Another use for all-thread rod!

[GriffinGuru]

I am posting in the DIY section because I have an example of someone's "resourceful" DIY solution to engine building. Note: I am not recommending this as a good way to repair head studs.

This is what I found on my car after I took the upper shroud off to clean the engine. It appears that a head stud was replaced with a section of all-thread rod. This is also the cylinder bank where I seem to have lower compression in Cyls. 2 and 4. Comparing driver's side to passenger side I also notice that the cylinder barrel fins on the all-thread side do not line up with one another between cyls. 2,4, and 6, whereas on the other side the fins all seem to be in line between cyls 1,3, and 5.

At this point, and where I am with this project I'm not going to mess with it because who knows what sort of genie I'll let out of the bottle if I go into this. Did the original break, pull out the threads, are the block threads re-drilled to some other size??? I'm of the mindset that if it is not currently broken, I'm not going to mess with it. Later on, perhaps after some more of the body is repaired I may return to the engine and look into the lower compression and the cylinder stud issue, but that may be quite a project...

[er-mine]

Although clever in a pinch...all thread is kinda soft...especially the threads

It's subject to stretching...unless it's the proper grade

Perhaps that is a source of low compression ?

[Scott V]

It appears that a head stud was replaced with a section of all-thread rod.
Did the original break, pull out the threads, are the block threads re-drilled to some other size???

the original prob pulled out the threads or unscrewed if someone took off the head. who knows if the block threads are re-drilled. is the head nut on that all-thread rod 3/8-16 or 3/8-24?

like you said its not a good fix & it should be done right.......install the correct head stud when you start driving the car. you can do the repairs w/o pulling the head.

-Scott V.

[French 63 corvair]

Hi' Scott, this kind of rod should give you some mess, soon or later... In fact all thread rod do not have the same mechanic property than the original one.
When your engine run, heat makes metal going a litlle bit longer, so it's important that all rods take lenght the same way at the same time. Even when you tight head's nuts, you have to play with rods elasticity, that 's why you have to use a dynamometric tool and follow a tightening procedure...
If not, heads could fail by distorsion... You shoudn't let this all thread rod in place, it'snt a good solution in time because it could occures more problems than the cure... Please apologise for my english, I didn't have practice for a while, hope my message could be usefull for you.....

Sent from my E6653 using Corvair Forum mobile app

[66vairguy]

Sorry, but that "all thread" is a disaster waiting to happen.

The Corvair head rods are VERY strong and tough. They had a modified thread at the block to create a seal. When the block threads fail you have to install a TimeSert and retread the stock Corvair head rod to fit the TimeSert. I've done it and even when using a top quality die and special lubricant the threads are difficult to cut - a very strong alloy!!

Note: on the 64 and later engines the head stud MUST NOT protrude into the crankcase or the rod cap may hit it.

Eventually you'll have to pull the head and remove the "all thread" and see if a proper (used is fine if not corroded) head stud turns in snug. If the proper rod is easy too turn, but the block threads look good, then install the proper head stud with locktite, BUT BE QUICK. If the block threads are bad, then ONLY a Time Sert works well - NO helicoil for the head stud.

BTW - the TimeSerts for the block are a special length and Ray Sedman of American Pi sells them. The thread pitch is standard and you'll need a high speed steel die from a good machine tool place. STP (yes that STP oil additive) works as a great cutting lubricant.

[French 63 corvair]

By the way, I' think all thread rod can't resist to the proper torque of head's nuts tightening... Threads would fail before half of the tightening procedure... All-thread rods for fixing the kitchen's table... Work, to have serious engine repair... Don't work at all ![WINKING FACE]

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[bbodie52]

For reference, here is the Clark's Corvair Parts catalog page for the proper studs...

http://www.corvair.com/user-cgi/catalog ... IN&page=13


http://www.corvair.com/user-cgi/catalog ... graygo.y=0

[Scott V]

Sorry, but that "all thread" is a disaster waiting to happen.
Eventually you'll have to pull the head and remove the "all thread"

BTW - the TimeSerts for the block are a special length and Ray Sedman of American Pi sells them.

i posted that you dont need to pull the head to do this repair..............but i should have also said you need a special timesert kit to do this.

ray sedman/american-pi has the special install kits.

-Scott V.

[xrotaryguy]

Or you can start building another engine now and hope you're done before this one bites the dust.

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[GriffinGuru]

Thanks everyone for your input. I have actually been driving on this motor over last fall and this summer and I have put about 500 miles on her so far. I will be looking into doing something about the motor, but probably later this fall or in winter. I have a lot do decide on, including if I want to spend the time on this motor or focus on another. I still have a 140hp motorlined up for myself, but I need to get it out of my uncle's garage and it is supposedly buried in the back of this garage somewhere.

Realistically, I'll probably be doing some work on my current 110hp motor as well, since I don't have the other and it will need a thorough going over as well. I was originally planning on re-ringing the motor due to the lower compression. Air leak tests I did when I first got the car indicated air loss into the crankcase for the low compression cylinders. This car being a 64 (though the block has 1961 stamped on it below the drivers side push rod tubes), most recommend that the pistons come out and put them in the top of the cylinders due to the notch. So I am looking at rod bearings too?

As far as the headstud, it appears not to be drilled out and that the previous owners just matched the thread, but I'm only going by look. The head nuts all look to be the same type. I won't really know the full extent of the repair until I take it the stud out though. For now I will be putting everything back together until I form a plan of action. I won't leave it as is forever, but it has gone this far without issue, a few more miles won't do any more damage than what is already done at this point. So I hope!