Head Gasket Failure & Replacement Saga
 

At 955 miles on a rebuilt Model "B" engine with a Synder's 6:1 cylinder head, its Best 573 Head Gasket failed between Cylinders 3 & 4 during a parade. At the time, the spark lever was advanced to about 15 degrees (30 degrees BFTDC). Running 87 Octane gasoline with GAV 1/8th turn open, TT10 Motorcraft Spark Plugs & 12V negative ground ignition.


Thinking about the cause of failure, I suspect: (1) Lugging the engine with too much spark advance during the parade; (2) Generally driving with too much spark advance (20 - 25 degrees ignition); (3) Loosening Cylinder Head Nut 8 to remove the distributor and not re-torque enough. The engine did not overheat since its rebuilding.



Replaced the failed gasket with a Best 509 Kevlar Gasket without sealant. Initially torqued head to 55 lbs-ft in steps of 30, 45 and 55. Overnight the gasket compressed without any engine run, so I re-torqued the head to 55 lbs-ft.



Timed the ignition at TDC #1 with the spark lever down 5 notches to regain full travel of the lever with the 6:1 head. With water as a coolant, I ran the car 13 miles, drained the coolant to add anti-freeze and re-torqued the head while it was hot to 60 lbs-ft. No leaks while engine is running.


More to follow as I put more miles on the car.

Re: Head Gasket Failure & Replacement Saga
 

Retorque head when engine is cold, and check two or three more times after it has gotten some miles on it and retorque again cold.

Re: Head Gasket Failure & Replacement Saga
 

Rotten luck this year, Bob, sorry to hear you’re having more problems.

Re: Head Gasket Failure & Replacement Saga
 

I NEVER put a head gasket on without sealer. Nuf said.

Re: Head Gasket Failure & Replacement Saga
 

Bob: Have you ever had your 6 to 1 Snyders head checked for flat? I personally have never had a Snyders head, but several club members have, and they tell me that the Snyders head straight out of the box can be as much as .012" out of flat at the head gasket mating surface, and had to be taken to a machine shop to be resurfaced. Installing the new head straight out of the box without checking has resulted in the same problems that you describe. Anyway, that's the word from the Rockford A's.

Re: Head Gasket Failure & Replacement Saga
 

The 509G seals well dry, if the mating surface is clean and flat. AER did theirs that way for years.

Re: Head Gasket Failure & Replacement Saga
 

I think the best way to keep the head gasket sealed is to check the torque of the head bolts/nuts often, for a year or so, then once a year after that. A head that is a bit out of spec for flatness especially needs to be kept tight.

Re: Head Gasket Failure & Replacement Saga
 

I use the graphite Best gasket with the copper coat spray adhesive. That has worked the best for me.

Regarding flatness, you can smear some blueing on a sheet of flat glass and then rub it on the head. The high spots will pick up the blueing and the low spots will not. If the glass rocks then you are in real trouble and will have to have it decked.

If the block or head has small divots, you can fill these with JB Weld after a through cleaning with acetone or lacquer thinner. Dress the cured JB Weld flat with some fine wet and dry paper mounted on a flat object.

Re: Head Gasket Failure & Replacement Saga
 

I think it was Brent Terry who first clued me in that JB Weld ExtremeHeat is good for this purpose, and easier to work with because it’s a metallic putty rather than an epoxy.

Re: Head Gasket Failure & Replacement Saga
 

I must have gotten lucky. I took my 6:1 Snyders head to the machine shop to be checked and he said that it was surprisingly flat.

Re: Head Gasket Failure & Replacement Saga
 

I checked the head and block with a straight edge, feeler gauge and light, and found both to be flat within a few thousandths of an inch, good enough to use.

As for the torque, I estimate the clamping force as follows:
The attached chart estimates clamping forces vs torque. Looking at 7/16-20 Grade 5, 35 lbs-ft produces 4900 lbs clamp-up. Assuming the torque relationship to the clamp-up is linear, then 60 lbs-ft / 35 lbs-ft = 1.7, so 1.7 x 4900 lbs = 8330 lbs clamp-up.

Raising the torque to 65 lbs-ft increases the clamp-up by 770 lbs.

Katy! Good catch re the stud size. I fixed my estimate for 7/16-20 Studs.

Re: Head Gasket Failure & Replacement Saga
 

Increasing torque doesn't do anything beyond the point needed to resist the combustion forces. It only increases the risk that the bolted joint fails. The failure point is likely to be the block itself. Those threads will shear off before the stud does.

Re: Head Gasket Failure & Replacement Saga
 

Your engine uses 5/16-24 head studs?

Re: Head Gasket Failure & Replacement Saga
 

Replaced the failed gasket with a Best 509 Kevlar Gasket without sealant. Initially torqued head to 55 lbs-ft in steps of 30, 45 and 55. Overnight the gasket compressed without any engine run, so I re-torqued the head to 55 lbs-ft.

Timed the ignition at TDC #1 with the spark lever down 5 notches to regain full travel of the lever with the 6:1 head. With water as a coolant, I ran the car 13 miles, drained the coolant to add anti-freeze and re-torqued the head while it was hot to 60 lbs-ft. No leaks while engine is running.


More to follow as I put more miles on the car.[/QUOTE]

Bob,
Based on my experience breaking engines in on a dyno, I believe there may be "more to follow."

The Kevlar/GraphTite (Best trademark) gaskets are prone to leak during the first couple heat/cool cycles. They often weep a bit of water until they fully seal. I find it takes an average of 3 heat/cool cycles for the gasket to bond to the surfaces. Changing to antifreeze with only one heat cycle may cause or allow the coolant to seep between the surface of the gasket and either the head or block. Once antifreeze gets between, the sealant imbedded in the gasket will not properly bond to the metal and then it leaks when put under load. I have proved this to be true multiple times with the dyno loading.

After observing a few failures when starting to use the Kevlar or Graphite gaskets, I now only run my new engines with clear water when on the dyno. I also ask my customers to use clear water for a couple hundred miles before changing to antifreeze. Since starting this practice, we have not had report of any failures. This procedure works for me.

Please keep this information in mind should you experience another failure.
Good Day!

Re: Head Gasket Failure & Replacement Saga
 

Great advice Dave, I’ll do that on my next overhaul.

Re: Head Gasket Failure & Replacement Saga
 

I did a second head torquing today while the engine was hot. Some of the studs at the center of the head needed adjustment. I plan to do more re-torquing while the engine is hot until all of the studs stay at 60 lbs-ft.

Re: Head Gasket Failure & Replacement Saga
 

Bob, without performing a deck thickness test either with a sonic tester or by measuring the deck to pain rail with a micrometer, I would be leery of torqueing past 55#. The cast will actually begin pulling the threads and the area unsupported by the head upwards which can/will cause the gasket to leak. Torqueing head studs in a Model-A/B (-especially a Model-B) is definitely an area where if a little is good, then lots is better does not apply. Also, I would refrain from torqueing when hot and allow the entire package to return to ambient temperature.

I completely concur with Dave's comments in Post #14 above as those are basically my experiences too.

Re: Head Gasket Failure & Replacement Saga
 

Like Dave I think coolant / water getting in between the gasket and the head / block shortly after putting on a new gasket can be the cause of a head gasket failure.

This is how I go about it.

Using the Best brand graphite gasket I start the engine without any water/coolant and let it run at just above idle for about a minute.
While doing this I hold my hand on the head at the front right (passenger side) so I can feel the temperature as it starts to warm.
I find that that is the area of the head that is the first to warm up. Once I feel heat start to come up in that area I shut off the engine and wait to allow the heat to saturate through the head. Keep feeling around the head after it is shut off and you can get a good feel of how the heat moves through the head.
After it has had time for the heat to saturate through the head I torque it warm.
Notice I say warm... I don't run the engine until it gets hot.
Then after this I allow it to cool completely and torque it again cold.
Then I repeat the process at least a couple more times, more if necessary until the torque settles in at 55 lbs.

After I'm satisfied with it staying at 55 lbs. I fill the cooling system with water, place a dial probe type thermometer into the top of the radiator and cover the front of the radiator with a piece of cardboard.
Then I start the engine and watch the thermometer like a hawk and bring the temperature up to 190 degrees. Then I slide the cardboard down a bit as needed to keep the temperature at 190 for several minutes. After that I remove the cardboard and allow it to idle for a little longer to bring the temperature down a bit and then shut off the engine.
Then I torque it hot, allow it to cool completely and torque again cold.
I repeat at least once and sometimes more until I'm satisfied that the torque is staying rock solid at 55 lbs.

Not a fast process as it usually takes two or three days for the entire process but it has been working well for me.

Dave

Re: Head Gasket Failure & Replacement Saga
 

Here are some photos of the head gasket failure & replacement:

Re: Head Gasket Failure & Replacement Saga
 

It would be a significant aide to our hobby if someone would take a scrap cylinder block, insert some studs, torque them to failure, measure the force when failure occurs and describe what failed.