Head studs leaking coolant
 

Looking for opinions on the best type of sealant to use on ARP cyl. head studs. Fresh BBC and only minutes after initial fire up some of the lower head studs started to leak. After checking the torque of 80 ft lbs and re-torquing the leakers to 85 ft lbs, we restarted the engine only to discover that many more were now leaking including the ones that had just been torqued.I had used ARP thread sealant and run a tap through all the holes prior to assembly. The studs are new, head gaskets are Fel-Pro 1017-1 on a GM 454 block, using GM "990" cast iron heads. Engine is now back out of car and on the stand.
Never had this problem on my old 468 using same stuff ?

Re: Head studs leaking coolant
 

One area you might want to double check is the tap you used to chase the block threads. I've been told some of the imported tap and die sets are poor quality and finish the thread outside of tolerance creating a "loose" thread engagement pattern. I might also have a machinist check the thread on the head studs (I kind of remember good block studs utilized a "close tolerance" thread on the block side) Did you chase the stud threads with a die as well? I would also double check the stud thread height to be sure you are not bottoming the nuts against the stud thread base instead of clamping the cylinder head. (a thicker head stud washer on severely milled cylinder heads may be necessary) By your post I'm assuming the block deck bolt holes aren't heli-coiled and the deck surface/threads aren't showing cracking. I wouldn't rule it out but it seems odd to me that the ARP sealant can't seal their studs unless there is a bad batch out there.

Re: Head studs leaking coolant
 

Starting to wonder if the nuts might be bottoming out on the studs as the heads have been planed down a fair amount. This might have given false torque readings.

Re: Head studs leaking coolant
 

I never had any luck with the white PTFE type thread sealers on stock BBC blocks .
Most of the blocks have pitting in the bolt holes from years of street use and as was mentioned can be further enlarged by chasing the threads with a tap.
The best thing I've found for sealing the studs is pipe thread sealer made for gas pipes. ...My brand of choice is Leak Lock from Highside Chemicals. Its blue in color and is a hardening type of sealant.
I've used it for 20 years on my old 468 spare engine and have never had any leak problems.
As you said in your last post ,make sure there is adequate clamping , I 've had to double washer some engines that have had the heads angle milled.

Re: Head studs leaking coolant
 

Sealing studs can be a challenge - BOLTS will seal with the ARP stuff, but NOT studs. Like Tom G. said, Leak Lock works, but it is very tough to get the studs out afterward, as it is a hardening type of sealant. I started using snowmobile case sealant ThreeBond #1211 (silicone based) with very good results. Take the studs out one at a time, clean, apply new sealant, then retorque.

Re: Head studs leaking coolant
 

Permatex makes an Aviation sealer called Aviation 3. GREAT stuff...............
Dan
http://www.permatex.com/products-2/p...-liquid-detail

Re: Head studs leaking coolant
 

Tim,
I use the Permatex White Teflon sealer, only because its a lot less expensive than the ARP stuff.
That being said, I have found that the trick to getting studs to seal is to put a healthy "glob" of the sealer in the hole in the block before you thread the stud in. I also put some on the threads of the stud, but not a whole lot. I think what happens with studs is for some reason if you only put the sealer on the stud, 90% of it gets wiped off as you thread the stud into the block. I don't understand why the same thing does not happen with bolts, but ever since I have started putting the sealer in the hole first, I have not had an issue with the studs leaking.

Hope this helps,

Re: Head studs leaking coolant
 

Thanks for all the suggestions thus far ... I can't get back at it until this weekend. Work gets in the way sometimes. Going to do a very careful disassembly and see what we can determine.

Re: Head studs leaking coolant
 

Permatex brown #2 or Indian Head Shellac.

Messy but works.....threads need to be reasonably clean.

Put it on the nuts up top as well....

Use laquer thinner to clean the stuff off.

Re: Head studs leaking coolant
 

Hold up on dat carwash genta-men! Ran into this issue on one of my big inch n20 motors. I knew the heads were torqued correctly as I could see the "crush" on the copper head gaskets. If you are sure about the torque on the heads and have no fastener issues, go get yo-self a bottle of Moroso ceramic block sealer and follow the directions. Easy and solid fix to a common problem.