[punkin]

After a morning of under car yoga and psych stress testing. I had to share a little FYI for someone else who might encounter this. Definitely not a dig against Doug's headers. They make a fantastic product and would absolutely purchase again.

I'm working on one of my two firebird projects. Installing a pair of 1 7/8" Doug's headers. The motor is an IA2 block with screw in freeze plugs. I also further added some complications by replacing all the front steering components to include the passenger side idler arm.

There are a lot of opportunities for stacking tolerances especially with these old uni-body cars but the motor mounts are new poly type, the body bushings are all solid aluminum and the chassis was verified for square and all the moving front suspension pieces have been replaced. All in all a pretty decent starting point.

Driver side header went in perfectly, nice and snug fits like a glove. An honest 15 minute job. Passenger side, not so much.

First fitment issue I ran into was one of the down tube were making contact with the passenger side steering idler arm ball-joint. I thought to put the old super-comp header in and they too have the same issue. I went digging through my old pile of junk and found the old idler arm. The new idler ball joint is just a little over 1/8" larger in diameter. A little torch work and a dimple, problem solved.

One more last final test fitment and problem number two surfaced. Upon final tightening of the header bolts, there seemed to be a very slight binding. Using a plastic tie wrap to feel around up in the blind areas, came to realize that the rear screw in freeze plug also presents a very slight interference as well. I'm thinking the screw in plugs weren't worth it and should have just stuck to the press in type.

Just a little public service announcement. I'm sure every car has it's quirks but if anyone is planning to put the 1 7/8" Doug's headers into a first gen with an IA2 block with screw in freeze plugs and if you've replaced the passenger side idler arm, may I suggest a good stretching session before starting

[Cammer-6]

Going back to 1969
I wanted a set of 4 tubes for my 65 GTO.
I spent the extra and got Dougs.
Starter was a PITA.
Then the next oil change came up.....
What a F******** mess.
should have bought a remote or an HO oil filter adapter

First time I fired the open headers in the carport....priceless

[muscle_collector]

i think headers have brought out the worst in all of us. back in 1981 my cousin bought a new trans am and wanted me to build him a 400 and put in it like i had my 80 pace car the year before. i was installing the drivers side hooker 4 tube header and as usual it was a chore. on the back center bolt from hell i got mad and stood up and threw my wrench very hard at the top of the wall about 15 foot away. i swear to this day i can still picture it like in slow motion the wrench bounced off the wall and came back and landed straight down on his windshield. i just knew it broke it. luckily it didnt but it bounced off of it and hit the hood on a 70 judge that was sitting there and it did leave a mark. i never throw wrenches anymore after that.

[punkin]

It's feeling like therapy guys...I'm not alone, it's not just me

[68azbird]

I had to cut and move a tube on my friends 69 bird that was hitting the steering on the driver side. It was stopping the car from getting a full turn out of the steering.

[punkin]

Yikes!

[JimFB400HO]

Why not just use longbranch manifolds? Is the HP gain that much better with headers? I recall a different pitman arm and an oil filter adapter are required,

[Cammer-6]

curved pitman arm was for all V8s
but the long branch manifolds didnt really need it.

Yea wish I had an oil filter adapter for big car and 400HO and RA Firebirds
on my 65 back in 1969.

[nas t eh]

Originally Posted by JimFB400HO

Why not just use longbranch manifolds? Is the HP gain that much better with headers? I recall a different pitman arm and an oil filter adapter are required,

> 500ci, big heads, big cam. Even if it was street use only, why do all that and then hold it back with manifolds and a 2.5” exhaust.

[JimFB400HO]

Originally Posted by Cammer-6

curved pitman arm was for all V8s
but the long branch manifolds didnt really need it.

Interesting. Thanks. I've studied the different part numbers and shapes but never knew that. I believe my 400HO has a Chevy pitman arm, installed by a dealer decades ago.

[Cammer-6]

As youve seen first hand the curved arm wasnt needed for the HO
OHC-6 cars got the straight arms,same as Camaros.

[JimFB400HO]

Originally Posted by nas t eh

> 500ci, big heads, big cam. Even if it was street use only, why do all that and then hold it back with manifolds and a 2.5” exhaust.

Got it! That makes sense. I think mostly in originality terms. Thanks.

[punkin]

Originally Posted by JimFB400HO

Why not just use longbranch manifolds? Is the HP gain that much better with headers? I recall a different pitman arm and an oil filter adapter are required,

Using a Kauffman 90 degree filter adapter which is overall a little shorter than original. It fits very nicely with plenty of room for filter replacement. No real issue there.

I do believe the original idler arm would have fit but the new replacement has ball joint slightly larger in diameter. The biggest surprise really was the screw in freeze plug fitment. They're a nice to have item I suppose but I wouldn't bother with them again for a street car. This motor is just a little more stout than the last one, producing a touch over 750 HP. I would have like to try a set of 2" primaries but now glad that I didn't.

As for pitman arm, no fitment issues around that at all.

On a side note, I learned a lot when putting my 68 together (which is a continuing project) and thought I had identified all the challenges with a conversion like this but it seems every one of these cars has it's own unique possible fitment issues. The 68 was a plug and play with the 4l80e install where the 69 required a lot of fiddling with motor/trans positioning and driveline angle tweaks. Also finding that collectors are tucked up a little tighter in the 69 as well which further limited driveline angle adjustment wiggle room.