I am replacing my drivers side exhaust manifold and my bolts are quite rusty, although they appear to be still usable. It looks like there are two types of bolts on the manifold (inner and outer ports) with outer being a flanged shouldered bolt and the inners being shouldered but not flanged. As far as my research indicates, the outer flanged are GM 3909821 and the inners are 3736035.
Just wondering if anyone has any of the above bolts languishing in their personal parts collections that they are willing to part with?
In your PM you mentioned you can still get the 3909821, and sure enough I see you can. I'm surprised because at one point many years ago they made us buy the 3736035. It must just have been a substitute or something.
Or my brain is just getting old...
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
It seems to me from researching BBC exhaust manifold bolts that some BBC vehicles in different years use the shouldered non flange bolts, some used the flanged shouldered and some used both. Its all over the map from my deduction. Like early big block Corvettes used non flanged, and those are readily available through ebay with ridiculous shipping costs imop. But, I also read online that some vehicles used both and my 68 had both (in addtion to the double ended studs for ps and air cond).
The flanged shouldered bolt 3909821, which you can still purchase at the GM dealer for 4.26 per bolt (ouch!) were on the outside of the exhaust port and the 3736035 shouldered non flanged which are no longer available at GM were on the inner port. I read online on other forums that this indeed was the case in some vehicles.
I don't know what the reasoning for using differnt bolts on the same vehicle was for but this apparently was the case. You can get jobber bolts for the 3736035 non flanged shouldered bolts online from Corvette sites as well as ebay but I think ppl are trying to make a bit of money on the shipping. And I refuse to purchase anything where your only shipping choice is UPS. My other options are to buff and use my old bolts, which are not that pretty anymore or get some shipped to the border.
My 68 did have exhaust manifold gaskets on it which your PM indicated that typically gaskets were not used on BBC's. My drivers side manifold that seventy2plus2 greatfully let go looks good (on the port surface) but my passeger side manifold port surface doesn't look as good. :(
Now the question is: To gasket, or not to gasket??
One thing I never thought to mention in the PM is you could use either a muffler cement type product, or a high temp sealant made for exhaust to fill minor imperfections on the mating surface. My brother had an exhaust shop that did a lot of exhaust work for over 30 years, and they did that as an economical option for repairing manifolds that weren't perfect. Piston Ring sells a muffler cement, I assume NAPA also does. Besides muffler cement, I think there's also a high temp sealer, it may even be a silicone for exhaust. I've never had to use it so can't say exactly who makes it or what it looks like.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
When I've done the exhaust on the 454's in both my 2+2 & Parisienne, I had the mating surface of the manifolds machined at the muffler shop so they were straight (done well in advance to putting them on), and I also used gaskets. No problems.
Every time I point that out to someone at the parts counter, they have the same response as you did. I think a lot of other manufacturers used gaskets from new but GM never even made gasket for our big blocks in those years from what I've seen.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
But then again, I've never heard of a big block having two different styles of bolts on the same exhaust manifold until Jake told me about his. Then I go online and read all over the place where the purists say the end holes use a flanged bolt and the rest use an unflanged bolt. News to me.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
