*SOLVED* Hesitation and Stumbling Under Load

veegish · Last edited by veegish on Wed Nov 19, 2008 3:57 pm; edited 1 time in total

Hey friends, I just found this site and joined right up! I have read all the posts on stumbling I could find and nothing quite matched what I am experiencing. Here's the scoop:

Engine is a '71 DP with dual Weber 34 ICT's, Bosch Blue coil and 009 dist. Timing is at 30 degrees at advance, carbs are fully sync'd, new NGK plugs with gaps at .024

A week or so ago my baby started running rough, it was cold and snowy and so i didn't want to get into it at the time (first mistake). After two or three trips to work and back (22 miles each time, freeway) I decided to figure out what the heck was going on. No real surprise, the dist. clamp was loose and toast! I replace it and got everything timed up just as above, but have a serious problem. The engine hesitates and stumbles under load at higher rpm's, seems fine in neutral if i gun it. I can only get to freeway speeds by gently and oh so minutely pumping the pedal, constantly finding the sweet spot that let's the rpm's get up there.

Help! I can't think of anything else to do besides the 'ol standby, start replacing parts (i.e. distributor, coil, carbs, engine, etc.). My wife HATES it when I do that, so I really gotta figure this out! Oh, yeah, and I don't have the cash to take it in...

Thanks,

Zak

Randy in Maine · Posted: Mon Nov 17, 2008 2:28 pm Post subject:

Dwell angle?

Timing?

veegish · Posted: Mon Nov 17, 2008 2:52 pm Post subject:

Pertronix Elec. Ignition

30 degrees BTDC at 3600+ RPM's (fully advanced)

gregthomas · Posted: Mon Nov 17, 2008 2:54 pm Post subject:

Just off the top of my head... bad, fuel filter, clogged up carb, bad plug, bad plug wire, valve adjustment or bad condenser. When was the last time it had a tune up?
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veegish · Posted: Mon Nov 17, 2008 3:06 pm Post subject:

new plugs, wires look fine, new fuel filter, no condenser.

this seems to have been a direct result of driving three days with a moving dist. as it was great before and now it's not. i know that random coincidence does happen, but not that often. why would my valves all of the sudden go out of adjustment after running with bad timing for 60 miles? or my plug wires fail? I am willing to replace what I need to, but don't want to replace what I don't have to. Oi

I will clean the carbs as well.

Randy in Maine · Posted: Mon Nov 17, 2008 5:50 pm Post subject:

Start by adjusting th evalves since that is free and easy to do.

See if any are tight.

jamesdagg · Posted: Tue Nov 18, 2008 2:38 am Post subject:

Test your fuel pump pressure. With a meter. Squirting in a can isn't good enough. Mine was low and had those symptoms.

jim
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veegish · Posted: Tue Nov 18, 2008 3:55 pm Post subject:

Update: Valves are perfect now, car runs better than it has for a long time, WHEN I PUMP THE FRIGGIN GAS WHILE I DRIVE! Arrgh!

I go back to my original post and pose the question: Is it possible that my distributor has been damaged by driving with the clamp loose for about 60 miles? If timed at 3100 RPMs for 30 degrees total advance, my idle is at 15 degrees. What I am saying is that my total distributor (009) advance is 15 degrees from idle setting to high rev full advance. This seems wrong to me. How can I get the often recommended 28-32 degrees at full advance and the idle setting of approx. 7.5-10 with only a 15 degree window? Or is it one or the other?

Could it be my coil?
Could it be my electric fuel pump, which worked fine before the loose dizzy clamp?

Zak

*note* this problem seems to only occur under load, when i am in neutral and behind the car revving it up, it is smooth and neat!

gregthomas · Posted: Tue Nov 18, 2008 4:12 pm Post subject:

The tabs on the end of the dizzy that engage the drive gear may have been damaged. Also, pull the cap off and twist the rotor, it should spring back to its original position. I've also had the tab inside the rotor that engages the dizzy shaft wear down and cause the rotor to move around.
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veegish · Posted: Wed Nov 19, 2008 7:40 am Post subject:

Rotor springs back, and the tabs looked good when I pulled the dist. to replace the bad clamp...

gregthomas · Posted: Wed Nov 19, 2008 9:58 am Post subject:

veegish · Posted: Wed Nov 19, 2008 3:57 pm Post subject:

SOLVED!!

The guts of the dizzy went south! I replaced it (with another 009, sorry) and I am back in bizness! All tuned up to boot! Thanks guys!

Zak

SkrapMetal · Posted: Wed Nov 19, 2008 4:01 pm Post subject:

swhitcomb · Posted: Thu Nov 20, 2008 5:14 am Post subject:

As far as I know, idle on a 009 should be around 7.5 degrees atc when the timing is correct. Granted, idle isn't what counts, full advance is. That's 7.5 degrees off, and could account for a hesitation. Probably why changing the 009 for another "solved" it. Personally, I'd have spent the extra on a SVDA. I've driven both. 009 just doesn't compare.
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gregthomas · Posted: Thu Nov 20, 2008 7:30 am Post subject:

Just out of curiousity, what's the full advance on the new 009?
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bugninva · Posted: Thu Nov 20, 2008 8:09 am Post subject:

gregthomas · Posted: Thu Nov 20, 2008 9:20 am Post subject:

bugninva · Posted: Thu Nov 20, 2008 9:26 am Post subject:

there is no known "ideal" as I stated all engines react differently.. there are general curves and ranges that work well for the majority... as I said, I've had the most luck with around 10-12 initial advance and 31 total mechanical. that is just the total advance, if you get into actually tuning a distributor to an engine it also involves setting the advance curve... this is easily done with aftermarket distributors that are designed with this in mind (I like the Mallory unilite) but not as easy with the stock type (and stock copies) distributors... with the available mechanical distributors, out of the box all you can do is set total advance and let the rest be... or you can open them up and experiment... but it's not really for the faint at heart...
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gregthomas · Posted: Thu Nov 20, 2008 9:33 am Post subject:


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