MTFCA Forum

My head bolts are stretched (see photo.) Does anyone use studs instead? Source? Thanks.

Studs should work. If you use studs with fine thread for the nuts, torque values will need to be adjusted.

Ask a Model A owner about head studs... the threads in the block may last a bit longer, but if you can’t get the head off... does it really matter...?!

But grade 8 bolts!!

Buy grade 8 bolts!!

As stated above god forbid if you need to remove the head again with studs. Horror show. Buy better bolts.

I do not know about other years, but the 26-27 firewall overhangs the engine, so you cannot lift the head straight up. If studs were there you would need to first remove the studs to remove or install the head.

Model A's have studs, I removed a Model A head once, what a job. The studs and head bonded together with rust and crud, what a nightmare.

I agree with the above. The Model T parts suppliers carry the replacement bolts, unless they are back ordered. I have had many Model A's in the past and the studs can cause the same problems as the bolts except that they don't need to be removed every time you remove the head. I even tried leaving the spark plugs in and starting the engine with the nuts off to try to get it up. If you can get it up far enough you can pry it up, but need to be careful not to damage the top of the block or bottom of the head with your prying tools.
If you strip the threads in the block they can be repaired successfully with heli coils.
Only way to get the head off a T without removing the engine if it has studs is to either pull the engine, or remove the radiator and loosen the engine supports and U joint and slide the engine forward. Or remove the body.
Norm

Norman Kling wrote: ↑

Fri May 27, 2022 1:22 pm

I agree with the above. The Model T parts suppliers carry the replacement bolts, unless they are back ordered. I have had many Model A's in the past and the studs can cause the same problems as the bolts except that they don't need to be removed every time you remove the head. I even tried leaving the spark plugs in and starting the engine with the nuts off to try to get it up. If you can get it up far enough you can pry it up, but need to be careful not to damage the top of the block or bottom of the head with your prying tools.
If you strip the threads in the block they can be repaired successfully with heli coils.
Only way to get the head off a T without removing the engine if it has studs is to either pull the engine, or remove the radiator and loosen the engine supports and U joint and slide the engine forward. Or remove the body.
Norm

.........Or, remove the firewall on pre 26 T's.
Studs certainly add a lot more time & effort to a head removal, but doable.
I wonder how head bolt strength compares between replacement V/S original bolts. Any feedback?
If originality was not important to you, go with grade 8's. You can remove the nomenclature to make it less obvious.

I would have to assume that the block threads would "give" well before stretching a head bolt !

I checked all the threaded holes in the block, and lightly chased them with a tap; they are all good. but many of the head bolts are stretched.

RajoRacer wrote: ↑

Fri May 27, 2022 2:30 pm

I would have to assume that the block threads would "give" well before stretching a head bolt !

Honestly, you're probably lucky that they were cheap bolts. I'd bet that even though they were not proper hardness, they likely were torqued to just under yield strength of the block.

Proper bolts, like Les said, and then judicious tightening will put things right.

BTW, though FORD never specified torque, he definitely supplied the workers with wrenches commensurate to the force you'd apply...TT truck axle nut wrenches were about 2 feet long... "T" rear axle differential wrenches were about 6 inches long. Use the correct FORD wrench or equivalent, do not strain yourself and you'll be in the range of correct tightness on any fastener on the car.

Thanks for all the incite and advice. Sounds like Gr8 bolts (really available) are a good option, provided torque applied is 'judicious.'

Sounds like studs (very difficult to source, i have found) would be ok too, and might be kinder to the block, but only if seizing and corrosion is rigorously mitigated.

I’m going to suggest something…Prussian Blue your bottom tap and run it in again.

I suspect that on that hole you have maybe only 3 active threads left? You can’t have bolts at one pitch…and taps at another…say they are from the same ‘set’…just doesn’t work that way.

When I look at those bolts...the stretch area appears to be in 'air', meaning the clearance area in the head itself and are perhaps the result of something called 'creep'? The shiny areas also indicate just how little thread engagement there really is.

Folks love to quote torque values from tables cause if it’s printed it must be true,eh? I have trouble with that on T head bolts. The design values in the tables were based on 9 threads engaged at this size….in a Model T you are lucky to have 6 threads engaged due to the max depth being based on 3/8” threads of the original T design. some get lucky and torque high just because they think they can…and some go 55-60 torque on aluminum heads. Some also wind up heli-coiling when going for torque.

As Scott points out, use the head bolt wrench, no cheater bar, give it a hard pull. Usually good enough to seat a head gasket….

CLEAN OUT THE BOLTS HOLES IN THE BLOCK!
ALWAYS do this first then run a bottom tap in the holes and use air to blow them out. Start from the middle and work your way out. Pretty straight forward to tighten the head down.

Doing the basic things first on old engines and especially flat heads is a must then torque the head down a good reasonable amount. I should have said tighten instead of torque to simplify the job. I never used a torque wrench until a few years ago on a T engine. Never a problem with stretched bolts, or threads in a block I worked on. Had a block or two that someone in the past stripped some threads for some reason. You don’t need to tighten a T head down with a 2 ft. cheater pipe or bar plus using studs to ‘get it good and tight’

I would NOT use grade 8 bolts on a T engine. They are not needed, and they may cause problems. They are hard and slick, so torque tables will not apply. They may have too little stretch for the application. A slight stretch in head bolts can be beneficial and is necessary in some applications. I'd look very closely at the threads in the block in question. I don't see how head bolts could get distorted like the one in the picture if it was screwed into good threads in the block, no matter how tightly. The new head bolts that are sold by vendors for T engines will work well if they are used in a block with good threads and installed properly.

To get a good cylinder head seal, the block and head surfaces need to be clean and in good condition, and the threads in the block need to be clean and in good condition. New bolts are inexpensive and good insurance. A torque wrench isn't magical, but it can aid in getting bolt torque uniform. Most all antique engines will need the head bolts (properly) retorqued several times after a head is newly installed. A torque wrench is handy here, too. High torque on a T engine is asking for trouble. Reasonable torque and correct retorquing will get the job done.

Regarding my photo showing the stretched bolts, as indicated by the thread gauge. The bolt threads that were within the block are fine, but the bolt threads that are above the block show stretch and necking from yield stress. I'm guessing that the tensile stress in the bolt reached yield, likely from over-torque, so it began to neck and yield at the weakest point: the minor diameter of the threads just above the surface of the block.

Comments deleted, since I can't delete my post entirely

Steven, I see the same thing and believe your assessment is spot on

pay attention to those folks who admonish you to clean the threaded holes...that is very good advice

also, when you're ready to button it up, put the head on without a gasket...then ensure all bolts will bottom on the head to avoid possibly bottoming out in the hole...which really will destroy the block threads before you know what hit you.

henryford2 wrote: ↑

Fri May 27, 2022 5:46 pm

..Nothing wrong with a grade 8 bolt if you follow the torque spec. for that size bolt, but it will and can can rip the threads out of the T block before the threads on the bolt fail if you exceed it...

Agree and understand. The modulus of elasticity of any grade of steel bolt is nearly equal, so the stretch (tension) relative to torque is the same too. But the strength of the bolt shaft and the treads is a lot stronger in a Gr8 vs Gr5 or lower. So in a battle between the strength of the cast iron internal threads in the block, and the Gr8 bolt, the block will lose.

Flivver wrote: ↑

Fri May 27, 2022 6:08 pm

henryford2 wrote: ↑

Fri May 27, 2022 5:46 pm

..Nothing wrong with a grade 8 bolt if you follow the torque spec. for that size bolt, but it will and can can rip the threads out of the T block before the threads on the bolt fail if you exceed it...

Agree and understand. The modulus of elasticity of any grade of steel bolt is nearly equal, so the stretch (tension) relative to torque is the same too. But the strength of the bolt shaft and the treads is a lot stronger in a Gr8 vs Gr5 or lower. So in a battle between the strength of the cast iron internal threads in the block, and the Gr8 bolt, the block will lose.

It appears that the bolt threads below the stretch are rather short. Not a good bite into the block. that adds to the possibility of pulling the block threads. Any idea what the torque was /is on these head bolts? Its clearly 5-10 #'s over max.

Our GM Holden 6 cylinder engines have higher spec but the same size head bolts as a T but the heads are 1/16" bigger. The real benefit in using them is they are a bit too long to use in a T. This means that I can get longer thread engagement for each bolt. I always run a drill down the holes in the block to break up any crud in the hole. Then a bottoming tap cleans up the rest. I fit the head with no gasket and adjust the head bolt length for maximum depth.
Any replacement bolt could be put through the same steps.
The above is particularly pertinent when fitting a Z head, with it's varying deck heights and additional washers under the bolt heads.

Allan from down under.

Either Grade 5 or 8 bolts will carry more torque than the block will likely survive if you want to plow that into it.

The stretch that that bolt underwent leads me to believe that it is a common Grade A that was severely over torqued for it's spec and may never have actually put that full torque into the block...thus the block threads surviving

unless the threads in the block are spectacularly pristine and you have the luck of the Irish, I'd stick around 40 ft/lbs without real risk to anything. I use a wrench length equivalent to what was originally used, put the "oomph" into it that I think a 40+ y/o guy could muster several hundred times in an 8-10 hour day and call it done. I've checked my work occasionally and it is generally around 40 ft/lb. Do that 2-3 times after a run or two and a couple days, and they stop creeping and everything seals. Life it Good.

As was said previously, I would not use studs. Many years ago we were trying to get the head off a flathead Pontiac six equipped with studs and nuts. After removing the nuts, applying penetrating oil, trying to pull it off with a setup that involved a couple of spark plug holes, and exhausting our supply of profanity, we reinstalled the plugs and started up the engine. It ran for abut a minute before it blew the head off. And yes, we did reinstall a couple of cylinder head nuts loosely to retain the head just in case...

Put a heli-coil or other thread repair in that hole. How can a bolt stretch in the middle of the threads if the threads in the block are good? It can't! Either the bolt was bottomed in the hole so that it could no longer turn and continued force began twisting the bolt and pulling the lower threads in the hole, or there is a middle section of bad or no threads in the hole. If all threads are good, properly engaged, and the bolt is not bottomed, then the "stretch" should be between the head of the bolt and the threads, not in the threads themselves. I doubt that you can barely even stretch a 7/16 bolt at 50 or 55 ft/lbs torque, and more than that often pulls the threads out of the block. As others have said above, there weren't torque specs given. Tools were designed to give reasonable torque. That is why wrenches get longer as the size gets bigger. In old service manuals you may find a torque spec written such as "a strong pull on an 8 inch wrench."

I had once suggested that at Chickasaw someone set up a fish scale on a table top with a D handle and ask the passerby to give it a firm pull...then record the results...to share the results. Lot's thought it was cute and funny yet it never happened

There seems to be some interest, and some confusion, regarding these stretched head bolts. Here is another picture, comparing a non-stretched bolt, a stretched bolt, and a 7/16-14 UNC tap. It clearly shows how the bolt has stretched mid-thread. Here is another photo showing why the bolts are stretching mid-thread. Notice that when fully installed (this photo is taken with the bolt depth exactly as installed - imagine I just made the head invisible) part of the bolt thread is above the block-head interface. The bolt stretched in the threads just above the interface. For completeness, these are 7/16-14 UNC x 3-1/4 long head bolts, removed from a 1926 T. I do not know their origin or what torque they were tightened to. (first time I have had the head off of this new-to-me car.)

They look like Ford V8 head bolts.

To my eye, both bolts matched to the tap are stretched at almost the same amount. In the length of thread each is stretched about 1/2 a thread. If you clean out the holes in the block, how much further can the bolts be screwed in?If you can get another 1/8" into the hole, you will have much better engagement. That will require longer bolts to maximise the depth of the bolts and lessen the chance of stripping the block.

Allan from down under.

Flivver wrote: ↑

Sat Jun 04, 2022 8:30 am

For completeness, these are 7/16-14 UNC x 3-1/4 long head bolts, removed from a 1926 T. I do not know their origin or what torque they were tightened to. (first time I have had the head off of this new-to-me car.)

Yes, that is the issue, you are re-using old bolts of unknown age, conditions of use like heating cycles, thread wear, oxidation, and other issues of old bolts.

The best policy for reducing breakage or thread pull out in the cylinder block is to use new bolts.

Here's photo of a new bolt (lower) and old used bolts, note the old bolt above the new one, it shows similar distortion. When tightening a head bolt, it will deform slightly, as the head of the bolt is fixed on the cylinder head, and when tightened down, the pull of the block threads will stretch the bolt some. More will happen with re-use too.
(Tad of anti-seize helps prevent a stuck bolt and risk of broken- off one, over long time engagement)


And take care not to use too much torque on these 7 /16" x 14 head bolts. A good pull with the Ford head bolt wrench will do about 40lb/ft, that is usually OK. Proper sequence of final bolt tightening, beginning first in the center of the head, then working out to the edges and ends for best gasket seal is likely more important than any torque values!

If all the extremely good, cleaned and flat surfaces, new head gasket, with a re-built engine, and all block and head cleaned and good condition bolt hole threads in the block, going up to under 50 lbs/ft ,in that aged old block, may be done. Anything after that is a risk IMO>

Hello T friends. I'm totally new here and making my first entry. Please excuse my bad language as I'm from Switzerland.
I'm following this topic with interest. I bought one a few months ago as a new Hobby Touring 1926 which I now want to get fit again. The head was dismantled and some threads torn out. I repaired this with Time Sert.
But then I was very surprised at the brief engagement of the cylinder head bolts in the block and then I discovered a number of posts about this problem in the forum.
So I rethreaded the block down to the bottom of the holes and got new, longer head bolts (I think these were from a Ford Capri).
These screws now grip 0.87" (22mm) in the engine block.
But they have a strength of 12.9! Is that too strong? Do I have problems with that? Thank you for your opinion.

Hi Newbee!

Just very, very light coat of aluminum anti-seize and torque to the the specs.

When replacing head bolts, grade 5 or grade 8.., do NOT forget to chase all new bolts with a die. #1 failure is a flaking of coating on modern bolts, which in turn cause an inaccurate torque. Don't forget bottom tapping the block too!


Hank

I recommend that the threads are clean and dry. Using lubrication drastically changes the bolt tension, which can lead bolt stretch.
I conducted a test to demonstrate the difference in the bolt tension. The tension with oiled threads is about 40 percent Ihigher than with dry threads. I torque the head bolts to 40 to 45 ft lb.
Not sure what I would do with an aluminum head

Art Mirtes

Before bolting down the head, chase the threads with a tap and blow out the holes with high pressure air. Using duct tape, tape over all block holes (cylinders, valves and water jacket holes) to prevent debris from bolt holes to fall into the holes. Once each bolt hole is blown out, screw in a bolt to keep debris from other bolt holes from going into the clean bolt hole.

When bolting down the head, to avoid cracking the head, be sure to alternate the bolts. Tighten down each one until finger tight, then alternate the tightening in 10 ft./lbs. until each bolt is torqued 50 to 55ft./lbs. Run the engine until hot. When it cools, torque 50 to 55ft./lbs. again alternating the tightening process using the attached diagram. Jim Patrick

This could account for a case where the head bolts were torqued to 50 ft lbs and the gasket blew! This was after the head had been re-surfaced, so the bolts would have needed to be turned down just a small amount more than before resurfacing. I am about to replace the gasket which blew, and will check out and maybe replace the bolts this time, because gaskets are hard to come by.
Norm

Thanks for the feedback

Some time ago I installed the cylinder head and the screws as you described. To look authentic I lathed the screw heads and painted them black as shown in the pictures. Thanks to the longer screws, I now have a very good grip in the engine block.

My only concern is the tightness of the screws. As I further informed myself, the European standard 12.9 is stronger than grade 8. I hope that doesn't cause any problems with the threads.

Greetings from switzerland

Vonau wrote: ↑

Sun Jul 17, 2022 4:57 pm

To look authentic I lathed the screw heads and painted them black as shown in the pictures. Thanks to the longer screws, I now have a very good grip in the engine block.

I really like what you did with the heads of the Class 12.9 bolts. Nice!

If you don’t have a lathe, you can get the same results with a drill press and sandpaper. I have done it plenty of times to remove modern markings from the top of hex head bolts. Jim Patrick

Vonau wrote: ↑

Sun Jul 17, 2022 4:57 pm

the European standard 12.9 is stronger than grade 8. I hope that doesn't cause any problems with the threads.

I’m a bit curious about the 12.9 grade screws, as all I have ever seen in 12.9 is metric thread hardware. The Ford blocks I have encountered here in the states are threaded 7/16”-14, are globally produced variations equipped with metric hardware...? Metric grade 12.9 is basically equivalent to grade 9, and are common grades for all socket head fasteners.

7/16”-14 (.437” x .0714”) is close to M12x1.75 (.472” x .0688”), is it possible that this block was tapped out to this slightly larger size...?

Hi

No, they are the original 7/16"-14 threads in the block.

When I looked around, we often found inch screws with a European standard. I could imagine that these screws are made in Europe and are therefore labeled with the European standard.

The Ford Capri from which the screws come was produced in Germany.

Greeting

We learn sumpin new everyday...!

I probably shouldn’t be surprised that the bolt grades are cross pollinating, but so far this has been my primary method of sorting hardware. I’ll have to watch closer...