Do you need thread sealant on BB head bolts?

[Rob Voyles CA]

? I thought you did....but my service manual doesn't mention it.

[CL440]

NO.

[djswwg]

CL440 is right. But you should have a very light coating of oil on the threads to get a proper tork when you tighten them ..........djs

[raymond]

Of course not this isn't a chev. Its a proper engine!!!!

[dave571]

You shouldn't put oil on the bolts unless it says to do so in the manual, or the torque spec is described as "wet".

This may be the case with the bb head bolts, but I don't think so, and I don't have a book here to check(it's at work)

Most head bolt specs are "dry" not "wet"

[Rob Voyles CA]

I ended up using ARP moly lube as per the ARP bolts instructions...torqued to 60 ft lbs (spec for aluminum heads).

[jelsr]

Virtually all torque specs are "lightly lubed". There are different specs for dry, plated, and other variables, but normally lubed with engine oil. The measurement is of the clamping force, not friction of the threads.

[djswwg]

dave571,WRONG! just say "no" to crack ......djs

[dave571]

Any head gskt I've done in the last 3 years, has specified very clearly, that the torque specs have been "dry".

As I said in my post, I don't remember if this is the case on a BB dodge or not. Most of the head work I've done recently has been on 4 bangers of various makes.

I said to check if said to lube the bolts in the manual, before doing so. If it doesn't say to do so, then I'm right. If it does say to do so, then I'm also right, because I said to check the procedure in the manual before doing so.

Generalizations about assembly techniques are very dangerous to make. As an instructor said to me once, when I was an apprentice "RTFB, read the fine book!!"

[dave571]

Actually read the head gskt installation procedure today. Read it in a 1973 plymouth/chrysler/ and imperial manual.

Here it is (abridged in places):

1)clean gskt surfaces of block and head

2)check with straight edge ..(provides runout specs)..ect. resurface as necessary

3)coat new gskt with a suitable sealer, chrysler number 1057794 or equivalent. Install gaskets and cylinder heads.

4)Install Head bolts. Starting at top center, tighten head bolts to 40 ft pounds in sequence(fig. 9)

Repeat procedure, tightening all head bolts to 70 foot pounds


...All that said, it is interesting that the manual very clearly details every step of the procedure. Clean the parts, how to properly check the head and block deck, what sealer to use, what tightening sequence, and to torque the bolts in two steps. All this detail, yet no mention of oiling the bolts.

Clearly the bolts are not supposed to be oiled. One reason that this might be the case, is that the holes are blind(no opening at the bottom). If the bolts are oiled, and too much oil is applied, it may cause a hydrualic lockup in the bottom of the hole. Completely distorting the torque reading, as the bolt will be tight, but only applying pressure to the oil, not the head.

Just trying to be clear here. I'm NOT trying to start a fight with ANYONE on these boards(I like the boards alot and value input from other mopar nuts). What I am trying to do, is make sure that people that read this page for reference information, don't have to second guess what has already been laid out clearly, by chrysler engineers.

Custom work like aftermarket bolts with aluminum heads, is a different story, where the recommendations of the parts manufacturer should be followed. In my experience, as a professional mechanic, automotive torque specs are always dry, unless otherwise specified. I'm not "super mechanic" but I do know how to read a service manual.

[jelsr]

Check a "Motors" repair manual, like independant shops use. "Torque specs are for clean and lightly oiled threads" That heading is at the top of the torque specs section for all makes, not just Mopar. They get those specs from the OEM's. If you check SAE (Society of Automotive Engineering) manuals on fasteners it will say the same thing and also give the different specs for dry, plated, and plain bolts in mill, grade 5, and grade 8 bolts regardless of application. It is also recommended to put a drop of oil under the head to eliminate friction that could interfere with the reading. The torque measurement is for the clamping force, friction interferes with the reading. The only dry spec'd application I can even think of is wheel lug nuts!

[dave571]

I guess we all have different experiences.

I operate an independent shop myself, and no one has ever told me all torque specs are lightly lubed.

Did a quick poll of the 2 guys who work for me, as well as the five guys I know at the dealership down the street, and lightly oiling the head bolts is news to them as well. One guy even laughed at the suggestion, and thought I must be kidding.

While you say you can't even think of a bolt(other than wheel nuts) that are torqued dry, I can't think of an example where they are supposed to be torqued with lube on them.

As for Sae guidelines(Society of Automotive Engineers, thats how I remember it from the SAE banquet I attended to recieve an academic scholarship), they are generalizations that probably applied to most things, when they were written in 1945. I don't see how they can be substitued for manufacturers procedures.

My understanding of why most specs are dry is because of the possibility of lockup in the bolt hole, and the fact that the clamping force is LESS consistant when oiled. The clamping force applied is not maintained after initial torque because the oil is squeezed out of the clearance between the threads and the clamping force is diminished. The guys who design the cars know this, and allow for the friction of the dry bolt when making torque specs. More friction, yes, but also more consistancy.


There is an SAE chart of generic torque specs in relation to bolt size/ thread pitch/ and grade, but noone would even consider substituing these generic numbers for the manufacturers specs for the application , would they?

To each thier own.

[djswwg]

Here's a quote from Fel Pro's book #486-96, dated 1996. First sentence. page 5. Under the heading installation tips. "Lightly coat bolt threads and the underside of the bolt head with motor oil." Why do you think ARP fasteners always come with a packet of lube for the threads? It's just common sense. If more mechanics would lube the threads on spark plugs before installing them, a lot less heads would need that kind of thread repair, especially aluminum ones.......djs

[jelsr]

Dave571,
Have to agree with you on the different. Talked to the other 2 shops in town and they agreed the lube was normal. Had to take a set of M&M heads to have seats installed in the exhausts this morning. The machinist, who builds a number of IMCA Mod engines and other performance rigs, responded like djswwg. "What does he think the lube package in the ARP sets is for?"
As for the SAE chart, some farmers here are using equipment older than me and no one has seen a manual for 20 years. It comes in quite handy at times. Specs for Gr-5 and Gr-8 have not changed by the way. Been at this for 40 years, I'll keep using the lube. I also cheat with anti-sieze on exhaust and other applications.

[dave571]

Well, I'm glad this hasn't developed into a pissing match, and that this discussion has stayed constructive.

Instructions in the arp head bolts say lube them, and they come with lube. That's great. As I said in an earlier post, performance parts manufacturers sometimes have specs of thier own.

I go along with that. No problem.

I'm just trying to show that generalizations about assembly can be dangerous. Oiling the bolts, or not, on abig block dodge probably won't make any difference to how it goes together. The bolts are under loaded for thier size, and there are so many that head gskt failure on this application is very rare.

One of my best friends, who works at porche, described a porche procedure today. It specified to oil the threads of the nut(studded engine) but the shoulder must be dry. Engineers think up some wierd stuff.

My brother in law, from ford, was telling me last week about a head on one of thier older applications, that is not supposed to be straight when checked with a straight edge. Its concave, and flattens out when torqued.

Also, on the new ford 5.4 truck engine, if the heads are not straight when you check them, you don't resurface them. You discard them. "Sorry sir but your head gskt is going to cost you $4500"

Like I said, glad this has stayed civil, and thought I'd share some weird examples with you

ps. Jelsr, I did check a 'motors' spec manual today at the shop, and although there were nearly 100 different footnotes pertaining to torque procedures, and spec info, there was no reference to lubing the fasteners.(thought you might find that interesting, after telling me to look there, not saying "I told you so" or anything like that) As for cheating, there's lots of stuff I cheat on too, perhaps we have a few in common. I can read the manual, but I don't feel I have to all the time, sometimes not as much as I should I'm sure