Regardless of length, shold all head bolts be uniform?

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Model T Ford Forum: Forum 2016: Regardless of length, shold all head bolts be uniform?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Tuesday, February 09, 2016 - 08:08 pm:

Replacing the head gasket on my 26/27 engine and had to deal with a helicoil in one hole. I've purchased the high head set of head bolts from one of the vendors. No washers.

Of the bolts I took out, one was broken, 12 were 3 1/4" in shank lengh and two were 3 3/4" in shank lengh. None had washers. The shorter bolts seem to have very little threads length left after passing through the head and copper gasket. All of my head bolt threaded holes are solid at the bottom, none are drilled all the way through and none appear to have been broached when I clenaed them all out with a welding rod and compressed air and a shop vac.

So, whould all my head bolts be the same length? And, with three of the head bolts used to secure the coil box on this engine, does that make a difference? Should I used a washer on all the head bolts EXCEPT for the three that hold the coil box and use the coil box bracket as the same spacer?

Just put the new bolts in, torque to 50 and stop fretting?

I'll hang up and listen.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Tuesday, February 09, 2016 - 08:23 pm:

Unless the head or block was surfaced and now is shorter, would just use the new bolts for the '26-'27 as it... guess you got the nickel plated ones?

To be real sure, just place a measure stick into each hole in the cylinder head to bottom out in the block, checking depth of each hole from the seat at the top of the head where the bolt will be. Then measure that stick to your new head bolts. The bolts should be shorter than the measure you made with that 'stick'.

Washers are not used on head bolts, and the same bolts hold the coil box on a '26-27. Washers (ss) are used on aluminum high compression heads under the bolts as turning steel bolt heads against the alum head will gall the heck out of your new head!

Torque with extreme care, 45 to 50 ft lbs with a new gasket (use a sealer on the gasket faces) and flat surfaces will make it most times, more torque and you might strip another bolt hole! Re-torque to the setting used after warm up or running 10 or so miles, a few bolts might take up whatever slack occurs after running.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, February 09, 2016 - 09:32 pm:

Ideally they should all be the same length. A good way to check is to put the head on without a gasket and tighten all the bolts. Just finger tight. They should all turn easily without binding. They should go all the way in. If you find one is too long, grind a little off it. Best to then grind all the bolts to the same length as the one you had to grind off. After you do that, remove the head and install the gasket and torque to 50 ft lbs. Start in the center and work out toward the sides and ends. Start with 35 ft lbs, then go back and tighten to 40 ft lbs , then 45 ft lbs finally 50 ft lbs. Then after you run the engine and get it warmed up tighten again to 50 ft lbs. Do this several times until they stay at 50 ft lbs.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd, ............Red Deer, Alberta on Wednesday, February 10, 2016 - 11:40 am:

You said you have a 26/27 engine, but are you sure that you have a high head?
It's possible that the head has been replaced w/a low head at some point, which would require the shorter bolts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, February 10, 2016 - 01:55 pm:

Robert,

With a new head gasket, those 3-1/4" bolts should have something just less than 7 threads sticking out.

You expected more? :-)

No, Ford broke the rules while in a panic induced shotgun fix effective at the end of the first 500 cars, and replicated that same technical 'mistake of convenience' for over 15 millions copies without blinking twice simply because it worked most of the time! :-) This is why IMHO pulling to 50+ foot-pounds should be discouraged unless the block has been Heli-coiled or inserts added. The original bolt material was "Bessemer Steel" which at best is a Grade 2 material...

The proper design length of engagement for 7/16-14 bolt should be 9 threads (for those who use torque tables)...and chances are that the top thread is near shot already on any 100 year old block (Block taps fail by not instant shear but rather 'pancaking' from the top thread down, so if the top thread 'wiggles' from prior wear n tear consider it gone as to providing strength.)

Long story short...folks are probably only working with 50% of the threads a 7/16-14 SHOULD have for the published torque tables. A few here will not go above 40 ft-lb and claim success. Sure, there was a safety factor and it may have been 1.5 to 1...may have been 4 to 1, I do not know but torqueing past 50 surely uses up a whole bunch of it! :-)

(Soapbox now tucked away)

Do assure your 15 tapped holes are clear to the bottom, and use the trick mentioned above by using the actual bolts (numbered) as a depth gauge!

Your head should be 2-11/16" high, (but may have been decked at some point)...A new gasket will be just a whisker full of 1/16" (a mushed one comes in at just about 1 millimeter/full, so base your final height on that [0.044"])...and you should leave something at the bottom of the tapped hole so that you will not bottom out.

Ford to the best of my knowledge never made a bolt longer than 3-1/4" shank length....however...

Knowing now the failure mode where Ford originally did not...knowing now that the top thread at age 100 or so is probably weakened to the point it should not be counted on...I could actually consider and condone taking the bolts used to hold the coil box on the block and add a thread to account for the change in engagement to the block!

Other opinion may vary!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Wednesday, February 10, 2016 - 02:21 pm:

To summarize, all bolts should be the same length regardless of coil box brackers or not. I'll wait till I get my new bolts in and slide them through the head and the gasket and see what is left sticking out the bottom. Should be 7 or 8 threads.
No washers.

If I get significantly longer threads sticking out the head and gasket, I'll make the determination of my head height and bolt hole depth and go from there.

So my Bubba bolts of two different lenghts were not correct and my coil box does not change any bolt decisions. No washers. They sell them as a set from the vendors, but must be for the aluminum heads only from what I've read here.

Thanks to all.


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