4" downpipe in an OBS

[JD3020]

Who here has actually put a 4" downpipe in an OBS? I'm looking for some pics on where to clearance the firewall to fit one without a body lift. This is how the truck currently sits, and i'm hoping to start putting it together in the next couple weeks so i need to get something done while its apart.

http://www.snowmobilefanatics.com/f...6_10203808077424838_5753421231780735960_n.jpg

Next question, does anybody make/sell a 4" downpipe? Or could i use the 4" DP out of my SD parts truck?

 

[ghohouston]

If you google it, there has been quite a few people who pulled it off. I researched it a while back, and looks like a good bit of cutting into the firewall.

 

[Magnum PD]

I'm having fun just getting a 3" in. Recommend a body lift.

 

[ghohouston]

The 3" down pipes I've installed weren't all that bad, but it also depends how far back the motor sits. He said he did t want to lift the body, so he will have to cut a large section of firewall/floor out, and then weld patches back in.

 

[Magnum PD]

Oval pipes are available.

 

[JD3020]

Do you happen to have any links or remember where you saw some posts? Currently on my phone so googling stuff is a bit of a challenge.


I do know in the past i've read where guys have cut out a large section of the firewall and welded in a piece of pipe to create a tunnel, but i don't think i've seen any pictures. Hell i don't even remember where i read that, and i couldn't find it the other night.

 

[ghohouston]

Send me a phone number and ill text you pics. I don't wanna hassle with uploading them. I saved two pics I found clearly showing the firewall mods...

 

[StrokerGuy86]

your truck looks like my twin i could of used alot of part haha. But a 4 inch will require tunneling you fire wall some. I have had some 3 inch pipes go in pretty easy. A 4 could be a little pain but very doable

 

[old man dave]

GTS used 5" exhaust pipe to form the tunnel for his 4" downpipe. He said it worked out pretty well.

 

[Bair]

Yeah I cut out a section of firewall on mine. Then semi flattened a 6" pipe to weld over the opening to clear a 4" down pipe. And my truck has a 2" body lift. Yeah it's tight.

 

[superduty4x4]

Jimmy, send a PM to strokersace, he did this a while back and he said the juice wasn't worth the squeeze in the end.

 

[Pwnm30rdi3]

If you did compounds you could get a 4" pipe to fit with ease! oke:

 

[golfer]

Who here has actually put a 4" downpipe in an OBS? I'm looking for some pics on where to clearance the firewall to fit one without a body lift. This is how the truck currently sits, and i'm hoping to start putting it together in the next couple weeks so i need to get something done while its apart.

Next question, does anybody make/sell a 4" downpipe? Or could i use the 4" DP out of my SD parts truck?

definitely not worth the effort and cab mutilation.

our 97 drag truck went 10's with a 3" DP and two mufflers, LOL...(truck was a sleeeeeeeper)

 

[Obsledpuller]

I agree with Dave here the time/cost to mod the firewall far outweighs the benefit. Unless it's one of those things you just WANT.

 

[Strokersace]

I've done it. Cool factor is there just to say I can use a 4" SD downpipe. But DEFINITELY not worth the time, effort, and fabrication!!! Do not, I repeat, DO NOT waste your time! Unless you just want to say you did it.

 

[JD3020]

definitely not worth the effort and cab mutilation.

our 97 drag truck went 10's with a 3" DP and two mufflers, LOL...(truck was a sleeeeeeeper)

That right there is enough proof for me!


Couldn't care less about the cool factor, goal for this truck is a clean 5-600hp sleeper. Figured that since the engine and everything is out it may be worth it. But if that truck is running a 3" DP without an issue i won't dick with it. But i'll still clearance the firewall so a 3" will actually fit in the damn engine bay. Plus do a little massaging up top so the 468 will clear good.

 

[m j]

very little to make the 468 fit
the downpipe for it is pretty major damage though
my truck had a 3" downpipe from the previous owner and I had to rape it a lot more to get the Irate downpipe to fit
best to add a section to the irate piece and have the clamp in an easy to work on spot

 

[Wayne]

I bet you could fit a 3.5" pipe by just stretching the firewall, and do a bit of extra work at the pinch weld. That might be worth the effort. I know with the work I did on my '84 bronco with the '97 7.3l conversion I could have fit one. I got aggressive as I could without tearing the metal, but tore it a bit at the pinch weld. I just filled the hole, and put some primer on it. Of course it wasn't a show truck though.