wrong 240Z manifold?

[Richard McDonel]

I have parts from three 240Zs; a Series 1, and later '71, and a '73.  From these I am building one - hopefully - very nice one.  I picked the cleanest looking of three exhaust manifolds and installed.  Now that I'm ready to hook up the exhaust piping, I find that the manifold-to-pipe gasket does not fit.  I have new gaskets from three different kits, and they all perfectly match the holes on the "pipe" side, but not the manifold (see photo).  Comparing the manifold on the car to one of the others I have, the centre-to-centre measurements are 7.1 cm from centre hole to corner hole on the manifold, while the other is 6.7 cm.  Corner hole to corner hole on the one in the car is 10.6 cm, while the other is 10.7 cm.   Does anyone have any idea of what the manifold is supposed to fit? Or what it's from? 

The photo makes it look actually closer to a fit than it really is; I did drill out a couple of the stud holes a few /64s.

Installing all the studs and nuts on the intake and exhaust manifolds is a royal pain, but with regrettable practice, I'm getting better at it.

many thanks,

[Zed Head]

Will the head pipe tube ends fit in to the manifold?  Detail A.  The gasket is kind of a secondary seal, it doesn't affect flow.  If the tubes fit in to the casting, you're good.

[Zed Head]

I'm pretty sure though, that the "good" gaskets have a metal crush ring around the hole.  MY 280Z gaskets do.  I assume that it's good, the ring has to add cost.  That gasket in your picture looks of lower quality.

Here's two other options from OReilly - http://www.oreillyauto.com/site/c/search.oap?year=1973&make=Nissan&model=240Z&vi=5142641&keyword=exhaust+pipe+connector+gasket

 

 

[Richard McDonel]

Zed,

Thanks for your reply.

My original photo did use as a model the cheapest looking of the three gaskets I had - I didn't want to try reaming out the stud holes in the good stuff.

I have two pipe assemblies.  With the good one, the pipes do fit nicely into the manifold as you suggest, but as you can see from this photo taken from below (1010012), the stud holes don't work.  The second pipe assembly (1010011) is likely the one that came with this manifold.  As you can see,  the pipes have been cut off flush with the flange, and some stud-hole widening has been done.

 Curiously, both manifolds have the same casting mark, "E30."  If anyone has any idea how all this came about, I'd love to hear about it.  In the meantime, it looks like I'm going to have to remove the carbs, manifolds etc. (nasty fit some of those studs and nuts)  and get the mis-fit stud hole filled and drilled.  

[beermanpete]

There are differences year to year in the exhaust manifolds and bolt spacing at the joint with the pipes. The first thing to do is find a manifold and pipe set that match and fit with each other. Hopefully you have a gasket that fits the set. If not, they are easy to purchase.

[Zed Head]

Maybe it's a Series I manifold!  Seriously, maybe it's just really old.

carparts suggest that there was a manifold change in June 72, but doesn't show a gasket change until July 73.  You have a puzzle.

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-240z-260z/manifold

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-240z-260z/exhaust-tube-muffler/to-jul-73

 

[240dkw]

Yes the manifold for a late 73 with the Hitachi carbs is much larger, as well the length of the two into one connector pipe is shorter to match the larger manifold. It is likely that your good pipe is off the 73. And the one you show looks like someone drilled it out to fit. I would try to find a good fitting pipe instead of modifying the manifold.
Dan 

[Richard McDonel]

240dkw Dan,

Thanks for this.  I've already taken the manifold into a machine shop to have the third stud hole re-drilled.  I decided to do that based in part on the fact that I already have a lot of time invested in it.  I plugged off the six air-injection holes from the outside, had them welded over on the inside, then carefully filed / ground down the welds.  The end result is a smoother port than I started with.  Having said that,  I'm open to suggestion, and when I get the manifold back I'll do some detail comparing before deciding which to install.   

Are you still in town?

 

[Richard McDonel]

Final chapter,

My machinist friend decided that weld-filling the existing hole in cast iron, then re-drilling would be very time consuming, and was not the best answer to the problem.  Instead, he filled and re-drilled the exhaust pipe flange.  In doing that, he made sure that the pipe stubs still fit snuggly in the manifold.  Result; manifold, gasket and pipe all fit like the proverbial glove.    

Thanks for all your thoughts and advice.