On Saturday I´ve got my 327 sbc back from my machine shop. I had the block bored .040 over, the crank polished and the new pistons mounted on the rods. They are high dome pistons and my book says that the dome on the piston should be on the same side as the rod bearing tangs( the gaps which avoid that the bearing turns in the rod journal).The pistons don´t have a pin offset as some of the flat top pistons do. Now I found out that 4 pistons are mounted with dome and bearing tang on the same side, the other four are mounted dome and tang on the opposite side. Any ideas?? The guy who mounted them is a very successful dragster driver and mechanic over here , I can hardly imagine him mixing things up, but my book definitly says: dome and bearing tangs= same direction. Any ideas??? The pistons are Speed Pro L 2166nf.040
I´ve spent another couple of hours thinking it over and found out it was my mistake. Strange things happen if you think too complicated....But everthings alright now.
It can get confusing when you're dealing with those "foreign" engines, can't it? I remember the first VW engine I tore apart, wow, that sure was different from a 235" Chevy 6! You should have four with tangs to the left of the "front" notch in the piston and four to the right. The bearing tangs go opposite the cam, or towards the outside of the block. So you usually have four set up for the left bank and four set up only for the right bank,(unless the pistons don't have a "front" notch and only have a top and bottom) Also, if you have reliefs cut in the domes, there are/may be different size reliefs for the exhaust and intake valves. In a SBC you want the smaller exhaust reliefs forward in #1, #2, #5, and #6, and to the rear on #3, #4, #7, and #8, or whatever it takes to have them line up with their respective valves in the head. otherwise you will have the bigger valve hitting the piston if it's relief isn't under it. Do you have the cam plug in the rear of the block and the plugs in the oil galleries back there too?....Just checking... Also, a lot of people like to spot weld the oil pump pickup to the pump after aligning it. A good trick is to put the pickup on the pump a little low on the pump on the block then trial fit the pan, pushing the pickup up up with the pan. then remove the pan and push the pickup up another 3-4 mm for some clearance, then spot weld it to the housing. you might want to take the gears out before spot welding. That's not absolutely necessary though. Theres probably more on the road just press fit than welded on. It's just an added precaution.
DrJ - thanks for that post. I can never remember which way they go and the engine I have to put together next has no notch in the piston so I couldn't tell which way to orient the rods. Something like this could go in Tech-O-Matic for future reference?
Thanks DrJ, that´s a great post!! I mounted all pistons facing the dome outside the block. But it was impossible to match the #5,#6,#7 and #8 pistons in a way to point the tangs in the correct front/back direction.Now I know for sure that they ´ve mounted the rods in the wrong direction.With dome pistons they should all be mounted in the same direction, I think, not like the flat top ones. Thanks once more DrJ ,I´m glad it wasn´t my mistake... even "dragracers/ mechanics" aren´t free from failure...they´ll fix it tommorrow. BTW, I´m more familiar with American V8´s than with european engines.They don´t rebuild engines at all over here. Today I wanted to borrow a piston ring compressor from my neighbour who owns a BMW garage.I tought the probably had some kind of high end professional tools for that. They don´t even have a regular one!!!!!They just throw the old engines away and get a new one.... weird. Usually I use my " How to rebuild / hot rod anything" books and go on step by step, but it said nothing about rods mounted in the wrong direction. Thanks again for that great post!!
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