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"
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(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."
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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."
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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."
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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"
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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.

[CTENTA1]

Some good info.Thanks for the research.

[Firebirdjones]

Interesting info. From what I've read here, it doesn't sound like any of them fit all that well.

[Brandoneh]

Originally Posted by Firebirdjones

Interesting info. From what I've read here, it doesn't sound like any of them fit all that well.

Yah it's like searching for the Holy Grail! I'm hoping something will present itself.

[Brandoneh]

updated the list.

[Yukon Jack]

In my 69 K20 I'm using Dynomax Cermacoated headers, part number 86022, designed for the 67-87 BBC 2WD. The headers for 73-87 BBC 4WD would not work. The engine is sitting in the small block engine crossmember using the original small block style engine mounts. To make these headers fit I did not have to make any modifications to the driver's side other than I did have to go with a shorter oil filter as this engine has an oil cooler setup which put the larger oil filter in contact with the headers. On the passenger side I had to remove a little bit of frame to give clearance for the first and second header tubes. I would guess I removed about 1/4". I also ended up grinding off a little bit of the engine crossmember tower as it was in contact with the bottom of the first header tube. I also used a 1/4" spacer between the crossmember and the engine mount to raise the engine a bit to help with header clearance. The above modifications have me comfortable with the clearance around the oil pan and passenger side headers.

These headers have 1 3/4" primaries and a 3" collector for round port size 2.1"

I'm running a hydraulic clutch and the stock z-bar would not have worked with these headers.

[Burt4x4]

Thorley collecters

[Brandoneh]

updated the list. the new headers Hooker Headers #520-2817 worked well for me.

[MB_70]

PROPOSED BUILD:
1971 4x4 Blazer (stock chassie)
427 BBC (estimated 500hp)
~ Aluminum heads, standard height valve covers
~ headers, dual exhaust
~ 9" Booster on the master cylinder
~ HEI Distributor
TH700R4 Transmission
NP205

Has anyone tried the SUMMIT brand of headers for a K20 4x4?

Is it best to mount the BBC to the crossmember, or should I lift it up with spacers?

Haw far up should you go with spacers?
~ When does Transmission alignment become an issue?

"Ive never built a 4x4, and I have never had a truck with a BBC in it."

I might be biting off more than I can chew .... but Im not going anywhere for a while.

[Firebirdjones]

Originally Posted by Brandoneh

updated the list. the new headers Hooker Headers #520-2817 worked well for me.

Thanks for the updates.

I'm curious how the collectors came out for you in relation to the transfer case. Low enough to clear without any fancy bending of the exhaust??

[MB_70]

ALL,

Below is the response I got from Sumitt Racing. I have not tried these because Im not that far into my build yet. Has anyone had any luck with these?

Hedman 69820 - Hedman Elite Hedders

Feature 14-gauge steel tubing, a bulletproof 3/8 in. flange and a thermal coating for intense heat conditions.

Part Number 69820 ;

Product Name ELITE Ultra-Duty Hedders

Application CHEVROLET,GMC BLAZER, JIMMY 1968-1981 V8 N ; 396-502 ENGINE SWAP HEDDER; 4WD

[2many]

I did TRY to run these with no luck. 454 / 700R4 / stock Blazer mounts/crossmember. WAY off on passenger side - would have to cut away nearly the entire top of frame. Driver side contact on crossmember. What is the solution here? Brandoneh - what crossmember/mount were you using that the Hookers worked? Any pics or clearance issues?

[Brandoneh]

I was using the DIY4x.com first gen crossmember. I had to have the motor raised a 1/4 inch to clear my oil pan but other than that the fit is pretty close.

[MB_70]

THANK YOU for all the great information, and for sharing your photos and discoveries .... I know what a pain it is to get the wrong part, return, get "the right part" only to have to go back yet again.

[Brandoneh]

Originally Posted by MB_70

THANK YOU for all the great information, and for sharing your photos and discoveries .... I know what a pain it is to get the wrong part, return, get "the right part" only to have to go back yet again.

No problem. Glad this thread can help solve the header ordeal with big blocks in first gens.

[2many]

Just wanted to follow up. For my situation (454, 700R4, stock SBC motor mounts and crossmember moved forward a couple inches) the Thorley 304Y was as close to a perfect fit I could find. Cut a 1/2" half-moon out of the pas. side upper frame rail to clear one tube and NO modifications on the driver side (other than reversing the lower shackle bolt to better clear the collector). Supposedly a good header for this motor as well - hope to find out soon! Found on Craigslist for $90, too!

[Brandoneh]

Originally Posted by 2many

Found on Craigslist for $90, too!

Nice find. price is sweet! Thanks for the update.

[Arfrce]

I'm putting a 427 Tall Deck in my 72 blazer.

Yeah I know it's a tall deck but it was 740 bucks. And low miles. I use the blazer for snow plowing and pulling my snowmobiles, and horse trailer. You get the idea.

Anyone know what headers would work for this before I have to play with sets.

And do I have to move or change the cross member vs the oil pan.
thanks
Jeff

479-426-4145 in case this is easier.

[montsb]

Hello all. This experience is from my dad's Blazer many moons ago lol. I was young, but seems I remember my dad had Hooker Headers "Compition" model. They did have some clearance issues, but not as bad as some i have read. I remember the passenger side being right up on the frame and maybe he had to do a little grinding to make room. But not too much. His was a L88 427. So, for what it's worth...

[Mr Banshee]

Arfce, I have a 72 Blazer that I did a build up of a Big block 396. I used the Hooker Headers #520-2817 that Brandoneh documented in this thread. They worked out very well for me. No triming on the frame rails. I did have to massage the collector on the passenger side to have ample clearance from the spring hanger. I used a 366 tall deck truck block and heads for my fabrication and fitting. I can snap a photo it installed to show you tonight if you would like?

[haminator]

Is there any new info regarding big block headers for a 70 K10? I bolted in a 402 in the small block location, no problems there. Its tight at the firewall but will work. The 71 truck manifolds wont fit. Corvette drivers side manifold wont fit. My 73-87 Thorleys wont fit on the pass. side. I'm trying to refrain from too much modifications. I might be ok with a small trim on the frame rail.

[BIG BLOCK JIMMY]

I wish I could help as I am wandering around in the dark kicking rocks and hating my life over this issue. I have a 72' Jimmy 4x4 with a 454. I'm on my third set of long tubes (currently Doug's Headers D303Y Tri-Y Header) that they claim will fit. They hit on the drivers side engine mount and the rear, lower bolt of the front leaf spring on the passenger side. I ordered the DIY4x.com first gen crossmember to help the drivers side issue and just because I wanted it.
I'm still trying to get the new crossmember gitup installed, but of course I have problems there too!
Is there a section on here for BBC folks to whine about our problems of things not fitting, so the smart guys can help us?

[simicrintz]

I have had great success on other projects (not my Blazer) with the Sanderson block huggers. You might try to give them a call; they have always been very helpful. These are not the block huggers but are for BBC:

https://www.sandersonheaders.com/cla...96-454-_502-8/

[BIG BLOCK JIMMY]

Thank you Bruce. Those Sanderson ones (Sanderson Headers BB8-SEC) were the second headers I tried. I thought about the block huggers but I'm still trying to be picking by having the ability to have straight plug boots and mid to long tubes. Once I get the new crossmember/mounts installed, I'll see where that leaves me as far as clearance and go from there.

[simicrintz]

Good luck, Damon; I'll be watching this to see how you end up!