Chevyguy358

I am trouble shooting some issues with oil pressure with a new motor and believe that I might possibly be missing some galley plugs. As far as I know there are supose to be three located in the front above the cam, three in the rear in the outer side of the block one in the main cap around the number 5 cylinder and i was told one more that is one more where the drive gear to the oil pump engages. i have been searching all over the internet tryin to locate a diagram showing thier placement with no luck. If one of these is missing would I experience no oil pressure? thanks to anyone able to help

jasonface

If any of the plugs are missig, there will be no oil pressure. If any of the three at the rear of the block are missing, you'll have a massive and very noticiable oil leak. Ditto for the single plug partially covered by the drivers side cyl head, at the rear just next to the oil pressure sender. All four of those are the screw-in type. The three at the front of the block behind the cam gear are push-in plugs. I don't recall there being a galley plug near the oil pump drive gear (under the intake mani), perhaps you're thinking of the one that is partially covered by the cyl head by the oil pressure sender? There is also a small steel "check ball" down in the passage below the #5 main cap, it seals the passage there (slight interference fit). I have heard of machine shops leaving out this ball after hot tanking a block, and that will cause a large oil leak past the main cap. Not sure if it would cause low pressure, or no pressure at all if it was missing.

Chevyguy358

thanks...I guess I will start dissecting my motor

Chevyguy358

So i went ahead and took out the pressure sending unit and cranked over the motor and alittle oil trickled out, but definately with no kind of pressure, so the pump is turning and sending out oil but none is reaching the top end...I tried hooking up a mechanical gauge and i couldn't get enough pressure to move the needle. I guess I'm going to take apart the front end and check to make sure the galley plugs are installed. let me know if you guys have any ideas or if I am on the right track. thanks

Chevyguy358

I went ahead and tore apart the top and front of the motor and everything looks good. I'm getting oil to the bottom end, when I pull the drive gear its soaked with oil (there seems to be a passage hole thingy right behind it), the filter is full with oil as well. I'm just not getting much of anything up to the oil passage for the sending unit. not entirely sure if that means the cam bearings arn't getting much either

jasonface

The cam bearings also have to be oriented correctly in their bores in order for oil to make it up to the top end. There are holes in the bearing bores that are supposed to line up with holes in the cam bearings, and if they aren't you'll have no oil to the top end, but the bottom end will have plenty. By "top end" I'm referring to the valves/valve cover area, you should have oil coming out from the holes in the end of the pushrods. The oil pressure sender appears to be taking pressure from down near the #5 cap. Looking at the back of my engine on the stand there looks to be a galley leading down from the top of the engine where the pressure sender is, all the way down to the cap area, where the oil pump is located. That would make sense, since you would want to know oil pressure at the mains, rather than the top end up around the valves. My engine is already assembled, or I would be able to tell you more definitively. Maybe somebody out there with a bare block laying around could take a look and verify the exact layout of those galley passages. However, if the pressure sender IS taking oil directly from the #5 cap/oil pump area, then it would appear that your pump itself isn't pumping. Only possible causes of that scenario that I can think of is the drive gear not engaged with the cam, or maybe your pickup has come loose. It would have to still be there and supplying some oil though, since you say there is oil getting into the filter. One more thought, since the oil filter has oil in it are you sure it was pumped there by the pump? If this is a new engine, most builders will pre-fill the oil filter with oil (when they put it on) before initial start-up, to help prime the engine, and shorten the time it takes oil to circulate completely through the engine on initial start-up. I guess you could remove the filter and try cranking the engine, just to make sure (a large catch pan would be a good idea if you do that). Just tossing out ideas, hope it helps.

Chevyguy358

Ok...well from what I was told by a reputable mechanic and from what it looks like is that the oil pressure sending unit (back side of intake) recieves its oil from the passage that goes through the lifter valley, though I dont know the direction of the flow. Is the position that you were refering to as there are two locations for the sending unit. I believe that when I put the filter on I only filled it partially and now it is overflowing when I take it off. I'm not sure it would be a good Idea to remove the oil filter and crank the motor as it supplies the oil pump I believe....but then again at this point Im not sure that matters. The pick up tube is welded so as to make sure it doesn't fall off

jasonface

http://books.google.com/books?id=GUC...hl=en#PPA64,M1

Here's some info an a standard SBC oil routing. The LT1 should be the same, except for some small differences, such as supplying oil to the mechanical fuel pump drive. I was wrong about the holes in the cam bearings, SB Fords use that system where the bearings must be correctly alligned, the SBC has grooves in the block itself, so the oil will pass around the outside of each cam bearing, then through a drilled passage to the main bearing. The way this looks, the oil flows in this order: From the pickup, to the pump, to the filter, out the filter up to the main galley (center one above the cam), where the oil pressure sensor picks up for pressure readings, then it flows towards the front of the engine through the main (center) galley, passing through the grooves around each cam journal down to the mains. The L/R lifter galleys are fed by the main galley, probably at the rear of the block since I can't seem to see any sign of dilled/intersecting passages at the front. The oil passes through the lifter galleys, through each lifter, up through the hollow pushrods, and squirts out the top of the pushrods lubricating the valves and rockers, then drains back to the pan. Therefore, since you have no pressure/flow at the sender, your problem MUST BE at the pump, pickup, or filter. There's nothing else before the pressure sender to cause a problem. Since your pickup is welded on, and I can think of no possible reason a filter could completely block flow (even an old, dirty filter will just bypass oil if it's clogged), the problem is the pump itself. Either it just doesn't work (very unlikely) or it is not being driven by the cam. Possible causes of this would be broken oil pump intermediate shaft, or broken upper oil pump drive. Make sure the oil pump upper drive is seated flush on its mounting boss in the lifter valley, and secured by the single bolt. At this point, might as well remove it and inspect it to make sure it's not broken in some manner. If it checks out, you've gotta remove the oil pump to check it and the stub drive shaft. The slotted part of the drive shaft fits into the upper oil pump drive, and the coupler part of the drive shaft connects to the oil pump.

jasonface

I'm also trying to find more info on the galley "ball plug" that is located under the #5 main cap. There are pics of it on pages 40 and 138 in my HP Books "How to Rebuild LT-1/LT-4 Small-Block Chevy Engines, but all it says is reinstalling this plug is "vital". Even if leaving it out would cause an internal oil leak, it doesn't seem like that could completely disrupt all flow to the pressure sender. I may be wrong, maybe checking with a machine shop familiar with the LT1 would help.

Chevyguy358

thanks alot for the info..I guess the one thing I dont understand is why I get oil coming up and out of the hole directly behind the drive gear but nowhere else

Chevyguy358

what should the the oil pressure be at for just cranking it over...b/c I have oil coming out the rear passage but with little to no pressure on a gauge.

jasonface

The hole behind the drive gear comes directly from the filter, but there should be more flow than the "trickle" you mentioned earlier. I would think it would be more like a small fountain. As far as pressure during cranking, I'm sure it would only be a few pounds, but it should show something on your gauge you hooked up. I keep thinking about that check ball in the passage below the main cap. How would it affect pressure if it's missing? I can't visualize exactly how the passages all come together there, I wish I had a bare block to look at. My old block that was in the car when I melted a piston is in storage, maybe I'll swing by there this weekend and take a look at it. Maybe then I can get a better idea what your problem might be.

Chevyguy358

well at this point i dont know if i should pull the whole motor out or button it back up and actually start to see where i stand. Since only a few pounds pressure should be seen on the gauge. i did hook up a high powered air drill to prime it and saw 45 psi, but the thing is rated to like 1800 rpm and the cam rotates at half speed of the crank, in effect 3600rpm.

quickSS

If you had that much pressure I would think the oil system is ok. I can only get 60psig with a 2500rpm drill so 45psig at 1800rpm is pretty normal I'd think.

Karl Ellwein
Ellwein Engines

jasonface

General rule is you need 10 pounds of pressure for every 1000 RPM. Most engines run a bit higher than that, bit 45 PSI at 3600 RPM sounds fine. What originally made you suspect a problem with the oil system? Did you actually start it and see no pressure?