Head bolts

[Doug&Deb]

The new head bolts I got have sealant on them. I believe they are small block Chevy. Should I add more or is the factory application sufficient?

[Loren]

Clean the threads in the block.

I always run a tap down every single hole.

Then spray some Brake Clean or Berryman’s in them.

An extra step is to make sure the bolts are not too long.

If the bolt threads are longer than the threads in the block they can corrode on the ends and be difficult to remove.

It’s better to put a washer under the head of the bolt than to trim the bolt ( it may corrode faster )

Bolts with sealant on the ends are “single use” they do not require any more sealant ( the first time you install them ).

Personally I don’t like “pre-sealed” bolts. It is hard to get a genuine torque reading on them. Most are “torque to yield” which means you torque them to a figure then turn them another 90 degrees. They are designed to stretch when they reach the proper torque. An idea I find a little scary.

 

The best head bolts are not bolts at all. They studs.

The gold standard for head studs are ARP brand. Very pricey!

You have to be serious to spend the $200 to 300 for ARP hardware for a flathead 6 engine.

The kits with head gaskets for V8 diesels will run you about $1,500, so don’t feel bad.

ARP studs are very nicely made but I have my own opinions on how to make studs.

ARP uses cut threads, if you made them with rolled threads they are 20% stronger. Rolled threads require a high precision centerless grinding of the stock. The rolling process forces the thread “up” making the threads a larger diameter than the shaft. Which I think is much better for use with aluminum heads. By making your own you can control the thread length a lot closer than using off the shelf studs and thus prevent the end corrosion problem. ARP uses a black oxide coating which is good but you could have them plated instead. Aircraft studs which see high temperatures are silver plated on the threads so they can be easily disassembled after long service without breaking.

[Young Ed]

What does it look like? Personally I'd clean it off and use the permatex stuff I've always used. But I've also always reused the old bolts....

[Doug&Deb]

One of the old ones broke during tear down so new ones are a must. I may clean them and use the permatext.

[kencombs]

Before deciding I would clean the breads in the block and try the new bolts for fit.  Run one in a few threads and wiggle it side to side.  If they are a good snug fit, just use them as is.  If they are not a good fit, add some sealer.'

 

There are many standards for thread fit, depth, width, angle etc and I have no idea which Mopar used nor what the maker of the ones you bought are.  But quality threads in the hole and on the bolt should be OK with the factory sealer.

 

Comparing the fit of an old one to a replacement should give you some idea.

[Los_Control]

Just do not pull a Fred when cleaning the threads.

I had a 218 engine given to me, was rebuilt & stored with the head removed for many years.

I cleaned up the light surface rust on the cylinders, then ran a tap through the threads to clean them up.

 

Then later I read that the thread pitch on head bolts is not course or fine ... they have a specific pitch. Is this true? I read it on the internet.

Only suggesting to check the thread pitch before running a tap to clean them up.

Just now, kencombs said:

There are many standards for thread fit, depth, width, angle etc and I have no idea which Mopar used nor what the maker of the ones you bought are.  But quality threads in the hole and on the bolt should be OK with the factory sealer.

I think this is what Ken is saying also  

[kencombs]

I think they (Chevy and Mopar) are both 7/16x14 thread size and pitch (threads per inch).  But they may or not that the same thread shape.

 

Here:https://www.engineersedge.com/screw_threads_chart.htm

is more than you ever wanted to know about the subject.

 

Even a small detail, like rounded edge, vs pointed edge can have a bearing on the quantity of sealer needed to fill the gaps.

 

Oops, meant to link this too:  https://www.sizes.com/tools/bolts_inch_threadFit.htm

Edited January 10, 2023 by kencombs

[rallyace]

If you have the Pioneer bolts, the sealant on the bolts will work although I will admit that I polished the sealant off and used a high quality pipe dope on the threads (Rectorseal #5). Pioneer bolts do have a rolled thread.

[LeRoy]

I needed 2 new head bolts to replace a couple that were missing (broken off even with the head) but I reused the rest of the old bolts. I chased the threads on the bolts and holes with standard tap/die. I used black RTV on all the threads that go into the water jacket and haven't had any leaks. I will say that when I retorqued after a few heat cycles the old bolts felt much nicer than the new ones. The new ones seem to stretch and have that soft gonna break in a second feeling. The old bolts were a tighter fit in the head holes (after cleaning before RTV) than the new ones. 

[Conn47D24]

I uses studs on my rebuild, purchased the military surplus ones that ome up on ebay or from Vintage Parts. 

Worked out well.

 

Typical of government though they come in boxes of 20.  Our engines of course use 21 !  

 

Two boxes bought by taxpayers for just one stud needed.   It never ends.

[James_Douglas]

I use ARP studs on my engines.  That said many years ago before they topped making them, some company in the south, I got their last stock of bolts. I have a LOT of them plus all the old ones from my many engines and spares.

 

I hope in the next year to go through all my crap and thin it out. When I get around to that, I will let let folks know via the for sale section if they want any of that stuff.

 

In the mean time if someone gets really jammed up, send me a private note and if I can find that box...I will send you a couple.

 

James