Cylinder Head Bolts

[TrevorK]

Hi,

Is there a reference somewhere that shows the location of the short/long cylinder head bolts. In installing my heads I ended up with one long bolt too many, so must have put a short one in a spot that requires a long one. I’m not too excited about the prospect of removing head bolts that have already been torqued to find the incorrect one. I seem to recall a diagram that showed the placement of the long/short bolts but can’t seem to find it now in the shop manual.

This is for a 1960.

[Roger Zimmermann]

This is a difficult question. By looking at the parts book, there are about 8 different bolts for the cylinder heads, depending engine with or without A/C. Unfortunately, the quantity is not mentioned into the book.

[Cadman-iac]

Trevor,

What I would do in your position, is to check each bolt one at a time  by removing it and checking the distance the head of the bolt stands above the cylinder head itself before you begin to thread it in. The short one should be obvious by this method. 
Of course I'm guessing that you have already torqued the head bolts down. Thus the reason for checking them one at a time.
If you have not torqued them yet, it should be a simple process to check the height of the bolts before threading.
I hope this may help some.

Rick

[fishnjim]

Somethings amiss if you have all the bolts in and some left over?   Or is the last bolt too long for the last hole?   
There might be a cut away in the parts list, but I don't have one that late.

A short bolt won't necessarily tighten/engage enough thread, if a long one goes there, unless something else bolts up under the long bolt.   You might have missed a bracket, part, or something?   

I know the 365 had one or so attachments that use a longer bolt so you won't know from the hole height alone.   I had to change a couple bolts when I put back in from the rebuilder.   Some of the kit bolts weren't correct either, stud v bolts, hex v 12 pt heads.
   
Not to chastise, but for others contemplating, why you're supposed to take pictures, diagram, and label as it's removed.   But one putting back not always the one that takes it apart.

[savemy67]

Hello Trevor,

Ouch!  If you had a leftover or incorrect exhaust system bolt, you needn't be too concerned.  With a cylinder head bolt, you need to be more careful.

I don't think there is a safe way to avoid removing all the bolts.  Assuming you can find in which position the long and short bolts are located, how do you know which position has the mis-matched bolt?  As there are several long and short bolts, you would have to remove a few to find the incorrect bolt.  At this point you would be unloading the torque on the cylinder head unevenly with a potential for future problems.

Generally, the longer bolts go through the thicker part of the cylinder head casting.  On the 390, I think the thicker part of the casting is closer to the intake manifold.  Also on the 390, if memory serves me correctly, the bolt pattern around each cylinder is roughly pentagonal, with some bolts "shared" in the pentagonal arrangement.  Without having had one of these cylinder heads in my hands for decades, my best guess is that the 9 bolts closer to the intake manifold - the bolts that form the top three vertices of the pentagonal shape - are the longer bolts.

Regardless, I suggest you consider removing all of the bolts in a reverse pattern to which you tightened them, and then sort your bolts.

Respectfully submitted,

Christopher Winter

[Clewisiii]

Do you have AC.  For 61 the AC bracket goes under one of the head bolts. So that bolt is 3/8 to a 1/2 longer.

[TrevorK]

Hi everyone, thanks for all of your responses. To answer some of the questions, yes I put all of the bolts in and they are torqued. When I got to the last one on the left side, the last bolt was too long and was left sticking out about 1/2”. I put the heads on a while ago, but my recollection is that there were only two lengths of bolts. To have one long one at the end must mean that I have a short one somewhere where it should be a long bolt.

This is an A/C car, but the bracket is only about 1/4” thick or less, so I’m not sure that is the difference.

I assume the only way to know is to take them out one by one to check, but I worry about messing up the head gaskets. It would be nice if I knew for sure which bolts are supposed to be long, so I’m only taking out those ones.

I’ve attached a photo of the two lengths. It looks like a short one could go in a long hole and would catch the threads, but not be seated all the way.

[hornetball]

I don't know about 1960, but my 1974 Service Manual was quite specific about the long/short head bolt locations on a 500.  Do you have a Service Manual (original GM) for your car?  Money well spent.

[Clewisiii]

Here is a 390 but from 61. 

That is the long bolt at the AC bracket.  My engine shop put it in the wrong spot to and the engine came back with washers under that bolt.   I gave them the accessories and brackets which are needed for proper reassembly due to various bolt lengths.  Everything was bagged labeled and I even made a diagram with all listed.  They ignored all of that.

[TrevorK]

Here is a 390 but from 61. 

That is the long bolt at the AC bracket.  My engine shop put it in the wrong spot to and the engine came back with washers under that bolt.   I gave them the accessories and brackets which are needed for proper reassembly due to various bolt lengths.  Everything was bagged labeled and I even made a diagram with all listed.  They ignored all of that.

I do have a shop manual, but don’t see anything on this point. I do remember seeing a diagram somewhere though.

[Roger Zimmermann]

I assume the only way to know is to take them out one by one to check, but I worry about messing up the head gaskets.

Don't worry as the engine did not run. As I wrote, there are different lengths, no no answer where your bolt should go.