What size tap to chase the head bolt threads in a 6 bolt? Do you even do this?

[Spoolin4Ever]

So it is time to put the head back on my engine.

I want to know; what size tap would I need to chase/clean the threads in the 6 bolt head? Where would I get the tap?

Who here does and does not chase threads first and what has been your experience?

I am using stock head bolts (new ones) by the way.

I don't hear much about it here or in general. But I don't replace heads that often (first time).

 

[lacroixdp]

12 MM x 1.25 - you can buy a bottoming tap for $8 off Amazon.com It needs to be done anytime the head is off.
Amazon.com: 12 MM x 1.25 High Speed Steel Bottoming Tap: Home Improvement
This is the one I have - it's lasted me for a while with no issues.

 

[Spoolin4Ever]

Alright; can you tell me what the proper way to do it is?

I understand you just put it in the tap and turn it. But do you spray any lube into the threads first or anything else?

By the way, I would like to do it this weekend, not sure if amazon can get it here quite that fast. Know of local tool companies that carry this? I will call harbor freight. But worried that someone that knows not the difference of a regular tap versus a bottoming tap will answer the phone.

 

[lacroixdp]

Yes - you'll want to use some good tap & die lubricant. Here is how I've always cleaned the threads:

A) Blow out hole on block
B) Clean tap & lubricate
C) Chase all the way down
D) Blow out hole on block again

The threads will be clean and shiny afterwards, which will give you more accurate torque readings. They have a very nice speed tap at Harbor Freight that ratchets - it's my personal favorite. You can always use a socket or wrench to drive the tap as well. You can look around for a tap at your local hardware stores. However, I looked at all the tap sets at Harbor Freight and could not find a kit that had this size. I believe it took Amazon 3 days to get this to me.

 

[Spoolin4Ever]

I ordered the one off amazon in case I can't find it fast locally.

 

[Rob10_99]

You say 6 bolt head, yet I think you guys are talking about the head bolt holes in the block, correct?
While your at it you could tap your valve cover and head if you have any stripped ones.

 

[Spoolin4Ever]

Yes, that is what I meant, thank you for clarifying.

Which size would I need for the valve cover bolts, I mean which size would you go to? I have about 3 stripped bolt holes. Only thing is, people are saying I can just use a slightly longer bolt for that instead. So still not sure which I will do. Umm, I mean I would try the longer first.

 

[TSIfreek]

Heli coil the stripped holes. You can get the kit from napa

 

[blcknspo0ln]

The valve cover bolts are 6x1.00; replacing them with some SS ones always is a good option

 

[Spoolin4Ever]

Yes - you'll want to use some good tap & die lubricant. Here is how I've always cleaned the threads:

A) Blow out hole on block
B) Clean tap & lubricate
C) Chase all the way down
D) Blow out hole on block again

The threads will be clean and shiny afterwards, which will give you more accurate torque readings. They have a very nice speed tap at Harbor Freight that ratchets - it's my personal favorite. You can always use a socket or wrench to drive the tap as well. You can look around for a tap at your local hardware stores. However, I looked at all the tap sets at Harbor Freight and could not find a kit that had this size. I believe it took Amazon 3 days to get this to me.

So for B, it says CLEAN and lubricate. What do you use to clean? I see you said tap and die lubricant for lubing, is that also for cleaning?

 

[lacroixdp]

So for B, it says CLEAN and lubricate. What do you use to clean? I see you said tap and die lubricant for lubing, is that also for cleaning?

Each time you use the tap, you need to clean it off. I clean it off with compressed air. Before you use the tap in the next thread hole, you'd just lubricate it again. If compressed air is not available, just hose it down with brake cleaner.

 

[Spoolin4Ever]

Each time you use the tap, you need to clean it off. I clean it off with compressed air. Before you use the tap in the next thread hole, you'd just lubricate it again. If compressed air is not available, just hose it down with brake cleaner.

Alright; this sounds pretty straight forward.

Let me ask you this: how much lubricant, and do you apply it on the tap or into the thread?

I searched in google and tap and die only brought up one product. So what are some of the names of the products?

Google search for tap and die lube:
"tap & die lubricant" - Google Search

Product I found:
Tap-Ease Tap & Die Lubricant at Wholesale Tool Company | Industrial Machinery + Tool Supply

 

[lacroixdp]

You just need a little bit of lubricant. Apply it to the tap so that it all doesn't pool down to the bottom of the thread hole. That lubricant you posted will work fine. It's a solid lubricant, which will make the previous sentence moot. However, in a pinch I've used motor oil with no ill effects as well.

 

[Rob10_99]

+1 just dip the die in some used engine oil.

 

[treebonker]

For cleaning and fixing minor cross threads, you need a chaser not a tap. Running a tap will visciously cut the undamaged thread and weaken it. Don't worry about the lubricant, use cutting oil, engine oil, or even WD-40, whatever is available. Just make sure to clean the holes afterwards.

 

[lacroixdp]

Me and my machinist have done it this way for years without issues, but I can see your point. Tom Monroe does it the exact same way as well, and he's one of the better machinist I know of. I suppose if you didn't start the tap correctly you could be in a world of hurt. The only place I know of to get chasers of this size is through ARP's catalog.

 

[Spoolin4Ever]

What about using one of the old head bolts, but cleaning it first?

 

[lacroixdp]

Bolts don't work as well as chasers or taps.

 

[Rob10_99]

I've tried that before, notching the bolt so it would scrape the threads clean. It works 'ok' but it isn't as big as a chaser or tap will be. So there will be crap in the threads still.

 

[Spoolin4Ever]

I've tried that before, notching the bolt so it would scrape the threads clean. It works 'ok' but it isn't as big as a chaser or tap will be. So there will be crap in the threads still.

So who has the chaser? You have used it?

So if I don't vhase it, the head gasket might go out?

If I do chase it with the tap I could ruin the threads in the block?

So I'm screwed either way, is that correct? Just want to clarify there.

 

[Rob10_99]

no not screwed either way, either look online or call up the parts store/snapon guy and get one or a set.

 

[Spoolin4Ever]

OK I will try. Difficult to find online so far. I will call around Monday.