I've had this drive line vibration problem for a while and have read the posts available on this. Just wondering, on a stock setup in a 64-72 chevelle, if you place an angle gage or inclinometer on the valve cover, what angle do you get. in other words on a stock big block setup, does the engine centerline point down front to back or is it level with the chasis centerline?

The carb mounting surface should be level.

My 66 service book says use a protractor on the valve covers.

I am in the process of checking and messing with this now also.

So, most aftermarket intakes I've seen have a carb mounting surface that is angled forward which would mean the design intent is for the engine crankshaft angle to angle downward from front to back.

edk, I must have seen the protractor on the valve cover in the manual also but I can't find it now, which section is it in?

Don't know much about this but.... wouldn't the factory chassis/motor mount bracket/correct motor mount with correct crossmember "insure" it once worked and was at proper angle. Could side to side wear in mounting surfaces (with torque of engine be a culprit? Wouldn't it be the same end result (in reverse consideration)as changing a pinion angle at rear to accomplish hook up etc. I thought most "vibration " problems were a result of imbalance of a rotating object

Don't know much about this but.... wouldn't the factory chassis/motor mount bracket/correct motor mount with correct crossmember "insure" it once worked and was at proper angle. Could side to side wear in mounting surfaces (with torque of engine be a culprit? Wouldn't it be the same end result (in reverse consideration)as changing a pinion angle at rear to accomplish hook up etc. I thought most "vibration " problems were a result of imbalance of a rotating object

from what I've read on this subject, the crank centerline\output shaft and the pinion centerline should be equal and opposite angles and parallel to get the correct operating angle of the u joints to prevent drivetrain vibration. I'm just wondering if there's a general guideline or factory spec on the engine angle to use as a starting point.

Having looked into this, there are a number of dimensions out there. The 66 service manual tells how to measure it, and what it should be, and then notes that it is adjustable on full size Chevys, but not Chevelles.

Then there are ride height dimensions for everything from six banger 2 doors up to coupes and trucks, which I guess are El Caminos. In the rear this is from the top of the axle to the frame above and seems to range from 5 inches to 8 inches for different models.

Then I found some dimensions for where the control arms should be when tightening the bolts, etc.

And somewhere I saw that a Chevelle ds is offset in the horizontal plane also.

Overall, I am trying to get less than 3 deg of angle at both joints, within a half degree, in the vertical plane. I had 3 deg down on the trans, and 3 up on the diff, and forgot to measure the ds angle, but the other two seemed to be where some improvement was warranted. At one point prior to changing anything, with the rear jacked under the axle, the trans and ds were at the same angle. Diff was still pointing up some.

I pulled the 3 in tall spacers our from under the rear springs Saturday, replaced with 2 in tall 2 in pipe close nipples, and it only lowered the car about 1/2 inch.

I need to be a bit more careful at measuring I guess.

The vibration seems to be getting better, and I am back to thinking my front brakes are the problem.

The carb mounting surface should be level.

Wouldn't that depend on if the vehicle itself is level or not?

GM typically grinds the carb mounting pad at a 4 degree angle. In other words, the engine usually angles down roughly 4 degrees toward the differential when the car is on a level surface.

John

Wouldn't that depend on if the vehicle itself is level or not?
It doesn't matter where your vehicle ends up the carb should be level.

thanks for the replys, thats what I was thinking, somewhere between 2 1\2 and 3 1\2 degrees