351 swap headers+ exhaust questions

[Brown_Muscle]

Gotcha! Summit has a large variety of hangers i may be able to bolt to the trans crossmember...i'll have to see. The last thing i want is my exhaust scraping anything...we have very large speed bumps around here. I will eagerly await your pictures, thanks!

[Brown_Muscle]

OK! another update post (weee....) I just talked with scott, and he informed me on a few different 351 swap header cars he did the stock 2.25 mustang h-pipe will bolt to them no problem. I'll be going with the chrome headers, walker stock mustang h-pipe (2.25") s-10 mids with adapters to fit in my flowmaster 2.5" mufflers. This new setup saves me around 200 bucks and maybe even the drivability issues johnunit has. Please still post those picture though john! Thanks!

[1987cp]

Sure you don't want the 2.5" midpipes to go with your 2.5" mufflers? Your choice, though.


And yes, Brown_Muscle, that looks like the same pipe. I'd forgotten that Cherry Bomb was a Maremont brand. Odd that it costs $15 more than I paid. Though like I said, I bought mine at Murray's, which isn't anymore, and I guess O'Reilly's, which took over their buildings here, sells only Walker. I think CarQuest sells Maremont, though - I distinctly remember them being unable to turn up a part in their in-store exhaust catalog when all I had was a Walker PN. So I guess you might call CarQuest, AutoValue, or others that don't do online catalogs and see if they can't get you a better price.

[Brown_Muscle]

Would the maremont pipe bolt to the 2.25" h-pipe though? It would make it easier to not have to use an adapter.

[86VickyLX]

OK! another update post (weee....) I just talked with scott, and he informed me on a few different 351 swap header cars he did the stock 2.25 mustang h-pipe will bolt to them no problem. I'll be going with the chrome headers, walker stock mustang h-pipe (2.25") s-10 mids with adapters to fit in my flowmaster 2.5" mufflers. This new setup saves me around 200 bucks and maybe even the drivability issues johnunit has. Please still post those picture though john! Thanks!

I did post pics,
And a fucking video lol. Y u no look at my readers ride thread?

[johnunit]

I think there's some concern that 351s screw up the relation between headers and h-pipe.

[Brown_Muscle]

I don't think it's a problem with the 351 swap headers though, scott says he's done it to a couple cars and had no issues. It appears to tuck better than some systems i've seen as well. Any luck with the pictures?

[johnunit]

I'm not gonna have the pictures tonight it looks like, but will have them over the weekend. Sorry, life intervenes.

[Brown_Muscle]

It's cool i totally understand

[Brown_Muscle]

For those actually interested: "The 7200 VV carburetor was also produces with a feedback stepper motor that controls the main air bleed. The stepper motor controls the pintle movement in the air metering orifice thereby varying the amount of air being metered into the main system discharge area. The greater the amount of air. the leaner the air/fuel mixture. A hole in the upper body casting of the carburetor allows air from beneath the air cleaner to be channeled into the main system discharge area. The metered air lowers the metering signal at the main fuel metering jets."

from:http://www.carkipedia.com/carburetor...arburetors.php

[1987cp]

Would the maremont pipe bolt to the 2.25" h-pipe though? It would make it easier to not have to use an adapter.

Should. With the ball flanges, I don't think it matters much whether it's 2.25" to 2.5" or whatever. I've only done 2.25" mids to 2.5" crossover, but the 2.5" crossover works fine with factory HO manifolds that are intended for a 2.25" crossover.

[johnunit]

well I feel like something of a douchenozzle, because this is monday, not the weekend (or the day after the day I previously promised pics), so to make it up to you here are a metric buttload of pics. That's 1.2 imperial system buttloads, or 3.9 craploads.

Just to clarify, this is a Non-police (that shouldn't matter too much) 351W Crown Victoria with stock heads.
The parts are: BBK 2.5" Catted 79-95 Mustang H-pipe, BBK 1 5/8 Mustang 351W swap headers in chrome with black header paint and grey header wrap, Flowtech 2.5" Mustang "starter tubes" or "extension pipes", a 5 inch or so extension after those, and Thrush Welded (flowmaster 40 knockoff) 18"total length offset/offset mufflers. The only hangers are from the stock location before the rear axle. It is currently dumped right at the mufflers. Overall thoughts are that (ignoring an issue I think is tuning related) it runs hard, sounds beastly, but drowns like a beast at low RPMs, and has the fitment issues detailed below.

Note that there are a few spots where the perception is a bit off, and things look closer together or farther apart or more bent than they actually are, so I'll try to point that out where applicable.

Also note I'm aware it needs rustproofing again, and a few other things. I don't post these as a how-to, just a "here what hasn't totally failed me yet."


As a bonus you can see the 4-5 gallon trail of gasoline my gas tank left on the pavement, part of the "life intervening" excuse from a few posts back.



Below you can see it hangs slightly low, but not too bad. It's sagged slightly over time because of the lack of a hanger for the h-pipe, and will sag more with more driving. The joint between the h-pipe and extensions (seen right in front of the door gap) will be about an inch higher with the h-pipe tucked right up against the trans crossmember. I've not had any issues with scraping over anything, and I don't baby it, but the exhaust is still the lowest point (except perhaps the axle) and that doesn't sit right with me.


another general clearance shot, taken with the camera sitting on the ground pointing up slightly



From the rear you can start to see some of the issues. I have the driver's side muffler up (1 notch on the hanger?) higher than the passenger's, but you can see that means it tilts the whole pipe system downward heading towards the h-pipe from the rear. This results in a slight leak where the bottom part of the ball flanges don't match up, because they don't meet dead straight. The passenger side, obviously, hangs lower at the rear but does not have a leak problem that I've noticed. This could be fixed if the H-pipe were modified or otherwise allowed to point close to upwards once it was past the trans crossmember.




here you can see the downward bend the h-pipe takes right at the cat (directly below the trans crossmember) and the resulting poor match with the extension pipe at the ball flange. This could be shifted around by rotating the extension pipe so that it was slightly straighter, but it never gets perfect. Rotating the extension pipes to an angle at which it's mostly straight with the h-pipe causes other fitment issues. You can see where I've added a length of pipe to the mustang H-pipe so it reaches the mufflers. Keep in mind that these will be different lengths on each side because a mustang H-pipe's ball flanges aren't in the same spot.




Here you can see the upwards kink and then downwards kink the h-pipe takes, and how that results in it hitting on the crossmember right at the front of the cat. There is about a half inch of clearance in this picture, but you can just make out the flattening of the cat heat shield from previously jacking it up as far as I could. Essentially, this picture is THE barrier to these fitting right on these cars. If it was a straight shot from the downpipe portion (about 5 inches to the left of this image) to the cat, with no curving at all, these would fit pretty much dead on. You may also want to have it bent slightly towards the outside of the car to fit in the trans crossmember's hump better. Those are the modifications I would personally make to my H-pipe given a welder and some time. The portion forward of the trans crossmember does hang lower than the oil pan, but not to the extent this image makes it appear. It also appears that the passenger side (background) piping doesn't have these bends to the same extent. I'm not sure you'd even have to modify the passenger side at all to get a 100% happy fit.

In general all the angles in this image look a bit more extreme than they are, but at least that's good for illustrative purposes.



again you can see the bend going into the front of the cat, and the clearance issues resulting.



You can see here that the passenger side is straighter and also nestles better into the trans crossmember's hump/raised section. Also glimpse the wrath of a leaky engine.. err.. I mean automatic undercoating system. In the extreme foreground you can see the (slightly rusted) hanger on the inside of the driver's pipe. This also appears to hit on the crossmember, and I'd recommend taking the time to grind it all the way down basically until it's only about 2/3 of the horrizontal section left, as any vertical section remaining causes interference. Of course in an ideal world you'd have replaced that section of piping with a straigther piece. It's hard to tell what's where in this photo, but the passenger side piping probably has at least 2 inches of clearance upwards.



The downpipe and header are actually nicely located on the driver's side, slightly difficult bolt locations aside. The bar for the trans lever isn't as close to the flange as it looks in this picture



a shot of the passenger side showing just how much clearance you have without the odd kinks of the driver's side. Shortening the downpipe section or making it slightly more horizontal is about the only tweak I could forsee.



I mentioned in a previous post that the flanges are weak junk for the Flowtech stuff. Here you can see that it's just a stamped flat piece. I've switched it (and the home depot hardware) out for something beefier on the driver's side so I can tighten things down for a better seal.



This just sort of shows the generally meandering path the exhaust takes. It also shows how far inward the drivers side pipe is from the center of the trans crossmember hump.





Here you can see how I've cut down the stove pipe to fit the headers. I left about an inch-long strip to still wrap around the header tube, and it had to be cut down on the top to not stick way up above the tube on the inward side. It's secured by two hose clamps, but something better may have been required without the header wrap also securing it. The header paint and wrap are holding up well at this point (6 months or so of use) but I will probably change to allen key header bolts with lockwashers or something along those lines. clearance is tight, especially with the wrap adding some thickness to the tubes. The steering shaft is not overly near any of the pipes, despite appearances.

I don't think the header wrap gained me any power. The local Mustang guru Paul Silva told me specifically not to expect any. It does, however, prevent any heat-related issues as far as HVAC, spark plug wires, knucks (!), and makes it a bit more subtle to a casual eye. Whether that vs. the loss of header warranty, slightly more difficult fitment and installation, and cost is worth it for you is your own choice. I'd to it again personally.





the collector flange is waaay down there. set up your nuts and bolts so that they're best tightened from the bottom (ie the bolt on the header side stays in place while turning the nut on the h-pipe/downpipe side).



here you can see a hose clusterfuck!

Oh yeah, and the headers down there. I cut out one of the lines to the AC compressor, but I'm not sure I couldn't have installed it without doing that. It was just to get the header physically into the general area, no interference when installed obviously. I seem to remember that I wouldn't have needed to if I'd modified the tubing to the smog pump ahead of time, but I'm not sure on that. As mentioned in a previous post you must move the air pump check valve (the rusty thing on the hose right in front of the AC cannister, as the stock position interferes with the header when installed. The modification is pretty self explanatory, cut the tubing below and replace with rubber tubing (in my case all the way to the h-pipe's air tube) and cut the tube to the air pump solenoids shorter so it holds the check valve up higher. In general you'll have to wrestle with hoses and stuff to get it in, but be methodical and use some elbow grease and you'll get it in there.

You can see the spot to attach the passenger side heat stove pipe, which is not currently in use because I have not yet installed the Mustang dual snorkel (thus dual stove pipe) air cleaner that will top the holley carb going on soon. I bought a stove pipe kit from Hedman Headers. It was literally smooth-ended cut of exhaust tubing with a metal strip welded to one end, two hose clamps, and a cheap looking accordian stove pipe tube. That's effing it. For 65 bucks or so. Needless to say I was pissed, and anyone adding a second stove pipe setup should try to fab it up themselves. I am buying a green Prius tomorrow and putting the Hedman sticker that came with this item on it because fuck you Hedman Headers. No, seriously, I am.




a closeup of the relocated check valve. you can also see that there is relatively close clearance between the plastic HVAC "suitcase" and the header. The close clearance and deterioration of the factory heat shielding on the HVAC is one reason for the header wrap.



more close clearance



control arm causes some installation frustration but does not come near hitting once installed



Farmer Smurf because SMURF YEAH



A nice shot of how much the headers actually open things up. the white lines highlight where the manifolds neck down. You can barely stick a finger in there (hold you comments boys) and it's pathetic.




Hope this helps you and anyone who is considering this swap.

[pantera77]

That H-pipe looks just like my non-catted summit one (albeit for a 302 obviously), in how the drivers side kicks down so low. Stupid fox bodies not being panthers.

[johnunit]

Stupid fox bodies not being panthers.

haha, the salient point I suppose.


And I love the simplicity and meanness of the glasspacks and dumps.

[marquisman]

this is why custom is worth it. like said, when i installed the headers on the 5.8L in the lincoln this summer, i had custom pipes bent to the glass packs/tail pipes. dont see a thing and is clean. and no pics till it comes out of stoage next year lol