Recurving pre-1969 stock points distributors

What’s the best way to recurve a 1968 stock distributor to move 34-36 degrees of mechanical advance from 4600 rpm to 2500 rpm?

I was reading Nicholas Sloop’s post here which seems to indicate you have to create a custom bushing and can’t use springs or weights?

https://www.v8buick.com/index.php?threads/power-timing-your-buick-v8.63475/page-2

I’ve also seen posts that seem to indicate you can but need the pre-1969 kit but these don’t seem to be available any longer? One seems to be Mr Gasket 925G which doesn’t seem to be available?

https://www.summitracing.com/parts/mrg-925g#overview

Are there any other kits available for pre-1969?

 

I used some kind of generic Chevy kit which came with a variety of springs. I think it was Crane branded, but it was a while ago.

A pro will have a machine that turns the distributer and measures advance at RPM. The rest of us have to feel our way through.

If you have a good timing light you can watch when the advance comes in with the engine running. That's what I did.

I think my advance is all in by 3200 RPM. Seems to run very well. Although fuel remains an issue.

 

Thanks. Maybe that’s the best plan. Send it to Everyday Performance and have them check it out and set it up.

 

It’s 1111260.

Thanks for the suggestion to look. I have a 67 430 and appears the 67 distributor came with it so it’s not a 68 distributor.

 

Ken @ Everyday has a excellent Sun machine to recurve your distributor, and also a novel way of limiting both vacuum and mechanical advance to your spec. He's in the vendor section of the board here.

 

And don't put all the advance in at 2500.. that's an old wives tale that was a started by someone who did that, and their car ran better because it masked some other tuning/combination mismatch problem..

I stumbled upon this fact by accident... about 8 years ago, I was just finishing a dyno session on a 550 HP Stage 2 street engine. There was a tight window to get that engine finished and on the dyno, so I had just taken the MSD billet distributor out of the box and installed it, with it's big coil spring like advance return springs and all. Session went well, it came with the 12* bushing in it, so that was fine... right at the end of the session (customer in attendance) I said " here, now we will get that advance in earlier and makes some more power.

So I pull out the big heavy springs, and but the middle size silver ones in.. Did a pull.

It looses power.. substantial HP and Torque.. 8-10 numbers each way, as I recall.

After some discussion in the dyno control room, as to if that was a real result of some type of fluke, we decided the best way to find out is to put the big heavy springs back in it
and pull it again.

Did that, the power cam right back, you could lay that sheet right down on the one before I fooled with the distributor.. numbers were right on.

I noted that, and the engine went back to MI with it's owner..

Over the next 8 months, I repeated that test on 4 different engines, all with very different builds, and the results were the same every time. Not one of them wanted the spark advance that quickly, it cost varying amounts of power across the build, but that early advance never helped.

Having it all in by 3800-4200 was the range that most of those motors liked.

JW

 

Is this true even if you are going for better performance at lower end for cruising?

I was wanting to recurve based upon Larry’s Power Timing thread suggesting moving all in to less than 2500 rpm to get more torque and horsepower at lower end and thought it made sense, but your post changes my understanding of things.

Thanks.

 

Yes, interesting.
I’ve always heard “get the advance in ASAP”
But then I’ve heard “1200, 2000, 2500 rpm is too soon”
Why is that?

 

one reason pinging or detonation what ever you call it. sometimes you don't even hear it.

 

That's later than I'd have expected. I'm surprised.

 

I’m going to try that this spring/summer/fall, whenever I get back to the track!

 

I remembered this thread when I was reading an Denny Manner interview in the August 1971 edition of Speed and Supercar. Denny suggests that early timing is a crutch for an over rich condition, and he found his factory settings actually made more power. Here's the article..

 

^^^ This!

I had all kinds of ignition issues trying to do this myself (plus the usual electronic ignition points conversion problems). Finally sent my original distributor to Everyday Performance for a rebuild and recurve, with points. Car runs way better now than it ever had previously.

 

Confusing, so locked out timing doesn't work ?

 

I hear you Larry. My cam needs all the advance I can give it.

 

As long as it isn’t rattling give it (any engine) as much timing as it will take, then back a couple degrees.

 

It's very interesting that the premature advance thing is mentioned as a "crutch" for overly rich setups. This makes sense to me in the context of racers who run the big Holly double pumpers. Of course, racers don't care about idle performance or fuel efficiency.