Distributor Experts, HELP PLEASE!!!

[tcb-1]

I think I found my problem, but would like to run it past you all before I go any further.

I have a '69 C-10 with a bone stock 350 running a points ignition.
new plugs gapped to .035"
distributor cap and rotor look good
points gapped. new coil and plug wires
no arcing when the lights are out
fresh gas, new inline fuel filter
carb is a fairly new 1405 Edelbrock with manual choke
choke is closing

it starts like a champ, and idles up to 1000rpm, but when I try to increase the rpm, it starts to stutter severly. when I kept the foot in it to "see" if it cleared out, I da#n near blew my Flowmasters apart. so there is major gas dumping straight into the exhaust. I haven't timed it, but will tomorrow.

so tonight on a thought, I check the vacuum advance. I hook up suction to the vacuum unit. it would not hold vacuum and it didn't move the advance plate any. so I take it out and tear it apart and sure enough, the vacuum unit's diaphram is split.

now....... other than timing, would a trashed vacuum advance cause my symptoms? anything else I'm missing that obvious? I don't think I have a sticking valve, but I guess I should do a compression check.

other than "natural causes", why would a vacuum advance go South?

need help guys, bigtime

[PanelDeland]

40 Year old rubber.Would you expect 40 year old tires to hold air?There may be other things to cause one to go bad but all things considered that would be my guess.If you're going to replace it you may want to consider upgrading to a HEI.It wont cost much more and will help the truck run better.

[tcb-1]

well, rubber in a wallet lasts...... but I digress. your right, I can imagine the vacuum advance unit is all of 40 years old. but I was wondering if I did "something" wrong to cause it to tear.

yep, I plan on going Pertronix after the holidays. a friend of mine installed the Petronix system on his '66 GTO and is extremely happy.

but I would like to get this mess figured out before I go any further with my upgrades....

[Green Machine]

If you can set the points with a dwell meter that is best. Gapping can be tricky if there is wear in the distributor. 28-32 deg is the spec. I suspect the points are not set right. I usually adjust to 28, as they wear they get closer to the 30-32, then re-adjust back to 28. If the distributor is really worn, it may not fire right or at all on some cylinders. Dwell meter needle swinging back and forth alot indicates distributor wear. HEI of course is better, but a good points setup will light the fire OK too.

[Boog]

Doug make sure the mechanical advance is free also. You know by twisting the rotor it should rotate a bit then spring back. Sometimes the mech advance will seize up also causing like symptoms. Maybe a good time to remove the dist and break it all down and give it a good cleaning. Could save having to go back in later.

[tcb-1]

Boog,
The mechanical advance rotated and sprung back freely without any bind. that was one of the first things I tried.

[68gmsee]

Has it run good up until now? A bad vacuum advance and timing can certainly affect the way it runs. As you know, the vacuum advance is disconnected while timing and I have revved mine up in the past but I don't get the symptoms you describe.

You mentioned it is throwing a lot of gas into the carb while it's missing out.
It's possible that your carb may be flooding the engine or you are sucking in air from somewhere. I just fought that on my 68. I had a leaking base gasket on my carb and it would start missing at around 65 mph.

I've also seen where a worn cam (flat lobes) will cause you grief at higher speeds. Bad valves usually are more noticeable at the lower rpms than at the higher rpms.

[BLAZERMAN]

I found this site to be alot of help when I was troubleshooting my ignition awhile back. http://www.classictruckshop.com/club...e/ignition.htm

[tcb-1]

Thanks Rob, I'll check the site out.

still thinking it's the vac unit. heading to NAPA tonight.

[1restorick]

Just a thought, years ago I had a Corvair that after winter storage started to run bad. It would start and idle fine but at certain speeds it would stumble and when I would let off of the gas at any RPM, it would backfire in the mufflers. After lots of troubleshooting, I found that when the vacuum advance would pull on the breaker plate, it would cause the points to mis-align. The primary cause was a low quality point set. The secondary cause was that the breaker plate was beginning to bind up on the bearing surface and needed lubrication. I would make sure the the point set is up to snuff and that the breaker plate moves freely. Best of luck.

Rick

[VetteVet]

This guy sells brand new HEI distributors on E-Bay. Several of the members have bought one and most have been very happy with them. You will pay more for the pertronics unit than $60. You will have to buy HEI wires also.
http://stores.ebay.com/whiteperformance1

[Sinister]

Originally Posted by VetteVet

This guy sells brand new HEI distributors on E-Bay. Several of the members have gotten on and most have been very happy wirth them. You will pay more for the pertronics unit than $60.
http://stores.ebay.com/whiteperformance1

Plus you might want to rebuild your old points dizzy with new bushings etc. = more $$$

[70rs/ss]

I have two of them and paid $50 each, the pertronix isn't any better than an hei, especially if the dist is old, worn shaft,/bushings, etc. Get an hei.

[tcb-1]

great point fellas. if my dizzy is crap now, it will be crap with a Pertronix or any other pointless ignition.

food for thought......

[Richard8971]

Originally Posted by PanelDeland

Would you expect 40 year old tires to hold air?

I know some 40 year old guys who are still full of air, hot air that is...LOL

Don

[PanelDeland]

That would be me Richard but I digress. I do know a guy who replaced a timing chain and did points at the same time.He could not get the car to start.It took about 2 minutes for a competent mechanic to tell him to get rid of the cheap points and use something worthwhile.New points and it started right up.

[tcb-1]

I hate to even write this, but I think my freakin' 4 month old plug wires are bad, or at least one. out of curiosity, I checked each wire with the trusty ohm meter tonight. 7 out of 8 test out, but one would not. I checked for arcing, but I never had someone increase the rpms while I watch or arcing; it was only at idle.

but on another note, I installed a new rotor, dizzy cap, and vac advance. probably didn't need to, but what the.....

new plug wires ths weekend. to be continued.....

[chipflyer]

Hi Doug,
To answer your original question, no I don't believe the vacuum advance is causing your issue. I KNOW I drove mine around for a couple months when it wouldn't hold a vacuum and didn't have your symptoms but did use a lot of gas out on the road. Did you check your wires to make sure they are in the right order on the cap? I had 2 wires switched one time and had the exact same issue you are seeing, it would start and idle great but when I hit the gas, bang!
Just a thought.

Jeff

[tcb-1]

Jeff,
the more I think about it, the more I think you have something there.

my truck did the same think you described. terrible highway gas mileage, but it would run.

now it idles, but will not increase rpm. but since it idles, that would mean that the plug wires are in the correct locations? which leads me back to faulty wires.

hmmmmmm. this sucks.

I may have to go back to motorcycle restorations. I could always figure those thngs out

[chipflyer]

I may have to go back to motorcycle restorations. I could always figure those thngs out

Don't give up to quick Doug, it just takes fuel, compression and spark!
Whenever I need to remove my HEI cap I always pull a couple wires to allow me to easily lay the cap to one side. I actually did this once and when I put the cap back on I had 2 wires switched but it fired up and idled ok but upon accelerating It backfired bad.
This could be the issue if you had the cap or wires off but if it just started out of the blue, without you touching the dizzy, well, nevermind!

Jeff

[Jokers69]

I'm pretty sure you have a bad condenser. I was just working on a 61 tempest with the exact same problem and it was the condenser.