I got my 455 back together last week, and got it in the car and running, but had a mysterious backfire through the carb. Moved the timing all over the place and looked for vacuum leaks to no avail. It ran a little better at 12 BTDC than at 8 or 4, but still backfired. Mostly under light load. We also checked plug wires to make sure they were installed in the right position.

An Olds guru at work told me that high mileage Olds distributors are well know to cause the points to misfire... That didn't occur to me, but makes sense after he told me. The rotor end can wobble around a little when the bushings get worn and that screws up the dwell and/or ignition timing.

I swapped in another used distributor I had and the backfire went away.

Eventually I may buy a remanufactured distributor ($38), or shell out big bucks for an HEI, but for now I'll tool around with this ~72k distributor that still works good.

Hope this info may help someone else too. Applys to small blocks too obviously. Tom.

 

I had a similar problem with a (non HEI) '73 Buick 455... turned out to be a bad timing chain.

 

I had a serious misfire on my '68 400, right at the traffic lights in town, sounded like a cannon and made me jump..but I had my seat belt on and I was not ejected... turned out to be a broken distributor wire- from coil to points- broken inside the insulation where you couldn't see it...

 

I am sure you can get a stock Olds HEI distributor from the auto parts store for less than $80. Go to a salvage yard and you can get one for $15. HEI is far superior to points.

 

You can tell your "Olds guru" that this "revelation" applies to every points distributor ever made.

Norm

 

Is this one any good?
They do reasonable shipping to UK so might get one if you guys think it's a worthwhile upgrade.

http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT

 

i purchased a similar "no-name" red cap distributor from e-bay to replace the points in my 70' 350. been running it for 4 months now with no problems

 

Beat me to it...

 

revelation is your word, not mine. I was trying to help those of us who don't know it all already.

 

I have a very similar problem with my 70. At idle the dwell was jumping all over the place. At part throttle cruising at around 45 and up it would miss like mad. Floor it and it ran like a bat outta hell. It was driving me NUTS.
I had a COMP 9000 that I got cheap so I dropped that in and no more missing.

I'd like to fix it, but I just don't think it's worth it.

 

Note that ANY distributor (points or electronic) can suffer from worn bushings. As the bushings wear, timing bounces around, causing performance problems. Bushings can be replaced, fixing the problem.