88xjchief
NAXJA Forum User
- Location
- Connecticut
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?
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.)
And, as an amendment to that, make sure the pipe dope is on the bolt threads, and not just under the head.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.)
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
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...
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
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.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.
gradon said:Dagnabbit Jon, see what you started? You were supposed to admit you're wrong!
(ribbing a mo late)
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.
88xjchief said:I was able to get new head bolts from napa for $35.