Lubing head bolts


#1

i know in general your supposed to put oil on head bolts when installed and the moly lube on arp studs. but recently i ran into the head bolts with the preinstalled solid looking putty sealer on them and just wonder the thoughts on what to do with them. i opted to leave them dry as to not affect the sealer this is on a gm 3800 motor where every hole goes through to coolant. was this the rite option? hould i add torque or leave them? these bolt also require a torque angle of 120 degrees which i was thinking wouldnt be affected by being oil free just the intial ft lbs


#2

bump


#3

Don’t oil the threads, but do apply a thin film of oil or bolt lube to the base of the bolt head. This will help greatly when trying to get to 120-deg torque angle. The sealer actually lubes the threads nicely.


#4

The "putty was on the threads? (I hope…) The bolts go into the coolant passage and need some sealer to work correctly and lube under the bolt head, per @BustedKuckles.

These are new bolts? Right? This engine has “torque to yield” bolts that should not be used more than once. The 120 degree torque angle stretches the bolt so much it is permanently a tiny bit longer and may break with the second use.


#5

these are new felpro bolt they come with the putty preapplied to the threads and on the bottom of the bolt to help seal the cooling passages. alldata didnt say anything about oiling them as i wouldnt espect them to. the bolts didn’t come with any installation tips or instructions. i was just wondering because ive aways had to put the sealer on myself and never had them come preapplied


#6

Fel-Pro was being nice to you AND it guarantees you are using the right sealer with the right friction for their bolts. Win-Win. Would be nice to have instructions, though.


#7

so oil when there is no sealant is that a pretty good rule of thumb


#8

Yep, dry threads give bad torque readings. Oil works unless otherwise stated… ARP super rod bolts for one.


#9

id like to reopen this discussion to get some more opinions on these bolts because i got low cylinder pressure in 2 cylinders. my leak down tester pointed toward valves but either way since im digging that deep again should i oil these bolts. the cylinder head was milled and i spent a while lapping the valves but im just going to have them cut this time around


#10

If the head bolts have been torqued down once they can’t be reused.

These head bolts are torque-to-yield type head bolts. Which means once they’ve been torqued down and taken their stretch, torquing the bolts again won’t provide enough clamping force seal the head gasket.

So if you torqued the head bolts once, throw them in the garbage and get new head bolts.

Tester


#11

This time, once you have the head off before you pull the valves, check the valve seal. Spray brake clean into the ports to test the seal. First the intakes, with the valves down, look for wetness in the combustion chamber. Let it evaporate, then do the exhausts the same way. If the valve job holds brake clean, you are good and have another issue. If not, have the seats cut, lap and check again before you put them back on.


#12

the set of head bolts i got came with a set for the front and a set for the back so im gona get rid of them and use the spares because i didn’t remove the back head. thanks for the tips guys i like the idea of putting the brake fluid in there. i was think of how to make my own tester by sealing something to the bottom of the head and running compressed air to it but that seems easier. but what do you guys think as far as oiling these i dont think it would hurt. it would add to the preload before the torque angle but then again the leak seemed to be coming from the intake area so i don’t want to overdo them


#13

Don’t oil the head bolts.

The sealant on the bolts is also the torque lube.

Tester


#14

@prowrencher‌: Brake cleaner…not brake fluid.
Not sure if it was a slip on your typing or you misunderstood.

Yosemite


#15

yes, don t oil the threads. tester has it right. the heat from the pressure and friction will liquefy the sealant


#16

i mistyped sometimes i miss stuff like that in my proof read thanks for looking after me though


#17

@prowrencher‌

http://www.felpro-only.com/tec_notes/Fel-Pro_Torque-Guide.pdf

This is lengthy, but the torque specs and the tightening diagram should be in there somewhere


#18

thanks guys appreciate the help the heads at the machine shop ill post one more update letting you guys know how it turns out


#19

had valve job done put the head on and torqued the head bolts. cranked over motor with none of the top end or exhaust hooked up and got much better readings on the compression test 170-170-180 opposed to 90-90-150 i got before


#20

It’s always a good feeling when all the work you have been doing pays off. My favorite moment.