freeze plug tap

What size tap do I need for the freeze plug holes on a d1 block ?

I keeping hearing about freeze plugs coming out on some peoples blocks and I don't want that to happen to me any help would be great.

1 1/4-11 1/2 NPT pipe tap

I bought a couple on ebay. Got some nice HSS ones in the $30 range.

I was thinking about doing this too, after talking to XolieX

I'm doing it too. Already have the plugs and tap. D9TE block but who cares? Never need replacing and never leak.

Most of the times I have ever seen a plug blow out was from a cracked block or blown head gasket pressurizing the cooling system. if I'm not mistaken the screw-in freeze plugs where used to strengthen the block.
I apply anaerobic sealant to the plugs before setting them in the block and then paint over them when I paint the block.

If I remember correctly, you will need to find a straight tap as well as a tapered tap. If you can't find a straight tap you will have to cut one of the tapered tap's in half. I don't think you will have enough depth to run a tapered tap in enough.

You need two tapered taps one with almost have cut off. the reason is to be able to tap the hole and let the plug get almost flush when tightened.

The un cut tap will start and tap, but bottom out against the cylinder wall before taping deep enough to allow the plug to engage deep enough. Then use the cut off tap to go on deeper.

IDT-572 wrote:You need two tapered taps on with almost have cut off. the reason is to be able to tap the hole and let the plug get almost flush when tightened.

The un cut tap will start and tap, but bottom out against the cylinder wall before taping deep enough to allow the plug to engage deep enough. Then use the cut off tap to go on deeper.

What he said!!

I didn't need to shorten a tap. Regular NPT tap has plenty of room in a big block. In fact, one block I did went a little too deep and had to buy some oversize plugs.

Small block on the other hand, you need to shorten a tap to get them deep enough.

For those who may have a freeze situation ie: Up North with a non heated shop/garage you may want to do 7-screw in plugs with a block heater in one of the easy to access holes, one based off of a regular freeze plug not one that bolts in, or do all eight and remove some or all for the winter.

dfree383 wrote:I've never had a freeze plug come out.

I haven't yet but I hear a lot of guys are popping them out going down the track with solid mounts.

I have run many combos with out the screw in plugs but it seems to be getting very common lately and nobody has a explanation for why or how so I'm just a little scared of it happening to me.

Thanks for all the help on this guys

gmsmkr wrote:

dfree383 wrote:I've never had a freeze plug come out.

I haven't yet but I hear a lot of guys are popping them out going down the track with solid mounts.

I have run many combos with out the screw in plugs but it seems to be getting very common lately and nobody has a explanation for why or how so I'm just a little scared of it happening to me.

Thanks for all the help on this guys

I can say learning the nitrous curve I have ventilated a few head gaskets, and popped a freeze plug or two, I have also had a thermostat failure (when I ran one) popped a plug, and once upon a time left water in my engine in a non heated garage and popped a freeze plug, probably all were a Savior for the blocks, the screw in plug definitely helps to keep everything together when you are hot lapping it in the ladder rounds and the cooling system needs help, because with a push in plug you may find yourself missing a plug and deciding how much you want to risk to go the next round less coolant and very hot....but remember when you eliminate the weak link you create a new one... Remember to deal with the cause of the question.

I popped a freeze plug at the track one night .Luckily nothing bad happened .After that incident I went with a 10 pound radiator cap .No more problems .I had been running a 16 pound cap .Screw in plugs are naturally a much better solution .Doug

IDT-572 wrote:You need two tapered taps one with almost have cut off. the reason is to be able to tap the hole and let the plug get almost flush when tightened.

The un cut tap will start and tap, but bottom out against the cylinder wall before taping deep enough to allow the plug to engage deep enough. Then use the cut off tap to go on deeper.

Yes and no. What I did was tap all the soft plug holes with a standard length  pipe tap. Then cut about 1/2" off the end in a wet abrasive cutoff saw. Now I have a tap to run back in the pre tapped holes and size them for the tapered plugs. You can buy Stainless or aluminum 1-1/4" pipe plugs from McMastercarr online. This is a one block only way of doing it. If you do another block you will need to buy a second tap.

Beltfeed wrote:

IDT-572 wrote:You need two tapered taps one with almost have cut off. the reason is to be able to tap the hole and let the plug get almost flush when tightened.

The un cut tap will start and tap, but bottom out against the cylinder wall before taping deep enough to allow the plug to engage deep enough. Then use the cut off tap to go on deeper.

Yes and no. What I did was tap all the soft plug holes with a standard length  pipe tap. Then cut about 1/2" off the end in a wet abrasive cutoff saw. Now I have a tap to run back in the pre tapped holes and size them for the tapered plugs. You can buy Stainless or aluminum 1-1/4" pipe plugs from McMastercarr online. This is a one block only way of doing it. If you do another block you will need to buy a second tap.

Exactly what I ment...........

I've never had a plug come out, but don't want to chance it. Current engine has screw in plugs, and the one on the stand will get them. I did not have to cut my tap, or use another.

So you guys tapping these freehand or setting block in a mill or similar ??

Gregaust wrote:So you guys tapping these freehand or setting  block in a mill or  similar ??

I did mine freehand. The cast taps fairly easily. I used a framing square to make sure I got the tap started in square to the opening and let 'er rip.

Nice work Thanks

I know I'm getting old  but I believe I've posted this up before, maybe a different Forum. An engine has two 'cooling system pressure zones' called block pressure and system pressure. We're all familiar with the system pressure which is dictated by the radiator cap (usually 15-24 PSI). The block pressure is dictated by the water pump's output and can exceed 80 PSI at high RPM (depending on where the reading is taken). The engine block's water jackets act like a manifold, flowing coolant (under full pressure of the water pump) to the head gasket orifices for uniform distribution. On some engines, the pressure zone begins to change here. (Ever notice how small the head gasket coolant holes are in engines like the small block Chevy?) The coolant flows through the cylinder heads and intake manifold, then it is subjected to a 'pressure drop' caused by the thermostat restriction (open or closed).
A mechanical high output water pump is capable of 180 GPMs and very high 'block pressures'. This is what blows out core plugs at high RPM. Using a high flow thermostat, a functioning bypass hose and not running your cold engine (thermostat closed) at high RPM is advantageous.

Also don't forget to take into account the area of a plug which is about 1.77 sq. inches, so the pressure pushing on it is probably around 140 lbs. Core plugs are also a stamped sheet metal part and are not what I would call a precision part. Manufacturers dies do wear and who knows how often they replace them, diameters could vary wildly   .

In all the years of racing and street machines, I've never had issues with properly installed pop in plugs.

bbf-falcon wrote:In all the years of racing and street machines, I've never had issues with properly installed pop in plugs.

Me either....but now I'm scared to drive my racecar.

Paranoia.

I think Doug Rahn might be the only poster in this thread to correctly refer to them as CORE plugs... Freezing has nothing to do with their intent/purpose.  Not a surprise with manufacturing being run out of this country..

While there may be a structural benefit to threaded core plugs, they simply aren't a fail safe for poor coolant mixture by the owner

DFI429 wrote:Paranoia.

I think Doug Rahn might be the only poster in this thread to correctly refer to them as CORE plugs... Freezing has nothing to do with their intent/purpose.  Not a surprise with manufacturing being run out of this country..

While there may be a structural benefit to threaded core plugs, they simply aren't a fail safe for poor coolant mixture by the owner

I think the most of us know in fact that they are CORE plugs,but we still sometimes call them "Freeze" plugs as habbit.

I've never lost one, but I have gotten to the track, then noticed one was leaking.... That sucked.