Underbody Exhaust Help...ERA 427 Street

[mickmate]

Originals used an oval muffler. Greg that's sweet with the tailpipes. I prefer the look and sound of that from inside it to the rear wheel side exits.

[mdross1]

Sure does look good.Those mufflers look like the Stainless Specialties mufflers on our car except they are under the driver and pass floor.

[427 Street]

From a friend and Cobra expert...he wrote a few books on the subject Make sure to wrap the tail pipes with header wrap where they go up and over the axles. I've seen a few original cars catch on fire from them when they aren't wrapped- ignites the fiberglass trunk pan. Also heats the living heck out of the tires, wheel bearings and brakes, etc. The more heat you can keep out of the wheelwell the better.

[my427cobra]

Thanks Mickmate. I went wth the mufflers under the rear quarters for a little extra ground clearance.

Yup mdross1, you're right. They are Stainless Specialties mufflers, 4" OD, 2 1/2" inlet/outlet. Drilled an additional 1 1/2'' hole in each end of the baffle to increase the flow though.

You make a good point about the heat factor, 427 Street. I am at least 4" from any fiberglass. 6" from any axle components and about 4" of tire clearance. I am using the Sunburst wheels with 255 BFG's on the rear so I have good tire to exhaust pipe clearance. I think I'm OK but I may bond some foil faced DEI insulation in a couple of places just in case. I'm not a fan of wraps.

And after living for years with sidepipes, the noise is just as loud but out the back is just fine for me.

Must be getting old!!!!!!!!

Greg

[Rare Iron]

Originally Posted by 427 Street

From a friend and Cobra expert...he wrote a few books on the subject Make sure to wrap the tail pipes with header wrap where they go up and over the axles. I've seen a few original cars catch on fire from them when they aren't wrapped- ignites the fiberglass trunk pan. Also heats the living heck out of the tires, wheel bearings and brakes, etc. The more heat you can keep out of the wheelwell the better.

IGNITE a fiberglass trunk pan? I have NEVER been able to burn fiberglass. Wrapping an exhaust pipe or header primary with heat wrap causes premature metal fatigue because it does not allow the pipes to cool down, plus it promotes rust bigtime.

[mdross1]

Originally Posted by my427cobra

Thanks Mickmate. I went wth the mufflers under the rear quarters for a little extra ground clearance.

Yup mdross1, you're right. They are Stainless Specialties mufflers, 4" OD, 2 1/2" inlet/outlet. Drilled an additional 1 1/2'' hole in each end of the baffle to increase the flow though.

You make a good point about the heat factor, 427 Street. I am at least 4" from any fiberglass. 6" from any axle components and about 4" of tire clearance. I am using the Sunburst wheels with 255 BFG's on the rear so I have good tire to exhaust pipe clearance. I think I'm OK but I may bond some foil faced DEI insulation in a couple of places just in case. I'm not a fan of wraps.

And after living for years with sidepipes, the noise is just as loud but out the back is just fine for me.

Must be getting old!!!!!!!!

Greg

Mine sound so good out the tailpipes that go straight out the back under the 9" do not dare mess with them.Your right about the side exhaust had a big block Vette when on road trips eventually produced headaches.Out the back sounds just right inside and out.Old? guess it is part of it.
Also run Stainless Specialties on all our motorcycles truly enjoy their quality and working with them.
Mike

[DanEC]

Originally Posted by my427cobra

/2'' hole in each end of the baffle to increase the flow though.

You make a good point about the heat factor, 427 Street. I am at least 4" from any fiberglass. 6" from any axle components and about 4" of tire clearance. I am using the Sunburst wheels with 255 BFG's on the rear so I have good tire to exhaust pipe clearance. I think I'm OK but I may bond some foil faced DEI insulation in a couple of places just in case. I'm not a fan of wraps.



Greg

Wow - 4 inches clearance to the tires! I'm running the same size tire but on a wider rim. With 2-1/2 inch tailpipes I have about 3/4 inch to the tire and 1/2 inch to the trunk box aluminum panel on my ERA. I am going to wrap that section of my pipes. I'm hoping that with the lower operating temperatures at the tailpipes that I won't have the severe metal corrosion issues with the wrapping. The NAF must have narrower spacing between the rear frame rails than an ERA to get that much tire clearance.

[my427cobra]

Hi DanEC. Took and actual measurement this morning and I have 3 1/4" of clearance between the exhaust pipe and inside of the rear tire.

I have always believed (an eyeball guess) that the NAF body had slightly more rear hip
(flared fenders) than most other replicas. Kind of a cross between the original wide hip and narrow hip bodies. My total outside dimension of the rear fender lips is 68".

My rear frame rails have a 35" outside width dimension.

My rear axle is 54 3/4" wheel mounting surface to wheel mounting surface.

Could be your rear wheel width and offset are very different than my original Sunburst wheels.

Greg

[DanEC]

Originally Posted by my427cobra

Hi DanEC. Took and actual measurement this morning and I have 3 1/4" of clearance between the exhaust pipe and inside of the rear tire.

I have always believed (an eyeball guess) that the NAF body had slightly more rear hip
(flared fenders) than most other replicas. Kind of a cross between the original wide hip and narrow hip bodies. My total outside dimension of the rear fender lips is 68".

My rear frame rails have a 35" outside width dimension.

My rear axle is 54 3/4" wheel mounting surface to wheel mounting surface.

Could be your rear wheel width and offset are very different than my original Sunburst wheels.

Greg

Greg - the ERA dimension from wheel mount surface to wheel mount surface is 53.64 inches. I will have to crawl under it to measure the frame outside dimension but I suspect it is more than 35 inches. I actually chose to go with the 9-1/2 inch wheel since the extra width over the 7-1/2 inch wheels (as set up for an ERA) is all, or mostly to the outside, which tends to place the tire thread and inner sidewall further to the outside. With 7-1/2 inch wheels I probably could not have fit a 2-1/2 inch tailpipe.

ERA does have an option for a slightly wider track in the rear for those who want to run 7-1/2 inch wheels in the rear but don't want the sunken into the wheel wells look that the wide hip body results in.

You have a nice set up. I have my exhaust system back from the ceraimic coating place and I hope to get it hung in the near future.

[my427cobra]

Hi DanEC. Look forward to seeing your exhaust set-up once it's installed. Attached is a pic showing how my tires fit the wheelwells.

Greg

[mickmate]

If you look at side pipes they run 3/4-1" away from painted fiberglass. Headers run 1/4-3/8" away from glass foot boxes on some cars. I wouldn't be too worried about a big air gap, especially as it gets further from the motor. Couple of pics attached. I have the street car fiberglass exhaust loop covers if you need them. You can see them here and in the attached pic. Spare Tray/Wheel Well 427 Trunk [] - - It's Free! : Acton Custom Enterprises, Custom Metal for Cobras

[DanEC]

Jeeez - Nick, I hate to be dense but I'm not seeing the fiberglass heat shields - if that is what the exhaust loop covers are? The catalog attachment is for a fiberglass trunk floor tire tub. I may not understand what I'm suppose to be seeing.

I agree about clearances. My 427 sidepipe Corvette has oversize chambered pipes and probably only have about 3/8 inch clearance max to the side pipe cover fiberglass heat shields. Yes the door sills get very warm and the aluminum covers are a little warm but no problems with the effects of the heat on the fiberglass shields.

[mickmate]

If you look at the two black pieces in front of the trunk floor you will see those covers. It is a rectangular cutout in the trunk sides that has the cover over the top of the exhaust loop.

[DanEC]

OK - those are kind of hard to spot. I noticed in this series of photos of a restored 67 Street Cobra, the rear wheel shot appears to show a similar shield on the front of the exhaust pipe loop over.

1967 Shelby Cobra 427

[mickmate]

You got it, this shot shows them on the insides of the trunk.

[redmt]

Nick, I don't see a price listed for the trunk conversion. Does it interfere at all with the fuel tank?

[my427cobra]

WOW. Those Canepa restoration pics are some of the best I have ever seen. A treasure trove of visual information for the resoration junkies. Thanks for posting them.
But I can't seem to "save" the pics. Are they protected somehow?

Greg

[mickmate]

John that is currently for the CSX frame, working on a CCX trunk for those with the intestinal fortitude to cut their trunk out.
Greg you can use Ctrl,Alt,Printscreen then paste it into paint and save it in whatever format you like. There is also a little download program called Zapgrab

[redmt]

Nick, I'm actually kind of glad to hear that. You have so many killer ideas that I can't wait until I win the lottery.

[my427cobra]

Related to other posts about the jack, grease gun and tool kit: great pics of the jack and grease guns and their mounts.

Greg