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Old 01-09-2013, 12:02 PM
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Buick 350....running rough, but seems like she wants to run

Just picked up my new project. 67 Skylark w/ Buick 350. I bought the car assuming the motor needed to be rebuilt, however I'd like to see if I can get some more life out of it.

As of now I have changed the oil, filter, fuel filter and plugs.

It starts up great and idles fine.

Car runs very rich. Carb is a 750 Holley 4160. Probably a good idea to change to a 600cfm carb? Anyway to make the engine happy with the 750?

Ticking coming from pas. side valve cover. Maybe a lifter. It's not constant though.

It will cruise down the road ok but as soon as you give it anymore gas it hesitates and stumbles continuously.

I did verify initial timing at 12. Haven't checked anything else. Still has points distributor, although it appears to have some new parts in it. Mechanical advance weights and springs look kinda rough.

I plan to get compression readings today.

So what's next?
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Old 01-09-2013, 12:48 PM
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Just checked compression:

1-160
2-170
3-150
4-162
5-165
6-190
7-165
8-175

So with those differences sounds like the valve seals or rings are going. Can anyone recommend methods to test for both to check the condition of both?
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Old 01-09-2013, 12:51 PM
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I also took those readings while the engine was cold. I'm not so sure it would matter with such differences in compression??
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Old 01-09-2013, 03:39 PM
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Originally Posted by jjack010 View Post
Just picked up my new project. 67 Skylark w/ Buick 350. I bought the car assuming the motor needed to be rebuilt, however I'd like to see if I can get some more life out of it.

As of now I have changed the oil, filter, fuel filter and plugs.

It starts up great and idles fine.

Car runs very rich. Carb is a 750 Holley 4160. Probably a good idea to change to a 600cfm carb? Anyway to make the engine happy with the 750?

Ticking coming from pas. side valve cover. Maybe a lifter. It's not constant though.

It will cruise down the road ok but as soon as you give it anymore gas it hesitates and stumbles continuously.

I did verify initial timing at 12. Haven't checked anything else. Still has points distributor, although it appears to have some new parts in it. Mechanical advance weights and springs look kinda rough.

I plan to get compression readings today.

So what's next?
Check the timing gears and chain, this engine has an appetite for these parts. If they fail it will be way more costly that timing gears and chain as the Buick will run the pistons and valves together, a mighty costly fix.

The cam gear is a nylon tooth ring molded to an aluminum hub; the nylon hardens with age and heat. It forms cracks as it gets old which spall off till the chain can jump time. A test (though not fool proof) is to jam the advance systems vacuum and centrifugal so they can't introduce any variability to the timing. Rev the engine up a couple, three thousand RPM (out of gear) then slam the throttle shut with a timing light aimed at the marks. If the timing wanders under and over the set base advance it can be a pretty good indicator that the timing set is worn which allow the cam to under and over run the crank position which will also make the spark timing wander about.

Go easy with this because if the gear is failing you don't want to put enough load on it to fail it completely.

Bogie
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Old 01-09-2013, 05:47 PM
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Useful info to know. Thats why I mentioned Im ignorant when it comes to buicks.

If my initial timing at idle is 12deg then it should return there during this check after returning the throttle to closed? Vacuum advance should be plugged right? What is a safe way to lockout the mechanical advance without welding or buying a kit?
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Old 01-09-2013, 05:56 PM
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Useful info to know. Thats why I mentioned Im ignorant when it comes to buicks.

If my initial timing at idle is 12deg then it should return there during this check after returning the throttle to closed? Vacuum advance should be plugged right? What is a safe way to lockout the mechanical advance without welding or buying a kit?
Disconnect the vacuum and plug the hose. Use a piece of wire to securely wrap the counter-weights to tie them down.

What you're looking for when the throttle is snapped closed is for the timing to wander about what ever the base setting you used. If it's 12 degrees then you're looking for excersions that go below say 10 to above 14. This is a test to see how well the timing gears and chain are tracking each other. The more the wear the greater will be the amount of change and it may keep wandering for 3 or 4 times as the before it settles down.

Bogie
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