Header Clearance Issue with Motor Mount

[Papa]

After I got the car started, I found that I had a very obvious exhaust leak. After pulling the driver's side header back off, I can see that it is hitting the motor mount and that is preventing a good flush seal between the header flange and the head. Can anyone offer a recommendation on how best to correct for this? I'm thinking brute force - hammer to the header, or trying to adjust how the motor is sitting on the mounts - possibly shimming between the mount and the block to raise the engine a bit. It doesn't seem like shimming at the frame will get me the clearance I need, but I could be wrong.

Thanks,
Dave

[Boydster]

Papa, I had this exact same issue with the same headers. Turns out I had a set of 302 headers on my 351/427. Once I got the correct headers, clears that motor mount nicely.

[BB767]

My headers were not allowing the spark plug wires to seat correctly. I took a dremel and ground indentations in the edges of the header flange. Could you do something like that or is it a more serious encroachment?

[Papa]

Papa, I had this exact same issue with the same headers. Turns out I had a set of 302 headers on my 351/427. Once I got the correct headers, clears that motor mount nicely.

My block is a 302 block so I don't think it's the wrong part. I'll ask Georgie at Gas-N what he thinks about that.

[Papa]

My headers were not allowing the spark plug wires to seat correctly. I took a dremel and ground indentations in the edges of the header. Could you do something like that or is it a more serious encroachment?

The plugs fit fine. The flanges used to make my headers are CNC machined with the angled opening for the plugs.

[Boydster]

My block is a 302 block so I don't think it's the wrong part. I'll ask Georgie at Gas-N what he thinks about that.

Yeah, I just saw this in your build thread. But I did try 3 different headers that all interfered with the motor mount. I believe another builder in my area had an issue, too, on a 302 based block. Since the ports on my 351 block are higher from the mount than a 302 block, seems toe the issue would have been less with the 351. Anyways, not part of your issue. Continue to work with Georgie.... He's pretty good at making sure he gets it right.

[BB767]

The plugs fit fine. The flanges used to make my headers are CNC machined with the angled opening for the plugs.

I meant could you just grind some indentations to clear your mounts? Was not sure if the clearance problem is in a critical area of the exhaust pipe or just a corner of the flange.

[Papa]

I meant could you just grind some indentations to clear your mounts? Was not sure if the clearance problem is in a critical area of the exhaust pipe or just a corner of the flange.

The issue is about halfway down the pipe where the Sharpie marks are. There is actually a slight indentation on the pipe where it is hitting. This essentially created a gap along the entire bottom edge of the flange with the worst area at hole #1.

I guess a picture would help.



I thought I included the picture with my initial post.

[rich grsc]

Take a hammer to the header, will not affect performance.

[Papa]

Take a hammer to the header, will not affect performance.

That was my initial thought, especially since it's on the back side of the header and won't be visible. I have a good ball-peen hammer that would work to persuade the pipe to a more agreeable shape.

[Lowrod]

Is there any way to adjust the clearance between the header and motor mount by removing material from the motor mount without comprismising the integrity of the mount?

[alv69]

lay a piece of pipe on the header and hit it with a heavy hammer to put a little indentation across the whole pipe.

[Papa]

I talked to Georgie and he said to go ahead and try to hammer the pipes to get them to fit. Even after reshaping the pipe more than I'd like, it still hits the motor mount. The gap at the flange is nearly perfect now, but the two rear-most pipes are still hitting the motor mount.

[CraigS]

I was going to suggest some washers between the mount and the block. Then I went back and read that it is the driver side you are having problems with. That side is also the one that it is common for the headers to be too high in relation to the body. So, I would ask for a new header.

[BB767]

Hey Dave, sorry to hear you are having teething problems also, you've probably seen my posts, I guess misery really does love company. I figure someday this will all make a good story. Looking forward to that drive in the Rockies and the beer afterward, then we'll have a good laugh about all this. Until then, stay thirsty my friend.

[Papa]

Hey Dave, sorry to hear you are having teething problems also, you've probably seen my posts, I guess misery really does love company. I figure someday this will all make a good story. Looking forward to that drive in the Rockies and the beer afterward, then we'll have a good laugh about all this. Until then, stay thirsty my friend.

I look at the exhaust issue as a minor setback that I know Georgie will help me get through. It's just going to take some time with likely some back and forth until we get a working header on the driver's side. I have lots of other things I can work on in the meantime. I'm closely monitoring your pinion angle thread.

Dave