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Discussion Starter #1
Jelloe again. For some reason whenever I hit about 3200rpm, driving or in neutral, the engine shakes pretty bad. But at idle and anything under 2000rpm, its just fine. What gives? Also at about 55 mph when I hold the gas pedal down to maintain 55, I feel a vibration in the pedal, and maybe the drivetrain. Kind of stops and goes in a regular pattern. It sucks cause I cant open it past 4000 rpm. Do you think it has anything to do with needing to adjust my valves, because thats what i'm doing today, and they need them pretty bad!!
 

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Generally, a misfiring or rough running engine at higher RPM is a sign of an ignition problem, not a carb or valve adjustment problem.

Ignition crossfire? Make sure your spark plug wires are not bad. You should especially separate cylinders in the same bank that fire in sequence. (Oh, dang! :eek: Which ones is it for small blocks? For Clevelands it is 7 and 8.) Yes, the wires look neater when they're straight and parallel, but you're inviting inducing a current in the other plug wires, also called cross firing.

Also check your distributor cap for cracks or carbon arc buildup. Check inside of cap for terminal corrosion, especially on the cheap caps that use aluminum instead of brass electrodes.

Points fried? Bad or incosistant signal to fire coil.

Coil going bad? Weak spark will cause misfire, especially at higher rpm when coil can't generate enough voltage (not enough time between sparks) for consistant spark signal.
 

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one thought here.... i replaced the fan cluth on my car with one that used a lil bronze bushing that went over the water pump umm.... support?? bushing?? snout? anyways, the first time i put it on and took the car out it would shake like hell when it got over 3K. i remounted the bushing and remounted the fan and clutch and all teh shakes went bye bye. just a thought.
 

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That bushing stops vibrations in the waterpump and fan clutch, without it you could kiss your waterpump/fan clutch goodbye after a short while. It shouldn't cause the engine to shake that badly.
 

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Discussion Starter #6
Alrighty then I've got something to go on. I do have all my wires running together (I just thought you cant have them cross at at a 90 degree angle), and I also got the ones that come straight up from the distrubutor, and I cant seem to find a way to route them without crossing atleast 4 of the wires, I also noticed that between 2000 and 3000 rpms my autometer tach jumps eratically in that rpm range, so I'm sure that would be a sure sign as well. . I'm using accel 8mm super stock wires. Would you guys suggest wires that have the 90 degree angle connector on the rotor? Also I'm also ggoing to check my flex fan and pulleys and see if they are n straight.
I'll check this stuff out tommorow and update ya. Thanks
 

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Hrm, do you have points? I don't know much about points as they were the first to go on my Cougar, but they could probably cause that. If your tach jumps at the sametime I would say your ignition system would most likely be the culprit. The wires would be the first thing to check, I have the $89 dollar MSD wires, and mine don't seem to crossfire anymore, and I have 7 and 8 together, but my previous wires did. Are your wires going to the right cylinders? I know on the Fords the car will run with the firing order off by one. Hows the cap and rotor look? One of the electrodes could be bad causing the problem.

Chris
 

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Check your tranny mount as well. Another thought, does your exhaust by chance dump under the car? I've seen harmonic vibrations from this setup cause shaking at certain RPM's.
 

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Discussion Starter #9
All the wires,cap amd rotor are new. The exhaust runs to the back, and I was also thinking about the tranny mounts, but it also does it neutral. However I do need to have the drive shaft rebuilt, so i'm sure that could be a little part of it. Yes I'm running points, but will be upgrading to the pertonix ignition system along with my msd box. As soon as it cools down, I;m going to tackle the ignition.
 

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Could it be the vacuume advance is not working,
or leaking diaphram.
 

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Discussion Starter #12
Funny you should say that. When I was out earlier re-routing my wires, and retiming my engine I noticed when I disconnected the vacuum advance, the engine didnt change any. So at that point I could have timed the engine without even disconnecting it. Its funny, I think all these things you guys have mentioned are part of the big picture. Keep em coming. Thanks Oh and about the points. I had a mechanic friend take a look at them and he adjusted them last week, said they were good, but I still want to up grane to electronic.
 

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what kind of carb is on it?
 

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Check your harmonic balancer... A few years ago I had a really bad vibration on my 289 that would occur between 2000 and 3000 rpm and get worse as the rpm's went up. After checking mounts, ignition, fuel, etc. turns out it was a hair line crack in the balancer. Normally they seem to last forever but... When replaced everything was smooth again. I don't think it messed anything up in the engine since it's still running strong.:)
 

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Discussion Starter #15
Alright here'e the deal. I'm running a Holley 650 on a holley dominator intake (wouldnt be my first choice, but they were given to me, so i'm not complaining)on a 1978 302 with 1969 351W heads on it. The timing marks are on the 11 oclock position on this damper, beacuase the water pump outlet ran out on the driver side this year, so what I did was find TDC and used some timing tape. The car idles pretty good (could be better) at 550 in gear and at 750 in N or Park. I checked all the wires an re-ran them and it seemed to help quite a bit especially with the Tachometer thing, but When I take off at a light it hesitates if I stomp on the gas (shouldnt I be leaving tire marks for atleast 1/2 block?) Something I need to adjust on the carb maybe? Ive got it at 6psi, So maybe I need to make it richer. But it goes pretty fast after that (until one of the rocker bolts come loose when i'm doing 75...what gives...I think I need to rocker bolts. And when I'm doing about 50 It sounds like a connecting rod htting only when I match the throttle to maintain speed. When I stomp on it it stops and when I let off the gas It stops. The fine tuning of the beast goes on...blah
 

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The electronic ignition will solve that slight hesitation, take it from me, the Pertronix unit gave my POS 1974 302 a reason to live. I had the same hesitation. Also, you might want to advance the timing a little bit, I could go to a stop sign and drop the pedal or get on the pedal hard and it would give me a slight hesitation, with minimal timing advancment I could light my tire up (Yeah yeah, tire, damn open rearend).
 

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My 67 had the hesitation too but it was a leaky vacuume advance diaphram. if your carb has a vac port just above the butterflies under the primary bowl, try hooking the vac adv line there, just dont hook it up to straight manifold vac as it will suck the guts out of the diaphram. you can test the vac adv diaphram with a hand-acuated vacuume pump (25$), with the dist cap off see if the adv plate rotates when vac is applied and holds the vac. you will aslo be able to see if the adv plate is operating smoothly with no sticking.
Wouldnt rule out the harmonic balancer for the vibration. if you have an accelerometer or velocity transducer and a analizer you could identify the vibration by its signature (sine-wave). hold that tiger.
 
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