[az67goat]

I have a new 67 400 engine installed and the builder suggested not running vacuum advance. After realizing that I was running too hot, I fixed the water pump gap and the shroud openings and improved the temps but it wa still high. George suggested trying vacuum advance...I did and it made a big difference, so I going to run Vac. adv. Now...
I purchased a Craftsman dial timing light and checked my timnig and here is what I got.
Initial advance - 8 degrees
mechanical advance - 16 degrees
vacuum advance - 24 degrees
Pretty goofy. Are these mech and vac numbers from 70's smog motors?

My plan is to get a moroso advance cam/spring kit and an adjustable vacuum advance and set things for
I - 12
M - 20-22 all in at 2000 rpm
vac - 16 or so

Is this the best approach or should I just get a different Vac can and springs? If so what vac can?
The engine was built like a 67 H.O., but 9.5 to one dished pistons. Idles at 13 inches vac.

[77TA406]

I could be wrong, so please don't jump all over me if I am, but 8 and 16 degrees doesn't seem like much timing for a Pontiac. 12 and 20-24 seems a little better for your average street driver. 34-36 total without vacuum works great on my 406 and my vac can pulls an additional 14 at cruise. Jmho
Chris

[amcmike]

Before you change the springs, optimize the total advance. First rev through 4500rpm to make sure you don't have any sticking due to worn bushings (I am assuming non-HEI). If you have 67 Heads. the engine would probably like more than a total of 40° intial + centrifugal. Assuming you are not running a huge cam, keep all timing from coming in all before 2800rpm. I would leave the stock springs and keep bumping up the initial towards 24° until you notice starter load under hot conditions is higher. One you have that, get an adjustable can and set it for the highest vacuum reading. under low-speed cruise conditions.

[az67goat]

I have 670 heads and I'm running HEI. I took the cap off. The cams look old/dirty. I think a new advance cam set with bushings would help. I'll check again up to 4500 rpm. Thanks for the onfo.

[amcmike]

I believe the 670s are the earlier closed chamber heads which usually like the extra few degrees of timing that I mentioned earlier. When you get everything cleaned up, find out what your centrifugal is giving. You could probably go as high as 40° (init. + cent.) with premium gas, but without an adjustable mechanical system you might not be able to set the initial high enough. The limitation will be if the starter is loaded too much under fully warmed conditions.

[az67goat]

I installed the Moroso advance curve kit and the moroso adjustable vacuum advance. The vacuum advance works great and it's easy to adjust.
The curve kit is only giving me 12-15 total degrees total advance. What might be limiting the centrifical advance? Using the medium springs. Runs O.K., but when I accelerate hard I had it cough a few times.
The timing mark jumps off of the 0 point sometimes. I added a drop of oil to the plastic pads to help the cams slide. Is that O.K.?
I'm not looking at the tach, can't see the hood tach from under the hood, I'm just running it up untill the timing mark stops moving.
Any thoughts? Thanks.

[amcmike]

Springs shouldn't limit the advance unless the weights are sticking. It only changes the rate. Which as I said you are probably better off messing with later, and dial in you initial first. Remember as you advance the initial your timing the curve is already coming in faster.

First get the initial dialed in with stock springs, then see where you are at with your max advance.

Then if it still needs to come in sooner change weights, and if you want more total, then you can grind some material off the centerplate or the weights. Remember you can't easily ungrind, so make sure you have the initial properly established before messing with the total.

BTW, most aftermarket plates and weights are junk. I only use the springs. But if you need to grind anyway...

BTW, you really need to get a seperate tach or have someone watch yours so you know when it's all in. It's probably coming all in too early, and you need a slower rate of curve. You also didn't say at what rpm you experienced this cough, and whether that was with or without the vacuum advanced hooked up.

[az67goat]

First of all, thanks for your time and help on this.

Originally Posted by amcmike

"Springs shouldn't limit the advance unless the weights are sticking. It only changes the rate."

I understand that.

"Which as I said you are probably better off messing with later, and dial in you initial first. Remember as you advance the initial your timing the curve is already coming in faster. "

I have set my initial at 10-11 degrees. With the medium moroso springs.

"First get the initial dialed in with stock springs, then see where you are at with your max advance."

When I set my initial at 11 my total max advance came in at what I think is low at 23 or so.

"Then if it still needs to come in sooner change weights, and if you want more total, then you can grind some material off the centerplate or the weights. Remember you can't easily ungrind, so make sure you have the initial properly established before messing with the total."

According to the directions, I should be getting a total mechnical(centrifical) advance of 22 to add to the 11 initial for a total of 33, but I am not seeing this. I should be seeing this without centerplate mods. I was also not seeing the expected centrifical advance with the stock weights. I don't know why.

"BTW, most aftermarket plates and weights are junk. I only use the springs. But if you need to grind anyway..."

I heard that the Moroso kit was O.K. all others junk. Where would I get the correct stock plates and weights?

"BTW, you really need to get a seperate tach or have someone watch yours so you know when it's all in. It's probably coming all in too early, and you need a slower rate of curve. You also didn't say at what rpm you experienced this cough, and whether that was with or without the vacuum advanced hooked up.

"

I have an old tach around that I should hook up. Cough was at idle when I tromped on it. Vacuum advance hooked up.
I'm not so much concerned about the curve right now. I just want to get 20-22 centrifical advance and can't seem to get it.

Thanks again.

[Sun Tuned]

az67,
If you still have the old HEI cam and weights what were the numbers stamped on them?

Please don't take my word for it, Rocky Rotella wrote a very nice piece on the aftermarket curve kits, that would be well worth reading.

That being said, the morso/mr.gasket kits leave alot to be desired.

Two problems with them are 1. very easy to install the adv. cam backwards, and 2. they will allow upwards of 25 dist degrees of advance if the rpm is run high enough. A positive stop is absolutely necessary with these p.o.s. kits. Readily apparent is my opinion of these things. Much better options, especially with possibly the stock weights and cam you may already have.

[az67goat]

Originally Posted by Sun Tuned

az67,
"If you still have the old HEI cam and weights what were the numbers stamped on them?"

Cam - 469
weights - 139

"Please don't take my word for it, Rocky Rotella wrote a very nice piece on the aftermarket curve kits, that would be well worth reading."

I've read alot of your posts and Rockys. Sounds like you guys know what your talking about. Alot more than me anyway.

"That being said, the morso/mr.gasket kits leave alot to be desired.

Two problems with them are 1. very easy to install the adv. cam backwards, and 2. they will allow upwards of 25 dist degrees of advance if the rpm is run high enough. A positive stop is absolutely necessary with these p.o.s. kits. Readily apparent is my opinion of these things. Much better options, especially with possibly the stock weights and cam you may already have."

O.K. I can only get a total of about 15 or so total centrifical advance from the stock or moroso parts. I'm totally open to using the stock cam/weights. This all started with the stock parts not giving me more than 15 or so total centrifical advance either. I tried the Moroso cam both ways. Appreciate your help.

[Sun Tuned]

Ok, that 469 center cam is only gonna give you 11 dist degrees (22 crank degrees). So if I read the first couple posts correctly this is about where you wanna be right? Or did I miss something? That 469 has a nice and generous ramp on it (read that as smooth) which is good. If you want to get only 10 dist degrees (20 crank degrees) then you got a couple options here....

Find a set of 045/053 weights, you may have some "spare parts" that will do it perfectly.

Or you could implement a positive stop by welding or using a fillister head screw.

Either will work fine.

[az67goat]

Originally Posted by Sun Tuned

"Ok, that 469 center cam is only gonna give you 11 dist degrees (22 crank degrees). So if I read the first couple posts correctly this is about where you wanna be right? Or did I miss something?"

You are correct. Now as I've stated above, I am only seeing 15-16 total out of this cam. My question is, what might be causing this?
I have never had a distributor apart so I am not familiar with the workings. What might be limiting the total centrifical advance?
I can watch the centrifical advance come in until it stops at 16 total. I don't have a tach under the hood to see at what RPM it stops at but I did'nt really care at that point. Once I get the 22 degrees centrifical advance that I should have, I could work on the curve.

"That 469 has a nice and generous ramp on it (read that as smooth) which is good. If you want to get only 10 dist degrees (20 crank degrees) then you got a couple options here....

Find a set of 045/053 weights, you may have some "spare parts" that will do it perfectly."

I wish that I had some other weights. Where might I get some?

"Or you could implement a positive stop by welding or using a fillister head screw.

Either will work fine."

Got any pics of how to do this?

Thanks again for your time.

[amcmike]

My point was, that if you can adjust the initial to get the total you want, then not only do you not need to change your centrifugal, but your engine probably wants the higher intial as well. Disconnect the vacuum advance, keep adjusting the initial while hot until you get too much starter load, and then tromp on it to see if the hesitation went away. Then you can re-hook the vacuum and dial that in for highest vacuum during cruise.

[Sun Tuned]

There must be a burr on the cam or the weight pins may be worn with a groove in them etc. I have tested numerous examples of center cams and weights and the 469 is a real nice center cam. There are obviously issues here. Now if you had the stock springs on there then you would likely have come close to running out of motor before you found the end of the travel. I don't like the super light springs as they will heat fatigue quickly as well as causing other idle issues as well.

Any distributor initial setting higher than 14 will cause the Hydrocarbon percentage to climb rather high. Usually time to pay Mr. Ruggles a call to help in the fuel mixer dept at that time to correct potential problems there.

This dist stuff isn't hard we just gotta figure out what the holdback is. Probably weight pins worn.

[az67goat]

Originally Posted by Sun Tuned

There must be a burr on the cam or the weight pins may be worn with a groove in them etc. I have tested numerous examples of center cams and weights and the 469 is a real nice center cam. There are obviously issues here. Now if you had the stock springs on there then you would likely have come close to running out of motor before you found the end of the travel. I don't like the super light springs as they will heat fatigue quickly as well as causing other idle issues as well.

Any distributor initial setting higher than 14 will cause the Hydrocarbon percentage to climb rather high. Usually time to pay Mr. Ruggles a call to help in the fuel mixer dept at that time to correct potential problems there.

This dist stuff isn't hard we just gotta figure out what the holdback is. Probably weight pins worn.

I took the Moroso stuff off tonight. Cleaned up the original parts and made sure that the cam was numbers down. I worked the cam back and forth without the weights to check for nice smooth movement. I could see the slots that control total movement. I installed the weights and could see how they control the total centrifugal(learning how to spell!) advance. Put it all back together and started the motor. Set the initial at 12 and adjusted the vacuum advance to 15.
I had the wife get in the car this time and run the engine up to the following rpm and noted the advance. This is with the Vacuum advance disconnected.
1000 - 12
1500 - 17
2000 - 22
2500 - 27
3000 - 32
3500 - 32
4000 - 32
I'm happy with these numbers. Must have been something restricting the movement, or probably I was just being lazy and dumb and not having the rpm monitored as I should have from the beginning.
Thanks for your help and patience.

[Sun Tuned]

Glad that got it running more to your liking. However you might when time allows pull the dist and remove the shaft assy. Pull the advance cam and weights from their positions and seperate the reluctor (the part with the 8 teeth) from the actual shaft. Clean both of these very well and note the shaft has a grease groove at the top . This needs to be filled back up with grease and everything lubricated so it does not bind. This causes lots of problems on older dists due to lack of lubrication and free movement.