Author Topic: Dual Exhaust and Our Crew Cabs  (Read 4115 times)

Offline ehjorten

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Dual Exhaust and Our Crew Cabs
« on: June 02, 2014, 10:44:47 AM »
This question might not be limited to just our Crew Cabs, but it is definitely related to the 4x4 crowd with 87+ TBI engines.  On the 87+ TBI engines the fuel filter is located on the inside of the RH frame rail, directly across from the transfer case drop.  It is about mid-frame.

This isn't a problem with the stock exhaust because the stock exhaust utilizes cast-iron manifolds and a Y-pipe to the Driver's side, single exhaust.  However, when you move to headers and dual exhaust it becomes a clearance problem!!

My truck is a 1991 V3500 with a TBI454.  I have been having fuel filter issues with this truck because the RH side, 3" exhaust prevents me from having the fuel filter in the stock location.  I have had to loosen the fuel line clamps and move the filter down to clear the exhaust.  The problem with this is that now the fuel filter is wedged between the exhaust and the transfer-case crossmemeber bolts.

This tight filter placement is causing the fuel filter case to crack.  It looks like I have room between the transfer-case drop, the frame rail and the bottom of the cab to tuck-up a better exhaust routing and get the filter back to the stock location.

I am curious if any one else has seen this issue and what they did?  Or...if anyone else has dual exhaust on one of our 4x4 TBI trucks?

I am thinking that I am going to have a totally new, dual exhaust made out of 2-1/2" mandrel bend tubing.  3" is just overkill and makes for loud exhaust.  Something that is not desireable when hunting season comes along.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline pholliday1

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  • 1990 V3500 Crew Cab
Re: Dual Exhaust and Our Crew Cabs
« Reply #1 on: June 02, 2014, 11:42:44 AM »
I like your 2 1/2" idea, my 1990 has manifolds but I cant use the y pipe because of the lift and clearance issues with the front driveshaft. So I used part of the y pipe on the passenger side and fabbed the rest. I went a different direction though, I brought the passenger pipe over to the drivers side by keeping it close to the bell housing and engine oil pan (routed it in between them) then ran the duals back from drivers side one above the cross member and one below. Then to a 2 1/2 y to 3" single pipe to a 3" inlet flowmaster to dual 2/12 output running it behind the rear wheels. the flowmaster and tail pipes and 3" single pipe were existing and new so that's why i went that direction. let me know and I can email you some picts. of the finished products. Also I'm running a np208 and your running a np205.
VETERAN AND LIFETIME NRA MEMBER. WHAT DO YOU STAND FOR?
1991 V3500 CREWCAB SRW 454TBI GMC
1991 v3500 crewcab SRW 454tbi 480le 6" lift
1990 V3500 crewcab Dana 60 FF 14b 5:38 ratio 40 inch 11" lift
1989 v3500 crewcab 454TBI 5" lift

Offline ehjorten

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Re: Dual Exhaust and Our Crew Cabs
« Reply #2 on: June 02, 2014, 12:37:31 PM »
Hey yeah...I was thinking about running the Passenger's side pipe over to the Driver's side!  Great minds think alike!  ;D

I would love to see some pictures of your setup!  Incidentally, My Driver's side pipe goes over the top of the transfer-case crossmember for added clearance and just to keep it tucked away.  I was thinking that the Passenger's side pipe could route over to the Driver's side and actually occupy the stock relief in the crossmember for the exhaust routing under.  I am guessing that this is how your's is routed?!

I would have to change headers to do that however, because from memory right now, I think the header collector is too far rearward to change direction and go in-front of the transfer-case.  I have Doug Thorley Tri-Y (THY-304Y).  They are in okay condition, but not great.  I would like to either send them out to Jet-Hot or get a new set.  Going in-front of the transfer-case might mean shortie headers?!

I am thinking right now that I might take my rig to Stan's Headers in Auburn and have them do a custom 2-1/2" stainless exhaust.  They do really great work!  I might feel them out and see what they think would be best.

Incidentally...this all precipitated from a broken exhaust hanger on the RH side that caused the fuel filter to get cracked really bad!  I had to leave the truck at work overnight because the fuel was spewing out of it!  Changed it out and jerry-rigged the exhaust up in the parking lot after work the next day.
« Last Edit: June 02, 2014, 12:41:13 PM by ehjorten »
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline pholliday1

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  • 1990 V3500 Crew Cab
Re: Dual Exhaust and Our Crew Cabs
« Reply #3 on: June 02, 2014, 03:19:18 PM »
I forgot to add that even though my way "isn't the most free flowing possible" I'm not real keen on the exhaust around the fuel lines. It's design looks more like an after thought. If you'd rathert me to text you the picts email me your number . Paul
VETERAN AND LIFETIME NRA MEMBER. WHAT DO YOU STAND FOR?
1991 V3500 CREWCAB SRW 454TBI GMC
1991 v3500 crewcab SRW 454tbi 480le 6" lift
1990 V3500 crewcab Dana 60 FF 14b 5:38 ratio 40 inch 11" lift
1989 v3500 crewcab 454TBI 5" lift