what have i done

[rja]

in my insatiable quest to NOT leave well enough alone, i am in a quandry. on my dual point, '74 1800 spyder i have developed a miss. put the timing light on it yesterday, just to check. timing showed about 15-18 degress before tdc. specs show 0 @850 rpm. so let's rectify this situation. turn the dist clockwise to retard, pause to increase idle at carb, turn again, engine pops thru carb and dies. will not restart at current settings. advance the dist 'some' and restarts, but a dead miss. shaking like santa's belly. while running pull the wires at dist cap one at a time and #'s 3 & 4 make little difference in shaking. commence pulling plugs and wires and swapping out, back and forth to no avail. 1,3,4,2, dist pointing @ #4 when at tdc-done. wires arc to cap correctly when running; arc to spare plugs when testing. as yogi berra would say, 'this ain't rocket surgery'! any and all donations (of info) very much welcomed. oh, cam timing seems to be correct, also.

[timinator]

What are the point gap and dwell numbers? What is the coil output at idle and 2000rpm? What is the condition of the plugs? Does your timing jump around at a steady 2000 rpm? What is the vacuum reading at idle and 2000rpm? Or better yet buy one of Mark's distributors.

[rja]

point gap at 15 thou; dwell between 55-60. plugs look good; tan. car has less than 35k orig miles. compression check 140-150 across all four. cam timing marks line up together w/crank. just don't get it how this can happen just turning the distributor a little.

[majicwrench]

Assuming you checked compression after it starting missin? Please confirm.
I dislike pulling wires from cap, that 40k volts jumps to SOMETHING SOMEWHERE. Better to get 4 short (2-3") hunk of fine wire and stick it alongside plug wire in cap, then short with test light or any piece of grounded wire.
POP could have popped off a vacuum hose, look in the area of 3-4 intake runner.
Keith

[seabeelt]

Check the wires going to the dizzy as well as inside the cap. Because of age they are often old and brittle and can short out through cracks in the wire insulation. Ask me how I know

[azruss]

0 degrees static advance. that seems very fishy.

[rja]

first off, thanx for all the replies. not a novice here; that being said, i'm still puzzled. got about 12" vacuum at idle, still missing on 3 and 4. of course engine smooths out about 2.5k-got about 18" then. all compression is 140-150 psi w/throttle wide open and less than 10 revolutions to get that. no apparent vacuum leaks-34dmsa-pollution controls all removed and plugged. has to be ignition related. i can switch plug wire 3 to 4 and back again w/the engine running and not make any difference in rpm. riveted plate in engine compartment calls for 0 degrees advance at 850 rpm . can see NO errant spark grounding anywhere. very confusing. plugs all tan and dry. 3 and 4 are firing between wire and cap when pulled loose and a good blue spark when grounding a plug against the head. acts like 3 and 4 are getting no gas. how can that be?

[kilrwail]

Have you ever pulled the distributor out? Sounds like it's off a tooth on the drive gear. Set the cam pulleys and crank pulley at TDC and verify that the distributor rotor is pointing at Plug #1 (or 4).

[rja]

took the car out this morn before storm. pulled the choke out to get it to idle and went for it. car accelerated well; pulled to redline in three gears. just won't idle. timing looks to be about 15-20 btdc at 850 shaking like jello.

[So Cal Mark]

12" of vacuum at idle is quite low. Since it's 3 & 4 I'd take a compression test first. Are you positive you didn't mix up the firing order?

[rja]

thanx for posting. didn't fiddle w/firing order before this happened. just twisting on dist and turning up the idle speed screw. can run the speed up to about 3k and see the timing mark advance. set the throttle cable at 3k and pull #'s 3 or 4 plug wire at the cap and hear the difference it makes in exhaust sound. just shakes @ 850 and can hear no diff when i drop out 3 or 4. weird. drop out 1 or 2 and engine just dies. comp is 140 to 150 across all four. i guess if it works, don't mess w/it. probably be trying plug wires, cap, rotor,etc. don't know what else to do.

[majicwrench]

I wouldn't be tryin wires cap rotor etc. They are fine or car would run like crap at higher rpm. Idle is very easy on secondary ignition.. Heavy load is hard on secondary ignition.
Got a long hunk of vacuum hose?? Stick one end in your ear and move the other around the intake gasket, carb gasket etc looking for vacuum leak.
Keith

[4uall]

I tried this method with success

https://www.youtube.com/watch?v=zMok2y05jNE

[rja]

vacuum leak. do these carbs not have gaskets-just the spacer?

[georgeramos]

do the centrifugal "weight" springs in the dizzy have a lot of play? it would seem that might cause an issue at higher rpms but i have had some issues with those springs in my single point setup...