Do square body 454 headers fit?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
Hey dudes. I’m in the middle of swapping a Gen VI 454 into my 95 454 2500 NV4500 4x4. The new engine will have no EGR or anything like that. One 02 sensor for the Holley sniper. I’m waiting on the cam and valve springs since it’s apparently on back order for another month. I’m considering going with headers while I’ve got everything apart. I don’t want to spend 500+ on headers though. I see 454 headers on JEGS for less than 200 bucks that are advertised to fit a square body 4x4 big block truck. I know the bolt pattern is the same. I’m not concerned about the port, I’ll port them to match if they don’t. I just want to know if they fit the chassis. Given how much cheaper they are than GMT400 headers, I’m sure somebody has tried it. Can anybody weigh in here? Thanks


Sent from my iPhone using Tapatalk
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,612
Reaction score
15,233
I'll speculate that they don't because IFS vs solid axle. Also, I believe the driveshaft runs on the opposite side? I'll sit back now and wait for others to chime in.
 

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
I'll speculate that they don't because IFS vs solid axle. Also, I believe the driveshaft runs on the opposite side? I'll sit back now and wait for others to chime in.

The IFS vs SAS is certainly a potential issue. I thought the front driveshaft was on the drivers side as well on square bodies but I’m not sure. I’m okay with some minor modifications to fit because I am a welder by trade


Sent from my iPhone using Tapatalk
 

ZRoe

I'm Awesome
Joined
May 7, 2018
Messages
139
Reaction score
89
Location
US
The IFS differences near the motor should be outside the frame rails, but I don't know the frame rail width difference between the IFS and SAS trucks.
The torsion bar bracket for the IFS could be and issue further back where the collectors end up.
If somebody could measure the frame rails on a square body truck we might have a better idea how they would fit.
I know the P30 motorhome headers won't fit between the GMT400 framerails but motorhome frames are much wider I believe.

The other issue with GMT 400 4x4 trucks and headers is the oil filter mounted horizontally coming out the side of the block in order to clear the front driveshaft. My truck is lifted so I was able to swap back to a vertical filter mount and still cleary front driveshaft.
A remote mount filter block could achieve the same thing for you.

Sent from my moto g stylus using Tapatalk
 

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
The IFS differences near the motor should be outside the frame rails, but I don't know the frame rail width difference between the IFS and SAS trucks.
The torsion bar bracket for the IFS could be and issue further back where the collectors end up.
If somebody could measure the frame rails on a square body truck we might have a better idea how they would fit.
I know the P30 motorhome headers won't fit between the GMT400 framerails but motorhome frames are much wider I believe.

The other issue with GMT 400 4x4 trucks and headers is the oil filter mounted horizontally coming out the side of the block in order to clear the front driveshaft. My truck is lifted so I was able to swap back to a vertical filter mount and still cleary front driveshaft.
A remote mount filter block could achieve the same thing for you.

Sent from my moto g stylus using Tapatalk

I’m probably going to do something with the filter regardless because I can’t stand the horizontal filter making a mess of everything during oil changes. Yea I know you can poke a hole in it to let it drain but still, it’s kinda ridiculous for any oil filter to not be vertical IMO


Sent from my iPhone using Tapatalk
 

yevgenievich

I'm Awesome
Joined
Jan 21, 2021
Messages
934
Reaction score
1,505
Location
TX
Gmt400 headers fits on a square with slight frame rail notch on passenger side(or dinging the tubes). Square frame is narrower, so might be a good chance it would fit, except the driver side oil filter on 4x4 as mentioned. Drive shaft on squares is passenger side, so header might not work nicely with driver side drive shaft.
 

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
Gmt400 headers fits on a square with slight frame rail notch on passenger side(or dinging the tubes). Square frame is narrower, so might be a good chance it would fit, except the driver side oil filter on 4x4 as mentioned. Drive shaft on squares is passenger side, so header might not work nicely with driver side drive shaft.

Thank you for that information. I think I’m gonna order them and see what happens. I’m sure I can make them work even if I have to modify a couple runners or something


Sent from my iPhone using Tapatalk
 

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
I went ahead and ordered them guys. I’ll try to remember to update this thread with info on how they fit and everything. 150 bucks shipped for 16ga 1 3/4” primary 3” collectors, gaskets, and 3/8” flanges is a good deal even if I have to modify them a good bit. Between the oil filter relocation and dropping the front diff 5” for the lift which gets the driveshaft out of the way, I don’t think I’ll have many, if any issues.


Sent from my iPhone using Tapatalk
 

Chillin Dylan

OBS Enthusiast
Joined
Oct 15, 2019
Messages
96
Reaction score
32
Location
Williamsburg OH
Any updates? I'm trying to find 1 7/8 to 2in diameter headers and they do t offer any for the obs

I’m still waiting on the cam and valve springs. Apparently comp is out of the blanks until the 31st. I can say that the flanges line up. A couple of the head bolts touch the flange, but that’s easily solved with a few seconds and a grinder. The drivers side does hit the oil filter with the factory 90 degree adapter, but don’t with the filter vertical. The passenger side clears the starter plenty fine. I don’t think the frame will be an issue but I can’t say for sure yet. The cheap cheap price makes them worth it IMO


Sent from my iPhone using Tapatalk
 
Top