halfmoontrail

I think there is only one set of weights, but more than one pair of springs, which should I use?

'69 427/435 hp tripower w/automatic

Thanks,

Steve

mbeeman350

I tried that kit in my last Vette. The springs were stronger than what I had and increased the rpm point when all the mechanical advance was in. The weights were lighter and I couldn't get them to work either. So I ended up putting my original weights and springs back in.

Maybe others have had a better expereience!

I did my tests on the car, with a timing light and the degress tape (avail from Jegs & Summit) on the damper. Best I could get was 20 mechanical degrees along with 14 initial for a total of 34 all in by 3200 RPM

This car I am going to get mine done on a Sun Distributor Machine, most likely by LARS
Mark

marshrat99

You'll have to experiment. Start with the lightest set of springs and use your original weights unless they're trash. Try to get a full 36* advance with the vacuum line plugged at 2500 RPM. If you're getting to much advance, then go with combinations of heavier spring and/or ligher weights. Too little advance, go with combinations of lighter spring and/or heavier weights. BTW, I ended up using the medium set of springs with my original weights.

jdmick

Per Lars you don't want to use the Mr. Gasket weights. Reuse the old ones.
For springs I ended up using one black and one silver.

Crash80

Yep, you want to promptly throw the new weights in the trash. It is not uncommon to use two different springs. I ended up a light and a medium spring as I recall. Recurving can really give you a bit more pep.

redc3

thats not right. you cannot have 36* total with the vac plugged. when you plug it back in it will go over 36 and that is generally to much
try setting initial advance at 8-10 deg. with the vac plugged off. then see how much timing you get with the new springs. should come in around 16-18 deg. at 2500 rpm,s. with initial timing and mech. advance only. NOW plug in your vac and it should end up around 36 deg total advance

initial timing 8-10 btdc add to

mech advance 16-18 = upto 28 deg. add to

vac advance should = 36 + or -
this is how ive always done it

marshrat99

"Small block Chevys (and most other GM performance V8 engines) perform best when the total timing (full centrifugal advance plus the initial timing setting with vacuum advance disconnected) is all in by 2,500 – 2,800 rpm and is set to 36 – 38 degrees" Quote Lars - http://www.corvettefaq.com/c3/HowToSetTiming2.doc

halfmoontrail

Thanks for the replies so far. The "original weights" I have are lousy, one set is from a chevy van, one is from an Olds Cutlass. Two sizes, and neither ride the posts well.

Has anyone had decent results w/the kit weights and springs?

Steve

kb2fzq

I used 2 lightest springs from an Accel kit and original weights,,no new bushings...seems to work well...just my 2 cents..

76project

I have the same problem, my weights are not original, any aftermarket weights better than others? Can you buy original weights, I havent seen any?

lars

You want 36 total with the vacuum advance plugged.
You then plug the vacuum advance in, limiting it to a 16-degree unit, and you end up with a total combined maximum timing of 52 degrees. That's correct.

redc3

news to me. i dont think thats correct

wnjlt1

where have you been? i have my car set up this way according to lar's recommendations... and she "rocks".

neoh77

You've got hidden power there then redc3! I followed Lar's method and it gave me a great performance and mileage bump.

Disconnect vacuum advance....I used the lightest springs in the Mr. Gasket kit with the stock weights. Rev motor until mechanical advance stops to verify it would happen a bit before 3000 rpm. Set this to 36 degrees at 3000 rpm. Reconnect recommended vacuum advance unit. Rev engine and verify about 50 degrees timing with full vacuum.

Definetly where the power is at.

-Matt

BigBlockk

It all depends on the loading of the engine. At WOT the Small Block Chevrolet likes about 36 degrees of ignition advance all in no later than 3000 RPM. At light load cruising speeds it will tolerate upwards of 50 degrees. It all depends on the load duty placed on the engine.

BigBlockk

Later.....

redc3

this makes 54 deg. sound more plausible, but i like to push the pedal past the halfway mark most of the time. there is obviosly some kind of mistake here. my family is no stranger to engine building. we ran dirt track for yrs. we built our own engines and won our share of races. 54 deg. is way out of the park so someone is not adding correctly or is using their own sort of timing scale or something. i know lars is respected here, but a sbc is definetly not rocket science! there have been a few other folks that have tuned one up over the last 40+ yrs. just my .02.

neoh77

A stock off the showroom floor vette would pull 50 degrees total advance....we're not doing something new and innovative here. When you hit the go pedal hard you have heavy engine load and close to zero vacuum. Then your total mechanical advance would be 36 degrees by 3000 RPM. Letting off the accelerator would cause high vacuum and the vacuum advance would pull in the extra 14 degrees of advance.

The vacuum advance is there for fuel economy at cruise and a little better throttle response in your street car. Race cars are always under heavy load and don't benefit from a vacuum advance really.

-Matt