Trimming Painted Body Advice

[Doc76]

When I really “get on” my Mk4 the Driver side pipe rubs the body.

Can anyone provide best advise how to trim my painted body around the top of my drivers side pipe that will be least destructive to the paint job?

I am aware anyway I do this I will see red fiber glass but just wondering if anyone can provide “best practice” advice.

[Dave M]

I would look into some stiffer motor mounts before I started cutting on a finished body.

[JohnK]

This could also be addressed with new headers that have ball-flange collectors which will give a bit of adjustability, and/or some wedges.

[Nigel Allen]

As others have said, fix the pipes, not the body.
Perhaps take it to your local exhaust specialist?

[Doc76]

This could also be addressed with new headers that have ball-flange collectors which will give a bit of adjustability, and/or some wedges.

The flanges are too close to the body already. Wedges won’t do anything.

[Doc76]

I would look into some stiffer motor mounts before I started cutting on a finished body.

I like this suggestion.
I’ll be pulling the motor in a year or two but until then like to just address this.
Any suggestions on motor mount types and/or sources?

[Doc76]

I would look into some stiffer motor mounts before I started cutting on a finished body.

Any suggestions on type and source for stiffer mounts?

[CraigS]

I'd try rocking the engine first. If there are sidepipe hangers remove the bolts to the frame. Really loosen the big nuts under the motor mounts. Loosen the bolts to the engine block and at the top of the mount. Jack the passenger side side pipe up as far as you can w/o it touching the body. If the engine doesn't move, remove the passenger side pipe and rig a wood block to jack at the end of the header just inside the body. I have also found a 4-5ft piece of pipe that will fit into one of the header tubes to use as a long lever. Sometimes this gets you some movement because you can jerk on it vs a steady pressure from a jack. If you don't get any movement, loosen the passenger side bolts to the block and stick a few washers between block and mount adapter. You may be surprised at how much this will lower the driver side. Finally, if you have to grind on the body, get a drum sander close to the diameter of the header tubes remove the driver side pipe.
https://www.homedepot.com/p/POWERTEC-2-1-2-in-L-Drill-Press-Sanding-Drum-Kit-with-1-4-and-1-8-Shanks-Spindle-Sander-Sleeves-Tool-Carrying-Case-20-Piece-71634/319322368?mtc=SHOPPING-BF-CDP-BNG-D25P-025_007_POWER_TOOL_ACCESSORIES-NA-Multi-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-PowerToolAccessories_2023&cm_mmc=SHOPPING-BF-CDP-BNG-D25P-025_007_POWER_TOOL_ACCESSORIES-NA-Multi-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-PowerToolAccessories_2023-71700000106432959-58700008273440514-92700079460122533&msclkid=344e8ca7e7e5135ebaa4ea4bf72bd003&gclid=344e8ca7e7e5135ebaa4ea4bf72bd003&gclsrc=3p.ds
Jack driver side of the car and get your self in a real comfortable position probably sitting on the floor so you can control your drill. Hold it so 90% of the drum is inside the fender so if it slips it will go up inside vs across your paint. Also hold it w/ the drill down/sand drum up at maybe 30-45 deg so you take off more fiberglass inside than outside. Finally go slow, real slow, and pause frequently so you do not warm the fiberglass and mess up the paint. If done right you may not even need to touch up the edge but 2-3 coats from a touchup stick will do the job if needed.

[egchewy79]

Any suggestions on type and source for stiffer mounts?

Energy suspension polyurethane mounts are what comes with the MK4 kits

[Doc76]

I'd try rocking the engine first. If there are sidepipe hangers remove the bolts to the frame. Really loosen the big nuts under the motor mounts. Loosen the bolts to the engine block and at the top of the mount. Jack the passenger side side pipe up as far as you can w/o it touching the body. If the engine doesn't move, remove the passenger side pipe and rig a wood block to jack at the end of the header just inside the body. I have also found a 4-5ft piece of pipe that will fit into one of the header tubes to use as a long lever. Sometimes this gets you some movement because you can jerk on it vs a steady pressure from a jack. If you don't get any movement, loosen the passenger side bolts to the block and stick a few washers between block and mount adapter. You may be surprised at how much this will lower the driver side. Finally, if you have to grind on the body, get a drum sander close to the diameter of the header tubes remove the driver side pipe.
https://www.homedepot.com/p/POWERTEC-2-1-2-in-L-Drill-Press-Sanding-Drum-Kit-with-1-4-and-1-8-Shanks-Spindle-Sander-Sleeves-Tool-Carrying-Case-20-Piece-71634/319322368?mtc=SHOPPING-BF-CDP-BNG-D25P-025_007_POWER_TOOL_ACCESSORIES-NA-Multi-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-PowerToolAccessories_2023&cm_mmc=SHOPPING-BF-CDP-BNG-D25P-025_007_POWER_TOOL_ACCESSORIES-NA-Multi-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-PowerToolAccessories_2023-71700000106432959-58700008273440514-92700079460122533&msclkid=344e8ca7e7e5135ebaa4ea4bf72bd003&gclid=344e8ca7e7e5135ebaa4ea4bf72bd003&gclsrc=3p.ds
Jack driver side of the car and get your self in a real comfortable position probably sitting on the floor so you can control your drill. Hold it so 90% of the drum is inside the fender so if it slips it will go up inside vs across your paint. Also hold it w/ the drill down/sand drum up at maybe 30-45 deg so you take off more fiberglass inside than outside. Finally go slow, real slow, and pause frequently so you do not warm the fiberglass and mess up the paint. If done right you may not even need to touch up the edge but 2-3 coats from a touchup stick will do the job if needed.

Thanks for taking the time for this direction. I did try to jack the motor on the passenger side. I put a 1/8” shim in there which seemed to make no difference at all. I was rather surprised .
I think I’ll replace the rubber motor mounts with new polyurethane mounts next.
It is rather weird and maybe the nature of these builds but the body is cut even side to side for the pipe holes and I have a ~5/8-3/4” gap above the passenger side pipe between the body and the pipe tube at its top. The drivers side has only a 1/4” at best.
The motor is sitting centered and quite level to the chassis.

They’re the BBK headers from FFR kit to the FFR pipes.
I wonder if I got a bad drivers side header that was just ever so slightly off kilter?

[rich grsc]

If your pipes move enough that they hit the body, the motor mount is likely broken. Replace both, 1993 Mustang convertible mounts.

[Doc76]

If your pipes move enough that they hit the body, the motor mount is likely broken. Replace both, 1993 Mustang convertible mounts.

Ok thanks Rich
Ya I think this’ll be my next move

[ggunter]

When I changed from a 347 to 427 the 347 headers from FFR fit perfectly. The FFR headers for the 427 did not come close to fitting at all. Had I cut the body to make them fit the side body holes would have been almost 2" higher. I ended up pie cutting the header just before the bell bending it down towards the current opening and having them rewelded. I still had to trim the body about 5/8" with a carbide bit and I had some leftover primer and paint and was able to cover the raw edge of the fiberglass. I have a finger width around the headers on both sides. It turned out well.

[Doc76]

When I changed from a 347 to 427 the 347 headers from FFR fit perfectly. The FFR headers for the 427 did not come close to fitting at all. Had I cut the body to make them fit the side body holes would have been almost 2" higher. I ended up pie cutting the header just before the bell bending it down towards the current opening and having them rewelded. I still had to trim the body about 5/8" with a carbide bit and I had some leftover primer and paint and was able to cover the raw edge of the fiberglass. I have a finger width around the headers on both sides. It turned out well.

Thanks for this.
I sent you a pm to you hoping to learn more about your swap experience

[Jeff Kleiner]

Looks like you should have plenty of clearance if it has poly mounts. Rubber mounts, like the Fox convertible ones, will allow more movement. If you don't already have the polys changing to them will probably make all the difference. As for trimming the openings after paint I have done it numerous times: put two layers of painter's tape on the body and then enlarge the opening by working carefully using a 1 1/2" drum sander in a pneumatic die grinder (or drill if you don't have the die grinder). You're only taking material from the edge of the opening, not the painted surface. Afterwards put color or black on the raw edge with a touch up dauber.

Jeff

[Doc76]

Looks like you should have plenty of clearance if it has poly mounts. Rubber mounts, like the Fox convertible ones, will allow more movement. If you don't already have the polys changing to them will probably make all the difference. As for trimming the openings after paint I have done it numerous times: put two layers of painter's tape on the body and then enlarge the opening by working carefully using a 1 1/2" drum sander in a pneumatic die grinder (or drill if you don't have the die grinder). You're only taking material from the edge of the opening, not the painted surface. Afterwards put color or black on the raw edge with a touch up dauber.

Jeff
Thanks Jeff
I have a feeling the mounts are rubber (builder can’t remember what he bought from Rockauto so probably rubber)
FFR can’t confirm a cross over mount kit to their kit that is out of stock nor can they tell me when they’ll get more.
From my homework it appears it would be the Energy Suspensions 4.1124G (fitment for ‘93 Mustang)
Given our local policy is no-returns on this type of product, can you or anyone confirm this is the correct part number to order?

[Jeff Kleiner]

That is correct.

Jeff

[rich grsc]

Not sure if they are worth $200 more than a set of 93 convertible mounts?

[Doc76]

Not sure if they are worth $200 more than a set of 93 convertible mounts?

I’m not sure. Are the polyurethane stiffer than rubber?
I’m told the poly are “superior” for longevity but not sure it they’re stiffer.

[Jeff Kleiner]

I’m not sure. Are the polyurethane stiffer than rubber?
I

They are. The engine will move less. Since your pipes are coming into contact with the body when the engine is loaded heavily that may solve the issue.

Jeff

[Dave M]

When you’re changing the mounts it will be easier to reposition the motor to maybe gain a bit more clearance.

[Doc76]

Thank you for all your feedback
Very much appreciated

[Doc76]

They are. The engine will move less. Since your pipes are coming into contact with the body when the engine is loaded heavily that may solve the issue.

Jeff

Jeff would you recommend it to be good practice of changing the tranny mount at the same time?
Looks like the kit is available with and without the tranny mount.

[Jeff Kleiner]

Jeff would you recommend it to be good practice of changing the tranny mount at the same time?
Looks like the kit is available with and without the tranny mount.

It's best to keep the material matching; poly with poly, rubber with rubber.

Jeff

[Doc76]

It's best to keep the material matching; poly with poly, rubber with rubber.

Jeff

Ok thank you
I’ve got the kit coming.
Curious if you’ve experienced the these mounts in regards to height.
Seems to be some guys online in the reviews (of the kit) stated these mounts were taller than stock mounts and caused their motor to be raised. This looks like it caused everything from driveline angle issue to hood clearance issues. Given I am trying to reduce my pipe flex to avoid driver side hitting the body, increasing height would cause more issues.
Have you experienced these mounts raising the motor?

[steno]

I had new factory replacement rubber mounts and had the pipe hit the body. Changed over to the poly mounts and that never happened again!

[Jeff Kleiner]

Energy Suspension mounts set the engine to the same height as OEM convertible mounts. Prothane mounts put the engine same as the higher OEM Coupe (hardtop) mounts.

Jeff

[Doc76]

Energy Suspension mounts set the engine to the same height as OEM convertible mounts. Prothane mounts put the engine same as the higher OEM Coupe (hardtop) mounts.

Jeff

In your experience is that height difference measurable (Energy vs Prothane)?
Given the application we are talking about is in a Cobra and not a Mustang and the issue is clearance, raising the motor using mounts that are taller would be counter productive.
I have the Energy Suspension on order already per your recommendation here.
Neither Energy Suspension nor Prothane post the dimensions of their mounts online that I can find.
The rubber Rock Auto 2726 mounts I have appear to be closer to the Prothane according to verbiage on the internet. If in fact the Energy 4.1124 is taller, do you know by how much?
A mount that is +1/8” I could live with as this would hardly raise the overall height more than ~1/16” but according to the internet they could vary 1/4-1/2”.

So again, given maintaining clearance on the body (along with stiffening up the mounts) vs pipe is the objective, going up in mount position would be counter productive.
Thanks in advance

[Doc76]

Steno What did you change them to?