Big Block Headers in a 4x4 Blazer

[Brandoneh]

Been reading up on a lot of threads and was hoping to bring out some fellas that might have not come up on the search feature.

I'm looking at putting a set of bbc headers in a 71 Blazer. It would be nice to have a thread devoted to what works and what doesn't. For me and future generations as well!

I'll put down what I've found.

Hooker Headers #520-2841
# Super Comp Headers1968-87 1/2, 3/4, 1-Ton Trucks; 1968-91 Blazer, Yukon, Jimmy, Suburban, Crew Cab BBC 396-502
# 2" x 35" Primary Tubes
# 3-1/2" Collector
(brandoneh)
"Pipes ran right into the shackle and also leaf springs on both sides. Also some major frame notching would be required"
----------------------------

(from AJ72's build)
Hooker 2455's
Hooker Headers #520-2455
# Competition Headers1970-72 Camaro; 1970-74 Monte Carlo; 1964-74 Chevelle, El Camino, Sprint, Caballero; 1971-74 Full Size 396-502
# 2" x 30" Primary Tubes
# 3-1/2" Collector
# High Temp Black Paint (Summit part# 2455HKR)

"The passenger side...not so good. The number 6 tube is hitting the shackle. The number 8 tube within a milllimeter or two of the firewall. Worst of all, the collector flange is not playing nice with the clocked up transfer case. This header is going to require a bunch of rework."
----------------------------

Hedman 69130
Hedman #500-69130
2WD
1/2-3/4 ton P/U 1968-87,
Blazer/K-5,
Jimmy/K-5,
Suburban,
1968-91,
396-502ci.,
2'' Tubes, 3'' Collector
(from AJ72's build)
"I figured while I was at it, I'd try out a different set of headers. These are Hedman 69130's. 2" primaries, with a 3" collector. They fit a whooooole lot better. The passenger side even clears the front driveshaft with the clocked up xfer case. I may try to coerce it for a bit more clearance, but I'm at least in a better starting point."
"While the fit of the Hedman 69130's may have been a bit better, I decided to send them back. Quality just didn't feel as good as the Hooker's. Header flange was 1/4" and subject to warping. And the tube material was a lighter gauge of steel."
----------------------------

Sanderson’s C6 header C7 header
(BB)
" I used a “set” of big block headers from Sanderson’s in So. San Francisco,(www.sandersonheaders.com) due to some clearance issues you can see in the photos I ended up with their 55-up Chevy pickup C6 header for the driver side, and their 68-up Chevy full size car C7 header on the passenger side. I had to cut the upper frame rail on both sides a little for clearance. If you look close on the photos you can see the black marker layout lines where I cut the frame.
I used the DIY big block motor mount kit. I moved the engine mount forward in the frame to the unused GM factory drilled holes on the driver side frame rail. If memory serves they are approx. 2.375” forward of the original mount location. I installed a GM serpentine belt kit and my crank pulley only has about a half inch of clearance behind the front cross member.
I haven’t put the tub on the chassis yet so I’m not sure if I have any valve cover clearance issues at the firewall."
----------------------------

Thorley 304Y
Header Style Tri-Y
Header Material Steel
Header Finish Nickel chrome plated
Primary Tube Diameter (in) 1 3/4 in.
Collector Attachment 3-bolt flange
Collector Diameter 2.500 in.
Tuned No
Primary Tube Gauge 14-gauge
Flange Style Standard
Flange Thickness (in) 3/8 in.
(Greg72)
"My 396 bolted right up....
Thorley 304Y headers fit fine too. Check my gallery pics"
"The collector flange is a bit "off" on the passenger side, so you either need to cut and re-weld it for a more straight shot down the framerail, or you need to put a rather odd kink in the exhaust tubing to straighten things out.

Passenger side framerail needs a small amount of clearancing on the top to provide adequate clearance for the middle header tubes. I'm talking around 1/4" of material off the upper "C" of the framerail...not too bad, but not a true bolt-on either."

(Burt4x4)
"They don't fit as well as other headers, pass side is way high and tight to the frame and the diver side is way low waiting to get SMACKED by a rock er somtin..

The Tri-Y design is only good for RPM levels upto 4500-5000..after that the power falls on it's face..I had my K5 dyno tested and tuned so I have the graph the shows the drop off.
For me the power gains at low RPM are worth it..I built my K5 for low RPM stump pulling power"
----------------------------

Hooker Headers #520-2817
# Super Comp Headers1983-87 1/2, 3/4, & 1-Ton; 1983-91 Blazer, Carryall, Jimmy Yukon, Suburban, 1-Ton Crew Cab, Tahoe 2-dr 4WD Trucks BBC 396-502
# 1-7/8" x 31" Primary Tubes
# 3" Collectors
# High Temp Black Paint
(brandoneh)"Headers look to fit real good. I did need the engine raised with kert's DIY4X crossmember. He lengthened the motor mounts. More pics on my build thread. You can see pics of the fitment here http://coloradok5.com/forums/showpos...1&postcount=54


Hope some others can "ADD/EDIT" to the list. It would nice to have a good index of information when looking into purchasing headers.