Hot Rod Forum banner

Oil Not Pumping To Top End On Newly Rebuilt Engine

14K views 12 replies 11 participants last post by  russ 61 
#1 ·
I have tried everything including taking the engine back to the machine shop to figure out why the oil is not reaching the top end. I have rebuilt a 1979 Chevy 305 H serires engine. There is 60#s of oil pressure and the oil is reaching the valley, but not the rock arms. No one has any answers for me and I am fresh out of "whys". The cam bearings are in place, all plugs are in place and the pump has been primed. Help!!!
 
#2 ·
Did the machine shop forget to install the plug at the 5th main bearing before reassembly. Where are you checking the pressure at. The location at the top of the block behind the intake will tap from the cam area, If pressure is evident there, then you have a cam bearing installed wrong or a the plug missing or your priming tool doesn't seal the dist bore.
 
#3 ·
All plugs are in including the plug under the 5th main. The block was cleaned and bored by machine shop. Checking pressure behind the intake. Priming tool is an old distributor modified. Push rods are not solid - have holes. A dripping of oil is coming through the push rods. Engine is now back in the car after going through it twice. There is just no logical reason (that I can think of!) why the oil shouldn't be coming up and filling the top end. Never had this happen before. Engine will run about 20 - 25 seconds and then starts to seize. You can hear it start to tighten up. I have to shut it down so that it does not lock up. Wait two hours and crank it - same thing happens. Fires right up loose with no problem, but starts to tighten - no oil in the top end.
 
#4 ·
I had the same problem.

I had this very same problem, so I am going to give you some ideas on how I solved my situation. I got a service manual that showed the circulation path of oil from the oil pan all the way up to the rocker arm.

l. The first place the oil goes from the oil pan is to the oil filter.
2. Second place it goies is to the crankshaft.
3. Third place it goes is the cam shaft and lifters.
4. Fourth it goes up the push rod to the rocker arm.

I started at the bottom and checked my oil filter and for some reason it was not filling up with oil. Pulled that new filter off, put another one on and got flow.

Second I used an old screw driver on a drill, for a priming tool, so I could look down in the engine and see what was going on.

I could see oil down in there after replacing the oil filter but I had to spin the oil pump with my homemade priming tool for about an hour (10 minutes at a time for 6 trys) before I ever got the oil to the top end. It took a really long time on this particular motor where on preveous projects the whole motor primed up in 2 minutes. Some engines are different than others.

You want to prime the engine with oil with your priming tool and make sure you have oil to the top end before you ever start the motor. Hope this gives you some ideas.
 
#5 ·
If the engine is starting to sieze, you need to pull it. However, if it was, letting it cool would not remedy anything. It would just seize after you start it. Not to be a smart ***, but the engine is not going to produce lube in the bearings while it sits.

That out of the way, I had a similiar problem a little while back. Turns out the valve train is feed through a couple small holes in the rear cam bearing area. One was plugged causing one side not to oil. I pulled the pipe plugs in the back of the block to gain access and blew the plug out with an air hose. Coincidently, an air hose is also 1/4 inch pipe plug. Just an idea.

Chris
 
#6 ·
Did you have the block tapped for pipe plugs in the end of the oil passages? or do you still have the expansion type plugs that you drive in?

If you or the machine shop installed pipe plugs (screw in type), you need to make SURE they are not too lone the middle one in particular (the one above the cam). If it is too long or if they tapped it too deep it will block off the oil flow.
 
#7 ·
HUMmmm. strange.rockers not gushing oil should not make the engine try to seize. However if the crank is not getting oil it will try to seize. But you said there was oil in the valley. Hummmmm

You have good pressure at the back of the block.Hummmm
without shooting in the dark with a lot of guesses, I'll have to think on this.

Troy:confused:
 
#9 ·
I really liked the solid pushrod theory, but since that didn't fly, how about the wrong lifters?

Chevy lifters in a Pontiac or Olds will screw up their oiling, so how about a lifter with the groove at the wrong height preventing the lifter from picking up the oil?

Take out a lifter or two and spin the pump. Should be oil squirting out the lifter bore. If no large supply of oil, then you have a problem before this. If there is a nice gusher of oil, then I would be very suspicious of the type of lifter.
 
#10 ·
what weight oil are you using? i used 20w-50 valvoline racing oil to break in a rebuilt 400 in my truck and it took a long while for the lifters to stop tapping( i had time to get them adjusted before the oil started splashing onto the headers) so on that note it took a while for the oil to reach the rockers..just a thought
 
#11 ·
MrReaves said:
A dripping of oil is coming through the push rods.

Engine will run about 20 - 25 seconds and then starts to seize. You can hear it start to tighten up. I have to shut it down so that it does not lock up. Wait two hours and crank it - same thing happens. Fires right up loose with no problem, but starts to tighten - no oil in the top end.
Based on this statement; oil is getting (slightly) to the top end. However, that is NOT your problem. No oil to the top end will not cause the engine to seize up. Pistons too tight in the bore and/or no oil to the bottom end (Not enough clearance) will cause the engine to seize up.

Sounds like a complete tear down to check evrything clearance wise is in order. :(
 
#12 ·
Different brands of lifters and different years will have the groves in different places, shouldn't effect oil pressure or supply.

You shouldn't adjust the lifters until the engine reaches operating temperature, and is oiling the top side at its max.

Troy

__________________
69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top