6500 Rev Limiting Rotor does not limit...

[jcarpio]

Hi all-

Replaced my ignition rotor on my last tune up and I noticed it does not limit at 6500RPM as it should. Part number 911-602-928-00-M14. So, I swapped it out with an identical one. Same issue, both purchased from Pelican. This is for a stock '72 T with MFI.

I revved the car to about 6700-6800 and there was definitely no limiting going on. Both rotors are mechanically limited and the springs moved freely.

Has this happened to anyone else? Maybe Bosch has put out a bad batch... AutoX season is quickly approaching and I really count on that thing working!

Thanks,

Jorge

[911pcars]

Not sure what to suggest other than to replace with a solid rotor and use an aftermarket ignition box with built-in RPM-limit circuitry (i.e. Crane, MSD, etc.). OTOH, keep the existing rotor. You already have an equivalent "solid" rotor.

Sherwood

[edmayo]

The cutout speed is marked on the rotor, is it marked as 6500?

[911quest]

How are you testing this are you just reving the motor to 6500RPM I would suggest hooking a timing light to one of the plug wires and rev it up and see if the light goes out...just a suggestion one other thing most of the Bosch stuff offered today is seconds that most parts suppliers get cheaper and sell for more...

[jcarpio]

Thanks Sherwood, I've been thinking about going that route if I can't get a rotor to work. I suppose I could put the old one back in, but it's pretty beat up.

Ed, yes, both rotors were marked 6500. They were Bosch parts, made in Spain. I flipped both over and made sure the spring moved freely. Strange, isn't it?

[JohnT]

How do you know you're revving to 6500?? Old Porsche Tachs (particularly when driven off of a stock distributor) aren't too accurate. This was exactly how I discovered that mine was off about 300/400 revs.

Pertronix make a good, adjustable, solid state rev limiter for your application. But remember that rev limiters come with a mechanical price too. They're hard on our old cranks.

johnt

[911s55]

Not totally sure but I have read that the rev limiting rotor will only function properly under load ( while driving ) they won't save you from a missed shift, so static test won't indicate function or not. Baloney? Bologna?

David

[Cornpanzer]

I think that you are confused. You dont need a load, teh rev limiting rotor works on centrifugal force, so load is irrelevant. However, no rev limiter can prevent a mechanical overrev, such as when you shift from third to second instead of fourth at 7000 RPM!

[dvkk]

You can alter the rpm cutoff by bending the tab that holds the spring.

[jcarpio]

JohnT, my only point of reference is that the old rotor limited me at 6500. The style is different than the replacement, but I imagine it should work the same. All three had 6500 printed on them.

I did test under load, while driving, fwiw. I was careful not to enter 7000 territory, which I don't think would be a good idea on the T.

Has anyone recently replaced their rev-limiting rotor with onethat actually works?