Replacing Stock Exhaust Manifold with Headers

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j5ball

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I am interested in replacing the stock exhaust manifolds on my 1968 Pontiac Lemans 350 2 barrel carb with headers. Do I have to pull the engine out to pull off the stock exhaust manifolds and put on headers? Any opinions on what headers to put on the car? How big of a job is this to pull the manifolds and put on headers? Thanks . . . JIMB
 
You dont have to pull the engine but depending upon what the header manufacturers instructions are you may have to disconnect a motor mount and jack up one side. To see what is available for your car try www.summitracing.com or www.jegs.com
 
Header match

How do I ensure the headers i purchase are an exact match? I don't want to drill holes or anything else. Thanks . . . JIMB
 
If you dont know who the manufacturer is and it's not stamped anywhere you have no way of knowing.
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Thanks for answering but I don't know what you just shared with me.
 
Im telling you if you cannt get the exact same set of headers you may have to do work to get them to fit your exhaust system.
 
ok. I do not have headers on the car now. I believe the car has the original exhaust manifolds. Does this make any difference on how I shop for headers?
 
sorry, I misunderstood your situation. If you specify on the site that you are buying them from, the type of car and engine you have they will fit. I recommend you also check the manufacturers site for any comments about compatibility with a/c or other options. You will also need a complete exhaust system assuming you dont already have a dual exhaust. If for instance you buy the system from Summit or Jegs they both should have a tech. line where you can get more details.
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Hooker Headers have Arrived - installation Q's?

Looking at the driver side I do not see any issues with installing the new headers (replacing stock manifold.) When I look at the passenger side I see where the Oil Filter and sending unit appear to be in the way. Can anyone confirm or deny the Oil Filter and sending unit will be in the way. if they are in the way, what are my options? I read somewhere about at 45 degree adapter.
Also, do I need to permanently raise the engine to allow for header clearance? Thanks . . . JIMB
 
No the engine is not permanently raised. Which manufacturer are you considering?
 
I bought Hooker Headers off JEGS . . item # 520-4901 / Comp Header Pontiac 1.625.
 
J5ball, do your heads have end bolt holes for headers? Some Pontiac heads don't have them. Without them, the ends of the headers won't seal properly.
 
I believe there are end bolts. There are 4 bolts on each header. Two bolts in the middle and a bolt on each end.

I took the old manifolds off. The driver side came off and out with ease. I did have to remove the oil filter and sending unit before I could get the passenger side manifold out.

I have the car on ramps but I need about another 3-6 inches before I can get the headers up into the areas. Close but no cigar.

I am looking to put the new headers on today. But I need to replace the motor mounts first. Picked up the new motor mounts at the Charlotte Auto Show yesterday.

Motor Mounts this morning . . . Headers later today.

More to come.
 
Took the motor mounts off today. What a pisser. Just taking the motor mounts off took all day. Tomorrow I will put the new ones on.

Back to headers and bolts. The manifolds I took off had 2 bolts in the middle then a bolt at each end (4 bolts in total for the old manifold.) But, there are 2 bolt holes on each end of the engine. Should I put two bolts on each end (this would now be 6 bolts in total for the new headers)?

Thanks . . . JIMB
 
Yes, otherwise the headers will leak.
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J5ball, I've heard of the 45 degree adapter too. I read this a long time ago it might help http://www.pontiacstreetperformance.com/psp/modoiladapter.html And yes I agree with what melsg5 said. You need those end bolts to get a good seal. Keep us posted on the install. I'm thinking of headers for my 72 Lemans and I'd like to know how much trouble they are.
 
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Hopefully not too late but when you tighten the bolts, start with the center 2 and then work your way to each end to get even torque across the flange.
 
Ok. Headers in. That took a lot of time and patience. While I had the old manifolds off I went ahead and replaced the motor mounts and frame mounts - they were really bad, did not know how bad they were until I had the new ones in. Once I was able to raise the engine and create some room - removing the old mounts (engine and frame) and putting new ones in were easy. Hold that thought for a second though. While I had the manifolds off and had access to the starter . .I went ahead and replaced the starter. Put the new starter in . . went to put in the driver side header and could not get the header up in there - not enough space. Had to pull the starter back out then put the driver side header in. Had to wire up the starter before I could reinstall . . no room to wire starter once in. Back to mounts. Went to install the connecting bolt between the motor mount and frame mount on the driver side . . and the nut on the engine mount was stripped (the engine mount came with a bold already welded in place.) Are you fricken kidding me! Note to self - test all parts before installing. Taking out the engine mount once the headers were in was very . . very difficult, and I did not want to take the header back out. Cost me about 6 hours. Other notes for installation. Had to slide the transmission cooler lines out of the way on the passenger side. Also had to take out the oil filter to get the passenger header up in. But once the passenger header was in I was able to reinstall the oil filter with no changes. All worked good. Car sounds like a BEAST!!!! Need to get dual exhaust installed now. I am still pissing of the neighbors . . way too loud. All good though. And some lessons learned. I would say I spent 30 hours on this . . but knowing what I know now . could do in 8 hours.
 
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