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Powder coating TPI will it seal?

2K views 6 replies 5 participants last post by  grumpyvette 
#1 ·
I bought this unit off of eBay and the surfaces are powder coated that require a seal between the surfaces. The surfaces are smooth like glass. Will it seal properly?
 
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#3 ·
I'm no expert at all, but these look like powder coated steel tubes to replace the cast aluminum stock L98 TPI tubes. I recall that there were larger Siamesed cast Al "tube" replacements available aftermarket back in the '80s, but I don't ever remember seeing steel tubes. Not sure why, but if I didn't just miss them, maybe they weren't offered because heat changes will make them expand and contract very differently from the cast Al manifold and the cast Al plenum/top airbox. This could place a LOT of stress on the gaskets these attach to and maybe the Al parts - or not. Again, I'm no expert.

Regardless, I doubt if the shiny surface will be the sealing issue. The challenge might be bolting these up (using plenty of silicone gasket sealer) so that they do not move around due to the temp changes under hood and not stripping the threads of the Al parts as you torque the mounting bolts. Don't forget the anti-seize. JMHO .... er.... guess.

BTW, if these new tubes are really powder coated, reworked Al then WOW. Nice job, and no worries. Just bolt them up with good gaskets. HOWEVER, if you are REALLY worried about the surface, you could use some fine sandpaper on the mounting surfaces to etch them just a little. Should end up looking a bit like annodized surfaces. Use a block of wood to assure you maintain an even surface across all of the ports.

Still not an expert!
 
#4 ·
If the surfaces are flat it will seal. The question is are the surfaces flat? If not then perhaps you might want to stick some sandpaper down to a table and run the surface back and forth on the sandpaper until the mating surfaces are flat.

A straightedge and a feeler gauge can tell you if the surfaces are flat. Alternately you can put the mating surface down on a flat table and put a flashlight behind it and see if you can see light between the table and the mating surface.
 
#5 ·
I agree with Autowiz. I had some older headers that I had powder coated and they warped. Would not seal without grinding down the high points.

As I said in a post on another thread I set up for this question, I would also be concerned if those tubes are metal, not cast Al. I'm no expert, but it seems logical that the metal tubes that mount to a cast Al manifold below and a cast Al plenum above, might tend to heat up and cool significantly differently than the material they are mated to, and could break the gasket seal...or I'm wrong. :huh:
 
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