BPHORSEGUY

How often do the cap & rotor need to be changed on a '77 with HEI, all is stock?

Big2Bird

50k miles is reasonable.
Truith is, i have run them till it misses.

lars

The HEI system was designed to reduce maintenance and increase service intervals. The HEI components will easily run 50,000 between cap/rotor replacements, and I've run them as much as 100,000 before getting misfire and issues (I put 500,000 miles on an HEI-system Vette that I used as a daily driver with no engine or trans rebuild or any other maintenance issues, replacing cap and rotor only when it started misfiring around 100K).

Lars

Big2Bird

My son had an old Seville with over 100K miles. I checked the cap, and the cap was melted around the rotor contact, almost burnt thru, and the car ran fine. Not a clue it was burning up.

BPHORSEGUY

Thanks guys!

HeadsU.P.

About once a yr, remove cap and wipe inside with clean, dry, paper towel only.
No cleaners, no WD40, no nothing.

calwldlife

I have changed them more frequent than
50k.
I might be on my 4th in 85k.
I finally went to a brass electrode cap.
thing doesn't show the arc wear the alum one do.
cheap part anywho.

lars

You were replacing HEI system components every 21,000 miles..?? That's crazy: That's the tune-up and service interval of the standard points-type systems. The whole design purpose of the HEI was that it would easily outlast points service interval by 100%. You must have been getting some exceptionally poor quality components - I've never seen HEI components fail after 21K, and I worked at the GM Training Center as an HEI Systems Instructor in the mid-70's - I had access to the failure and service records. There were occasional module failures, but never a cap or rotor failure in 21K. Never.

Lars

calwldlife

no failure.
just got tired of sanding the arc trail
off the inside of the cap.
like i said cheap part and just made me
happy to have it new.
never a running issue.