Inlet manifold

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-JC-
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Inlet manifold

Post by -JC- »

Finally getting around to doing my bike carb swap (see quote in my sig :oops: ). The new manifold is a lot thinner than the one from the DGAV, so the bolts are bottoming out in some places. I went to the local hardware store and bought some of the right thread and shorter length, but my dad pointed out that they might not be suitable if they're not the right kind of metal? I.e. shearing etc? Should I get some proper ones?

Second issue is that I didn't realise they would bottom out until after I'd applied gasket sealant which dried out by the time I got back. What's the best thing to do? Scrape it off or just buy new gaskets (was advised to use 2 for extra thickness to ensure a good seal with the alloy/alu manifold.)
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Paul G
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Re: Inlet manifold

Post by Paul G »

perhaps you could put a couple of extra washers on the bolts to stop the bottoming out.
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Re: Inlet manifold

Post by mjcapri »

Good old 8.8 (tensile strength) mild steel are perfect. Check what you bought though because if they’re from a diy store they may not be 8.8 and may if fact be made of polystyrene....

As for the gasket, personally I’d use a new one, and I do mean ONE; gaskets on top of gaskets aren’t a good idea!
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Re: Inlet manifold

Post by nigecapri »

gaskets on top of gaskets aren’t a good idea
Not usually but;
I tried a full weekend to get mine to run right with every carb tweak available and got carbmonox poisoning into the bargain. The exhaust manifold just kept glowing on anything above tickover. Back on with the Weber and a trip up to BoggsBros. Just about to refit the bike carbs in their car park before putting it in the garage for a tune up and the gaffer told me to put two gaskets on it because with the thinner metal of most custom built manifolds they always warp leading to air ingress and lean running, hence the glowing manifold.
If the paste is a flat film then that side put face-to-face with another gasket plus some a thin veneer of paste should work o.k.
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Re: Inlet manifold

Post by -JC- »

Thanks guys
mjcapri wrote:Good old 8.8 (tensile strength) mild steel are perfect. Check what you bought though because if they’re from a diy store they may not be 8.8 and may if fact be made of polystyrene....

As for the gasket, personally I’d use a new one, and I do mean ONE; gaskets on top of gaskets aren’t a good idea!

Hmmm, it does say "8.8 CW" on the head of each bolt. That do then?
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Re: Inlet manifold

Post by mjcapri »

Yes they’ll be fine. Interesting that Nige had trouble sealing his new manifold and had to use two gaskets; maybe that is the way to go after all!
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Re: Inlet manifold

Post by fordperv »

I hate gasket sealer but before you put 2 gaskets on, try using one gasket with both sides lightly smeared in grease then run the engine up to temp, its old school but works (Got told it many years ago when i was a lad by my dad When he was teaching me to spanner, I've not had a gasket leak) my bike carb manifold doesn't leak
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Re: Inlet manifold

Post by -JC- »

Thanks for the tips. Was thinking the gasket sealer would increase the chances of getting an airtight seal, but I guess I can always apply sealer later if it doesn't work without it.
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