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.

Re: Head studs leaking coolant
 

Tim…Try Aviation PERMATEX, make sure the threads are dry...problem solved. MB.

Re: Head studs leaking coolant
 

I m just wondering why studs instead of bolts on cast heads,bolts seal 99.9 percent of the time

Re: Head studs leaking coolant
 

Engine had studs before I bought it and we replaced them with new ones as part of the freshen process. Block is fairly old (30 years approx) and compression is 13 to 1. I do recall a pile of black silicone type sealer on the old studs and some of the threads were in tender shape so we chose studs in an attempt to preserve block and apply that "more even clamping force" that studs offer. Unfortunately coolant got into the oil and now it no longer turns over smoothly. It is out of the car and partially apart,pushed to the side and my old reliable but tired 468 is back in. Just got tired of wrenching on this 496 and want to go racing before our season is over.I think block could use heli-coil inserts for most if not all the head bolt (stud) locations.

Re: Head studs leaking coolant
 

On a 454 block with a few bad threads in the head bolt holes, has anyone used recoil inserts offered by Fastenal ? Any better method ? Some head bolts spin at 30lbs torque, one is completely stripped. Thanks

Re: Head studs leaking coolant
 

Dave,
The recoil inserts are basically Helicoils. I have used them but prefer Timeserts. The only problem with the Timeserts is that they have a flange at the top and I think there are a couple of bolt holes that put them too close to the gasket sealing point for my likings.
If you get Helicoils make sure to buy some of the longer inserts. Same with the Timeserts. The ones that come in the kits are probably ok for a lot of applications but for head bolts or studs I always get the longer ones. You will probably have to order them from MSC or McMaster Carr

Not sure where you are located but Mechanics Tools and Bits is in Pa and has a nice website. He also has Helicoils and Timeserts

Hope this helps,

Re: Head studs leaking coolant
 

Thanks Bill !!

Re: Head studs leaking coolant
 

If you purchase the Timesert kit, it has an alignment tool and also a counterbore so the flange will sit flush on the deck.

http://www.timesert.com/html/inchsert.html

There is also the Keysert which does not have a flange, however, it requires a special tool to install.

https://www.fastenal.com/products/fa...eyserts%22%7C~

Re: Head studs leaking coolant
 

More great info, Thank You!

Re: Head studs leaking coolant
 

If you do not need to remove the studs to remove the heads, simply install the studs with Loctite 271 Red. They will not leak water.

To do that, clean the bolt holes and the studs to near sterile condition. Have the heads read to bolt on temporarily. Be prepared to fully install the heads and torque them to 25 ft/lb. You do not need to permanently install them, or even use head gaskets.

Quickly put 3-4 drops of Loctite 271 Red on the coarse thread end of each stud and immediately screw it into the block, installing each one in the correct location, without bottoming them out. Quickly install the head, and torque the nuts down to 25 ft/lb. Let them set overnight.

You are now ready to install the heads and finish the engine.

You can use chemical agent or a small amount of heat and a stud removal tool to remove the studs later.

Also, make sure that you are using a good quality bottoming chase tap when you clean the threads, and follow it with a stainless wire brush. Using a cheap tap, and especially a cutting tap, will ruin the bolt hole eventually.

Time-serts are indeed the ideal repair for stripped bolt holes, but properly installed Heli-coils will do the job just fine. I ran one 454 block for close to a decade that had a Heli-coil in every bolt hole on both decks. Last I saw that engine it was still running and making 900HP.

Re: Head studs leaking coolant
 

85 FT LBS on head studs on a OEM block that's alot !!!

Hopefully you block was plate honed with studs torqued that much ?? GM blocks are pretty frail compared to an aftermarket block.

If not a leak down test at TDC and 40 degrees Before or after TDC will not be good.

http://www.chevelles.com/forums/13-p...te-honing.html

Head studs are always a pain to seal and should be lock tightened in

ARP sealed works the best, Never seen Aviation sealer work on head bolts once it gets hot it solidifies.

GM seal tabs work great for leaks P/N 10-108

Re: Head studs leaking coolant
 

All I ever use is black, or clear silicone. Seals every stud, bolt, etc. never a problem.