chasing head bolt threads in the block

Cyrus

Cyrus

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Apr 21, 2008
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should this be an absolute bear of a job? i feel like i'm doing something wrong.

i am using a standard 1/2" T-handle tap wrench and i can't turn the thing without using a 12"+ cheater bar. ive done 3 holes so far and it has been like this on all of them.

im using a 12mm x 1.25mm plug tap (im using ARP bolts, not studs so im risking going without the bottoming tap). ive tried using a standard lubricant (Tri-Flow Superior Lubricant), 5w-30 motor oil, and most recently some cutting/tapping fluid. doesnt make a difference, it is still hard as fuck to turn this tap wrench.

i am able to hand thread an arp bolt all the way into the holes ive chased so far, so i dont think im doing anything too bad to the block... just wanted to check in and see what other's experiences have been with this.

thanks!
 
Cyrus

Cyrus

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i've been going 1 full rotation clockwise, 1/2 rotation counter clockwise.

yes, i am 100% this is a 12mm x 1.25mm plug tap.

there have been absolutely no chips. in fact, about the only thing that has come out on the tap has been some thick gray/black grease.

2 hours later, i just finished the last hole. holy fuck. that was absolutely exhausting. by far the most physically challenging thing ive had to do for this rebuild so far.

the arp bolts thread in absolutely perfectly, into every single hole. dunno why that was so fucking tough, but i really hope i dont have to do that again anytime soon. ;)

i ended up sticking with the Tri-Flow Superior Lube product. it seemed to help the tap glide the best of the various lubricants i tried.
 
Cyrus

Cyrus

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this tap was brand spankin new. straight outta the carded package into my tap wrench. feels plenty sharp to my finger.

i was thinking maybe the block being cast iron had something to do with it, because when i chased the threads for my exh manifold studs in the head, it was smooth and easy.
 
I

IJ.

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Cyrus;1844506 said:
i've been going 1 full rotation clockwise, 1/2 rotation counter clockwise.

yes, i am 100% this is a 12mm x 1.25mm plug tap.

there have been absolutely no chips. in fact, about the only thing that has come out on the tap has been some thick gray/black grease.

2 hours later, i just finished the last hole. holy fuck. that was absolutely exhausting. by far the most physically challenging thing ive had to do for this rebuild so far.

the arp bolts thread in absolutely perfectly, into every single hole. dunno why that was so fucking tough, but i really hope i dont have to do that again anytime soon. ;)

i ended up sticking with the Tri-Flow Superior Lube product. it seemed to help the tap glide the best of the various lubricants i tried.
Click to expand...

Albert;1844519 said:
Where did you buy the tap from?

And were you using any type of oil?
Click to expand...
;)
 
Cyrus

Cyrus

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hahaha IJ i think ill have to start going to the gym more often... ;)

albert, it is an Irwin tap. 12 mm - 1.25mm high carbon steel plug tap.

bought it new in a carded package from a local auto supply store.


so it is safe to say, it should not have been so hard to chase those threads?

is it possible that someone lock-tite'd the old head bolts in, and i was forced to chase out the leftovers that had turned to something resembling cement?
 
Turbo Habanero

Turbo Habanero

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I'm not exactly a big guy lol.

And I just did Mine recently and they were just filled with oil and dirt and grime, but still pretty easy to do.
 
B

bluepearl

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Were the head-bolts difficult to remove? What size tap handle were you using? If the engine was apart before, is it possible someone used hardning permatex on the bolts? Even when dirty, that should glide thru like butter.
 
kotu100

kotu100

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Either way, I think this thread proves why you should always chases the threads before installing head bolts/studs.
 
Cyrus

Cyrus

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bluepearl;1844534 said:
Were the head-bolts difficult to remove? What size tap handle were you using? If the engine was apart before, is it possible someone used hardning permatex on the bolts? Even when dirty, that should glide thru like butter.
Click to expand...

head bolts came out easily enough. they were stock head bolts, w/ the hex socket style head. once i broke them loose, they came out easily enough. seems unlikely the engine had ever been taken apart in the past. i noticed while i was tearing it down that it had all stock OEM toyota gaskets. and the head had never been resurfaced, according to my machinist. i am inclined to agree with him, as when i measured its thickness, it was what a new OEM factory head would be (116mm if i recall correctly, +/- .02mm)

anyway, i dont know what happened to the bolt holes. maybe when i left the engine block open to the elements for 2 weeks, they developed some rust or something. all i know is, it was a job and a half to get those things cleaned out. it was worth it, however, as i was just able to successfully install the head with ARP hardware. the bolts went in smoothly, and held 90 ft/lbs of torque without issue.
 
NashMan

NashMan

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sounds like you have issue pouring milk from a 4 litre jug into your cereal in the morn...... hehe:icon_razz
 
suprarx7nut

suprarx7nut

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Nov 10, 2006
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FWIW, when I chased threads on my first GE motor, it was pretty tough. I was afraid I was tapping a new thread or something crazy. Turned out just fine and every motor since has been easy. Not sure what makes some threads that much harder. I didn't even get much gunk out of the threads. They weren't really nasty or anything. :dunno:

Glad you're done and you didn't accidentally tap a new thread or anything! :)
 
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