Please check my pic from my old main bearings, any ideas what cause those wearings circulated? Have you seen same before?
Hot spots for sure. Highly worn in some areas. Some pitting visible. Some causes are high miles, poor oiling, inconsistent maintenance, high RPM abuse, detonation, excessive water in oil, off-center crank due to core shift and no correction with prior rebuild, crank out of balance, bent (!), wrong bearing size/improper installation with damaged caps, defective/damaged bearings on the back side, engine sat for a long time and then was run hard with no oil change, ran low on oil/overheated, etc. To fix, align hone (or bore) block where crank goes, turn crank and use oversized bearings. Rebalance rotating assembly once assembled. Make sure to use good oil (higher ZDDP content), and change it on a regular basis. Make sure oil pressure is good, from 10-15 lbs. per 1,000 RPM on stock-moderate engine build. Get a few sets of bearings, use the ones that are closest to each other in clearances for even wear/friction reduction (oops, a trade secret). Get that rotating assembly to move as smoothly and freely as possible without opening up clearances too much. If any of this has been previously mentioned, please overlook my comments. Gary
Hmm, seems I should have paid more attention to the dialog within this thread. I'm running out of time, so I must be brief. The cam you describe sounds exactly like the Melling sbc-11, which is not a 2 barrel cam per se (though certainly fits one nicely), but the post-'75 Buick engines both 2v and 4v. All prior cams were the same for 2v and 4v, to the best of my knowledge, such as the Federal Mogul CS647 and Melling sbc-5, which were not only used for the GS engines, but for ALL Buick 350's in those years. Those cams have 112.75* and 112.5* LSAs, respectively. I'll have to check more closely with the Melling cam's timing events, as I am not as familiar with that one as I am the CS647 cam, but according to the quick reference, that's where it sits. And yeah, there's a lot to camshaft science, as we all know. The more one digs into it, the more one realizes just how much one did not know! No shame in learning here. I've come a long way myself. Gary
Bearings were 5 years old, no idea how many miles, when I bought car 2 years ago engine vibrated badly, it had wrong flex plate without welded weight at all. When I changed proper flexplate almost all vibrate was gone but there was still some left. Im thinking should I get block align honed, I really would like to but again my budget says nay. Crankshaft is std size, it is polished and checked by machine shop and it is in really good shape he said. Checked new main bearings with plastigauge, all are .002 or very little under. Endplay is .003. How lightly crank will usually spins when you spin it by hand after mains are torqued? Mine spins maybe 1/4 - 1/2 turn. I got new pistons and rings, crank goes to rebalancing when I'll get my new harmonic balancer from TA. I balanced rods and pistons within 1g. I always use ZDDP additive in oil and change them regulary. I have booster plate and my oil pressure was always good. Now I opened oil suction line and got bigger pick-up.
I would find a way to check the main bores' alignment before deciding on line honing or boring. I was thinking severe crank flexing until you mentioned the out of balance problem. I'd be comfortable assuming most of your bearing damage was from that. The edge of too much rpm and off balance tends to flex the ends of the crank (where the counterweights are. Note the flexing around the center).
If everything else checks out ok, just make sure you get your rotating assembly balanced. Sounds like that was the culprit. Gary
Oil by-pass valve in oil pump cover, is it replaceable? With this for example: http://www.amazon.com/ACDelco-25014006-Professional-Engine-Filter/dp/B000EPT4U8 ? How critical is if by-pass is not absolutely leak-proof? When I look it against light from spring side I can see some tiny light coming thru at one corner. Or does it even matter at all?
The bypass valve only works if the filter becomes clogged and that should never happen. Leave it alone. Sometimes they can be a bit off their seat and all it takes is pushing in gently with a small screw driver to straighten them out. http://www.taperformance.com/prodimages/TA 1512A.jpg The more important relief valve is replaceable and comes in the oil pump kit, along with the Stage 1 spring (white). http://www.taperformance.com/prodimages/TA 1508.jpg
When I changed proper flexplate almost all vibrate was gone but there was still some left. The flex plate that you put on will not be perfect. When you have the assembly balanced be sure to balance the flex plate with all the parts. Dan
Ok, I already have TA adjustable relief valve. I believe new flex plate is ok but previous engine builder who changed pistons did not got crankshaft balanced. Yes I will take my new TA harmonic balancer and flex plate along with crankshaft to machine shop for re-balance. Gladly my new pistons were 27g lighter than old ones.
Do you US guys call or use email when ordering stuff from TA? I've been waiting a week answer to email, yes I know its nothing but when summer is coming it feels eternity.
