I have ran headers on all my poncho's. And yes they are a nightmare to install. But the gains are great :thumbup: I'm sorry to say i dont believe you will ever get long term gasket reliability with the four bolt heads. The front and back bolt holes can be drilled and tapped. but sadly that requires the removal of the heads

The four bolt heads were a short cut done by gm. It only worked so-so with a cast manifold. It was ditched after a couple of years in favor of the more common and dependable 6 bolt config

 

The four bolt heads were a short cut done by gm. It only worked so-so with a cast manifold. It was ditched after a couple of years in favor of the more common and dependable 6 bolt config

I believe they went to the 7M5 in 73. At least that's what came on my 73 LeMans SC.

 

Thanks for the replys

I know that there going to leak eventually, im only going to be using them on this motor for a few months. (not much driving) while i finish my 455. the heads i have are the 6 bolt pattern :thumbup:

Just finishing bolting up the header again.

Do you really gain that much more flow with the headers? the exhaust manifolds didnt look that restrictive.

 

The headers will give you a seat of the pants improvement right off the bat.
It's not as much about the restriction but the scavenge effect of the long tubes that help pull the spent exhaust from other cyl. I put 3 tube on my 350 years ago and there was an imidiate improvment right off idle, pedal was real touchy, power was right there and you can improve as much as 15 hp just with headers on a stock engine.

 

The headers will give you a seat of the pants improvement right off the bat.
It's not as much about the restriction but the scavenge effect of the long tubes that help pull the spent exhaust from other cyl. I put 3 tube on my 350 years ago and there was an imidiate improvment right off idle, pedal was real touchy, power was right there and you can improve as much as 15 hp just with headers on a stock engine.

15 hp is a lot on a engine that is rated at 160 hp.

 

Well! the drive was great! tightened up one bolt that was loose and its amazing how much different it sounded

I think they were advertized at 180 stock hp. I think with the 4bbl and the headers im somewhere around 220-230?

How much timing should i run? im at 30 degrees

 

Here's a way around the missing header bolt problem: Head L Brackets

As far as timing, every engine likes something a little different, but I'd shoot for 34 to 36 degrees. Your engine should like the additional four degrees on the initial when you bump the static timing.

 

Ya those 6 bolt heads are a real pain to bolt headders up to I must say let alone installing the headders to an 8 bolt head anyway! One thing i must say no matter what head you are using, when running headders on a pontiac use the REMFLEX brand exhaust gaskets. They are about 1/8 inch thick and compress 1/16" and will almost guarantee not to leak. I had a leak with my headders 2 months after installing them and I used those gaskets and have not had any issues since. I also use them on my newer 455 and the work sooo good. They even have great customer service and are known to replace a gasket if one blows out for free! I also can't believe how much power you can loose with an exhuast leak on the headder with our pontiacs. I lost a bunch and my friend did too with his 400 and after I replaced the gaskets it almost felt like I gained HP. I told him my experience and he took my advice and hasn't had a leak yet either. My 2 cents.

 

Ya those 6 bolt heads are a real pain to bolt headders up to I must say let alone installing the headders to an 8 bolt head anyway! One thing i must say no matter what head you are using, when running headders on a pontiac use the REMFLEX brand exhaust gaskets. They are about 1/8 inch thick and compress 1/16" and will almost guarantee not to leak. I had a leak with my headders 2 months after installing them and I used those gaskets and have not had any issues since. I also use them on my newer 455 and the work sooo good. They even have great customer service and are known to replace a gasket if one blows out for free! I also can't believe how much power you can loose with an exhuast leak on the headder with our pontiacs. I lost a bunch and my friend did too with his 400 and after I replaced the gaskets it almost felt like I gained HP. I told him my experience and he took my advice and hasn't had a leak yet either. My 2 cents.

Headers. don't hate me! :mwink: I had no problem with 3 tube headers on my 455 73 lemans SC. I think all of the Pontiac heads have a weird angle on the exhaust ports unlike chevy engines and can be a PITA trying to bolt them up no matter how many bolts.

 

Headers. don't hate me! :mwink: I had no problem with 3 tube headers on my 455 73 lemans SC. I think all of the Pontiac heads have a weird angle on the exhaust ports unlike chevy engines and can be a PITA trying to bolt them up no matter how many bolts.

you know its gonna suck when you have to "make" your own special wrench to tighten some of the bolts.

 

you know its gonna suck when you have to "make" your own special wrench to tighten some of the bolts.

Maybe your on to something there. You could call it a "custom Pontiac header wrench".
I'm picturing a Half moon open end/box end wrench made with titanium that doesn't stretch and round off bolt heads and doesn't slip off and bust your knuckles. You know that if you make a custom tool, every wrench head in America will want one. :mwink:

 

lol sounds pretty close to what i did. O took a cheap craftsman 7/16 wrench and bent the open end in so it has more angle then i ground the box end down to about 3/16" thick put a small arch in the middle of the handle then torch hardened the whole thing. WORKED PERFECTLY!