VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 head bolt torque for a 34

hi there,
what is the correct torque setting for the head bolts on my 34 std , and the tappet settings, inlet and exhaust.

I ask because my 2 chev repair manuals give different specification for the tappets and absolutely nothing with regard to the head bolts. In fact there is no mention of torque settings in any books?

I wonder if back then they just did everything up very tight, depending on where the fastener was on the car?

Peter

From my June 1959 Warren & Brown Torque Wrench book,it gives the following information:

Cast iron cylinder heads:tighten to specified loading,run to
operating temperature and then re-tighten(assuming you are
using a copper/asbestos head gasket).

Not knowing the diameter of your head bolts,the following is a
guide only:

7/16" Whitworth or UNC: 44 - 48 ft.lbs.(non high tensile)

1/2" Whitworth or UNC: 70 - 75 ft.lbs.(non high tensile)

If the bolts are used,err on the side of caution,and go for the lower figure.If new,go with the higher torque setting.

The book only has torque settings for 1935-1948 cars,so these may be close:

Head bolts: 75 - 80 ft.lbs.
Connecting rod: 45 - 50 ft.lbs.
Main bearing cap bolts: 100 - 110 ft.lbs.

hi there CJP,
thank you for the information.
when the engine was rebuilt, I cannot remember if the head-bolts were replaced with new ones, the man who did the rebuild has now passed away.I will go for the lower number as advised.
Peter

Head Bolt Torque I know you didn't ask about the main bearings but I would not torque the mains to 100 ft lbs or at least the center and rear. The front is OK at 100 ft lbs but the center and rear are 7/16 bolts and should be torqued accordingly.

This is a great thread and I hope we can reach a concensus on torgue values.
One thing I have been told by engine rebuilders is that uniform torgueing of the head bolts is more important than an actual value. Yes we still need a certain amount of torgue, but uniform torgue and doing it in a certain order is most important.

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The link above ****HEAD BOLT TORQUE*** as posted by A B BUFF, will give you the correct torque sequence for tightening head bolts on chev 6's .
If ???? final torque is 75 pounds, then do all the bolts to 65 foot pounds and then come back and tighten them in sequence to 75 pounds. Preferrably do this with a CLICKER TORQUE WRENCH that makes a snapping noise and feel when you hit the specified setting on the wrench. If you have a friend who has one, borrow it. Makes life easier.

Wrench should always be rolled back to 0 immediately after using it.

mike

I have been using a 'clicker' type torque wrench for 10 years and do head bolts as Mike described but ONLY after examining each bolt with a magnifier, caliper and thread gauge. Irreversible bolt stretch prevents you from getting proper initial and long term torque.
My recent experience- assembling my '34 Standard motor, I torqued to 65 lb/ft left it for a few days to do other work, came back to assembly, checked the head bolts again.finding about half the bolts loosened I retorqued and had three bolts break before reaching 55 lb/ft!!! Off came the head and as expected about half the bolts showed stretch- thinning near the top. Suspecting my torque wrench,I compared it's performance to an old Hooke's Law type and they gave equal numbers. I keep 3 old '30s Chevy parts motors around so I spent an hour pulling head bolts and examining. About a third of them showed irreversible stretch.
When I hear of guys blowing head gaskets or coolant leaks into cylinders I wonder how often loose, stretched head bolts cause it? Personally, new head bolts seem like a pretty good investment.
Dan

I will differ with most on torquing bolts. I use a beam type torque wrench because it allows loosening as well as tightening without much fiddling with the wrench.

Why is loosening necessary? Try torquing a bolt to say 50 ft/lbs. Then note the position of the wrench. Back off the bolt and then torque again to 50 ft/lbs. Notice that it is necessary to turn the bolt head a little further the second time? What is happening? It is the threads on the bolt and threads in the hole meshing a little better each time. If you were to look through a microscope at the thread surface it would not be smooth but have ridges and valleys. As the two surfaces rub past each other it helps to smooth the ridges and give a greater contact between the two parts. Yes it can be done with a "clicker" but takes a bit more futzing with the wrench.

Also make sure that the threads are lubricated. Oiled threads slip past each other much easier and produce a more accurate "pull" from the bolt.

When both of the above techniques are used changes you should find very minimal change in bolt position when retorquing after running the engine.

D F C ---DAN is 100% correct, all head bolts and manifold bolts should be checked on the shafts for stretch and thinness.

Scenario...person discovers they have a leaky cylinder head gasket, sees bubbling in radiator water, they isolate the cylinder by pulling plugs and seeing which one is running super clean. Now they grab their 18 inch long socket bar, slap right size socket on it and proceed to reef on the head bolts around that cylinder, easily exceeding the recommended torque specs for that size bolt.

They might get the leak to stop or not. But what they have done is stretch the shaft of that set of bolts they reefed on. They no longer have the clamping ability they once did.

The over tightening did not work, still leaks, so they buy a new old stock head gasket and proceed to install it. Motor keeps blowing new head gaskets.....block is straight , head is straight, what could be wrong ??? That Gasket King in Canada is selling me NOS faulty gaskets !!!

I do not know how many of those conversations i had with people over the years , when i was doing that, it was a lot ! When i would talk to them , invariably they were the one who over tightened the head bolts.

If you cannot buy quality replacement head bolts for your motor, then purchase allen heads style ***GRADE 8*** and use hardened steel washers underneathe the head bolt.

" Another trick is to soak the headgasket in water. The asbestos in the head gasket will absorb the water and allow the gasket to be compressed to a greater degree. When the motor is run the gasket dries out and expands making for a much tighter joint. " as quoted from a 1932 Fitzgerald Gasket company of torrington CONN. gasket application book....quoted from memory.

mike lynch

Sounds great Mike , but do the new head gaskets contain asbestos? I certainly agree about using new bolts.

Another question about bolts:
If I wanted to replace all the head-bolts with hight tensile type, and not replace the head gasket, would it be permissible to remove one bolt at a time and replace with the new bolt and say torque to 50 ft/lbs and so on? then re-torque to 65 ft/lbs as recommended in previous posts?

Peter

quote=m006840] Sounds great Mike , but do the new head gaskets contain asbestos? I certainly agree about using new bolts. [/quote]

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Original gm head gaskets ( black ) were made by detroit gasket out of asbestos. It has a metal core and the asbestos is bonded to both sides. The other supplierss , gasket companies also supplied this type.

Copper and asbestos ( sandwich style ) copper both sides asbestos in the middle were also used and made by McCord gasket company, Victor Gasket company, Fitzgerald gasket company and later FEL-PRO gasket company....but fitzgerald actually supplied them too fel-pro .

Metal and asbestos ( sandwich style ) were also produced back in the 30's.

The new cylinder head gaskets are made out of either hi- pressure diesel steam material, or a mineral fiber of some sort.

Asbestos was not known to cause all the health problems until the 70's i believe. It is most dangerous when particles are airborn. Its the reason i sold the gasket king business and stock...scared the hell out of me when i found out about asbestosis.

mike

Peter , i have never done this , but i do not see why it could not be safely done as you laid it out.
Probably somebody else has tried this one at a time and will offer their advise or results.

mike