head gasket

Im replacing the head gasket on my XJ and the manual says put sealant on the head gasket. I have replaced a few head gaskets and never had to. Do I have to put sealant on the gasket or do it dry?

88xjchief said:

Im replacing the head gasket on my XJ and the manual says put sealant on the head gasket. I have replaced a few head gaskets and never had to. Do I have to put sealant on the gasket or do it dry?

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I have NEVER built a motor with anything on the head gasket.

I have however seen people use "spray copper sealant" on the block and head prior to assembly.

No need to apply sealant if you ask me.... ESP on a 4.0

XJR

Most modern head gaskets do not require sealant. Iv'e built two 4.0s with felpro gaskets an no sealant with absolutely no problems.

On subaru's it is recommended to lightly coat both sides of the cylinder head gasket (multi-lam steel and graphite) with permatex high tack, I think its more to hold the gasket in place while torquing though. I have heard the same for neons
Mine went on dry on my 4.0

No. Just be sure to put LocTite PST or Teflon/PTFE "pipe dope" (the paste stuff) on the threads of the driver's side front cylinder head screw, and tighten it to only 100 pound-feet (vice 110.)

Also, if you see paint marks on the screw heads, replace them! If you do not see paint marks on the screw heads, paint them! The cylinder head screws may only be reused once, and then they'll fail on installation. Sets of new screws are available in the aftermarket (any bright colour of touch-up paint will serve, the mark just has to be visible.)

5-90 said:

No. Just be sure to put LocTite PST or Teflon/PTFE "pipe dope" (the paste stuff) on the threads of the driver's side front cylinder head screw, and tighten it to only 100 pound-feet (vice 110.)

Also, if you see paint marks on the screw heads, replace them! If you do not see paint marks on the screw heads, paint them! The cylinder head screws may only be reused once, and then they'll fail on installation. Sets of new screws are available in the aftermarket (any bright colour of touch-up paint will serve, the mark just has to be visible.)

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New screws????
You mean bolts. Although the one bolt thread dope is a good recommendation... I have built MANY MANY 4.0L's... NEVER did i buy new bolts. not one head gasket has failed that I have installed.

The 4.0 is a cast iron block and cast iron Head. Last I heard they don't use stretch bolts on cast engines. Maybe I am wrong here but I have always reused and NEVER had a problem.

Now if we were talking a toyota motor with an aluminum head, then yes, you *should* replace the bolts but you can get away with reusing them if you are on the side of the road putting in the head gasket.

XJR

5-90 said:

No. Just be sure to put LocTite PST or Teflon/PTFE "pipe dope" (the paste stuff) on the threads of the driver's side front cylinder head screw, and tighten it to only 100 pound-feet (vice 110.)

Also, if you see paint marks on the screw heads, replace them! If you do not see paint marks on the screw heads, paint them! The cylinder head screws may only be reused once, and then they'll fail on installation. Sets of new screws are available in the aftermarket (any bright colour of touch-up paint will serve, the mark just has to be visible.)

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And, as an amendment to that, make sure the pipe dope is on the bolt threads, and not just under the head.

The guy who built my engine screwed up and I had a coolant leak from the front exhaust manifold bolt. Drove me crazy till I figured out what the problem was

XJRubicon said:

New screws????
You mean bolts. Although the one bolt thread dope is a good recommendation... I have built MANY MANY 4.0L's... NEVER did i buy new bolts. not one head gasket has failed that I have installed.

The 4.0 is a cast iron block and cast iron Head. Last I heard they don't use stretch bolts on cast engines. Maybe I am wrong here but I have always reused and NEVER had a problem.

Now if we were talking a toyota motor with an aluminum head, then yes, you *should* replace the bolts but you can get away with reusing them if you are on the side of the road putting in the head gasket.

XJR

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The paint/replace tip and the PST aren't my "suggestions" - they're per FSM. Apparently, the OEM screws are a modified "torque-to-yield" design (a bit like those used on Diesels,) and they'll fail if they go through a third torque cycle. I do note that the installation torque on them is a bit higher than most - aren't SBC screws torqued to about 80-85 pound-feet?

As far as "bolts/screws" goes, I suppose it's a semantic difference. In an engineering sense, a "screw" is a threaded fastener that mates with female threads in a hole in the part, while a "bolt" is a threaded fastener that mates with female threads in a removable part, viz. a "nut."

Put a nut on a "bolt," and it's a bolt. Put a "bolt" in a threaded hole, it becomes a screw. It's just something that was hammered into me in school, and I've kept the habit. Makes it a bit easier to look at my prints an estimate work - everytime I see "screw, machine thread," I know I have to drill and tap a hole...

5-90 said:

The paint/replace tip and the PST aren't my "suggestions" - they're per FSM. Apparently, the OEM screws are a modified "torque-to-yield" design (a bit like those used on Diesels,) and they'll fail if they go through a third torque cycle. I do note that the installation torque on them is a bit higher than most - aren't SBC screws torqued to about 80-85 pound-feet?

As far as "bolts/screws" goes, I suppose it's a semantic difference. In an engineering sense, a "screw" is a threaded fastener that mates with female threads in a hole in the part, while a "bolt" is a threaded fastener that mates with female threads in a removable part, viz. a "nut."

Put a nut on a "bolt," and it's a bolt. Put a "bolt" in a threaded hole, it becomes a screw. It's just something that was hammered into me in school, and I've kept the habit. Makes it a bit easier to look at my prints an estimate work - everytime I see "screw, machine thread," I know I have to drill and tap a hole...

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The OEM manual also says you should apply sealant to the head gasket.
But head gaskets have advanced.

If they say that the third torquing they will fail, then wouldn't this guy be good with running the BOLTS one more time? I never had a problem.

As for the bolt and screw thing. If I had to order a set of HEAD BOLTS and I called them screws.... What do you think would happen? Most people who are not in engineering would be thinking of the little metal things that hold the doorknob on the front door to their house.

A power steering pump is a hydraulic pump. If you went to the part store and told them you needed a hydraulic pump they would look at you funny.

In engineering, calling it a screw is fine. in the automotive world it is a headbolt. Period.

XJR

XJRubicon said:

The OEM manual also says you should apply sealant to the head gasket.
But head gaskets have advanced.

If they say that the third torquing they will fail, then wouldn't this guy be good with running the BOLTS one more time? I never had a problem.

As for the bolt and screw thing. If I had to order a set of HEAD BOLTS and I called them screws.... What do you think would happen? Most people who are not in engineering would be thinking of the little metal things that hold the doorknob on the front door to their house.

A power steering pump is a hydraulic pump. If you went to the part store and told them you needed a hydraulic pump they would look at you funny.

In engineering, calling it a screw is fine. in the automotive world it is a headbolt. Period.

XJR

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I know - like I said, it's a semantic difference. Torque wrenches are calibrated wrong - "foot-pounds" is a unit of work, while "pound-feet" is a unit of energy. Torque is listed in "pound-feet." The metric system has it right - "Newton-metres." They're using the wrong unit - and have been for years.

It's common to call a hex-headed threaded fastener a "bolt" - even though, semantically, it isn't always correct. But, I was taught by an ME at an early age, and that's how I learned it (and verified it was correct through my own research afterwards.)

And not all parts guys are going to "go blank" if you ask them for "head screws" or "hydraulic pumps" - I didn't, and I dealt with a few engineers while I was holding down a counter myself. I had one come in and ask for a "hydraulic pump" one time, and I threw him by replying, "Sure. Which one?" You see, the water pump can also be considered a "hydraulic pump" - more correctly, a "hydraulic circulating pump." ("Hydraulic" has to do with the circulation of a liquid, viscous or not. If you're using it to do work, it's "fluid power" - whether that fluid is liquid or gaseous doesn't matter. Pneumatics also falls under "fluid power.")

Just for fun, I'll have to check my later FSMs (1990-up,) and see if they recommend sealant on the gasket proper. I wouldn't think they did - I'm sure I'd have commented on it by now if they had (but the FSM has also been known to be wrong - they recommend GL-5 gear oil for the AX-series manual transmissions. The added sulphur in GL-5 is antagonistic to yellow metals - like the bronze synchroniser rings...)

dude... technically its a screw

I never said you were wrong.

I simply said that in the automotive industry, ITS CALLED A HEAD BOLT.

Though it may be technically wrong, that is how it is man, you can't deny it.


Ask 10 people that have done head gaskets what it is. How many are going to say its a screw?!!

We are both right.

XJRubicon said:

I never said you were wrong.

I simply said that in the automotive industry, ITS CALLED A HEAD BOLT.

Though it may be technically wrong, that is how it is man, you can't deny it.


Ask 10 people that have done head gaskets what it is. How many are going to say its a screw?!!

We are both right.

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Screw , bolt whatever! auto parts share several names ,EXAMPLE: spark plug wire, high tension wire, or japanese conversion: spiral cord, and roll connector,clockspring. etc ,etc, etc.

Bolts, screws, rods, fastners, whatever, any way you slice it I feel screwed :laugh3:today, Went to 5, that is FIVE, major national auto parts chain stores today and none of them sell much less stock these little beasties. So I am placing an order on line at headbolts.com since they claim to have them on their website.

Unfortunately I had settle for buying them as "head bolts" as that is all they list on their web site, :laugh3:, but I did look for head screws!

So when they arrive hopefully I can just screw :laugh3: them into the head and block and be back on my way!

Sorry guys, I just had to have some fun with this, been a long day.

I was able to get new head bolts from napa for $35.

Dagnabbit Jon, see what you started? You were supposed to admit you're wrong!
(ribbing a mo late)

gradon said:

Dagnabbit Jon, see what you started? You were supposed to admit you're wrong!
(ribbing a mo late)

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Hey - prove to me I'm wrong, and I'll readily admit it!:laugh3:

Seriously - the difference between a "screw" and a "bolt" is generally in use - if it goes into a mating removable part (a "nut",) it's a "bolt." If the mating threads are in the part, or the fastener cuts/forms its own threads, it's a "screw." Head style doesn't matter - socket head capscrews, hex head capscrews, flange head capscrews - all are different ways to drive the same thing.

The 60* vee thread is commonly called a "machine thread." Why? Because it's designed to mate with a machined thread. The fact that most machine screws are used in machinery is largely coincidental - the receiving thread is machined into the part (lathe-turned, cut with a tap, ...)

"Wood screws," "sheet metal screws," "tapping screws" - all are screws in the strict sense of the word - they form their own threads in the mating part. However, if it's a thread machined into the part, the fastener is still a "screw."

I know it's nitpicky, but it's the way I use the language - and I like to make sure everyone else can understand what I'm talking about when I say it. "Potayto/potahto," I know...

:twak: :twak: :twak: :laugh3:

To answer 5-90. Torque on a small block chevy 7/16 head bolt is 65 lbs.

Part number for a head bolt kit from ARP (Automotive Racing Products) is
112-3601. Jobber is $67.11

Hope this helps.

Russ Pottenger said:

To answer 5-90. Torque on a small block chevy 7/16 head bolt is 65 lbs.

Part number for a head bolt kit from ARP (Automotive Racing Products) is
112-3601. Jobber is $67.11

Hope this helps.

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Thanks. So, a good deal higher than most (which is odd, because an SBC usually runs a bit higher CR. Even accounting for the SBChevvy having five screws per cylinder, vice the four for the AMC six...)

88xjchief said:

I was able to get new head bolts from napa for $35.

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Do you know the part number? My NAPA guy says it is not in their computer, so he checked the hard copy books and only found a head bolt set for 96-02, which sounds like they changed in 96. Mine is an 87, Renix.