Elvira : Rebuilding the 36hp, episode 7 : intake manifold
episode 7 : intake manifold
Same issue as with the pushrods : the intake manifold is now too long to fit, since I've modified the cylinder heads... Gotta admit, I didn't see this one coming!
Since I did not want to modify my original 36hp manifold, I found a spare one on LeBonCoin...
There we go, I cut using a hacksaw, and I remove the dreadful 6.4mm! I take advantage of the accessibility opportunity to clean the inside of the heater tube, which was in dire need of some TLC. Definitely easier to do this while it's opened like that!
I MIG-weld the parts back together... Starting with the thinner, upper tube, the one that brings the air-fuel mixture to the heads.
To make sure to whole thing is air-tight (not easy to make air-tight MIG welds on the first try!), I close up the extremities using bit of a bike tire inner tube ; I use the valve from the same tube to put the whole thing under pressure (cue Queen/Bowie's music). This gives me a way to pin point any remaining holes, which I grind, weld close, and file again (why on earth did I wait so long to buy myself an electric file??)... On the fifth try, it is air tight. I still have one or two micro asperities, that will be closed by the layers of paint. Plus, while running, the manifold is under depression, not under 5 bars of pressure... (the first one to talk about Jusdon gets a slap)
I then weld back the second tube, the heater one (the exhaust gaz go through this one to heat up the manifold and prevent freezing). This one is easier to weld as it's much thicker, there's less risk to "go through" with the MIG. Therefore I can grind nice chamfers before I actually weld..
But I don't have access to the cut other side of the tube, next to the first tube I welded. I hoped that a nice clean weld on each side would do the trick, but when I wput it under pressure, it was leaking all over the place. So I got the Dremel out, and cut a window to get to the inside of this cut and weld it from there. I welded the window back in place, and this time it was air tight on the first try!
Next step is as usual : sandblasting, 2 coats of rust-preventing primer, 3 coats of paint... And TADAAAAA!! Here's your 6.4mm shorter manifold! Yep, all of the above just for 6 f***ing millimeters! Dayum, you gotta love your compression ratio, right?!