[steve25]

Just note that if the heads are still original to your 65. ( not 68 or later) that they do not burn all the fuel as efficiently as the later heads, and especially so at low rpms, and this is felt in term of power, not only fuel usage and engine temps.

This means getting the balance right between mechanical advance and vacuum advance more tricky.

I have found that more initial advance seems to be the way to go while limiting the vacuum advance.
The way to do this and still have the motor hot start well is to rework the advance weights and springs so that your only running about 4 degrees of initial timing and then having the mechanical timing bring in another 3 to 6 degrees at 600 rpm.
This takes a bunch of time to accomplish even with a adjustable timing light, but it makes a big improvement.
If your at all leery about doing this then send your distributor out to someone who can get it done for you.
It’s worth every penny !
I will look and see if I still have the details of what I did, but it’s been a long time since I have run anything but a HEI.

[uttergto]

I have a dial back timing light. It is the original harmonic balancer, no tape. What I did was set the initial at 10 deg. and ran the RPMs up until it did not advance any further, started moving the dial on the timing light until the zero on the balancer lined up with the pointer, then read the dial. As far as the heads, they are the original high compression, small combustion chamber heads. I am not trying to make this a hot rod, all I am attempting to do is get the timing close to what it should be. What type of advance should you see at idle if the vacuum advance is connected with 10 deg. of initial advance?

[uttergto]

Steve, every thing is original on the engine. I have had as much as 12 deg. initial advance and did not have any starting problems. It has the original vacuum advance can. The heads are the small combustion chamber, 10.75 advertised compression ratio with a thick head gasket. The idle RPM is around 900.

[Cliff R]

Determining how much timing the VA adds is easy. Most are marked telling how much they add but I don't always trust those numbers.

If the VA is not in the distributor or the distributor is out for repairs just measure the travel that it has with a drill bit as a measuring device.

You can also simply unhook the vacuum source to it, hook it back up and use the dial back timing light to see how far it moves on the balancer. This assumes that your engine has enough vacuum to fully employ it, which most stock engines do.....

[Kenth]

No need to rev the engine to the moon.

Set centrifugal ignition timing using a points distributor (vacuum advance disconnected):

1. Mount a 1/4" bushing on the advance stop pin.
2. Remove springs from weights.
3. Use a dial-back timing light.
4. Set total timing to whatever you like at idle rpm´s. I like 26-28° for a 4.21" stroke and 30-32° for a 3.75" stroke.
5. Mount springs at weights.
6. Check initial, if 8-12° you´re good. (This is where it usually ends up with.)
7. Add vacuum advance (ported or full vacuum source, use what engine likes the best)
8. Jobs done!

[steve25]

You do need to bring the motor up to at least 5k for a few seconds because I have seen some aftermarket springs ( and combo of springs ) allow the timing to bounce around a lot, and besides the power loss that makes for the timing then can go above what you think your max is set for.

I helped a fellow Pontiac racer out at the strip one time and his plugs showed signs of detonation under my magnifier, at high rev’s about half track I could hear his motor breaking up, a sure sign that something is wrong.

He had a few weeks before under the prevailing bad info going around at the time installed a Mr gasket timing curve kit and used the crazy light silver advance springs thinking that having all the timing in at 1400 rpm was the magic ticket into the 11s.
When I lent him my timing light and we got the motor up to 5300 rpm the timing was all over the place.

Luck for him we where pitted just just 2 cars away from each other!

He never had taken the motor up that high when he was setting the timing on his own, so he never new about the condition or that something was a muck until running the car at the track.

[Kenth]

Setting total timing at idle speed w/o the springs mounted means the total will NEVER exceeds the setting with springs mounted, not even at 5 K rpms.

[68 Firebird]

Agree with Kenth. When I went to chk mine I first set initial,
then took the few extra minutes to remove both springs and
Run the motor for just enough time to verify where total
Would be. Total was exactly like expected.
I run heavy HEI springs so I don’t feel comfortable running
engine rpm very high while I am right next to motor.

Gerry.

[mgarblik]

I should have mentioned and sorry I didn't, if your going to run the engine at high RPM's with a timing light on it, PLEASE wear a full face shield. I had a friend almost killed setting total timing on a Chevy when a fan blade decided to exit the engine compartment. He lost an eye and was severely cut. So protect your face.

[uttergto]

Cliff, this weekend, I will check the initial advance with the vacuum line disconnected then connect the vacuum line and check it again. The original factory vacuum advance unit is marked M 243 20, if that means anything. Thanks

[Kenth]

243 are the last 3 digits of the full part-#1116243 and 20 is the max amount of ignition advance 20°.
It will start @ 8-10 in/hg and have max @ 15-17 in/hg.
Very nice unit.

[Bill S]

Just getting my car back on the road since 2021, after refreshing my 455. It never ran well as I expected for the previous 8 years due to multiple issues discovered. Just checked the timing and sure enough the springs were light weight. screwing up my initial measurement. Had an old stock dist and used those springs. Now 12 initial, 32 total.
Question on at what rpm it should optimally get to total. Jim Hand's book states all in by 3000 rpm. Mine is about 4200-4300 rpm.
Setup is 455, 6X ported per Jim's book, 9.4 CR, hyd roller 230/240, 114, installed at 111, Cliffs Qjet 800cfm, 3.31 gear, M20, 67 Firebird. Thanks

[steve25]

Well before even determining that, have you nailed down that 32 is truly all the motor wants?

Most motors like yours at least on the dyno like 35 to 36 total, but in real life gearing can effect that.

[uttergto]

Kenth, thanks for the information. the distributor band has the following information, 1111078 and 5 B 5. What are your thoughts on a Petronix pointless conversion, some people say they are no good while others say positive things?

Thanks

[lust4speed]

You are not stuck with light weights and heavy weights. Try mixing them for a little faster curve. I like to see full advance between 3,000 and 3,400.

Sounds like you have a dial back light so take the springs off and start the car and set distributor for 38°. Shut it off, put springs back on, and don't worry about where the initial falls. My feelings is that 36° is being conservative with iron heads and 9.4:1.

Failure rate for Pertronix in our GTO club is about 75%. If you feel like you're lucky enough to be the one out of four that doesn't have problems go for it.

[Cliff R]

"Failure rate for Pertronix in our GTO club is about 75%. If you feel like you're lucky enough to be the one out of four that doesn't have problems go for it."

+2, 3, 4 and 5.

I have had so many customers call up here complaining about "carburetor" issues that we traced to piss-poor working Pertronix units I wouldn't touch one with a 200' pole!

IF you want some stories I've got PLENTY of them........

[Bill S]

I have a about 15 year old Crane XR-i unit, as I thought the rev limiter was a useful feature.

Anyone have feedback on this unit's reliability ?

[Formulajones]

I've installed a couple of the Crane units for people several years back and haven't heard any complaints on those. Pertronix on the other hand, I've had my go around with those. Won't use them anymore.

Honestly I just prefer points. If I want a rev limiter I prefer to do it with a box that has a soft touch rev control (varies the cylinders) and is much easier on the engine and I get a multi spark feature at low rpm that helps keep the plugs a bit cleaner up at the high elevations I drive in where I have the cars running a pinch on the rich side. In fact, I've been happy with a points system that fires a box. Dead nuts reliable and super simple.

[uttergto]

Thanks Mike, how did the Pertronix fail?

[Cliff R]

Karma, a few hours after posting had a customer call up with "carb issues", backfiring, explosions in the exhaust at WOT, woln't rev much past 4500rpm's, etc. He suspected the carb but installed another one and EXACTLY the same issues.

It's a new build and he "upgraded" the distributor with a Pertronix, has about 45 miles on it.

I told him to remove the Pertronix and put the points back in it........will upgrade this post later after I hear back from him......