Restoring Rusty

[Gregski]

~ P A R T S ~

whoa, wait what? Seriously, you sure don't waste any time Greg

but whacha gone out and git a new distributor for?

well I got it on the account of the engine ticking noise, I thought it be comin' from that cheap Proform distributor I gone out and got last year

(now in all fairness Proform makes a $100 HEI distributor and a $150 HEI distributor, and you can guess which one I bought, the cheaper one)

now this here is a genuine GM Chevrolet Performance High Fidelity awesome possume High Energy Ignition

part number: nine three four four zero eight zero six

[Gregski]

one thing I is a learned is that cheap parts seldom come with Specs where as good parts come with all sorts of words and numbers, case in point:

Mechanical Advance: - - - - - - - - - - - - - Vacuum Advance:

RPM - - - - - Advance - - - - - - - - - - Vacuum (in. Hg) - - - - - Advance

1100 - - - - - - 00.0º - - - - - - - - - - - - - - - 3.00” - - - - - - - - - - 00.0º
1600 - - - - - - 12.0° - - - - - - - - - - - - - - - 7.50” - - - - - - - - - - 20.0º
2400 - - - - - - 16.0º
4600 - - - - - - 22.0º

[rich weyand]

Originally Posted by Gregski

one thing I is a learned is that cheap parts seldom come with Specs where as good parts come with all sorts of words and numbers, case in point:

Mechanical Advance: - - - - - - - - - - - - - Vacuum Advance:

RPM - - - - - Advance - - - - - - - - - - Vacuum (in. Hg) - - - - - Advance

1100 - - - - - - 00.0º - - - - - - - - - - - - - - - 3.00” - - - - - - - - - - 00.0º
1600 - - - - - - 12.0° - - - - - - - - - - - - - - - 7.50” - - - - - - - - - - 20.0º
2400 - - - - - - 16.0º
4600 - - - - - - 22.0º

Look at that advance can for a minute. "691 20" is GM part number 1973691, off the 81-82 Corvette, 79-82 Camaro, and 79 Firebird. That is, it's a late pollution-era vac advance canister.

20* of vac advance. That's crankshaft degrees. So 10 camshaft degrees at 7.5", starting from 0* at 3". That's a lot of vac advance at pretty low vacuum for what you got there in a non-pollution-equipped engine. What was your idle vacuum again?

My concern is that without a very conservative (pollution-era) base timing in the 4* BTDC range, you are going to ping like crazy, because you will need to get into a LOT of pedal to get out of vacuum advance.

Better fit for what you are running is probably the AR23 can: 7.5 camshaft degrees at 11.5", starting from 0* at 6".

OK, so, timing. You want 36* total, base+mech. With 22* (at 4600!), you want 14* base timing. But 36* total plus 20* vacuum advance gives 56* at cruise with it all in. You want to be around 52* with it all in, not more. So you need to back off to about 10* base timing so as not to go over 52* at cruise. And I am worried with as low a vacuum as that can pulls in, you'll ping even at that.

Switch to an AR23, and 36* total plus 15* vacuum gives 51*, so you're good with a 14* base timing. Which will give you more goose when you get on it. And no pinging.

The AR23 can be hard to find, and so can the Echlin VC1853 equivalent. Here are the other listed equivalents:

AIRTEX 4V1054
CARQUEST 57-7563
WELLS DV1853
GM 19138053
GM 1973482
ACDelco D1321A

[Gregski]

what do you mean you don't rip apart your brand new parts when you acquire them Lonnie Earl?

note the numbers on the weights, the center plate, and the vacuum advance

I have no idear what they mean, but I'm sure glad they is there, ha ha

[Gregski]

350HO Deluxe Engine (19210008) Specifications

Specifications Part Number 12487544


Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve.

[rich weyand]

Originally Posted by Gregski

350HO Deluxe Engine (19210008) Specifications

Specifications Part Number 12487544


Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve.

<sarc>Wow. They've redesigned how gasoline burns! Impressive.</sarc>

Uh, no. Complete nonsense. Same thing on the instructions for the 350/290hp crate engine. BTDT, it's wrong. Higher vacuum ==> lower cylinder pressures ==> slower burn ==> earlier spark required for best performance and mileage.

Trust me, I've done a lot of research and experimentation on this, and I had a lot of access to people who know what they're talking about.

Read this for the real skinny on ignition timing.
http://67-72chevytrucks.com/vboard/s...d.php?t=689321

[Gregski]

Originally Posted by rich weyand

<sarc>Wow. They've redesigned how gasoline burns! Impressive.</sarc>

Uh, no. Complete nonsense. Same thing on the instructions for the 350/290hp crate engine. BTDT, it's wrong. Higher vacuum ==> lower cylinder pressures ==> slower burn ==> earlier spark required for best performance and mileage.

Trust me, I've done a lot of research and experimentation on this, and I had a lot of access to people who know what they're talking about.

Read this for the real skinny on ignition timing.
http://67-72chevytrucks.com/vboard/s...d.php?t=689321

I'm with you Rich that's why I posted it, I was like WTH? Not to mention their Turn Key specs contradict their Long Block specs, ha ha, I thought the Turn Key built on the Long Block, so why for example they say use AC Delco R43LTS spark plugs in the Long Block, but in their Turn Key they say use R44LTS, that's just one example.

[rusty76]

I'm glad you fellas understand all this. I'm still scratching my head. Lol

[Jake Wade]

You want to use vacuum advance, just not that much. Limit the travel with a stop plate. I trim down old feeler gauges and spot weld them with a mig.

Around .120 pin travel usually equates to about 12º

[Gregski]

Originally Posted by rusty76

I'm glad you fellas understand all this. I'm still scratching my head. Lol

who said anything about understanding this stuff, LOL, personally the more I read the more conflicted I get, I am literally collecting opposing articles on this subject of ignition timing, most are from people who write for Hot Rod magazine, or Super Chevy, or Car Craft, etc... one says use ported vacuum, the other says use manifold vacuum, one says set your initial timing, the other says set your total timing, and let your initial fall where it may, it's enough to drive you bunkers

[rich weyand]

Originally Posted by Gregski

who said anything about understanding this stuff, LOL, personally the more I read the more conflicted I get, I am literally collecting opposing articles on this subject of ignition timing, most are from people who write for Hot Rod magazine, or Super Chevy, or Car Craft, etc... one says use ported vacuum, the other says use manifold vacuum, one says set your initial timing, the other says set your total timing, and let your initial fall where it may, it's enough to drive you bunkers

On those two controversies:

1) the big three used manifold vacuum for 30 years, from 1938 through 1967, and switched to ported vacuum to accommodate pollution-era de-tuning. They weren't wrong for 30 years. And they only switched because additional criteria were imposed.

2) the critical issue is performance in the tall part of the horsepower curve, where SBCs have a peak at 36* BTDC. Set that, and adjust the mechanical advance to get the base timing where you want it.

[Gregski]

alright, nothing to it but to do it

The Three Amigos: Point Dexter, ProForm, and General Mayhem

[rich weyand]

Which vacuum cans are on the other two? You could play mix and match to tone that vacuum advance on the GM down. They should all be interchangeable.

[Gregski]

Originally Posted by rich weyand

Which vacuum cans are on the other two? You could play mix and match to tone that vacuum advance on the GM down. They should all be interchangeable.

Thanks Rich, don't forget I also have that Crane Cams adjustable vacuum can.

But for now I just tried the GM recommended setup:

10° Initial + 0° Vacuum (in other words vacuum canister not connected) + 22° Mechanical = 32° Total

Truck runs very very good, but not perfect, what I mean by that is the only problem is when I accelerate right after switching to say 3rd or 4th gear, it goes vrooom-vrooooooooooooooooom, instead of just a smooth vrooooooooooooooooooom, forgive me for the childish explanations, I don't know how else to describe it.

Not sure if it needs more Initial timing say 12° or even as much as 14° to raise the Total Timing to 34° or even 36° or if I ought to connect the vacuum canister.

I think I am going to try baby steps, and report back to you all.

[Will206]

Wow, I hadn't checked on this thread in awhile, I just spent two weeks on the west coast helping my company open a new location.

I have my engine together although it runs it doesn't idle for ****. I didn't get very scientific on the timing, just brought it up on tdc, with rotor pointing at #1 and spun it a bit till it fired and ran. Gonna try and figure out how to properly set a base timing this weekend as well as check for vacuum leaks. Also I'm thinking I should dump the 3" spacer I have, the bottom end is more important and its entirely where my leaks could be. I worry that its going to mean replacing an already too short $60 Lokar throttle cable though.

Anyways, glad you found the leak and look on the plus side, you've already got 1 of 8 conrod bearings replaced...

[Jake Wade]

Set you initial at 12º-14º with the idle as low as you can get it, park brake on in gear with vacuum advance disconnected. GM claims 22º advance in that distributor, you should end up with 34º-36º based on those initial settings. At what RPM it peaks depends on the springs and weight combo. Keep in mind vacuum advance is zero at WOT.

Keep the 41/375 weight combo and install two blue springs from the Crane kit and you will be golden.

[Gregski]

Thanks Jake, I am so close I can feel it

Originally Posted by Jake Wade

Set you initial at 12º-14º with the idle as low as you can get it, park brake on in gear with vacuum advance disconnected.

Jake is that the procedure for an automagic trans-a-mission? Cause the Greg be runnin' a Manuel

Originally Posted by Jake Wade

GM claims 22º advance in that distributor, you should end up with 34º-36º based on those initial settings. At what RPM it peaks depends on the springs and weight combo.

I tested the GM distributor and it is spot on to the specs they gave but I could not get more than 32° of Total Timing out of it just out of the box even North of 4500 RPM.

Originally Posted by Jake Wade

Keep in mind vacuum advance is zero at WOT.

Yes sir in theory, but how often are you, am I, a street driver at WOT, that to me is such a misconception, in the [ahem] real world you are always pulling some sort of vacuum, I have driven around with a vauum gauge in the cockpit and watched the needle and under normal driving conditions it never pulled 0 vacuum, sure when I gunned it, to see what it do, it went to 0 for a split second, but not under normal driving not even under aggressive street driving.

Originally Posted by Jake Wade

Keep the 41/375 weight combo and install two blue springs from the Crane kit and you will be golden.

Wait won't that change how fast my mechanical advance kicks in, instead of how much? I think I like the curve right now just wish it went up higher.

[Jake Wade]

[QUOTE



I tested the GM distributor and it is spot on to the specs they gave but I could not get more than 32° of Total Timing out of it just out of the box even North of 4500 RPM[/QUOTE]


That's all you going to get if initial was at 10º.

[Gregski]

Originally Posted by Will206

...I have my engine together although it runs it doesn't idle for ****. I didn't get very scientific on the timing, just brought it up on tdc, with rotor pointing at #1 and spun it a bit till it fired and ran...

Hi Will, glad to have you back, yeah I was gonna do a write up on my experiences with stabbing the distributor in and I have come to a similar conclusion that as long as you get it on the right tooth and are not 180° off and have the rotor pointing at #6 instead of #1 your advance can be anywhere between 0° and 18° I kid you not and the truck will start and run.

The stock(ish) spark plug wires when connected to the HEI cap will prevent you from rotating the distributor too much one way or the other as well, its almost as if they made the thing idiot proof. lol

So in other words Ray Charles can stab a small block chevy distributor in with his feet and that rig will run, may not drive good but it will start up for you and allow you to at least check the timing with a timing light and tune it further, so any of you readers out there worrying about taking your distributors out, go and pull them out right now, we'll wait, and set them right next to your keyboards, ha ha

[jwilson645]

All this timing talk has me on the edge of my seat. I've never understood it but there is so much great info here that I am finally learning it. I'm about to fire off my newly rebuilt 350 so I will be putting this info to good use soon! Thanks, Gregski & Rich!!

[Gregski]

Originally Posted by jwilson645

All this timing talk has me on the edge of my seat. I've never understood it but there is so much great info here that I am finally learning it. I'm about to fire off my newly rebuilt 350 so I will be putting this info to good use soon! Thanks, Gregski & Rich!!

here is one piece of solid advice, take everything you read with a grain of salt, everones rig be different, hewk you will find out your rig be different for sure during the changing of the seasons, hewk even on the same day, when its cold in the morning vs when its hot in the afternoon, that's why they invented computer modules for cars, LOL, those things adjust timing advance a couple times a second from what I hear, but listen brothers and sisters let's not Sell Out to modern day technology this is a Square Body forum after all, ha ha

good luck to you bro, take your time, don't be skierd, and you'll get it, with every turn of a bolt you will get that much more confidence so just keep turning them

[Gregski]

Side Note & Fun Fact: Whilst adjusting my timing advance I was controlling the RPMs using the idle speed screw on my Holley carburetor and I learned that the highest RPMs it can get up to with the screw all the way in was only 3500 RPM, which is fine cause that's not what it is meant for, we usually idle below 1000 RPM fer sure. However in my case that was not high enough to get the total timing yet.

[rich weyand]

Yeah, you can dial the initial up to 14, but not if you keep that advance can. The vac advance will be too much and hang on too long and you will ping like crazy. Dial the initial up to 14, put the adjustable can on it, dial it back to 12-15 total vac, and keep it 0 advance at maybe 5-7" of vacuum. Vac advance ought to be all in at 12". That ought to get you where you want to be.

[Gregski]

Truck Runs AmazeBallz!!!

[Gregski]

so now that we took care of the big exhaust leak I can actually hear the new Flowmaster 40 Series exhaust, and I'll be honest with you, it needs some work

first it has a drone sound, around 1500 RPM it sounds like you are driving in a 4 door car and your kids rolled the windows down in the back, whoa whoa whoa... annoying to say the least

so it pays to have car buddies, I convinced my Mopar buddy Seth to loan me his brand new DynoMax mufflers for a test run (on the account of his Dodge truck being sidelined do to an enjin rebuild)

Notice how you can see right through the DynoMax mufflers, they have that straight through design, you can't see through the Flowmasters like that, some will argue that they flow better than the FlowMasters, I can't say either way. Also I've been told these are not directional, you can mount them offset in front or offset in the rear, there is no Input and specific Output.

so since these be 2.5" like mine they just bolted right up, and what's the verdict?

Well, they do sound different, these have a much more raspier sound, he calls it 60s muscle car sound, but more importantly they drone as well, so I am convinced that most if not all mufflers will drone unless you tune your exhaust system (more on that later)