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Hi guys..slowly working my way through this genuine low miler (50k) TR7 and I'm replacing all the rubber parts..hoses/breathers etc.
Decided to change the oil rotor etc standard servicing stuff...Got the dizzy cap off and removed the 2 screws that retain the delco rotor.
well...I say removed one came away nicely the other ...somebody had forced a metric in there so it snapped...excellent..I have drilled it out.
So...2 questions please?

1. what on earth are the threads on those delco screws? My service kit ( it was in the boot) didn't come with replacement screws.
2. There is a Piranha electronic ignition unit beneath the rotor and as the screws came away a plastic part which appears to be fastened just under the weights with a screw/bolt on each side holding it has come loose..any ideas what it is?
Cheers
Bonnietiler

2BA?that is what is fitted to mine but that could have been altered along its chequered past.The plastic bit could be the pickup but just guessing.Steve.

2BA?-does that question mark mean `unsure`? -because a BA thread (British Association) would be a tad unusual in a GM derived product of the 1970`s era.
If the size is about right it could be 10-32 UNF as the diameters are very very close 0.185" c/w 0.190" and the threads per inch (tpi) also very very close at 31.35 c/w 32 !!
I`m just asking the question here--does somebody have a fact based answer?

Howard,
I have a spare AC Delco distributor from which I got the thread pitch dimensions. I used a tap to fit to the thread that has 8UC32 stamped onto its shaft.
Does that make any sense to you or help?
Michael

Well I`m not sure that it moves things forward-what size thread tap did you use?
As 2BA and UNF 10-32 are so close dimensionally they are virtually interchangable and I don`t think a thread tap would give a definitive answer whereas an accurate measure of an original screw probably would-as would a detail manufacuting drawing!
It`s all slightly acedemic but it would be good to know the correct size for the record.

2BA threads have a thread angle of 47.5 deg, a thread pitch of 0.810mm, a thread density of 31.5 per inch, and a diameter of 4.7mm (0.1850")

Whereas a 10-32 UNF thread has a thread angle of 60 deg, a thread pitch of 0.7938mm, a tread density of 32 per inch and a diameter of 4.8260mm (0.1900")