View Full Version : Thread Sealer on Wet Liners?

07-25-2009, 01:27 PM
I'm in the process of assembling my TR4 engine and the ARP head and rod bolts I bought came with a tube of ARP thread sealer. I was wondering that since the connection between the block and the cylinder liners almost acts like a threaded one, would it be advisable to smear a little of the thread sealer on the lower portion of the liner prior to slipping it into the block? i wouldn't use it at the FO8 gasket, just on the part that slides into the block.

07-25-2009, 01:42 PM
Never heard of ARP studs coming with sealer ... are you sure it's not lubricant?

In any case, I wouldn't use sealer on the liner spigots. The Fo8 gasket is what seals that joint, and anything that might get hard inside the joint will make it terribly difficult to get them out next time. Plus I believe the liners are supposed to be able to "float" a little, so they keep pressure from the head onto the Fo8 gasket.

07-25-2009, 04:49 PM
Didn't read this from the S-T manual directly, so the advice may be wrong, but when this was discussed on the TR Register forum someone quoted as follows:

<span style="font-style: italic">but looking at the ST Service Instruction Manual, the figure of eight joints, are "metal (presumably steel) and the plastic coating ensures a good watertight joint". However the use of a "light coating of Wellseal is recommended"</span>

I've been thinking that a thin, non-hardening sealer would help prevent any leakage.


07-25-2009, 06:59 PM
My mistake, you're right, they did not come with the thread sealer, I purchased it separately. The thread sealer is a Teflon based sealer with a rust and corrosion inhibitor and can be used with aluminum, steel, stainless steel, etc. It's supposed to deliver a flexible, leakproof seal against coolants, water, gasoline, etc. It's primarily intended for head studs that pass through the water jacket.

I'm not worried about it ever hardening or restricting any movement, supposedly it won't do that. I was just curious if if may add a little extra protection against a leak that could possibly squeeze past the FO8's. In any event, I don't think I want to be the guinea pig here so I'll pass on it.

Randy, I'm not sure what "plastic" coating they're referring to. The FO8's I have are aluminum and have no coating at all. I'll most likey just use a little bit of that indian head stuff.

Thanks for the input guys.

07-25-2009, 07:00 PM
Did not do that when I rebuilt a four, but I don't think it will hurt. Probably most of it will squeeze out.

07-25-2009, 08:26 PM
There are different types of Fo8 gaskets; the steel ones did have a plastic coating. The copper and aluminum ones don't, AFAIK. In all cases, a little sealer on the Fo8 gasket probably is a good idea.

I can't really comment on your sealer, since I don't know what it is. But most Teflon-based sealers are for tapered threads, where the Teflon actually acts as a lubricant so you can tighten the taper more. I can't see any other reason to include Teflon, as it's not particularly strong nor heat resistant, nor sticky at all.

And as yet, Hylomar is the ONLY sealer I've found that doesn't eventually set up hard. Permatex "non-hardening" will literally get hard as a rock, given enough time and heat. I have literally used a chisel and hammer to chip it away (although usually solvent and time work much easier).