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Too late now, but ARP makes rocker studs in different lengths in case you ever want to get rid of the washers. FYI

Feels good to have some success, right? I'm glad it's coming around for you.

Good catch on the rotor. The 'joy' of aftermarket parts from different suppliers.

Something else to watch for: I'm running a Davis HEI on my 69. I discovered that it was possible for the weight pins and/or the holes in the weights themselves to wear enough so that there's some slop there -- enough that if you aren't careful, it's possible for the ends of the weights to get into an orientation where the ends overlap each other. If you then install the rotor and screw it down, it will clamp down on the weights so that they can't move even though the rotor is still sitting 'flat' like it's supposed to. They don't run too well with no mechanical advance and timing stays at your initial setting, no matter the RPM. It'll act just like a nasty carburetor problem - bucking, spitting, backfiring through the carb whenever you try to get heavily into the throttle. I got bit by that one - big time.

Bear
 

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Discussion Starter #42
You said it, feels good, really good! I can now do burn outs WITHOUT using the brakes!!! :) And until I let off or run out of room!! :ROFLMAO:

So, thanks for the information... I did't want to make a long story out of it but I tried getting ARP bolts from Summit and they had none in stock. As I mentioned I can drive to one of their stores, so I ended up at Butler and you know the rest.

Ended up testing every thing under the hood... seems I have a vacuum leak in my headlight system (have a new headlight switch already) so I'll have to track that down and get a new check valve for my brake booster as well.

Thanks again Bear... a question, what should be my total timing when I start at 12 base? because of the rotor issue I was at 42, now I'm at 49 at approximately 2650rpms. That seems high.

As far as engine with exception of roller lifters and a slight larger cam than stock it's as close to stock as you can get.

Thanks in advance, Dan
 

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Yeah, 49 seems pretty high to me. The best way to optimize timing for your car involves taking it to the track, making runs under "as close as you can get them" identical conditions, making small changes until you find what nets the best E.T.'s

Which heads are you running?

Something in the neighborhood of 35 total (no vacuum, 2500 rpm) is in the ballpark for "most" open chamber heads. I don't remember... which distributor are you running?
Factory points distributors and HEI's have a pin that limits the amount of advance travel. You can reduce the amount of travel and thus how much mechanical advance they add by putting a bushing over that pin --if you need to-- like if (for example) the engine likes 35 total but doesn't want to idle well at the initial setting that gives you that. In the "old days" , aftermarket advances recurve kits with different weights and springs usually also included a bushing for that purpose.

Bear
 

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Discussion Starter #44
62 heads... not sure on the distributor. On the bushing you mean where the weight pivots? See pic. I'm fairly certain those are the weights that came with the car. The springs are new, I'd have to look up the paper for the stiffness.
PC010055.JPG
 

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You have to pull the distributor, remove the gear, and remove the shaft to get enough access to the pin (if it has one) to be able to stick a bushing on it. It'll be on the center "T shaped" ears that the springs clip to and will stick 'down' through a slot in the larger plate - the one that moves. The pin will be on the 'back side' of one of the pins that the springs clip to. You might be able to see it, if it's there, with a mirror so you can see the underside of the center plate - the 'other end' of one of the spring pins or maybe feel for it with a thin feeler gauge blade. I'm having a faded memory (I'm olde) that some HEI's don't have that limiting pin. Instead the advance limit is controlled by how the 'tails' of the advance weights meet each other. It that's the case, then the amount of travel can be tuned by carefully bending the small tails of the weights so that the springs can't pull them "together" as much. Some HEI advance kits may have weights with different shapes - not sure about that.

Here's links to photos of what the pin (with a bushing installed) looks like on the factory points distributor.
Points distributor advance limit with bushing
Alternate view


Not all HEI's are the same. Looks like some may use limit pins that are accessible from the top side.
HEI with limit pins
Your photo kinda looks like yours might be like that.

Anyway, hopefully this helps. The idea is to limit the amount of mechanical advance movement that's in the distributor so that you can get both a TOTAL and an INITIAL setting that makes your engine happy. The total value being the more important of the two, because that's where the power is.

Bear
 

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Discussion Starter #46
You have to pull the distributor, remove the gear, and remove the shaft to get enough access to the pin (if it has one) to be able to stick a bushing on it. It'll be on the center "T shaped" ears that the springs clip to and will stick 'down' through a slot in the larger plate - the one that moves. The pin will be on the 'back side' of one of the pins that the springs clip to. You might be able to see it, if it's there, with a mirror so you can see the underside of the center plate - the 'other end' of one of the spring pins or maybe feel for it with a thin feeler gauge blade. I'm having a faded memory (I'm olde) that some HEI's don't have that limiting pin. Instead the advance limit is controlled by how the 'tails' of the advance weights meet each other. It that's the case, then the amount of travel can be tuned by carefully bending the small tails of the weights so that the springs can't pull them "together" as much. Some HEI advance kits may have weights with different shapes - not sure about that.

Here's links to photos of what the pin (with a bushing installed) looks like on the factory points distributor.
Points distributor advance limit with bushing
Alternate view


Not all HEI's are the same. Looks like some may use limit pins that are accessible from the top side.
HEI with limit pins
Your photo kinda looks like yours might be like that.

Anyway, hopefully this helps. The idea is to limit the amount of mechanical advance movement that's in the distributor so that you can get both a TOTAL and an INITIAL setting that makes your engine happy. The total value being the more important of the two, because that's where the power is.

Bear
Perfect!

Thanks Bear! Looks like I do indeed have an HEI with bushing adjustment under the cap. I'll let you know.

Much appreciated!

Always something to learn with these cars!! This latest adventure has made this a hole new car! :)
 

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Dan, you won’t have bushing on that dist you will need a curve kit for GM HEI, the new weights change the configuration of the centrifugal advance limits and lighter springs will help.

ditch that vacuum can also, see that number on it it is giving you 20 degrees of timing advance, way too much on today’s gas....

Hook your new vac advance to full manifold vacuum, to get a cool and steady idle.

The vacumn can you want is Standard Motor Parts SMP VC 302,....O’Reilly calls it a BWD V482.....Napa calls it a VC 1703.....Rock Auto calls it VC 302.....

all are made by standard.

a good curve kit is Moroso #72300 for GM HEI ,,, Mr. Gasket, Crane also make them.

do not buy the Moroso #72310....it is for points distributors.

You got way too much timing at 49, and your vacumn is adding 20....

that vac can I gave you will pull 8 to 12 degrees timing at the crank...usuallly pulls 10.

good luck let us know how you do
 

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Discussion Starter #48
OK, so I understand...

I know the springs control how fast the mechanical timing comes in… Also understand ported versus manifold vacuum.

If I want to get a total timing advance of 32-35 (engine builder said it should like that) I can reach that by using vacuum advance and mechanical methods.

I.E. If I use Ported Vacuum I set the base timing at 12 degrees (idle timing), Vacuum kicks in at a predetermined RPM (current vacuum canister is a 20 degree advance can) so I get 22 degrees then at a predetermined RPM the vacuum drops off and the weights are supposed to take over. Weights are currently setting my advance to 49 degrees which is too high - adding 27 to the vacuum advance. This means I am adding 27 degrees mechanical and the weights are traveling too far out (hitting my old rotor) for what I need - obviously since I’m at 49 degrees in the current setup.

So, if I get the 8-12 degree vacuum can which usually pulls 10 degrees advance and use manifold vacuum which gives me vacuum full time I set my base timing at 12 degrees and the vacuum can pulls 10 more for 22 total…

How many degrees will I get form the new weights suggested?

Thanks for your help!!
 

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Let’s restart. You want total timing to be 36 BTDC. Total timing does not include vacuum timing. Total timing is not tied to any RPM’s.

It is the total amount that your timing can advance at WOT. When no vacuum is present. Total timing is a combination of base timing, set with your hand and timing light, and the centrifugal timing advance by the weights. Springs don’t matter here.

it is how far the weights will advance, and then stop by hitting their hard metal stop.

base timing and centrifugal timing must be matched to achieve 36 degrees. So if your centrifugal total is 24 degrees you set base timing at 12 degrees =36. If centrifugal 26 set base at 10 = 36.

Now vacuum timing, Vacumn timing is a great benefit to make your car run cooler smoother and better accelerate. It adds the necessary advance above total timing, 10 degrees is perfect, for all that benefit.

the reason you need it is at idle and cruise the mixture is leaner and needs spark much earlier to get a complete burn.

use the vac can I told you hooked to full manifold vac.

Now the springs and how everyone talks this advance shorthand wrong. ”I got 36 degrees at 2500 RPM” they say. So I am good. If that is your total timing you are good, but if your timing advances beyond that to 49 degrees at 4000 Rpm.. you are not good.... as you are not reading total timing just springs at various times.

once your total timing is established, then you can adjust when it comes in at what RPM with springs. You want to bring it all in near 3000 or so 32 3400 even for good running.....

springs are meaningless until all other parameters established.

Base Timing is set by hand and locked down. Centrifugal timing is Weights and springs and Operates on RPM’s only.

Vacumn timing is tied to your gas pedal...light load, more timing, pedal down WOT no Vacumn timing.

you will get it, think about the 3 methods of timing at play...base, Centrifigal and Vacumn.

sync em all up and it will run great!
 

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PS curve kit weights vary....as do wear on distributors....anything mid 20’s is good.

that will put your base at 8 to 12 or so.

then when you add the 10 from the vac can your idle timing ...base + Vacumn will be 20, 22 or so. It will idle real smooth and cool there.
 

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Amen - get it out of your head that vacuum has anything to do with the 32-35 total you're shooting for. It doesn't. Vacuum advance is there only for 'extra' advance during part throttle, light load conditions. It helps with engine cooling and fuel economy under those conditions. Power during heavy load / wide open throttle comes from the combination of initial timing and how ever much mechanical advance the system is adding at a particular rpm. Under heavy load, the engine doesn't make enough vacuum to activate the vacuum canister at all.

The Davis HEI my 69 is capable of a range from 0 to 20 degrees mechanical depending on rpm, so to get 35 total requires 15 initial. With my head's (72 cc round port Edelbrocks) my engine seems happy.

Bear
 

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Exactly Bear, and sometimes I curve em at 18 base and 18 centrifugal and add 10 degrees vac. For the real radical roller cam that will give 28 degrees advance at idle...

18 base + 10 vacumn....the overlap reversion really leans those mixtures so some engines take it. But most ....18 to 28 centrifugal advance....
 

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Exactly Bear, and sometimes I curve em at 18 base and 18 centrifugal and add 10 degrees vac. For the real radical roller cam that will give 28 degrees advance at idle...

18 base + 10 vacumn....the overlap reversion really leans those mixtures so some engines take it. But most ....18 to 28 centrifugal advance....
Hmmm.... that gives me an idea. At idle RPM with my new cam, it's definitely on the "knee of the curve" as far as manifold vacuum goes. As little as 50 RPM makes a big difference in vacuum which makes it really tough to get a good idle mixture, especially when the a/c compressor and/or the electric fans kick in, so much so that the idle mixture goes super lean when either of those things happen. I might try more initial lead to see if that helps make it less sensitive. Just before I pulled it to get into the current re-do, I tried some smaller idle air bleeds which seemed to help some. This might help too.

This cam is a solid roller - 251/257 @ 0.050, 110 LSA, .620 net lift at the valves with 1.5:1 rockers. From Bullet, I'm told it's got the tallest lobes (0.4300 lobe lift) that can physically be installed in stock dimension cam bearings.

Thanks for the idea.

Bear
 

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Yes you can likely take some more idle timing...don’t be afrai of 28 even 30 as long as you can take it out of the centrifugal...

agree on idle air bleeds, I use a QFT carb and can curve the idle circuit, and all the circuits easy.....
 

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You could try 38 total , without any major changes, just dial up you base 3 more to 18...you have 29 centrifigal...that is 38....

some of these big Pontiac engine take that..

but you have to then test drive it and make sure that you don’t get pinging/detonation..

if you don’t it may help that lean idle mixture
 

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I know Davis is a great outfit first class on their stuff. But I don’t like those adjustable vac cans that I one I use a lot on HEI’s pulls that timing in at very low Vacumn and only gives 10 degrees ...perfect.
 

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I set idle timing with it disconnected and have never looked at what the can adds.
 

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Check it, it tells you what it really is. That is also the timing when you set your carb idle circuit. So that is where it runs.
 
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