C10]

Since we were trying tip figure out your rattling problem it's best to start low with the timing. We all still need too know if this rattling issue was prevalent before you messed with the timing.

Sent from the dust in front of you!

Are you down with the change to 15* va, as the next change?

 

[350runner]

Was the rattling sound there b4 the timing change?

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[73 C10]

Was the rattling sound there b4 the timing change?

Sent from the dust in front of you!

I don't think so. Thinking back, I was a 12* base when I went out to do some 0-60 runs.

Then I added 4*. I must have test drove but don't remember hearing anything at that point.

The next morning I went for the 40 mile drive. I think I was just light footing it through town and onto the highway.

I drove about twenty miles. 1000' up hill. I got off the highway and floored it up a county road hill.

That's when I first remember hearing it.

I wonder if it was there earlier and I hadn't tuned in to it yet? Or if it was progressive. I don't know.

 

[rich weyand]

Timing went up and down as they tried to meet pollution standards in different ways. Best performance and best mileage are when timing is as advanced as possible without detonation.

Suggestion is to keep the timing lower than optimum until you get the mixture straightened out and nail down the knocking thing.

Note that an adjustable vacuum advance with 20* on the crankshaft as the maximum is like saying "no one will ever want it higher than this" or the mfr would allow the adjustment to go higher. That suggests that most people would want it less, and in fact the factory spec is 15.

45 is hotter than 44. Hotter plug is better to burn off oil foiling, worse for detonation. The S is for "short", which helps get your wires in around the headers.