stunthanger.com
Engine basics => Engine set up tips => Topic started by: PatRobinson on May 21, 2007, 06:04:50 PM
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Hi guys,
I did the crockpot clean on several engines that had set up too long.
One of these was an OS FP40 that Randy Smith had setup.
I had taken off the back plate and when I started to put it back on I found that one of the holes in the case had stripped when I had disassembled the engine. Question : What do I do? I vaguely remember hearing about someone tapping out a stripped hole with a 5-40 tap and then using a 5-40 screw and I noticed that Micro Fasteners has both of those items available.
So, what do you guys reccomend as the best way to go?
Pat Robinson
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My old faithful Tower 40 has a stripped head thread. I tapped it out 5-40 and put a 5-40 socket head in. Now I just have to keep things straight when I take it apart.
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not knowing what size was in there stock, You might be able to install a 4-40 heli-coil and that reverts the thread to a 4-40 screw. If it was already a #5 size, and then stripped out, I believe the hole would be too big to install a 4-40 heli-coil.
Bigiron
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I had to drill/tap the header attachment bolts for my PA 51 from 4/40 to 5/40 took maybe three minutes total and 2 of those were looking for the drill bit and tap! LOL!!
it has worked flawlessly since then. y1
Does the Tower 40 follow suit with the OS 340Fp it is cloned from and use metric screws?? If so, I am not real sure what size is next up in metric, but it seems a 5/40 would do. If you do, i would retap all the back plate screws and replace them with 5/40. makes life a lot simpler. ;D
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The stock screws are 3mm x .5's currently standard. The old standard was 3mm x .6's (ST .60, ST .46, OS .35S, etc.). The standard fix for these engines, now that those 3m x .6 screws are pretty much unobtainable, is to use 5-40's.
Therefore, there is not going to be any material to tap, to screw the 5-40 into. A 3mm x .5 helicoil would be the right thing to do, and maybe the only thing to do. It might be cheaper to find somebody to fix it, than buy the drill, tap, and helicoil plus the installation tool. OTOH, if you have to pay postage both ways, you might be better off buying the drill, tap, and helicoils and make your own install tool from a machine screw. Or, you might be able to buy a new crankcase from Tower? I'd sure look. H^^ Steve
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The 5-40 deal works fine.
But heres how this frequently happens. The cylinder head bolts are usually longer than the back plate bolts. What do you think is going to happen when you try to tighten a head bolt in the back plate hole? HB~>
Pay attention to where the bolts come from when you dismantle your engines. n1
And BTW, connecting rods can go in backwards too! The chamfered end goes against the crank shaft.
Ward-O