The Stovebolt Site Forums The Shop Area Engine Shop intake manifold leak - 235

Well, I seem to be down to the carb issues. After checking the torque on the manifold bolts as best I could - inner bolts are hard to access, I cranked up the engine and proceeded to dribble fuel over the intake manifold to cylinder head junctions (not to be attempted by those with a fear of self immolation - but it works). The front and rear ports have a significant leak. Is this a common problem? What do I do - add more gaskets, resurface my manifold?

1. more gaskets, or a thicker gasket might solve the leak problem

2. have the mating surface on the manifolds planed/surfaced at a machine shop.

I've found things work better for me if I leave the two manifolds loosely attached (they'll wobble around a little), then attach both intake and exhaust manifolds to the head, get them tight against the head and once that is done tighten the intake and exhaust manifolds together where they meet. Hope that makes sense.

Good luck!
Jon

Thanks all. I will try building up the gaskets before pulling the manifolds. Jon's suggestion also sounds solid.

Try using a Remflex gasket. It is a one piece gasket that takes care of both the intake and exhaust manifolds. Made of graphite it is supposed to span gaps up to 1/8 inch thick. Kind of pricey at around $35 but cheaper than machining the manifolds. Take care on installation and do not bend or it will break and be ruined. With no carbon compounds in the material it is supposed to last much longer than standard material.

Kent
P.S.You want stock number 2027. You are supposed to torque to 20 ft.lbs, with no re-torquing required.

Sometime the port rings will hold you out, so check that they are inserted correctly and not to thick. Ive had to dress mine down after I had the manifold machined.


I also found to helpful to leave the heat box loose and tighten it in sequence.

Manifold torque
20 ft/lbs on center clamps
30 ft/lbs on outer

In your situation, unless there is a leak between intake and exhausts manifolds, do not disconnect them.

Otherwise, try the Remflex at $49 +shipping

Find a wrench which better fits in the tight spots on the middle bolts, or grind or heat and bend the wrench that you already have.
Loosen all of the bolts, then tighten each one to less than final torque specification (10 ft-lbs).
Proceed to tightening them to final specifications (20 ft lbs center bolts, 30 ft-lbs outer bolts).

"inner bolts are hard to access"

Get a thinner/better box end wrench, or use an open end wrench. You should not have to torque the nut more than 20-40psi.
inner bolt are torqued tighter than outer bolts (if that really matters)
See page 16-19 - that spec should be OK for a 235.

Shade-tree/farmer specs:
Tighten lightly/snugly, all nuts
Then, retighten each nut a little more to an even/equal resistance for all
Then, retighten each nut a little more

I was planning to use a crowfoot wrench for the bolts. It might even help me to get my torque wrench on the bolt.

The specs are interesting - I have a copy of something from the internet that shows the inner and out bolts are just the opposite values - but it was not copied from a manual. I believe that I will go with yours.

" I have a copy of something from the internet that shows the inner and out bolts are just the opposite values "

dyscalculia?

maybe I have the dyscalculia?
maybe I read in wrong?
maybe they changed the specs?
maybe one of the manual's "specs" is wrong?

http://www.canadianmilitarypattern.com/Resources/Specifications%2016-19.jpg

My guess is that the two outer bolts are longer and the clamp is about 1 1/2 futher away from the head
might be the reason for the original torque spec?

Also, check figure 6 in the Engine section:
http://www.canadianmilitarypattern.com/1960%20235-261%20Engine%20Manual.htm

That is for a 1960 261 engine.

I checked a few more manuals:
1955-2nd 235 - same as the 1948-51 specs
1959 235 - same as the 1960 261 specs

http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm0640.htm
http://chevy.oldcarmanualproject.com/shop/1959trucksup/59ctsms0801.html

If I remember when I go to my garage, I'll check 57/58 specs (for those who are interested).
It would be interesting to see if this changed with the higher compression 1956 "848" head?

added after checking Shop Manuals:
- "old" specs up through 1957
- "new" specs 1958 and thereafter

The face could be warped, its not all that common but is certainly a possibility. A reasonably well equipped machine shop should be able to face the manifold assembly. Don't take it apart, have the manifolds faced as a unit if you decide to do this. Otherwise, get a Rimflex gasket as above recommended. The Rimflex works really well. Tight spot on the inner bolts, yes. Some wrenches just wont fit. I have an extra long Mac wrench, and a smaller wrench that I modified, to fit and snug down the clamp bolts.

I decided to go with the Remflex gasket. It arrived today, and guess what - the package had been bent! Now, the gasket is not "broken", which means to me to be in 2 or more pieces. But there is a slight crease in the face of the gasket between the bolt hole and the center intake hole. There is less of a crease across the center intake hole. looking at the edge of the gasket, I see no visible damage. Do you think it is worth taking a chance on this gasket?

Bob

Remflex look great, however, they are not made for many engines.

Ed

Contact the company and ask if the gasket is ok to use.🛠

To follow up, the Remflex solved all problems with the leaks. The crowfoot and a "click" torque wrench allowed access to all but the bolt right behind the carb, which had to be guessed at by hand.

I use the “flat method” on bolts I cannot get a torque wrench on

Basially you mark the bolt head on a bolt you can get a torque wrech on after tightening them hand tight

Then notice how far the bolt head moved after final torque

Thghten the one you cannot get the torque wrench on the same diatance.

Outstanding!