ok good points i have not done this because he said he has done it. but if he happens to stop in again i'm going to start from scratch and pull the plugs for gap. check the compression ohm out the wires and the coil and if i have to pull the distributor to make sure all is well i will. he said he took it to a place he frequents often called downtown auto and he said i put a scope on it and the scope showed all is good. but i don't think he really know how to interpret it. he sees a bunch of lines on the screen and figures all is well. not many novices know how to read a scope. hell i had to show the mechanics when i was working how to read a voltmeter.
i can't tell you about under a load but they way he talks, he has to take it out a drive it, i'm thinking it is doing this only under a load. and not when he is just plain driving it but when he is horsing it.
it is hard to get a straight answer out of him and like i said before he has a slang he uses and half the time i have no clue what he is really talking about anyway. but thanks for those ideas. bp.

 

So this perceived vibration doesn't happen in the garage while just manually accelerating the engine?

 

to be honest i don't know for sure. this is what is making it so hard to diagnose. and to get help with others. he says it does it setting in the yard and then when he drives it home i ask him how did it go and then he tells me he can't tell until he gets it out on the road and hammers it. but then next time i ask him he says it is still the same. he has it in my driveway and i rev it and i can't see or feel anything, i don't feel it in the steering wheel or see it in the steering wheel. but he maintains it is vibrating. the hard thing is he says it vibrates all the time so you would think it would vibrate just by driving it down any road. and any speed.
yesterday he said he can't get the rpms in the right spot. i told hom to drive it any gear that puts the engine in the range this happens. but he seems to think he has to be in high geat all the time. so i wonder it what he is feeling is the engine lugging. and he is trying to power it to speed instead of using the gears to keep the engine in a power range. for some reason this guy thnks he need to be in high gear as fast as possible. so now that we are talking about this i wonder if that is his problem. engine is lugging and that is the vibration issue? what say ye?

this makes it hard to repair. and i know your guys are setting back wondering as well. i just can't give you a firm symptom. if i had one i could most likely fix it. but because he complains about it at those rpms and it is a vette i ask you guys for any help that may be particular to these cars. if it was a corvair i would be fine. i think my best bet is to just have him leave it and i will take it out and do some of my own tests. and then i will have it to do a complete troubleshooting. plugs wires dest. carb timing etc. then i can give you guys a better problem to help me with.

or maybe just have him take it the dealer. again thanks bp.

 

Loose manifold bolts? What about the fly wheel? LOL I wouldn't be surprised at this point. Check all the pullies and mounting brackets too.

 

thanks for those ideas.
was just about to give an update on this. i went for a ride today and this is what is really happeneing.
1. he goes thru the gears and it is good so he says. but then he is in 4th gear at 15oo rpms and hammers it and it vibrates a bit.

2. normal driving thru the gears and it performs good. some shaking i believe is form the road due to stiff suspension.

3. i told him i believe when he is doing 25 mph and 1500 rpms and nhammers it the engine is lugging down and might be also due to the fact he has the timing set to 17 deg at idle and pulls into 37 deg total that the power curve may be causing some kickback on the crank.

4. i also told him he could be having the engine is getting a big slug of mixture and can't fire good at that rpm range and the plugs are just not firing good at the operating parameter.

so any thoughts on these points? one or all may be his issues. also he is using a pertronix module and that could be giving him fits. they do go bad and still let the engine run i had one do it. thanks bp.

 

That's a lot of timing at idle. Wonder what the advance curve looks like.
Does he ever let you drive it?
Still think the best approach is go back to stock and make one change at a time. Very hard to determine effects on performance when more than on change is made at a time. That was the main reason I hated to work on my friend's '66 427/425 roadster. Damn Holley just had too many adjustments.

 

i told him yesterday he needed to get the distributor back to stock and then go from there on thing at a time. i told him to take the pretronix out and put the points back in and then see what he has.

i had a pretronix that went bad and he was there when it did and it did not just quit. in order to start the engine i had to advance the distributo like one complete tower position and after it started i had to retard it to 0 that threw me for a loop for hours until i put the points back in and i got it timed in 1 minute. so they can go bad and still run the engine with poor results.

lets see if he does that for testing. thanks bp.

 

ok here's the update. he came over today and i took out the distributor. i found it had missing thrust washers so the rotor could move up and down which was in relation to the cam gear driving it. that would cause a bunch if time issues. like 10 degrees or more. and that could have been happening at the rpms he was talking about.

then i found the weights were not bringing the points cam back to the same place every time. they were rusted to the point that if i moved one weight it would stay out about half the travel. then i found the springs were stretched some and did not bring the weights back to home at all so he had a variable advance form that and that could have been giving hem those issues as well.

so i got it back together and tight so if i move any weight it returns to home even if i move them ever so slowly or even just a small amount they return home. i had to make a thrust washer and use one from my corvair parts bin to get the thrust slop out of it. also it now is set to 12 deg btdc on the timing tab

now to let him drive it and tonight i will be at dinner with them and he will tell me if it is better the same or worse. he has been gone now for 30 minutes so it must be at least the same because if it was worse he would have returned by now. bp.

 

Why won't he let you take it for a test drive after you do things to it?

 

he most likely would but to be honest i think the car is behaving just as it should for the kind of car it is. he now want to find a distributor and see if his distributor may be what is giving him a fit. this is going to be a never ending story if you know what i mean. i want to tell him to live with it but he stands here like a beggar and i'm not the type to turn him away. we will work on it for awhile more and he will see it is not doing what he thinks it should, then some other guy will tell him it is normal and then it will all be good. you know what i'm talking about you have been down that road as well. thanks bp