Going to try and get my Chevy 235 fired up this week and was having a look over the motor before I do so. I noticed something strange. Stock oil filter is in there, but bypassed for some reason? There is a line that comes out of the block, then just goes right back into it...bypassing the filter completely for some reason. Also in this line is a "T" with a line going up to a hole in the top of the head, dead center for some reason...any ideas before I fire it up?
Why? I dunno... stupidity? My guess is something is wrong in there and this was how the PO decided to "fix" it.
I just read an article on another site that said this was a fix to get more oil to the rockers...apparently something that was done quite a bit in the past (wrong or not). Im fine with that, but would like to add the filter back into the equation somehow. So do you think I should add that T after the oil goes through the filter or before...or just do it stock, and plug up the mystery hole? This is of course after I make sure the oil pump is getting oil up to the top of the motor...
There is a valid reason for a oil filter,,I would plumb it back to original. Without a filter you run the risk of damaging the engine,,and like the old Flatheads running without a filter means changing the oil very often. HRP
Those old Chevy sixes had an oil galley running up to that center head bolt bore, passenger side. The galley would get MAJOR clogged down below, 145 PSI of compressed air wouldn't 'blow it out'. The fix: Remove the head bolt, find a piece of cold rolled rod that fits tightly in the head bolt bore. (head is 3-3/4" thick before you get to block threads) (1/2" dia., if memory serves...we used a Plumb drift, with a 4" shank) Fill the bolt hole with 140 wt. gear oil. Set the punch and hit it HARD, 2-3 lb. hammer...Just hit it once or twice, stop before hitting the block threads. Do this 3 or 4 times, then crank the engine and watch for a 'gusher'. If the rocker shaft is clogged, you'll have to clean that out, obviously... But this fix saves a teardown...and it's a GOOD one. (been doing it since 1956)
We should remember the oil change interval in those days was 1000 miles. Very few could afford the new on the market "detergent" oil. After all, it was 20 cents more!
OK, finally had a minute to get into the motor. Took off the valve cover and turned the oil pump with a drill...Im getting oil to the top of the motor no problem...still have that extra line. Should I leave it just to be safe? Seems like it was added for no reason
I added the line that you talk about to my 261. When the PO rebuilt the motor he put a regular head bolt in there and I wasn't getting any oil to the rockers. That specific head bolt has a groove in it to let oil up to the top of the motor. I added the line as extra insurance. T'd off the line that returns from the oil filter.
those old filters didn't filter more than 10% of the oil anyway. you could get by without one and just do reg. oil changes.
They only filter part of the oil but they filter it very clean. All the oil goes thru but it takes 1/2 hour or so. Any filter is better than no filter. Take one out after 5000 miles and see how much grit and sludge it kept out of your bearings.
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