Printable View
Hello ! im new to the board here and have been reading for a few days about the oil mods that have been being done. I am in the process of rebuilding a 304 1979 and the block is at the machine shop now, i did not see a definate answer on what size tube and fittings are used for the oil valley mod. Also are the undersized pushrods and cam bearings worth it if i am having the other mod done? or could i do just the bearings and pushrods and not the oil valley mod?
thanks for your time
mike
depends on what you are doing with the motor. if you are going to see high RPM's often then the valley line is needed otherwise use the undersize pushrods and bearings
Like most things there are both yes and no opinions on the need for the oil line mod.
There is a thread here that shows pics of peoples different lines.
Seems anything from 1/4" to 5/8" diameter tube is used.
Supposedly the stock AMC oil pump is a high volume pump, long pump gears.
The bigger the tube size, the more diffucult to clear the intake PCV baffle.
I chose to use 1/4" ID stainless braided teflon lined aircraft type hose & fittings,
since the valley line is just supposed to make up some lost oil volume.
Figured a large tube size would hold a larger oil volume,
take longer to "fill" at start up, and be less "responsive" to oil "demands".
You can imagine how much oil is gonna squirt out of 1/4" at 40 PSI
and the oil volume that squeezes out from around all the bearings cant be that much.
The bearing fits are the restriction in the oil system that create the pressure.
And ya know AMC motors have ran more than 100,000 miles without one.
Good question though, I haven't seen a good answer to it either.
Quote:
Originally Posted by AMX69PHATTY
I'll give you my best reasoning for my "not needed" opinion.
1) The secondary feed paths from the lifter gallery to the crank bearings are smaller and therefore more restrictive than the lifter gallery - so adding a second feed path from the front to the rear of the lifter gallery will not increase flow to the bearings.
2) As stated above, it is the restriction through the bearings for a given flow rate from the pump that determine system pressure. For a given size of restriction the only way to increase flow through it is to increase pressure.
3) If there is any pressure in the system at all, flow rate from the pump must be in excess of the leakage rate through the bearings and valvetrain. To suggest that pressure decreases as you move downstream from the pump is to suggest that the bearings and valvetrain are able to pull oil from the feed paths in excess of the flow rate of the pump, and that cannot be the case if pressure exists. This is not a free stream system like a river with open capillary branches - at least not until the oil has left the bearings and valvetrain and begins to gravity flow back to the pan - it is a closed pressure system up until the oil has passed through the restrictions at the end.
4) If pressure exists it must be equal from one end of the system to the other. If it is not equal at both ends of the lifter gallery there must be a blockage. If there is a blockage in the lifter gallery that is more restrictive than the feed paths to the bearings you have bigger problems that need fixing.
5) Pressure measurements taken at both ends of the lifter gallery during dyno testing show no measurable drop in pressure from one end to the other. The valley bypass line is in effect tied back to the same feed source at both ends and therefore must have equal pressure at both ends. A line with equal pressure at both ends will flow nothing. The lifter gallery bypass line is therefore of no use.
6) Extended high rpm operation has been known to deplete the oil capacity in the pan by pumping all the oil up top before it can drain back down, resulting in the unporting of the pan pickup and subsequent system pressure loss. Higher capacity pans, improved drainback, and smaller ID pushrods to slow the flow of oil to the top are probably the best solution to this problem.
7) In my opinion the only oiling mod a common lower rpm jeep motor may benefit from, aside from a properly functioning pump and clean system, is a larger capacity pan with either baffles or a swinging pickup to help feed the pump during operation in unusual (high angle) attitudes (more unusual than my own).
but will having the valley line even hurt anything even though the engine may not see a ton of high rpms. Even a jeep engine gets revved out now and then.
I don't think it will hurt anything, so long as the installation does not cause any other interference to flow and does not ever develop a leak.Quote:
Originally Posted by Patf10
As far as high RPM is concerned it would have no effect on the usefulness, or lack thereof, of the bypass line even if the system pressure should drop for some reason.
thats what i figured, but there really isnt a reason why it would start to leak. And wouldnt that reflect in oil pressure if it did
The main reason for using a valley line is it switches the amount of available oil to a different part of the engine buying time. Image a strait line of hose with .125 " holes every 1" and lets say this hose is 20 feet long and we are pushing water through it. The holes on the other end of the hose are barely trickling out yet the first part of the hose are shooting out water. Now take and feed the water to the center of the hose instead of the end of the hose and you have changed the amount of volume/pressure the center holes will spurt out. This is adventageous to a AMC V8 because the amount of bleed from a .904 lifter bore is great and the amount of oil going to the top end is great as well. To keep the volume/pressure high at the rear of the block is key to survival at EXTENDED RPM's and is not needed if your not holding your engine throttle above 5500rpm. AMC engines feed oil from the front of the block to the rear but do not prioritize the mains.
You are not taking in effect pressure caused by friction. Oil gets hot because the molecules are constantly moving over each other. The Dyno test you speak of was done not at a sustained rpm and with a extra capacity oil pan. Pressure in a system with linear holes and moving parts cannot be the same in any one point in the system. It is my understanding of the engineering and physics behind this system. If in fact their were no moving part and only oil feed hole then the volume would be less at the far hole than the first. I agree that smaller hole cam bearings, smaller oil feed hole rockers would be great for a lower rpm motor.Quote:
Originally Posted by 82Waggy
Correct me if I am wrong :wink:
That hose analogy only holds true if the combined flow rate through all of the .125"" holes exceeds the flow rate of the pump feeding them (this would be a free stream system). Such is not the case in our engines.
If you like hose analogies, consider a sprinkler system with a series of low volume heads - they all flow the same because the total flow rate does not exceed that of the feed source, thus pressure is maintained throughout (this would be a closed pressure system). This is analogous to engine oiling systems.
I agree that the valvetrain is likely to pump too much oil to the top at higher than normal rpm operation - I like the reduced ID pushrods for this situation.