Tri power manifold rust

neilswheels

Well Known Member
I’ve just drilled and tapped my manifold for vacuum take off, which resulted in finding a fair bit of rust inside the manifold. I’ve decided to clean it with a tub of citric acid, I’ll let you know how it performs. My question is, how can I stop it happening again? I’ve seen pics of inside of blocks painted, and the runners in my heads have been painted, but it’s kind of hard to get in the manifold runners. I thought maybe dipping it in a light oil to cost the inside while it waits for fire up, my thinking being that the oils would burn off and not harm anything. Any thoughts?
Pics are of the outside of the inlet, it had some really knarly casting lumps that bugged, one thing led to another...
 

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Don Jacks

Well Seasoned Member
Supporting Member 3
How too stop it from happening again? Put it on an engine and run it.The engine heat will disperse any moisture that it takes in.Yes a coating of a light oil or rust remover like WD-40 will help prevent any build up,just keep it sealed off until the engine is ready to be used as being exposed will cause dust and dirt too adhere to the oily surfaces.
 

409gang

Well Known Member
Supporting Member 1
I’ve just drilled and tapped my manifold for vacuum take off, which resulted in finding a fair bit of rust inside the manifold. I’ve decided to clean it with a tub of citric acid, I’ll let you know how it performs. My question is, how can I stop it happening again? I’ve seen pics of inside of blocks painted, and the runners in my heads have been painted, but it’s kind of hard to get in the manifold runners. I thought maybe dipping it in a light oil to cost the inside while it waits for fire up, my thinking being that the oils would burn off and not harm anything. Any thoughts?
Pics are of the outside of the inlet, it had some really knarly casting lumps that bugged, one thing led to another...
That intake got rusty from sitting in someones cold damp garage or a shed and not on a engine, like Don said put it on a engine and run it or keep it in a climate controlled environment.
 

neilswheels

Well Known Member
Feeling slightly foolish, I’ve realised the rust was coming from the water ways in the manifold, not the fuel runners, which are actually pretty clean. I’m still gonna de rust it tho, all that crud won’t do the water pump or radiator any favours.
Another question tho, does anyone know what size this thread is? It’s the hole just behind the thermostat housing, next to the corner of the carb mount. The stud I removed measures up at 21/32, does that sound right? Could it be 5/8? I assume it’s npt..
 

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neilswheels

Well Known Member
Quick update for those interested, I tried the citric acid in a small tank, but found that it needed to be fully submerged on its side to let all the air escape, otherwise you end up with rusty areas where the oxygen is trapped, that’s the first pic. So I made a bigger tank, and submerged it on its side. Came out really well, all rust gone, back to a factory cast look. I’ll need to do a little more cleaning on the top before I paint it, Because I was concentrating on getting all the moisture off the bottom and inside the manifold, so the top has lightly flas rusted in places, but overall very pleased.
 

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