360 heads on a small block

-
dustermaniac

dustermaniac

Senior Member
Joined
Oct 23, 2009
Messages
6,186
Reaction score
289
Location
Modesto, CA
Probably a dumb question. I changed out the heads on my Duster about a year and a half ago and used a pair of stock heads off a 360 motor. I have noticed that the compression is low and it seems as though the top end is starving for oil and has low oil pressure. I get 30 psi at start up, and drops down to about 20 psi at normal operating temp. In gear it is only about 10-15 psi. When I drove the car a couple miles the oil pressure came up to only about 20-25 psi. My question is I have a set of stock 273 heads and was wondering if I was to swap these 360 heads out for the 273 heads would I possibly get better oil pressure to the top end? I have a new oil pump,distributor,lifters, push rods, oil pump shaft, double roller timing chain and gears, camshaft and windage tray. There does not seem to be any rapping or knocking in the lower end of the motor. Oil is clean and does not smoke when running. Please any help with this would be appreciated. I did not change out the camshaft bearings when I replaced the stock cam. Did not think I would need to.
 
Tom, changing the heads shouldn't make any difference. Yes the pressure is a little low, but under normal cruising shouldn't harm anything. Are you getting ticking/tapping from the top end? Have you had the valve covers off while running to see if the top is dry? Is the gauge still good?
 
The reason i asked whether the top end could be dry is, that's plenty of pressure to oil the top end. Especially if it's one side making noise, i'm wondering if you have a exhaust leak?
 
It is definitley a low pressure issue. It seems to be from the top end starving for oil. Both stock rocker arms are on correctly. When I first put this motor back together I had some sort of blockage which caused the oil pump shaft to break. I tore it down and put in a new pump, shaft and pickup tube. I have tried three different gauges and get the same readings. When I drive the car and accelerate I am getting about 20-25 lbs pressure but I do not want to drive the car due to the fact that I am getting such low pressure when I stop at a stop light in gear. (about 10-12 lbs max) I did install a Summit aftermarket cam which was larger than stock but I do not recall the specs on the cam. As noted before I did not change out the cam bearings due to the fact that the old cam (stock) seemed fine, I was just seeking a better "lump" to the engine idle. I got that now. It idles like a beast but the oil pressure is the issue.There seems to be some oil getting up to the top end but not enough to register sufficient readings on the gauge. With the old set up I was getting over 35 lbs psi when stopped at a light with the car in gear. Now I got to put the trans in neutral and feather the gas pedal to keep it running when I am stopped at a light. Timing is on as stated before the car starts right up and idles fine when cold but as soon as it reaches operating temperature you can hear the ticking of the lifters and especially when you drive down the road you can hear the top end noise. I thought that maybe these heads were the wrong ones and maybe needed to be milled. But I am no expert at engine work.
 
No noise from the lower end though??? Only sounds like lifters at top end are starving for oil. No rapping from bottom end at all.When I tore the motor down after the oil pump shaft issue, there were no shavings in the pan or screen. Just a fiber like substance which I was able to clean out. Oil is clean. I tore open the oil filter and checked if there was anything in the filter and there was nothing to indicate that there was a blockage.
 
I had a 318 like that low oil pressure when warm you have enough pressure so no noise but if you check you bearing clearance I bet you have 6-8 thousants. You may get away with some 20w50 and stp for a summer or two.
 
Possibly a dumb question here, but have you checked the oil filter? I'm guessing you put a new one in but I'd take it off and check if for being defective if you haven't already.
Changed mine and a few days later I had low oil pressure, filter collapsed internally (made in china) lol
 
it seems as though he did not have this low oil press. problem until he changed the heads, gaskets, and cam, so, I dought the bearings are the issue. Did you have the heads you installed checked for cracks? did you match the new head gaskets to the old gaskets to make sure there the same? just some ideas...
 
It's bearings.
You don't have to have noises for the bearings to be loose.
Cam bearings are going to be critical to oil pressure, especially to the top end.
 
Did you use Moly on the cam to break it in? Moly can clog a good filter. Sometimes it takes a few oil and filter changes to get it out of there.
 
You must log in or register to reply here.
-

Back
Top