Point bounce RPM
 

My Sun machine set a record today with a distributor. A customer sent in a distributor and he had previously purchased the parts elsewhere (Mac Van Pelt). I installed his supplied points, bushings, rotor, etc. This was a typical 1937-40 68 series distributor.

I had previously run three other distributors tonight, with most having the points start to bounce at around 5300-5850 rpm's. This one ran all the way up to 7870 RPM's before the points started to bounce. While a flathead will never see those RPM numbers, that is a record for me. Hats off to Mac Van Pelt for selling quality points! They appeared to be the same points I have used but this set exceeded the norm.. Many "larger" vendors are selling crap points that make setting the dwell a nightmare if even possible and can rarely exceed 2600 rpm's before point bounce starts.

Re: Point bounce RPM
 

I commonly get > 5000 with NOS Ford points on my Sun machine. I usually back off as that is unreasonable territory for most flatheads, valves will float before then on stockers. I commonly take my avatar to 5500 when pulling onto the freeway. On that car I have 200 lbs pressure going over the nose of the cam.

Re: Point bounce RPM
 

Yes, I agree, I do however out of curiosity run all of them to the point of seeing what they will actual handle. Our results differ, is the MOST I have ever gotten from a NOS set is 4400 rpm's (crank). The newer quality points seem to have quite a bit more spring tension thus likely why they will handle more RPM's, however I am also aware that too much spring tension will cause the rubbing block to wear much sooner.

Regardless it is all irrelevant as 99% of the flatheads out there will never see these rpm's

Re: Point bounce RPM
 

Nice new record Mike . . . thanks Mac for good quality points! Most of the ignitions I tend to screw with have magneto points - so they tend to spin up pretty damn high.

This is one situation where "More is Better'! LOL

Re: Point bounce RPM
 

What’s the solution to prevent bounce???? Increase spring tension???

Re: Point bounce RPM
 

Higher spring tension will increase the RPM's before point float, BUT..... Higher spring tension wears out the rubbing blocks and pivot post on the breaker plate at a much quicker rate. In my opinion if they can hit 5000 Rpms they are good to go as a flathead would in the real world hardly see those numbers. The tension springs can be bent by hand to manipulate this as well. I have to do this on all the Early distributors (32-36).

Re: Point bounce RPM
 

Spring tension is one factor, the other is the type/characteristics of the actual distributor cam. Many performance distributors/magnetos use more of a "ramp" to lift the points, than a super-sharp peak. Makes sense that the ramp is less susceptible to causing point float.

Re: Point bounce RPM
 

Bored,

That is correct, however I can only speak in context to original Ford designs. The Lincoln V-12's have a much more subtle cam design with a more rounded cam lobe.

Re: Point bounce RPM
 

What are these "points" you speak of?
These are the only points I'll put in a distributor....

Re: Point bounce RPM
 

Michael,

I didn’t know you had a distributor tester too.
That is good to know,,,,I have some work for you.

Tommy

Re: Point bounce RPM
 

The SBC dist dist is good for 6500. Works well on 6 volts, set it forget it. The stock crab worked well on the stock car up to 5K

Re: Point bounce RPM
 

I set them all at 2500 to 5000....lube well and let them run for a few minutes at 5,000 .plus.

Also soak every fiber block in marvel mystery oil , found out years ago that will extend the life of the point a ton......(and i like the smell)))

Re: Point bounce RPM
 

Jim,
Welcome back!!

Re: Point bounce RPM
 

Thanks Mike i just edited the post , must have been on the drugs when i wrote that one.

Glad to be back home after 10 days in hosipital......getting back (again) , slow but sure i guess...:eek:

Re: Point bounce RPM
 

I did not know you were in the hospital. Good to hear that your out. I need to stop by the shop and give you and Terry a hand soon.
I have been so dammed busy at home I think I need to step back and approach from another angle.