Corvair Forum

I have a daily driver 64 greenbrier 4-speed 3:55 gears. points ignition dual bushed distributor. correct weights & springs, new clarks 217 vacuum advance. 110 engine, distributor, carbs all rebuilt about a year ago. 2 month old tuneup using blue point points condensor rotar cap, seth emmerson wires and NGK B6HS plugs. new fuel stones & in-line fuel filter at tank. points are clean and dwell is at 30. plenty of fuel pressure and flow with mechanical fuel pump.
engine runs great with good power.
a few weeks ago, i intermittantly started to get a miss at about 3 grand when accellerating to shift. no miss at 3 grand while cruising on the freeway. it feels like an MSD rev limiter but no MSD 6A box installed.

points bounce?

abou me

i am in so cal. this is the third engine i have succesfully rebuilt. have rebuilt many carbs and 3 distributors. i have rebuilt both front & rear suspension. electrical is my specialty but can hold my own with mechanical.

any thoughts? Sent from my SM-G930V using Corvair Forum mobile app

dave t wrote:I have a daily driver 64 greenbrier 4-speed 3:55 gears. points ignition dual bushed distributor. correct weights & springs, new clarks 217 vacuum advance. 110 engine, distributor, carbs all rebuilt about a year ago. 2 month old tuneup using blue point points condensor rotar cap, seth emmerson wires and NGK B6HS plugs. new fuel stones & in-line fuel filter at tank. points are clean and dwell is at 30. plenty of fuel pressure and flow with mechanical fuel pump.
engine runs great with good power.
a few weeks ago, i intermittantly started to get a miss at about 3 grand when accellerating to shift. no miss at 3 grand while cruising on the freeway. it feels like an MSD rev limiter but no MSD 6A box installed.

points bounce?

abou me

i am in so cal. this is the third engine i have succesfully rebuilt. have rebuilt many carbs and 3 distributors. i have rebuilt both front & rear suspension. electrical is my specialty but can hold my own with mechanical.

any thoughts?

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sorry this is my first posting pictures. i did not mean to post all of them

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dave t wrote:...a few weeks ago, i intermittantly started to get a miss at about 3 grand when accellerating to shift. no miss at 3 grand while cruising on the freeway...

Just a wild guess...

I was trying to think of what is unique about running the engine up through the gears that could cause a disruption in the ignition system, but may not occur at a steady cruising rate?

Could the vacuum advance activity that causes motion of the breaker plate as engine speed picks up be causing a problem? The coil to ignition points wire has been known to break down over time, as the internal wire strands are continually subjected to flexing as the vacuum advance moves the breaker plate to advance the timing as the engine transitions from base timing, through vacuum advance, and then on to centrifugal advance. If that wire is breaking down internally could the intermittent connection to the points be causing a miss? For fault isolation of this possibility, try temporarily disconnecting and plugging the vacuum advance hose, and then take a short test drive to see if the problem goes away.

SEE THE COMMENT FROM THE CLARK'S CORVAIR PARTS PAGE ABOUT AN "INTERMITTENT MISS" HIGHLIGHTED IN YELLOW BELOW...

http://www.corvair.com/user-cgi/catalog ... IN&page=75

Part number C530: 60-69 DISTRIBUTOR POINT LEAD

Weight: 0 lbs 2 oz
Catalog Pages(s): 75,77(11«),77(19)
Price: $ 7.85

bbodie52 wrote:

dave t wrote:...a few weeks ago, i intermittantly started to get a miss at about 3 grand when accellerating to shift. no miss at 3 grand while cruising on the freeway...

Just a wild guess...

I was trying to think of what is unique about running the engine up through the gears that could cause a disruption in the ignition system, but may not occur at a steady cruising rate?

Could the vacuum advance activity that causes motion of the breaker plate as engine speed picks up be causing a problem? The coil to ignition points wire has been known to break down over time, as the internal wire strands are continually subjected to flexing as the vacuum advance moves the breaker plate to advance the timing as the engine transitions from base timing, through vacuum advance, and then on to centrifugal advance. If that wire is breaking down internally could the intermittent connection to the points be causing a miss? For fault isolation of this possibility, try temporarily disconnecting and plugging the vacuum advance hose, and then take a short test drive to see if the problem goes away.

SEE THE COMMENT FROM THE CLARK'S CORVAIR PARTS PAGE ABOUT AN "INTERMITTENT MISS" HIGHLIGHTED IN YELLOW BELOW...

http://www.corvair.com/user-cgi/catalog ... IN&page=75

Point Lead - Intermittent Miss.jpg

Part number C530: 60-69 DISTRIBUTOR POINT LEAD

Weight: 0 lbs 2 oz
Catalog Pages(s): 75,77(11«),77(19)
Price: $ 7.85

good point. (no pun intended) the wire is about 3 years old from the new rebuild. i have several new point to coil wires in stock. i will swap it out anyway and see what happens.
thanks for the input.

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Had my 110 timing set at 18 advanced, had to back it down to 14. I was getting a miss just as it shifted to drive at high RPM.

Dave - Still at OPGI?

Your problem could be many things, but if all runs well at 3,000RPM cruise, but not under acceleration then what's the difference --- first thing that comes to mind is higher cylinder pressure at WOT could result in misfiring due to a spark plug issue or weak spark. Pull plugs and check color. If you have a Flamethrower coil it may be a problem (I've had a number fail and won't use them). I now use a good name brand replacement coil that fits any mid 60's Chevy V8.
Don't forget the vacuum advance is in a different position on cruise vs. WOT and a worn points plate will cause issues as when the vac adv lever moves the points gap will change. And finally, new points are really not that great. I went to Petronix 1162a module years ago and won't use points again.

Good luck.

High RPM miss can also be caused by 50 plus year old weak valve springs. I set my points in 2013 when I first got my 64 & it's my daily driver & I checked the points this spring & they were still at 19. If it ain't broke don't fix it.

Too rich will also cause your symptom. Dirty air filters or slightly high fuel levels. Temporarily remove the air filters and see if that fixes it.

64powerglide wrote: ↑Mon Sep 03, 2018 9:29 pm High RPM miss can also be caused by 50 plus year old weak valve springs. I set my points in 2013 when I first got my 64 & it's my daily driver & I checked the points this spring & they were still at 19. If it ain't broke don't fix it.

Dave said it runs fine at 3,000 RPM EXCEPT under load while accelerating - not a valve spring problem. Classic ignition or fuel problem.

My 76 Lincoln 460 had 2 broken valve springs, ran fine until I accelerated hard then it missed & backfired through the intake. With weak lifters or springs the rockers will float at high RPM under a load & the engine will miss & the other guy will beat you to the finish line!!! I also posted that I had to back my timing off to 14 because I was getting a miss under full acceleration just as it shifted.

Found the problem!
I disassembled the distributor. the little dab of grease on the advance weights must have been too much. it was all gummed up and the weights were sticking. i cleaned up the weight "SYSTEM" and installed a set of NOS springs that i had. this should have not caused the problem but the engine no longer cuts out during acceleration. while i was there, i also replaced the points wire as suggested with a new one. the one that was installed did look good but i replaced it anyway since i was there.
thanks for all the help.


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Glad you found the source of your problem! I seem to remember reading somewhere that it is advisable to avoid the temptation to lubricate the centrifugal advance mechanism, as it tends to gum-up the mechanism as dirt accumulates and bonds to the grease. I guess you just confirmed the soundness of that advice!


I guess the vacuum advance system did its part at the low to mid-range engine speeds, but as the vacuum advance "stepped aside" to make way for the centrifugal advance mechanism, the centrifugal advance turned out to be a "no show"!