Inliners International Forums General Discussion Engines 250 intake/exhaust manifold install

Can someone tell me the best way to install an intake/exhaust manifold on a chevy 250 motor? I'm asking because mine is leaking from the center two bolts. Seems that my gasket is blown. I want to make sure this time I get them bolted down correctly. Someone told me to start from the center out.

Do you have the orginial intake/exhaust setup? If not, then measure the boss or flat heights where the clips with bolts hold the two onto the block. There can be a difference in the height between the two. When you bolt/toque the two up one may be loose, the other tight. If you do see a difference in the measurments, use a spacer of the right size and shape to make up the difference. The only other thing, and this should be done first, is to measure the mating surfaces to the block of the two pieces. Have them machined flat if they are not already. Good luck.

Also start from the center and work your way to the ends when bolting it down. THEN REPEAT. Then repeat once the motor has gone through a heat cycle.

I had mine milled flat at possible together, and I think retightening while it is hot or after it has been hot once, will help too. I have learned that inlines like to leak there, and I have a burned valve to prove it.

I agree - center out. If possible get a tap or a good bolt and chase all the bolt holes cleaning them with some WD-40 as you go. Put them all in finger tight and tighten in about 3 steps.
The hot torque is because metal heats up and cools down differently. It is all cast iron but maybe the cylinder head has more Alloy than the intake/exhaust manifolds which are more pure cast iron. Plus they are hollow so transmit heat at a different rate.

I've had to re-torque my bolts several times after I replaced the gaskets..only while trying to rectify a "rough idle" problem did I realise it was loose manifold bolts causng the problem.
Check them often for a week or two after they have been disturbed.
And as pinebluffdude says..running a tap down each bolt hole is a must.

What's the torque sequence? From the center out is the right sequence? And what torque pounds?

Pretty much any Haynes or Chiltons Manual you purchase at the Auto Parts store will have Torque Specs.

I was trying keeping from buying a manual...:) and hopeing someone already have done it and knew the pounds.

My '62 shop manual says to tighten the center bolts 25-30 foot pounds
and the outer bolts 15-20 foot pounds. I don't see any mention of a
sequence but I'd say do it from the center out.

Thanks. I did find the specs on Autozone.com, they have everything in there.

Do it similar to torquing a cylinder head. Start in the center, and work your way outward toward each end.

When you're torqueing a cylinder head, manifold, or any other part held with more than 2 bolts, ALWAYS start the torque cycle from the center and work outward in a circular pattern. That is, start with the center bolts, then the right and left bolts closest to the center bolts, and so on. And as pinebluffdude said, tighten the bolts in 3 steps. First step is 1/3 of the final number of foot-pounds of torque that's needed, then 2/3, and then the last step is to torque to the final amount of torque needed. Two other things you want to do are to clean the threads with a tap or thread chaser, and lube the bolt threads before you torque the bolt. When you torque dry threads, friction will give you a false reading due to friction between the bolt and the threads of the hole or the nut that the bolt is being screwed into, and the bolt won't be as tight as you think it is. I usually use either engine oil or Super Lube for a bolt lube. And don't try to economize by not buying manuals. You can never have too many manuals, and the info they have is worth more than the weight of the manual in gold a lot of times.

Is there a haynes for an inline six nova? I've only seen v8 haynes/chilton.

Neon,The Chilton's manuals that I have for '60s &'70s pickups have good coverage of 250s &292s.

Chilton's ChevyII Nova 1962-79

Be careful with the bolts all the way at the end of the exhaust manifold. If you have them there. I over tightened mine and cracked the ear off the end of the manifold, I have seen photos where some engines only have a pin there and no bolt so I was lucky because the next bolt inward holds the exhaust tight enough so the cracked ear doesn't seem to affect it as there is no leakage.