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psybock
10-04-2004, 01:31 PM
I'm in the process of assembling my new 454, and was wondering if somebody could help me out with an oil pump question. The pickup is press fit into the pump, but the guys at PAW told me that I should get it either tac welded or brazed to make sure that it doesn't shake loose over time. The guys at the metal shop were a little worried as to what method to use, since the pick up is steel tubing and the pump is cast piece. One guy suggested tacking it with a tig welder, using silicon bronz. Sound right?

ProdigyCustoms
10-04-2004, 02:13 PM
The cast has to be heated to 400 degrees, then tig welding is the trick. Weld it! I have a few horror stories about not welded tubes.

10-04-2004, 03:57 PM
Pre heat isn't necessary on something that small that you're only going to put a tack or two on.

Do NOT cool it with water. You can tack it with a TIG, MIG or stick, with normal mild steel filler (6010/6011/6020 for stick). If you were welding it all around, it'd be a different story all together.

After you've tacked it, peen it. Peening is taking a small ball peen or chipping hammer and lightly tapping it all over the heated area as it cools. Peen it until it's about 150, or until you can hold onto it comfortably with your bare hands.

The key to cast iron is to not heat it up too quickly, and, more importantly, to not let it cool down too quickly. If it cools too quickly, or is restrained too much as it cools, it'll crack. It's one of lifes few garuntees.

The other key to cast iron is cleanliness. Don't grind it, as that only smears it around. Allways use a cutter. IE: machine it, or prep it with a rotary burr in a die grinder.

psybock
10-04-2004, 05:20 PM
thanks a lot you guys! I got it tacked using a tig welder and let it cool really slowly. Can't wait to fire my baby up after the heart transplant!

ProdigyCustoms
10-04-2004, 06:06 PM
Tack welding is a leading source of cavatation in oil systems as it can heat the tack spot and cause a relief area beside it allowing a air gap. Ring welding is the only way to go. Many a racer has lost an engine due to cavatation (sucking bits of air). Keep in mind the oil pump is not submersed at the pick up tube to oil pump area.
It's only your oil pump, you can do it half ass if you want.

10-04-2004, 08:35 PM
Good point!

So, at that point, psybock, Put a few more tacks on it to pre heat it, then weld solid in 4 stages. Either peen or stick it in a pre heated oven @ 350, then shut the oven off and let it cool with the oven.

907rs
10-05-2004, 07:16 AM
Hey Matt, what does peening actually do to the iron as it cools?

10-05-2004, 08:00 AM
Hmmm, is this a test? :icon996:

Cast iron is very brittle, and if it cools (contracts) too quickly, or it is significantly restrained as it cools, it has a tendency to crack.

Peening relieves the stress that comes from contraction by displacing the grain structure in the material so it has "room" to move. That's why you don't peen just the weld, but the HAZ too, since that can be where the worst problems are. The HAZ is more critical than the weld because the filler used is (when done correctly, IE no stainless fillers) much more ductile than the base material.

So do I pass?

907rs
10-05-2004, 08:04 AM
Yeah, you passed. :icon996: Thanks! You learn something new every day!

airrj1
10-05-2004, 11:02 AM
If you are going to do any more than tack weld it, be sure to remove the pump bypass spring. You don't want to change the tension of the spring.

SDMAN
10-05-2004, 03:44 PM
There is a much better way to retain the pickup without welding on the cast pump body. Install the pickup in the pump. Set it exactly where it needs to be. Fabricate a small bracket that will have one end welded to the steel pickup tube, and the other end has a hole drilled where one of the bottom plate bolts are. When this bottom plate bolt is installed, it clamps the bracket to the pump body and since its welded to the pickup tube it cant go anywhere. I have seen tubes welded to cast iron come apart, and I have seen bottom plates warp due to to much heat.