Saturday I changed my advance curve on the HEI. It cost about $10 to do it and the results feel like $100! To anyone who has not done this yet, do it! You'll be amazed with the results $10 will give you!

 

Where did you find a kit? I can't seem to find one for my pre-HEI distributor (1974).

D. Ocean
Miami, FLA

 

Found mine at AutoZone in the chrome/performance section. Summit also has them but I didn't want to wait.

 

How do you change the "advance curve"? I am pre 74 as well. I believe I have major tuning problems right now so i may explore a kit.

James

 

i work at Napa and see that all the time! whats wrpng with me...is this just a simple instalation? i have a 79 and was wondering how hard t would be.

 

It's relatively simple to change the advance curve but you need a few specific items. In order to read the timing accurately you either need to have a degreed balancer or a timing tape to put over the balancer or a timing light with an advance feature. On my car I have a balancer cover that's degreed. First disconnect and plug the hose for the vacuum advance. You then take a reading of the timing as it currently sits. In most cases the full advance from the timing will come all in at over 4K rpm. What you want to do is change the springs in the distributor so that you get full advance by about 2800 rpm. Sometimes this can be done just by changing the springs and sometimes you have to change the weights. When you go to a lighter spring set leave the distributor slightly loose so you can move it a little and then accelerate the engine to 2800 - 3K rpm. Set the timing at that speed so you have around 36 degrees advance. Let the engine idle then and see what your initial advance looks like. Try the engine like that and see if you get pinging. If you do it's possible that the vacuum advance unit is pulling in too much advance and you will have to change it to one that limits advance to about 10 degrees. Lars has some part numbers in his faq and you should look at it. Once this is done you should have a decent curve. If you want to experiment you can add a bushing to the distributor pin that limits advance. This will have the effect of raising your initial advance. I've done this in my 74 and my advance works out to 16 degrees initial, 36 degrees when the full mechanical is in by 3K rpm and another 10 degrees (46 total) when the vacuum advance is connected. This setup makes for a very peppy engine without problems like hard starting or pinging. Read lar's sheet on how to do this. It's where I got my info.

 

I got mine from Jegs but I noticed they have them at a local auto parts store too. It may take some filing of the bushings to make everything move freely. The other plus is my old bushings were non existent. I don't know how much advance I was getting but it couldn't have been much.

 

Has lars done a guide to rebuilding a distributer?

 

Lars sells or used to sell recurve kits. I think he had a few forum posts on the subject as well.

You can e-mail Lars V8FastCars@msn.com

 

Lars does not sell recurve kits anymore. I inquired with him about two weeks ago.

Lars recommended Mr Gasket part #927 or #928 which is a spring set and said to use the gold springs - you do need to check your timing and make sure you get close to 36 mech adv early on. For vacuum advance you should look at corvettefaq and read the tech specs on the vacuum canisters to get the vac advance you need on top of mech adv - you want close to 52 total. I used vc1862 --- this is for my specs though on a 350/375.

 

I`m looking forward to this spring to setup my new MSD. I used to run with a Unilight but everyone i talked to said that the MSD unit with Vac should do wonders on a streetmachine.I`m really glad to se posts like this promoting the dist as a "powermaker" because its not the first thing to come to mind regarding power and driveabillity(sp?) of the car

 

I was lucky enough to send mine to Lars a few years ago. One of the best moneys spent on the car.

 

I agree with Vettefixr except I thought you wanted all the mech advance in by 2500 rpms...

 

You have to play with it a little. When I had mine coming in all at 2500 it just didn't feel right. Now that it's at about 2800 it has a snap to it. The only downside I have right now is when it's very cold ( 0 to 10 degrees F) the engine runs crappy until it warms up for 5 minutes. Then it runs perfect. I also think you have to make adjustments for a stick vs. automatic. Bottom line is it's not a science, more like black art. But once you get it right it feels good.

 

I dont have a timing light with the automatic degree feature. So from reading these posts I think that there is some kind of timing tape that can be fixed onto the harmonic balancer to determine the total vac. advance.

Cant this also be graphed out to plot the advance versus the rpm to determine the best springs to use.

I had to replace the springs on my distributor earlier, and I bought a kit with black, silver and gold springs. It looks like I am going to be playing with my timing sometime this month.

thanks for the information on this.

kdf

 

A number of aftermarket vendors sell timing tapes in different sizes but personally I think they suck. They're hard to put on accurately and they don't stay put very well. I got a balancer cover from Proform that fits over the balancer and is degreed. The nice thing about it is that it bolts to the center of the balancer so even if your balancer slips your timing marks will still be accurate. I also got an adjustable pointer from Summit since the stock one covers the numbers. Check Summit or Jegs for this part.