Manifold fitting - an alternative to slotting

[bobfather]

I'm considering alternatives to slotting the bottom bolt holes because I'm fitting ARP's with nordlocks and I'm worried that the smaller shoulder area of the ARP's will reduce clamping force if I cut the slots

I'm looking for thoughts from those who have struggled with this job. I can see the potential for this to go wrong by a bolt slipping off during fitting but it still looks good to me

Any thoughts?

[bobfather]

Yes carsy, ACT st st precatless manifolds.

[bobfather]

My biggest problem was that the top bolt on the starter motor was threatening to shear so I decided to take an alternative route to the last bottom bolt

[bobfather]

Chuffmeister said:

Not a bad idea actually. Just pop in a bung when you're done.

It'll have to be heat resistant. The hole is very close to the manifold

[bobfather]

ARPs do appear to be harder than the nordlocks, that's the wrong way round. The nordlocks would be more effective if they were used with the old mild steel bolts

[bobfather]

This sounds like the benefits of ARP's may be outweighed by reusing the original mild steel bolts with nordlocks. The nordlocks will bight into the bolt heads and manifold flange so they will never loosen. More difficult to fit but you never need to retighten

[bobfather]

Would it help if the contact surface of the ARP's was roughened prior to fitting? The nord's would then have something to lock onto

[bobfather]

but if they could be roughened that would provide an interference surface that the nords could latch onto

ETA perhaps using a centre pop to pop-mark the surface

Edited by bobfather on Friday 30th January 20:15

[bobfather]

Actually very easy, bolt in a vice, centre pop all round. It now latches to the nordlock very strongly

[bobfather]

They look good. In hindsight I would have looked further rather than just buying what appeared to be popular and I think ACT selling the ARP/norlock combo gives a degree of undeserved credibility.

The ARP flange is too small and as you say the polished surface works counter to the nordlock process. I'm always wary of over tightening into an alloy block. I have had to run a tap down several of my bolt holes to enable the new ARP's to find a start, that also runs the risk of oversizing or otherwise weakening the female tread.

Perhaps the only true benefit on ARP's is the small AF size and corrosion resistance

[bobfather]

With ACT manifold flange, ARP + nordlock and standard metallised gasket I get 11mm of insertion thread

[bobfather]

I can insert 2mm +/- 0.3mm on all but two. Those two are both 5mm. This measured at the point that the bolt can no longer be withdrawn

I therefore generally have 9mm with two at 6mm of engaged thread. Not much considering the weakness of alloy threads and the bolting force needed to create a flat gasket seal

[bobfather]

I still have my original mild steel bolts and can see from the point that corrosion stops that they didn't have much engaged thread either. If you consider the force that can be applied to a standard nut and bolt fastening and consider the length of engaged thread in the nut then we're 2 to 3 times more than that.