Chasing Threads

[72miura]

Alright I may have a problem.
Rebuilding an engine. To clean the threads, a normal tap was used for all the holes. I know they make "thread chasing" taps that are a bit undersized to not weaken the holes.
My question is, should we have used those instead? Will the holes be weaked that much that they can fail?

The engine is a inline 4 cylinder, GM Ecotec 2.2L. It will be turbocharged and making around 400hp in a street car.

Would you just rebuild as normal or should I buy Timeserts and install them in all the holes? Or just critical ones, such as mains, headbolts etc.?

Thanks

 

[MintJulep]

Since GM claims that they can get 1000 HP out of that engine using production components, you will probably be alright.

 

[72miura]

I assume it will be ok, I will be using ARP head studs and brand new main bolts, which are torque to yeild.
I just want to make sure that i didn't crititcally fail the threads.

 

[Heckler]

What type of cleaning do you mean? To clean the dirt/oil out of a blind hole or was their visable thread damage that warranted the chasing? I'm assumming you used some lubrication during this cleaning? You could always use a thread gauge to check all the critical measurements.

 

[72miura]

To clean out dirt, oil and aluminium shavings from edge deburring around the block and head.
The threads were fine and I used lubrication.
I guess I will get an internal thread gauge and check if the threads are in spec. Hopefully they are.

Just can never be too careful. Thanks

 

[berkshire]

72miura
here is a link to a thread gage mfg.

http://www.micron-inc.com/threadg.htm

Their prices are better than the $200 to $300 prices I have ben quoted from other suppliers.
B.E.

 

[Screwman]

Miura,
Given the lengths of thread engagement in that block you should be fine. The key when thread chasing is to just use your hand to turn in the tap, then you can feel if it is tight and starting to cut. Always use a flood of lube or cleaner when doing this to keep the hole clean. Make sure to follow the lubrication and torqueing instructions provided by the gasket company to obtain the preload required to obtain your gasket stress for sealing under those turbo pressures.

When I was working on IRL cars we always used Helicoils on internal threads into soft metals. These components generally came apart at the end of each weekend so we couldn't afford the thread damage caused by the repeated assembly cycles. On a street engine that will only come apart a few times in it's life, they are overkill.

Dick

 

[72miura]

Thanks Dick, I appreciate the advice.

Hunter