[kyle_blake]

Hi,

I'm going to be taking apart my spare distributor because i want to try and run it. My question is, I notice my daily driving one in the car and this one use a plastic bushing which limits the amount of mechanical advance. I've ran both units in my car and observed essentially 18 degrees total mechanical advance. I did it by using the method of revving to 3300. I heard a better way to test if it adds any in upper rpm is to take off springs and just start the car. Then see what it is. I have dial back timing light btw.

My goal is try and achieve 22 initial so i can bring down my initial from 18 to something like 14.

So my question is what are the guru's doing to accomplish this? Does one just use the moroso bronze bushing that comes in their advance kit? I have one.

Can you buy bushings that some company has already determined how much mechanical advance it add's?

Thanks. I also will post some pictures of the weights i have tomorrow.

I want to know which are stock weights and which one are after market.

[ponyakr]

"...So my question is what are the guru's doing to accomplish this?..."

It's been posted that, over time, those plastic bushings can crack and fail.

I think Cliff has posted that he welds up the slot a bit, to reduce amount of advance, if needed. I think he even posted a pic of one he did.

The last pic on this post shows how he welded the slot of an HEI. You can easily see how this would reduce total mechanical advance. If it reduced it a little too much, you could grind it out slightly. If not enuff, you could add more weld. That's one way to make a positive advance stop, tho not the only way.

http://forums.maxperformanceinc.com/...08&postcount=1

[TCSGTO]

I’ve been meaning to try this:

https://www.tapatalk.com/groups/raci...less-t765.html

And yes, you can remove the springs in a point distributor and check total advance without revving the engine.

[steve25]

While you are into the guts reworking things be sure to check how the insulation is on the wire running under the breaker plate, as many times it's dry rotted and coming apart just waiting to short out on you and kill the spark.

Ask me how I know this, lol!

[dataway]

Originally Posted by TCSGTO

I’ve been meaning to try this:

https://www.tapatalk.com/groups/raci...less-t765.html

And yes, you can remove the springs in a point distributor and check total advance without revving the engine.

That's interesting, I would like to see some comments from our in house gurus. I do wonder about how it would effect curve ... since the tang of the weight intersects the cam on the top of the dist. shaft which has different shapes for different applications that control the CURVE, not just the total advance.

Point about spark scatter makes perfect sense though, that can be seen with loose springs as the weights flop around with idle oscillations.

[kyle_blake]

Awesome , thanks for letting me know about springs taking off = test full advance. Makes sense to weld in a full stop then one has to never worry about the plastic bushing wearing. Add/remove weld to get one's 18-24 that is what is "typically wanted".

Let's move on to the re-curve method. Is it not advantageous to find a spring combination that starts at 1000 rpm and then reaches max advantage say around 3000 rpm? Since I'll know max advance from my previous test I can obtain this answer, right? You wouldn't want it to REACH max advance at like 2000 rpm because you used a spring combo that was too light?

[TCSGTO]

Originally Posted by kyle_blake

Let's move on to the re-curve method. Is it not advantageous to find a spring combination that starts at 1000 rpm and then reaches max advantage say around 3000 rpm? Since I'll know max advance from my previous test I can obtain this answer, right? You wouldn't want it to REACH max advance at like 2000 rpm because you used a spring combo that was too light?

It's hard to find aftermarket springs that don't start advancing at too low an rpm making the idle unsteady. The ones that come in the MSD kit are about the best I've found. Most of the cheaper kits have springs that lose tension after they are run for a while and get heated up making it worse over time. That's one of the reasons for bending the weight like in that link. It will stretch the springs more at their start position and help the weights return at idle. You could also wrap the eyelet of the spring tighter with a needle nose pliers to make the spring a little shorter and give it more tension.

Total advance can come in just above your flash stall speed with an automatic. I've never noticed a loss of performance having it come in a little later but have had surging and pinging getting into the throttle at cruise speed with a little to aggressive of a curve. IMO most people go overboard trying to get the curve in too quick when there really isn't much to be gained unless you have really low compression and/or too much cam.

[steve25]

Near every motor/ car ( car in terms of rear gear and trans) is different in terms of how much advance is needed and then how much the motor car tolerate at any given point in its amount of throttle opening.

Since it seems you are willing to play around and find out what your needs are then by all means do so just keep in mind that 67 and heads will likley never need more the 36 degrees without vacuum advance and with working under cruse conditions never more then 50 total.

[tc]

If I remember correctly, that Moroso bushing was too big to fit tight on the post of the points dist. I made one to fit tight, but you could silver solder it on there.
When using lighter than factory springs the timing bounced at idle because the mech adv would not set at one place. The factory heavy springs worked best and has full mech adv before 3000 rpm. Also, the advance starts right off idle speed.

[kyle_blake]

Wow, thanks for clarifying everyone. I'm armed with the right info to move forward and I'll update when i go to install the bushing. The idea of bending the weights seems like something I'd try after go through this process, perhaps.

[389]

I solder up the slot with silver solder then file it down as I take readings. It will also compress two degrees from use. I like the single points distributor the best. I use it to trigger a CD box and think its one of the best street ignitions going.

I make file a line on the damper at 30 BTDC.. I prefer running high initial with a low mechanical, usually 16 to 20 initial with 16 to 20 mechanical.. No vacuum advance..

[steve25]

Why is it that so few people misunderstand the need/ reason for vacuum advance?
The fact is that more motors have had Rods exit the side of the block from having too much total timing without vacuum advance then any problem that having vacuum advance is likely to cause.

If you never cruse with the car then having no vacuum advance is fine, but on any motor that will see such I.E. rpms above idle with only part throttle you need to run vacuum advance due to the weak air and fuel charge needing far more time to burn then at full throttle!

To accomplish this timing well above 36 degrees is needed on a street strip motor that will see more street time then strip.

Not running enough total timing for part throttle running means your long term washing your cylinder walls and rings down with unturned fuel with the resultant ware from that taking place, period!

On the darn 450 hp 454 motor that Chevy had in 1970 they still had vacuum advance on it my friends so that's saying something to me as I am sure Chevy would have wanted to save a few bucks by leaving it off if they could, anyone else feel the same?

To me 389 you are confusing the street section you posted in for the race section!

[AROWHED]

https://www.hotrod.com/articles/how-...e-in-pontiacs/

[unruhjonny]

which issue of HPP was that article in?
I ask so that I can dig it up.

[steve25]

It was not in HPP if your questioning the above post link.

[Skip Fix]

When I raced NMCA Top Stock they factored your cam HP by the engine vacuum-classes were wt/factored HP. Every one ran vacuum advance! And usually a pretty rapid advance curve.Guys running in the 10s ran vacuum advance.

[unruhjonny]

Originally Posted by steve25

It was not in HPP if your questioning the above post link.

the pictures are all watermarked as being from HPP;
After Hotrod magazine dissolved HPP, they incorporated all their artilces into the HR archives.

[kyle_blake]

Here is a curve ball, I saw somewhere on facebook that an engine builder or maybe hobbyist, no sure - he essentially removes springs period.. drives, runs and tunes for I guess 30-36 degrees. i should of pm'd him so i'd have a record of who he was. Maybe he is on here too, not sure. maybe i can find him again one day. i had to double check with him, i'm like are you sure? how the hell do you start a car that has 36 degrees advance ... oh well.

[Frank R]

Thanks AROWHED for posting that article. When I built the engine for my 67 I installed a Mr. Gasket curve kit. Once running I set the timing @32 total. After reading this post I picked up a protractor and checked my advance. I didn’t realize my distributor had the short .390 advance slot and with the bushing from the kit I was only getting 6 degrees mechanical advance (12 crank). I removed the bushing and now I’m right around 22 crank. I used my stock weights this time and 1 heavier spring. Full advance comes in @3,200. The vacuum advance adds 12 degrees. Base timing is 10 and total 32. My car has much better drivability now.

[ponyakr]

"...how the hell do you start a car that has 36 degrees advance ..."


Easy ! ON/OFF toggle switch. Get the crank turning, THEN flip the ignition switch on.

LOTS of race guys run with the advance locked out. A local sbc dirt racer told me that he runs 40°, locked out. He & his sons have always run up front--very competitive.

https://www.google.com/search?q=runn...hrome&ie=UTF-8