Inliners International Forums General Discussion Engines 261 oil lines

Need help, have my 52 chevy 1/2 ton pu at a shop and they are wiring it and doing the plumbing on the carbs and oil lines. the motor is a 1958 261 w/235 head. the motor is already in truck and radiator. I was told this was a full pressure motor,I have done a lttle reading here and there but still confused. Not much good on car & trk motors. does someone have some pics they could email me(maddog359@gmail.com) of the oil line routing. i was told that i could not put a beehive filter on this engine because of line size? all pics and info greatly appreciated. Thanks,Larry

Look in the Tech Tips section on the Home page, it might help answer some questions.

Emailed you the oil line routing as pictured in the factory manual.

If the block is a true full flow motor, you should have the larger oil feed and return lines, i actually forget the size. Runs all of the oil out of the galley into the filter and then back into the galley, under pressure. So all of the oil is filtered. The earlier blocks, and even some later blocks, for example the Canadian Pontiac 261 blocks, have the smaller bypass oil lines. That is the oil is essentially bled off the main galley, sent to the filter, and then simply dumped back into the pan. Only some of the oil gets filtered, so to speak. The trick with the bypass motors is that you have to use the smaller lines to restrict the amount of oil coming from the mains or else you will bleed all of the pressure from the motor and kill the bearings. Not so with the full flow. The beehive filter is strictly a bypass filter and so is opposite in that using the beehive with a full flow block will starve your full flow motor which is of course something to be to be avoided at all costs, lol.

I have hesitated to put my 2 cents in, but,(you know me, I can't shut up) if you have a '58 or later block the full flow filter was an option, there are 2 larger oil outlets on the drivers side, one on the lower galley and one higher up. Just above the lower one (which is the pressure side) there is a plug, or whatever, that if it is flush with the surface renders the block to be a bypass filter system. If the plug has been driven in to block the transfer galley it is imperative that the full flow filter is in place. The lower one is 'IN' and the upper one is 'OUT' I sold a High Performance '62 261" to someone who thought his buddy's opinion was better than mine and seized up in about a block.

Just sayin'

Tim

Titan, I remember someone either telling me that or me reading it somewhere but maybe you could clear something up in that regard. Is it possible to have a bypass motor with the large lines? Would that not kill the oil pressure by bleeding off to much oil? Or do those motors, instead of dumping the large line bypass oil back into the pan, like the small line bypass motors, put the by pass oil back to the galley?

If the bypass plug is not 'set' hooking a filter to the IN-OUT lines would have no effect because there is no signal for the pressure to pass thru the filter. I am not completely sure, but, I would venture that the factory bypass filter drew off of one of the large ports (thru a restriction, like .030 or so...), thru the filter, and dumped it back into the crankcase like the earlier models. You are correct that bypassing the pressure thru a filter and dumping it directly back into the pan would kill the oil pressure and flow. With the early technology, and sometimes the absence of apparent logic, it's a wonder we have these beauties to play with.

Tim

old52pu, When using a 235 head on a 261 block you need to drill some holes in the head to match the ones in the block that route coolant to the head. There are a number of excellent treads with pics on how to do this. Just do a search. Failure to make this modification is sure to lead to over-heating problems.