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Topic Review (Newest First)
08-09-2010 07:14 PM
stfinney Nevemind, I tried that little trick and it worked!! I am now getting 20deg of timing on my mechanical...YAY. Still needs some fine tuning, but runs alot better. Thanks!
08-08-2010 04:40 PM
stfinney Hey, I read that you can grind a little off the center weight to gain a little advance. Has anyone done that and does it actually work?
08-08-2010 02:16 PM
stfinney The ones that came out were not stock ones. They were changed out years ago when it was on a 1975 350 motor. They didn't keep the stock pieces, just the replacement ones. I will keep trying different things to it and see.
08-08-2010 05:58 AM
ericnova72 Put the stock weights and center cam plate back on and only use the springs from the advance curve kit if you are using weights that came with a kit. Most kit weights are poorly made compared to factory. Weights don't have to be matched pairs either, you can mix and match different tension springs to further fine tune it.
08-08-2010 02:02 AM
TheMonster I say its the springs in the distributor as well. Just keep playing with it and you will get it eventually.
08-07-2010 07:37 PM
stfinney I am getting around 20 degrees advance from my vacuum. Yeah, my total timing is only around 22. I am not sure how to make the mechanical advance go higher.
08-07-2010 06:08 PM
ericnova72
Quote:
Originally Posted by stfinney
Ok, here's an update. I just changes the weights and springs out. Using the light springs I am at 10deg initial and another 12deg with the mechanical. I am around 42deg altogther at 3000rpm. Shouldn't I be getting more on the mechanical than 12deg? The instruction sheet showed the light springs giving close to 20deg advance. Any reason why I am getting 12deg? Could the center weight be causing it? It is slightly smaller than the previous one.
I guess I don't understand 10 initial plus 12 in the mechanical mechanism is 22, how are you getting 42?? Leave the vacuum advance out of the picture right now.
08-07-2010 05:26 PM
stfinney Ok, here's an update. I just changes the weights and springs out. Using the light springs I am at 10deg initial and another 12deg with the mechanical. I am around 42deg altogther at 3000rpm. Shouldn't I be getting more on the mechanical than 12deg? The instruction sheet showed the light springs giving close to 20deg advance. Any reason why I am getting 12deg? Could the center weight be causing it? It is slightly smaller than the previous one.
08-07-2010 04:36 PM
ericnova72
Quote:
Originally Posted by cobalt327
That's the one best info and links is in the last 3 or so pages

All my street/strip performance engines get full manifold vacuum advance... I'm not about to throw 2-4 mpg, cleaner idle and cleaner plugs out the window just because I don't want to take the time and effort to taylor the mechanism to the engine.
08-07-2010 01:31 PM
cobalt327
Quote:
Originally Posted by sqzbox
Can't find the thread. Can you link me up or something?
Here's one of many- http://www.hotrodders.com/forum/port...=ported+vacuum
08-07-2010 10:04 AM
stfinney Its a stock HEI unit that came off my old 1975 350 motor. It has been quite a few years since reworked. It was running fine with my old setup and figured it was fine, but I guess not.
08-07-2010 09:03 AM
pepi not sure what brand distributer your using but this is what you are after, it is not unusual for those parts to wear. BTW this is for a mechanical advance distributer.

http://www.summitracing.com/parts/MSD-8428/
08-07-2010 07:55 AM
stfinney I took the cap and rotor off and really examined the mechanical parts. The springs look like light springs and the little wings pieces are a bit worn it seems. There was a snap ring missing on one side of the weight also. I guess I will be buying a new kit. Will a local auto parts store carry the travel stop? I know they have the recurve kits. Thanks for all the help!
08-07-2010 06:37 AM
sqzbox
Quote:
Originally Posted by ericnova72
Sqzbox, you are completely wrong about the vacuum advance. Ported vacuum is an emissions device and is rarely used on a performance engine. Same to Bubbahotep, you guys need to read the "ported vs vacuum" thread here at hotrodders, very informative for those who don't know
Can't find the thread. Can you link me up or something?
08-07-2010 05:46 AM
sqzbox
Quote:
Originally Posted by sqzbox
Right now, your vacuum advance is giving you more than you need. that's why your having problems with the total amount at 3000 rpm. You need to limit it so you can run more initial without too much total timing. I don't have experience with adjustable vacuum cans but I know from other post's that there is a key that you can install that will limit the amount of advance from the vacuum can. I'm sure that someone will pop up on here and tell you all about it. Hope I explained it good enough for you. Hang in there! Wait for the reply's
Thanks Cobalt. And Ericnova, A vacuum advance really has no bussiness being on a performance engine. You can do so much better with an all mechanical adjustable advance dist. like mallory has or had. It's been a long time for me (70's) since I had one but with a good dist. machine you can tailor your rate of advance and total timing so easily without having to rig a vacuum advance to work. I used one when I was in the army as we had one in the post shop and even though I had to pull the dist 2 times to get it right,
The reward was worth it. My engine pulled through the rpm range a lot better and times droped at the track over whatever I tried with the vacuum advance system. My Crower 3/4 cam 280D/460L didn't make much vacuum and was a dog off the line. The mech. adv. really woke the engine up. Just by installing the mech. adv. dist. bumped my car into the next fastest bracket
by .100 that by itself was a big improvement in the racing world, especially at a desert track , above sea level, with 0 humidity. and hot air temp.
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