Shane

Did you fell any fiction in the weights? That is odd that it keeps sticking at 29. You might try using some elec lube in the weight pivot area, it may be sticking when the tension from the springs is added. Leave the vac adv off until you are ready to drive it and test the full adv, you car will act diff with load then it will just free reving meaning you might get pinging with load where you do not with no load.

Keep chasing it, you'll figure it out.

 

UPDATE

I used one light spring and one medium spring. I advanced my timing with the springs in place. I now have 39 degrees total timing. However, I also now have 33-34 degrees initial timing!

I'm not quite sure where I need to go from here. I checked the weights with the springs in place. They move nice an freely so I can't understand how they would be binding up.

 

Something is not right for sure. Send Lars an e-mail, he will probably know exactly what to do or check and save you mucho time. My guess is bushings like stated before since your mech adv seems to stop at about 8 to 9 degrees when you put the springs in. You might try replacing the bushing since it is quick and easy and and can only help. Check every where the weight pivot for any sign of wear and replace any part that might be suspect. I believe all those parts are pretty cheap so it may be worth it just to replace the weights and bushings to eliminate those.

 

Fevre:
I did notice something. When I had both medium springs in the total at 3000RPMs was 29 degrees. I then switched one light spring in place of one medium spring. The total advance went up to around 31-32 degrees.

I'm going to drop Lars an e-mail.

 

Ya you should always check to see at what rpm you run out of adv. You may have had a sticky bushing and freed it up when you did the no spring timing set. Now you may need the light spring to get the full adv in by 3000. Lars should have the answer. :yesnod:

 

Something is not right with that dist. It is not allowing enough mech. advance. Either the bushings are incorrect or sticking. You should be getting about 20 to 24 of mech advance, over the 12 initial. I'd yank it out and find someone with a dist machine and have it set up. It helped mine big time.

 

Imagine how that thing is going to run with the timing set correctly!

 

:iagree:
Don't know exactly what the HEI unit looks like. But my dist has something like a cam that gets pulled by the weights and makes the mech advance. Sorry- can't really describe that too good. Anyway: These can wear over time and this may be the restriction to the ~10 deg mech advance you get.

Check it out and good luck!

Stefan

 

I got your e-mail and responded to you. Something ain't right. Check those weights and springs inside cap for binding etc and the other things I listed in E-mail. Check that advance limiting bushing and slot and the vacuum can itself for binding internally or it's linkage.


JIM

 

It sounds to me like yur getting only 10 degrees out of yur mechanical curve which is about normal for a stock HEI. I just got a summit HEI and put it on my truck. Its curve length was only 12 degrees. On the HEI the part that limits the advance length is the center cam that the weights rotate around. You should be able to lengthen the curve by modifying the center cam. If you flip the weights to the advance side with yur fingers, you should be able to determine where to grind away material from the cam to allow the weights to swing farther out. You can also remove material from the portion of the weight that contacts the cam to increase the throw distance. once you get the length to yur liking you can then come back and expieriment with different spring tensions that fit yur idle setting and desired "advance all in" rpm. The vacuum advance will help yur part throttle cruise response and part throttle off line response. But for drag racing, which you do, its irrelavant. At WOT vacuum is so low that the vacuum advance is next to nill.

 

forgot to say...you need to lengthen the mechanical advance curve. Forget about the vacuum for WOT. For instance, i suggest you run 36 total. With yur idle of 1500rpm, I would suggest an initial of about 18 to 20 degrees. 36-18=18. Thats how long the curve needs to be, 18 degrees. Mod the center cam and weights to allow 18 degrees of mechanical advance. Then come back and try different springs till you find a set that holds it all back at yur idle of 1500, and lets it all come in by the desired rpm.

 

Bence, if you are checking your timing at 1500 rpm you are NOT seeing initial, you are seeing initial PLUS the amount that your centrifugal has added by then. With light springs, centrifugal will start around 800-900 rpm and will have added a bunch of timing by 1500. In your case, it sounds like most of your centrifugal is in by 1500.

It also sounds like your need to do some tuning. If you are having drivability problems without such a high idle speed, something(s) isn't right.

 

Great point Vetterodder. And not to argue but, trust me guys, the advance curve length on some of these HEI's is rediculously short. You should cut the idle back for testing and see how far back it drops. Figure out how long the curve actually is. I wouldnt be suprised if you find its only 10 or 12 degrees long. In that case, to get total of 36 or more, you would need to run initial of as much as 26 degrees. Thats why its important to find out how long the curve is first, then lengthen it if needed, then follow up with spring testing.

 

Shane:

With the Mr. Gasket recurve kits, the center plate (the one held in place with the e-clips) can esily be installed upside down. If that is the case it will limit the amount of centrifical advance. Just something to check.

Pete

 

Also consider this, as Vetterodder has stated you may already be into some mechanical advance at 1500. If so, when you shoot the light on the mark, most likely the mark will dance around a few degrees since its not down on the stops. This is how I had previously figured out my springs were too light. The timing mark was dancing since the weights were somewhere in the middle of the curve and not held solid against either end of the spectrum. With the weights hanging in the middle somewhere they will cause a slight fluctuation that can be seen by the dancing mark.

 

Some things I am wondering about...most have already been mentioned...

Why do you want to run 39 degrees total? This is WAY more than any big block (or small block) setup I have seen. I recommend starting at around 34-35 and increasing in 1-2 degree increments until max MPH is achieved consistently at the track.

Next...your distributor will limit the total amount of mechanical advance added to initial. To get 39 (or 36 degrees) total remove the springs and set timing first. Then re-install springs and there is your initial. Period. If it seems to be too much then buy a re-curve kit, most come with a new advance cam that will change the total mechanical allowed so you don't have to run so much initial to get your desired total. Alternatively, MSD Billet distributors have a bushing so you can dial in the amount of mechanical advance added in a few minutes. It's not cheap, but I recommend a fresh tight distributor for accurate timing.

Disconnect your vacuum advance when measuring total advance for race conditions. As already mentioned, you should have very low vacuum under WOT with a heavy load (racing conditions) so checking the timing with the vacuum advance connected while reving in the driveway with no load doesn't tell you crap. Vacuum advance is for part throttle driveability. It can make your idle readings inaccurate as well if you are idling so high (1500 RPM).

Why is your idle so high?

Jeff