Engine running rough above 2000 RPM

[Timothy B.]

Re: Engine running rough above 2000 RPM

Michael,

Keep us posted if the problem turnes out to be the Petronics. If it's bad and you still want a electronic switch consider the Breakerless SE as it';s protected if the switch is left in the in position. I installed one in my 67 300 hp distributor and I think it works great, it's like having new points all the time.

[Michael J.]

Re: Engine running rough above 2000 RPM

After a very frustrating day replacing the old Pertronix with a new unit and trying to get it to run right, I gave up and now she has points and condenser back in, and runs like a champ! The new Pertronix unit make it run rough through the whole RPM range after installation, I thought the hood would shake off. After adjusting the "air gap" about a dozen times (and if you think setting points gap is bad, nothing like this), it finally started up a little rough and then after a few minutes it just smoothed out and sounded fine, until I revved it up above 3000 RPM and then like a switch going off, it went back to being rough. I thought, why am I dealing with a black box when I know points will run fine. And they do. My last adventure with "new tech", that's for sure, life is too short and adjusting points ain't so bad.

[Rich W.]

Re: Engine running rough above 2000 RPM

That makes me very happy..glad to hear its running the way it should..Petronics makes good stuff..I know a few people that run the new 3..and so far so good..but I think these cars are meant to have points..I don't drive the car enough to wear out points..and I know the car will have spark..can I ask what type of points you put in?

[Timothy B.]

Re: Engine running rough above 2000 RPM

Michael,

Glad to read you have found the problem with the car. I have a friend that installed the Petronics 3 in a 350hp motor and we had a terrible time timing the engine. Timing jumped all over the place, I guess because of this multi spark thing but I did not like any part of it.

After hours trying to figure this out I thought there were ground or voltage issues with his wiring until another friend installed the same unit in his Olds 455 and the same thing when timing.

IMHO, don't be afraid of the electronic switch, consider the Breakerless SE if you want trouble free simple performance. Points are fine but they are subject to resistance to ground for many reasons and the result is that little skip at idle etc. etc... Also, make sure the spark plug wires are routed as per the AIM and properly installed in the rubber insulators.

[Rich W.]

Re: Engine running rough above 2000 RPM

Hope not to be off topic to far..but when I put the pet 3 in my friends 72 I did the total timing without a problem..set at 35@ 2k mech..idle was a little erradic..timing it that is..idle quality was great..the rev limiter was nice too..could it be the timing light itself doesn't work for that..which type did you use?

[Duke W.]

Re: Engine running rough above 2000 RPM

Unless you verified the total centrifugal advance and at what RPM it tops out you are likely WAAAAAAAAAAAAY over advanced.

Most OE curves max out at 3500 to 5000 and emission controlled engines generally have less total centrifugal than pre-emission engines.

A lot to guys set "total advance" without knowing the centrifugal curve including where it tops out. BIG MISTAKE!

Duke

[Rich W.]

Re: Engine running rough above 2000 RPM

I did write that..35 degrees at 2000 rpm..I did change the springs also to to get it that low..I just wrote it in code!! Thanks for not letting me blow something up..as it would if it was set wrong!!

[Michael J.]

Re: Engine running rough above 2000 RPM

..I don't drive the car enough to wear out points..and I know the car will have spark..can I ask what type of points you put in?

Me either, and I put in Standard Blue Streak points. The NAPA guy recommended them as the best he had. I am suspicious of my harmonic balancer when I use a timing light to set timing to factory specs. I think it is old and has slipped. I tend to set the timing by feel, hearing, RPM, and vacuum. I usually set it to max vacuum and RPM at idle, run it at higher RPM on the road and feel how it does, then back it down a bit until it "feels" right as I drive it. When I rechecked with the timing light it usually says something near 15-17 degrees BTDC. I'm not sure that is right, as the harmonic balancer may be out of whack.

[Rich W.]

Re: Engine running rough above 2000 RPM

I like blue streak..they were in the car when I got it..my 5 year old plays with them now! ! I like the accel ones I put in..idles great and don't float..

[Ronald L.]

Re: Engine running rough above 2000 RPM

Michael, I've changed points and not even had to adjust the dwell was right on, and I use Delco, the 112's are still plentiful, just avoid the gougers on the bay.

There is probably a good thread from a year ago when I was chasing a stumble, turned out to be mostly sticky original weights.

Short story is:
Set dwell to spec, probably 28-32 range and yes that correlates to the best sound too.

Timing initial - set it a 8* w/ vac adv plugged.

When you rev the engine you should see the weights kick in and advance timing to 32-36 range.

If the damper was slipping I'd expect you to have other problems if it keeps moving.

It should continue past 15 deg if that is real.

[Michael J.]

Re: Engine running rough above 2000 RPM

OK, thanks for those tips. I set the dwell at 30, then went out for a test drive. I am getting some roughness, I suspect the timing is advanced too far. The problem is not a stumble on accel, but rather a subtle feeling of stop and go (pulsing feeling) at cruising speeds, I call it roughness, surging and stutter. Anyway, I will test out the new timing setting when the grader finishes grading my county road access.