Aaron65 Posted October 27, 2007 Share Posted October 27, 2007 Hello, I just had my 263 straight 8 rebuilt by my local machine shop…I’ve broken it in and have driven it about 75 miles or so. The hot idle oil pressure is low. Here’s what I’ve done. I drove it 30 miles today, went out and got a mechanical oil pressure gauge and hooked it right to the threaded area in the block where oil pressure is normally taken. I started it up and it had 17 lbs. of pressure at idle after sitting about 90 minutes. I drove another 20 miles and it had 7 lbs. At this point, winging the motor (not to redline or anything) in neutral brought the oil pressure to about 37 lbs. When I started it before the ride (not with a cold engine, mind you) it had 42 psi…My machinist, when I asked him, told me the mains, rods, and cam bearings all had between .0015 and .002 clearance. This doesn’t seem loose enough to have this low of oil pressure. The oil pump was not changed, as it was in excellent shape. I am running 30wt Brad Penn Break-in oil at this time. My machine shop will stand behind their work, but I’m wondering if there’s anything I’m missing…plus I’d rather not yank that big thing out of there again (although, of course, I will if it comes down to that)…any ideas? Thanks for any help… Link to comment Share on other sites More sharing options...
Guest Straight eight Posted October 27, 2007 Share Posted October 27, 2007 What is oil pressure at 30-35 mph warming up and hot? Link to comment Share on other sites More sharing options...
Aaron65 Posted October 28, 2007 Author Share Posted October 28, 2007 I wasn't able to chack warming up, but hot (guessing, because my gauge was under the hood) I'd say about 27 lbs...which is low according to the manual. Link to comment Share on other sites More sharing options...
Aaron65 Posted October 29, 2007 Author Share Posted October 29, 2007 Looks like the rocker shaft is bleeding too much oil by it...they cleaned up the rocker shaft and they left too much clearance or something...more to come! Link to comment Share on other sites More sharing options...
The Old Guy Posted October 29, 2007 Share Posted October 29, 2007 Aaron It is a possibility that they replaced the brass fitting where the line goes into the head. The original fitting has a small orfice to slow the oil to the overhead. If they put in a standard fitting, that would cause low pressure. Link to comment Share on other sites More sharing options...
Aaron65 Posted October 29, 2007 Author Share Posted October 29, 2007 Hi Old Guy, Same fitting in the head...They turned the shaft around to let the rockers ride on a new surface and cleaned up the rockers...apparently that's where the oil's bleeding past. Did you get my email about buying your extra rocker shaft? Link to comment Share on other sites More sharing options...
The Old Guy Posted October 30, 2007 Share Posted October 30, 2007 Aaron I got your E=mail, but haven't had a chamce to see where it is. I will try and check tomorrow Link to comment Share on other sites More sharing options...
Aaron65 Posted November 17, 2007 Author Share Posted November 17, 2007 Joe, After comparing my cylinder head fitting with a picture of an original, it seems like I do not have an original cylinder head fitting...I just ordered 2 from the Buick Farm (one for a spare)...maybe that will help my oil pressure...I cleaned up and installed a good used rocker shaft and pressure went up to about 9.5psi at hot idle...if this fitting brings it to 11 or 12 I'll be happy. Link to comment Share on other sites More sharing options...
The Old Guy Posted November 17, 2007 Share Posted November 17, 2007 Aaron 9.5 at hot idle is good enough. If you never have a bigger problem, you will live to be 100+ Link to comment Share on other sites More sharing options...
Aaron65 Posted November 20, 2007 Author Share Posted November 20, 2007 Thank you for the perspective, Joe. One more question for you...I did not have a numerical gauge on the car before, and just went by the dashboard gauge for comparison between pre and post rebuild. Is it possible that the amount of crud and sludge in the oil passages of the engine was causing an erroneously high reading, and now that the engine is clean and it's reading about the same or even a little lower, it's really higher? Just a thought I was curious about... Link to comment Share on other sites More sharing options...
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