Exhaust manifold bolts - Should I use Locktite?

[stugilmour]

Have replaced manifold bolts with regular steel socket head bolts for ease of removal. The two bolts under the thermostat housing have loosened a couple of times, causing exhaust leak issues. I have purchased replacement socket head bolts in SS from ray at rdent, and plan to change them all this weekend. Wondering if Locktite would be appropriate in this high heat application, and if so which product number/colour? Should I consider a flat washer in addition to lock washer? The shoulder of the socket head may be a bit smaller than the stock hex head bolt, causing the lock washer to loosen?

[rgh0]

I have always used loctite nickel antisieze on the exhaust manifold socket head bolts together with a lock washer. Never had a probelm with them coming loose.

However I check the bolt tightness after the first few weeks of use as the gaskets can compress over time with heat cycles.

You could use a loctite. The cylinder head itself remains cool so the loctite will not exceed its design temperature in the threads in the head. Use a medium strength thread locking compound such as the blue 243. If you do use a loctiite you would need to remove and replace the bolts individually if you wanted to check gasket compression which is why I dont use it.

cheers
Rohan

[stugilmour]

Thanks for the info Rohan.

I received my replacement SS hex head screws from Ray this week. I think I found my problem; the steel ones I was using that have loosened were 1/4" shorter than Ray's. Today I serviced the gasket I had difficulty with on my trip without Locktite and the car is way quieter. Will check them over in a few weeks.

[CBUEB1771]

I received my replacement SS hex head screws from Ray this week.

If you use SS fasteners with Loctite you need a special primer from Loctite. Loctite requires free iron ions to catalyze the curing reaction and with SS fasteners in an aluminum casting the Loctite may never cure. The Loctite primer contains iron ions.

[Sea Ranch]

Great info here!

On the topic of hex head/socket cap screws versus studs/nuts, I believe the argument in favour of studs is that you don't risk fatigue of the head threads when you re & re the headers (studs stay in place, only the nuts are removed.

Argument in favour of removable screws is that the headers come off easier without having to pull them sideways to slip free of the studs. Is this correct??

Stu, I believe I have one exhaust port leaking, too; good to hear that the noise level goes down appreciably when they're all sealed

Randy

[rgh0]

The other major advantage of the socketed headed set screws is that it is easier to get at them with a ball headed hex key especially if using larger diameter headers where clearance to the pipes is small and hard to fit a socket over a nut.

cheers
Rohan

[stugilmour]

Great info here!

On the topic of hex head/socket cap screws versus studs/nuts, I believe the argument in favor of studs is that you don't risk fatigue of the head threads when you re & re the headers (studs stay in place, only the nuts are removed.

Argument in favor of removable screws is that the headers come off easier without having to pull them sideways to slip free of the studs. Is this correct??

Stu, I believe I have one exhaust port leaking, too; good to hear that the noise level goes down appreciably when they're all sealed

Randy

I think you are basically correct with the reasoning. The 'gotcha' part is it is pretty close to impossible to remove my headers with studs in place anyway, so they are probably coming out anyway. Pulling my two-piece Bean headers with engine in place was a two man job for sure. When Malcolm pulled the engine & transmission recently he mentioned he left the headers attached and the Spyder chassis had good clearance.

To remove any stubborn studs you can try jambing two nuts on the end and using a deep socket to keep them jambed and back the stud out. It's the ones below the thermostat housing that are the most awkward, particularly with dual boosters installed. You may have to get them from below.

Randy, if and when you remove some of the exhaust studs, use lots of penetrant, take your time, soak overnight, etc. I successfully used Locktite Freeze-Off to get several stubborn ones, and lot's of recommendations to carefully use heat. If you are really tugging they will break off, and getting a drill in there for an easy-out is very difficult/touchy.

The hex head fasteners from Ray are nice SS. As they are 1/4" socket head, it is easy to fit a 1/4" box end wrench on to the ball shaped Allen tool to apply sufficient torque. The ball shape tool works very well, although it is a 'by feel' job for sure. Other nice part of the Allen fasteners is you just need to loosen them and sequentially remove the bolts to centre the gasket holes and insert the fastener. I think with the studs the header has to be pretty much removed to get the gaskets placed.

Russ, thanks for the tip on SS, Ali, and Locktite. Learn something every day! Trying to remember where else I may have used SS into Ali!

[twincamman]

----drill the heads with a small drill bit and safety wire the bolt heads ----no loctate or any stuff to consider when removing them ----ed

[Sea Ranch]

Okay, this is great. Another example of why I'm so enthusiastic about this forum

Thanks for the explanations, Stu and Rohan. I was waiting and wondering if Stu would update us on the leaky exhaust header after your trip back from Vancouver. I really feel one of my ports is leaking based on the telltale single cylinder quiet "putting", but haven't figured out which one yet. I could save myself the trouble and re-gasket them all. And I think I will order the socket/cap screws instead of the nice SS studs and nuts; save some money, too

And if I'm REALLY ambitious, then I'll cross-drill the heads of the screws and wire them, Ed. Looking like boy racer. Come to think of it, my hobby-machinist friend would probably make short work of cross-drilling, as long as I supply him with the right bit.

Thanks again, gentlemen!

Randy

[Foxie]

Previous discussions here about using socket head bolts instead of studs have mentioned the possibility of opening out the aluminium threading in the head with repeated use

To avoid this it was recommended to helicoil all the head threads, no doubt best done with the head on the work bench

[rgh0]

While long term helicoiling may be needed it does not need to be done immediately when changing to cap screws provided due care is taken when tightening the cap screws and the threads are keep clean and corrosion free and are in good condtion to begin with.

cheers
Rohan

[ecamiel]

Does anyone have a method for removing the manifold bolts under the thermostat housing with (TT) big bore headers?
I use the small head aircraft bolts from Bean but it's still a bitch.
I use anti freeze on the bolts and they have never loosened.
By the way, big bore headers really added both power and torque to my modified (ca. 165 HP) motor but helped even when it was near stock.
Eric
64 S1 Hart

[Foxie]

Does anyone have a method for removing the manifold bolts under the thermostat housing with (TT) big bore headers?
I use the small head aircraft bolts from Bean but it's still a bitch.
I use anti freeze on the bolts and they have never loosened.
By the way, big bore headers really added both power and torque to my modified (ca. 165 HP) motor but helped even when it was near stock.
Eric
64 S1 Hart

The socket head (Allen) bolts would be easier. I have a TT manifold, and find it easier to remove/refit the engine/gearbox and manifolds in one piece.

[mr.vman]

Not all stainless bolts, studs and fasteners are the same, be aware. Most stainless fasteners for looks might be equal to, SAE #2 maybe. Drilling the heads and using safety wire is a great idea if....the stainless fastener can be drilled. My other concern is doing bad things to the aluminum Lotus thread in the head, there is a reason for studs. Stu, don't forget the the exhaust gaskets from an old type 1 VW beetle will fit well on the exhaust side of the Twin Cam. Hope this can help, Steve V.

[alexblack13]

Another big advantage of using steel inserts in the head, (Use good deep ones) is that one can apply 1.25 x the standard torque to the fasteners. That could be useful.

Don't just think that nice n tight means no leaks. Those flange faces must be flat and true also.

I thought about doing this mod' too when I had the lot out of the car recently (5 speed box fitting) but I decided it was not required. I recon' it's all down to how often one is stripping the thing down and I am hopeful that was my last time doing so!

Optimism! You cant beat it.

Alex B....