Head bolt thread chasing

[Fastback50]

Hey guys, I am ready to put my head on after getting a valve unstuck but am running into a problem.  When chasing the threads my 7/16-14 tap is VERY tight after about 4-5 threads, to the point I stopped and didn't go any further because it felt like I would be removing steel rather than rust/debris.  Is 7/16-14 the right size?  Am I doing something wrong?  I'm using 3 in 1 oil and drenching the threads and tap beforehand, and started, then backed off, repeat, but can't get further than the first four or five threads.  

Also, I bought Pioneer bolts, but noticed they have less threading than the stock bolts--did anyone else notice this when they did theirs or did Pioneer change something?  I only wonder because it looks like it would be real close in terms of having enough thread to get proper torque specs.  Thanks all.

 

 

[knuckleharley]

Have you shined a bright light down in the hole to see if there is any debris in the bottom?

When you use a wooden dowel or something to push a cloth inside the hole,what does it look like when you take it out? Rusty color? Rust flakes? Dirt?

If you suspect there is a combination of dirt,grease,and rust in the bottoms of the bolt holes,clean them of all oil and then pour them full of vinegar and let them sit for maybe two days before pulling it all out using paper towels. Look at the paper towels as you clean each hole to see what story it tells. The vinegar will eat any rust in the threads.

Finally,get a bottoming tap and CAREFULLY use it to clean out the threads close to the bottom of the hole. When it starts to feel like it's jamming,take it out and they use air,a magnet,paper towels with light oil on them,or anything else to clean out the debris that has fallen to the bottom of the hole,and start again.

Finally,and what should probably be done first is run a small wooden dowell down into each hold,and mark it where the top of the block is. Measure that distance and then measure the threaded length of your head bolts to make sure you have the right bolts. An alternate way to do this is use a depth mike if you are a tool freak like me,or just use a set of caliphers and run the long end down in the holes and read he measurement.

[Fastback50]

52 minutes ago, knuckleharley said:

Have you shined a bright light down in the hole to see if there is any debris in the bottom?

When you use a wooden dowel or something to push a cloth inside the hole,what does it look like when you take it out? Rusty color? Rust flakes? Dirt?

If you suspect there is a combination of dirt,grease,and rust in the bottoms of the bolt holes,clean them of all oil and then pour them full of vinegar and let them sit for maybe two days before pulling it all out using paper towels. Look at the paper towels as you clean each hole to see what story it tells. The vinegar will eat any rust in the threads.

Finally,get a bottoming tap and CAREFULLY use it to clean out the threads close to the bottom of the hole. When it starts to feel like it's jamming,take it out and they use air,a magnet,paper towels with light oil on them,or anything else to clean out the debris that has fallen to the bottom of the hole,and start again.

Finally,and what should probably be done first is run a small wooden dowell down into each hold,and mark it where the top of the block is. Measure that distance and then measure the threaded length of your head bolts to make sure you have the right bolts. An alternate way to do this is use a depth mike if you are a tool freak like me,or just use a set of caliphers and run the long end down in the holes and read he measurement.

Knuckle you've come to my rescue once again--thanks.  I'll do these things--was hoping to get my head put on and see if I couldn't get her running tonight, but looks like I have a bit more homework to do.  That's okay, I bought some VHT paint for the head so I guess I can take care of that while the vinegar works it's magic.  Headed to the store for some dowel....

[Don Coatney]

A shop vacuum cleaner works well to suck all the ship out of the holes.

[busycoupe]

You can make a bottoming tap by grinding the guiding point off of a regular tap using a bench grinder.  Of course, this is a one time modification of the tap.

[Don Coatney]

23 minutes ago, busycoupe said:

You can make a bottoming tap by grinding the guiding point off of a regular tap using a bench grinder.  Of course, this is a one time modification of the tap.

That also removes the temper so the tap is no longer harder than the object being tapped.

[Dodgeb4ya]

You really want to use a thread chasing tap not a threading tap which will remove thread metal.

I have use old worn out taps at times to clean threads.

[Jerry Roberts]

Long ago it was mentioned that you can take an old head bolt and cut groves in it lengthwise ( with a dremel ? ) and use it to chase the threads to prevent removing any metal . 

[knuckleharley]

59 minutes ago, Don Coatney said:

That also removes the temper so the tap is no longer harder than the object being tapped.

Leaves burrs,too. Plus the "new" bottom cutters are dull from having been ground AND you have ruined a perfectly useful tap.

Just go ahead and buy a new bottoming tap and be done with it.

http://www.mutualscrew.com/product/irwin-71614-nc-tap-set-taper-bottoming-plug-192025.cfm?source=froogle&gclid=CI-2u6eAhs8CFdgMgQodPT8Emw

$13.75 plus shipping and you have a new regular tap,a tap for taper threads,and a bottoming tap,and you haven't ruined  a good tap and you haven't wasted perfectly good working time while doing it.

[Young Ed]

Don't the head bolt holes do down into the water jacket? That would mean no need for a bottoming tap

[knuckleharley]

43 minutes ago, Dodgeb4ya said:

You really want to use a thread chasing tap not a threading tap which will remove thread metal.

I have use old worn out taps at times to clean threads.

Somebody correct me if I am wrong,but isn't a bottoming tap by definition also a thread chasing tap?

I haven't worked in a machine shop in over 30 years,but that seems to be the way I remember it.

[knuckleharley]

20 minutes ago, Young Ed said:

Don't the head bolt holes do down into the water jacket? That would mean no need for a bottoming tap

I am sure some do,but surely not all of them? I haven't pulled a head from a flat 6 Mopar yet,but can't remember ever pulling a head from anything where all the head bolts ran into the water jackets.

[Jerry Roberts]

It has been mentioned on this forum that vinegar will soften cast iron . 

[Niel Hoback]

Who wouldn't buy a tool from a place called "mutualscrew.com" ??

[knuckleharley]

1 hour ago, Jerry Roberts said:

It has been mentioned on this forum that vinegar will soften cast iron . 

How would that even be possible? AFAIK,the only thing that will soften cast iron is enough heat to make it glow cherry red.

Vinegar will completely dissolve a cast iron head if you soak the head in a tub of vinegar long enough,since it is around 5 percent acid content. Probably take a couple of decades,though. Heads are pretty thick.

[Fastback50]

Okay all, so I got busy this afternoon and grabbed a bottoming tap (which Knuckle, as far as I can tell, is the same as a thread chaser) and cleaned up all the threads using 3 in 1 oil, followed by PB, a bore brush, compressed air, a magnet, and one final blast of air.  My "gauge" was when I could thread my new head bolts all the way in by hand with little to no resistance.  And yes, many of the bolt holes thread into the water jacket, which is why I didn't use the vinegar--I wouldn't have had enough and didn't want another trip to the store.  Anyway, it seems to have worked well, and while all my bolts were threaded in I cleaned more carbon off the deck, painted the head with VHT, and drained the oil and radiator.  Tomorrow the head with new gasket and bolts goes back on and with any luck I can get this beauty running...fingers crossed. 

[Plymouthy Adams]

oh no....a "P" head

[Fastback50]

Not a fan of Philadelphia Plymouthy?  I had to research this to find out what "P" stood for haha....you had me worried that something was wrong for a minute 

Edited September 11, 2016 by jxc330

[Plymouthy Adams]

nor Pittsburg either.....