Exhaust manifold nuts loosening

[dlgis]

Hi All, I’ve never managed to cure my problem of the downpipe to exhaust manifold nuts loosening up. I have stainless steel downpipes and standard cast manifolds, and use Nordlock washers on the studs. The car’s been used 4 or 5 times since the last time the downpipes were removed, and after each use I need to tighten up all 8 stud nuts. So for example, yesterday, the car was driven for 200 miles and afterwards (when cold) I again had to tighten all 8 nuts, with the worse ones requiring approx a 1/4 turn and the best just needing nipping up.

Any ideas how I can fix this? Would it be any less of a problem with mild steel downpipes? At some stage I want to invest in some new manifolds as the coating on the current ones has disappeared so perhaps that coupled with new studs might resolve it?

[DWW]

Yes I had that too which reminds me to check again, I will tomorrow. It will be good if someone has a solution though......

[bitsobrits]

Your sealing 'donut' maybe on the verge of failure, causing the joint to lose tension.

Back a couple of E types ago, when I ran the factory manifolds with stock type downpipes, I used stainless steel studs with unlubricated double height brass nuts and basic stainless lock washers. The brass nuts were squeaky tight, and never loosened once tight. Nor did they seize/gall on the studs. The studs I was using (and pretty much the only studs I use if possible) are made by ARP and are a high tensile stainless alloy with beautifully formed rolled threads. ARP are the folks that make rod bolts/studs and cylinder head studs for the racing community. Pricey, but last forever.

[dlgis]

Thanks bitso, I have used ARP products before and as you say they are highly rated. I’m currently using the double height brass nuts with the stainless Nordlock washers, and the “donuts” are fairly new. Studs however haven’t been replaced. I’ll change those for ARP if the problem continues and I splash out for new manifolds