what tap do i need for chaseing the block threads?

[78fordf150]

what tap do i need to chase the threads on the block for head bolts i know a bottoming by what pich

 

[icanfixall]

I'll give you the tap for both the 6.9 and 7.3 blocks because you didn't post what you have..... The 6.9 is a 7/16x14 thread and the 7.3 is the 1/2x13 thread....

 

[Diesel JD]

The best tap for this is a bottoming tap, but they can be hard to come by. I just used a normal tap that was otherwise correct for the 6.9 and it was fine, but the most correct one is a bottoming tap. Gary I'm surprised you didn't instruct him on how to make a bottoming tap from a normal tap. One more thing: ALWAYS put a handle that is bigger than the water jacket or bolt hole on these taps, otherwise you might not like the result.

 

[RLDSL]

. One more thing: ALWAYS put a handle that is bigger than the water jacket or bolt hole on these taps, otherwise you might not like the result.

It's fine as long as you dont go trying to poke the tap down holes that don't have any threads in them like happened to a buddy here on a recent head replace job Luckily I've been down that road a time or two before and fished it out without too much trouble. Once they lay down in the bottom of the water jacket a pencil magnet and a pick will get them out with a little patience.

Trying to make a bottoming tap out of a plug tap isn't the greatest idea, the metal gets REAL brittle and can break off easily in the hole leaving a mess to deal with.Best to just get the proper tool

 

[hce]

You should have special thread chasing taps. They only clean the threads and do not remove material from the block.

 

[icanfixall]

You are correct sir... I'm being a little remiss these days... Its easy to make a bottoming tap from any starting tap. Just cut off the tapered threads but do not allow the tap material to change colors from the heat buildup. In the past I used a cutoff wheel thats very thin. Cut for about 5 seconds and cool in water. Continue till your done. If the tap changes colors you have overheated the metal and it will break. A good metal supply store will have the bottoming tap. McMaster Car and Grainger sells them too. One tap is all you need for all the threads on both heads. Use a thread tapping lube Like Tap-Eze. Thats stuff works like magic to reduce the surface tension on the tap to cast iron...

 

[Knuckledragger]

Those are fine for running through cruddy nuts, but do not have the same effect. A bottom tap will create threads to the very limit of the hole (hence the name bottom) so the studs you are installing do not gall near the bottom and give false torque readings.

Bottom taps are not any more expensive than plug taps, and are easy to get from industrial and/or hardware suppliers. O'Reilly's, NAPA and Kragen may not have them.

 

[OLDBULL8]

One tap is all you need for all the threads on both heads.

What? Clarify that.

 

[SkipBurney]

If all you are trying to do is chase the threads and clean the trash out of them why not just use a bolt with the correct threads and some lube then wash the holes out with carb cleaner and a quick shot of compressed air?

 

[icanfixall]

Using a bolt will not clean out the threads because it had no cutting ability. It will push the dirt deep into the threads instead of cutting it off the threads. Even making cute in a bolt will not work like a tap because the tap is harder material and its designed to cut or clean threads. Good question too...

 

[SkipBurney]

I have done them both ways using a bottom tap and a bolt and unless the threads have been damaged and need restoration I will use a bolt and spray carb cleaner in the hole and blow it out with air. A 1/2 13 tap is hard to break but it can happen and if it does you are gonna be a really unhappy boy.

 

[RLDSL]

The thing is the residue from the factory bolt lube has oxidized and turned into a hardened crud that has solidified in the threads, then to top that off, moisture has found it's way in there from various modes of condensation and rust has formed in the threads on many of them leaving heavy deposits that will give you completely inaccurate torque readings. Just running a bolt down there with some cleaner is not going to remove these deposits, they are too hard. A proper bottoming tap is required. This is one of those cases where when all else fails, follow directions. THey put it in the manual for a very good reason.. This should be done on ANY engine when rebuilding or replacing the heads
I also use bottom taps on the intake manifold holes in the heads and a number of other places where critical torque is required.( exhaust manifold fasteners rely on a certain amount of friction for proper torquing and their threads are best left alone aside from new fasteners being used making sure the proper torque is applied for the type of bolts used)
They aren't that hard to find, even here in the middle of podunk nowhere. You can either do a job correctly or you can do it twice, take your pick.

 

[rhkcommander]

This is the Internet. Things are cheaper and there's no excuse for not being able to get it

http://www.wholesalepowertools.com/...16-x-14-nc-carbon-bottom-tap-tpcb-437x14.html

That'll do for a 6.9 right? It's pretty cheap is there a certain alloy to go with or is this good?

 

[icanfixall]

What? Clarify that.

Gees... I see what you mean. What I was attempting to say is buying one tap of either block is all you need to buy. One tap will clean all 34 bolt holes in one block easily. I didn't mean ... Buy one tap and it will clean the threads in both the 6.9 and the 7.3 blocks... Sorry... My thoughts were clear but the works were not....