BB manifold still tapping PS box

[sixt9x33rs]

I put new motor mounts on my 69 L35 convertible but still have this annoying bumping of the manifold on the ps box. It only happens when the car is in reverse at certain rpms. Not a problem going down the road. I installed correct smog manifolds on the car hoping this would cure the problem. The previous manifolds were wrong and the problem worse. Still have not worked it all the way out. Any ideas?

[buenymayor]

I just looked at my BB 4 speed car, and I've got a good 1/2" clearance between the P/S box and exhaust manifolds. Are you sure you have the right engine mounts/frame stands/cross member? The L and R frame stands aren't swapped side to side, are they?

[sixt9x33rs]

I took a mirror and a flash light to make sure I had the right part number frame stands. The motor mounts are right. As far as I know the cross member is right? But can't say for sure. Any other ideas? Something is obviously not right..

[z28z11]

The motor mounts are right. As far as I know the cross member is right? But can't say for sure. Any other ideas? Something is obviously not right..

I think the BB crossmember is offset compared to the small block - just slightly, but might be enough to clear. Checked your underside of the crossmember for the bolt opening ?
Just thinking -

Regards,
Steve

[sixt9x33rs]

My car is an automatic. Are there two automatic cross members? SB and BB?

[sixt9x33rs]

Just read on the site that the Camaro and Firebird TH 400 cross members look similar but different. I am going to confirm I have the Camaro Cross member. Let you know.
Thanks
Lawrence

[HawkX66]

My car is an automatic. Are there two automatic cross members? SB and BB?

Just read on the site that the Camaro and Firebird TH 400 cross members look similar but different. I am going to confirm I have the Camaro Cross member. Let you know.
Thanks
Lawrence

The 69 Camaro big block manual cross member looks almost identical to the Firebird cross member. The only visual difference I could find is the offset. The 69 Camaro big block auto cross member is completely different though.
Pics came from "TJs" if I remember right.

[sixt9x33rs]

Looks like I have the correct cross member. I measured the distance from the inside of the frame rail to the mounting pad, and the passenger side is approx 1/2" closer than the driver side. So I must assume the offset is correct. Take a look at how close the manifold is to the steering box. Is the manifold deformed? This has me stumped.
Thanks
Lawrence

[Mike S]

Can you see the casting number on the drivers side exhaust manifold? I believe it should be 3909879 if my memory is correct. That has a recess to clear the steering box. I'm assuming the steering box is not loose on the chassis.
Mike

[HawkX66]

Did you measure the height of your engine mounts? You said you confirmed they're the correct frame stands too right? I have headers and even they aren't that close.

[BSMIT59]

Crazy question but could the steering box be incorrect? Are castinings different for manual v power? Z28 v SS or standard shift v auto?

[sixt9x33rs]

Did you measure the height of your engine mounts? You said you confirmed they're the correct frame stands too right? I have headers and even they aren't that close.

I bought the listed motor mounts from NPD. I assume they are right?

[sixt9x33rs]

Crazy question but could the steering box be incorrect? Are castinings different for manual v power? Z28 v SS or standard shift v auto?

Casting number is correct and the assembly date of the steering box matches the build of the car?

[sixt9x33rs]

Here is a picture from the top side showing the manifold and the steering box.

[Mike S]

 Two questions:
1- "....but still have this annoying bumping of the manifold on the ps box."
   Judging from the above comment I assume this always occurred?

2- Does the fan look centered (Horz. and Vert.) inside the shroud or does it look off to one side.

Mike