Getting Enough Oil

bradbeyer

I have a question about the oiling issues on an AMC 360. I am rebuilding my AMC 360 and have heard and really know for a fact that the rear mains do not get enough oil. I will have everything in it new and have been doing a lot of reading and it is confusing me more than helping me. Here are my questions: (please be detailed as possible on all questions) 1. What oil mods do you want to do to fix the rear mains not getting enough oil? 2. What does it mean by cross drilling your crankshaft? 3. Where do you drill holes at for the distributor gear to get more oil? 4. What other mods would be recomended? I have a new crankshaft, RV cam, 30 over pistons, oil pump, and the basics that come with a rebuild kit. I also have TBI and edlebrock intake. Please give me any help you can. Thanks, Brad Beyer

jeepsr4ever

Crossdrilling a AMC V8 crankshaft should NEVER be done without other heavy mods already in place. One mod you should consider is either the smaller hole cam bearings or the valley line and always start with a good close tolerance cover. Those two mods, starting with a good cover and running either smaller hole cam bearings or a valley line are the only ones we will reccommend below 6000rpms

seth gordon

Please elaborate on the pros/cons of cross drilling the crank. I have some old literature from Randall that mentions grooving the main journals. I have also read about drilling out the rod journal centers. Thanks, Seth 68 AMX 390 4-spd & rally pac

jeepsr4ever

Seth a good set of mains will have the top journal grooved. The bottom journal takes the brunt of the force from the combusiton chamber firing. The reason people do not crossdrill their mains is becasue the rods are fed through the mains and if you cant get oil to the rods you spin a bearing. The main bearings are larger and require much more oil than a rod based on a term called bearing speed which the mains have a much higher bearing speed per revolution because of their size compared to the rod bearings. Take the width of the bearing and the diameter and then calculate the revolutions per minute (RPM) and figure in a .001" of lubrication around the bearing and you end up with a very large number surface area per minute that the bearing needs. Then you can take the hole size (.319") feeding the mains and generalize a psi for the rpm your calculating for and you can get your oil flow requirements. Keep in mind the rod comes after the mains as it is crossdrilled to the main journal. Does that help?

seth gordon

Still a bit confused. I thought that crossdrilling the mains allows more oil to the rods by connecting the two rod feedholes on #2,3&4 main journals and makink a new feed hole on mains 1&5. So, the crux is if the mains are crossdrilled so that rods get oil for 360 degress instead of 180 the mains will be starved.Also, although each rod would get continuous oil, the pressure would be lower since the volume would always be split,on #23&4. I am assuming that rods normally do not get much oil when the feedhole is traversing the lower bearing shell.Under what conditions is crossdrilling the crank beneficial? My other question was about just machining a narrow groove in the main journal, not having a grooved lower bearing shell. Also I am still wondering about drilling the rod throw to lighten that part of the crank. Another question involves the report that rod bearings no longer have the notch to feed the squirt holes. were the factory engineers overdoing the amount of cylinder lubrication? It seems that alot of oil drains through the cam tunnel holes and many people try to divert oil from the valve covers directly to the sump which suggests that drainback through the tunnel holes is not necessary to lube cam lobes etcetera. My question is if the squirt holes are disabled and oil is diverted away from the lifter valley will the cam lobes & cylinder walls get enough oil? In general, will rod bearing clearance need to be increased without the squirt holes? I noticed that you offer a crankscraper. Is the scraper only for very high performance apps or does it benefit a more moderate engine too? Thanks, Seth

jeepsr4ever

There in lies the problem. The main lines can only supply a certain amount of oil at 60psi with their stock diameter. We open up the last 3 mains to .339 which is .020 larger than the stock .319. After calculating the flow requirements this is the solution I have concieved. Crank scrapers keep your crank case from foaming past the centerline of the crank and are good at any RPM.

seth gordon

So if oil feed to the main bearings is increased, crossdrilling the crank is acceptable. My intention is to rebuild the engine with a moderate roller cam and have a redline around 6500. The shop which rebuilt the engine back in '84 supposedly installed the valley line and maybe drilled the main galley from the pickup to the pump.Still curious about cylinder wall oiling without squirt holes and diverting oil from the lifter valley. I know that some engines rely on oil throw-off from the rod journals to keep cylinders lubed. Was AMC simply providing extra oil as insurance for the rings? My concern is limiting windage without starving the rings or cam lobes thanks, seth

AMX69PHATTY

I'm no expert, but the rod brg oil notch can be added by hand if desired to new rod brgs that lack this feature. Think it was 1980_CJ that did this on his 401 2nd rebuild this year due to timing chain installation sna-fu. It appears to be an ongoing debate as to the need for the con rod oil squirter or not.

Wonder what 82Waggy did on the new motor he just built ?

jeepsr4ever

Oil holes in the rods add way too much oil to the spinning mass with all the foaming happening. You can run a crank scraper with oil holes (Which is ideal for high rpm)

seth gordon

Inspection of a 401 crank revealed that rods 1,3,5 &7 have their oil feed hole within the upper main bearing when the piston is at TDC. Rods 2,4,6&8 have their oil feed hole traversing the lower main bearing at TDC. This suggests that rods 2,4,6&8 are somewhat starved for oil during the power stroke, which probably is not desireable. That is why I am curious about cross-drilling the crank. Tom Monroe published a book about race engines and he states that cross-drilling is important but does not elaborate about other oiling system mods. that would be necessary to increase total flow to the bearings; Mr. Monroe was a chief engineer on the Bricklin project. thanks, seth

milnersXcoupe

jeepsr4ever wrote
Crossdrilling a AMC V8 crankshaft should NEVER be done without other heavy mods already in place.

Which other mods specifically ? :shock:

jeepsr4ever wrote
We open up the last 3 mains to .339 which is .020 larger than the stock .319.

since AMC rods are fed AFTER the AMC mains -
and one reason people do not cross drill the mains is
because the rods are fed through the mains
and if you cant get oil to the rods you spin a bearing......
but you've rods 2,4,6&8 conceptually "somewhat starved
for oil during the power stroke, which probably is not desirable"........

how does one solve this AMC dilemma ?

Increasing the amount of oil delivered by the main galleries -
which could necessitate rifle drilling them out by how much safely ?

and -

running a supplement oil line to the back of the block ?

might just add a can of STP and call it even =D> #-o :roll:

AMX69PHATTY

I'm no expert, but I thought by cross drilling the mains it allowed more continuous oiling to the rods since one of the now 2 main journal oil holes would then always be exsposed to the one main bearing half that contains an oil groove which main journal in turn then continuously feeds adjoining rod bearings ? :-|

82Waggy

Crossdrilling is BS - it requires that the oil flow through the main journals reverse direction twice per revolution - pulses flow to the rod journals and slows flow. All engines rod bearings are fed after the main journal bearings -duh. Screw all that nonsense. Make sure your pump is in good working order and your bearing tolerances are good - get over 20 PSI at idle and you are fine. Just say no to valley bypass line leaks - what a crock of moronic engineering. AMC's have a better oiling system than most - including Fords and SBC's. Tell them all to bite you and go on down the road.

tarior

82Waggy wrote
AMC's have a better oiling system than most - including Fords and SBC's. Tell them all to bite you and go on down the road.

As much as I love AMC, the stock oiling system is really only adequate for street passenger car use. Even today, guys have trouble in road race applications, unless they use a dry sump.
Modify it for long life.

Kevin Johnson

tarior wrote
82Waggy wrote
AMC's have a better oiling system than most - including Fords and SBC's. Tell them all to bite you and go on down the road.

As much as I love AMC, the stock oiling system is really only adequate for street passenger car use. Even today, guys have trouble in road race applications, unless they use a dry sump.
Modify it for long life.

A classic problem in crank oiling is air entrainment. The more air that is entrained the further the oil departs from the behavior of an ideal fluid. Apart from the pickup being possibly exposed in high G maneuvers, the oil conditioning that a dry sump offers (deaeration) is testimony to this.

The scraper helps keep down air entrainment. Another thing to think about is running a vacuum pump on the crankcase. This makes it more difficult to entrain air in the first place. It also allows you to safely run lighter tension rings which in turn reduces parasitic drag.

Goose

Another thing to think about is running a vacuum pump on the crankcase. This makes it more difficult to entrain air in the first place. It also allows you to safely run lighter tension rings which in turn reduces parasitic drag.

This brings a question to mind.. Old school drag racing, we used to run a breather line from one of the valve covers to the exhaust behind the header.. This actually imparted a bit of vacum to the crankcase and helped.. But I dont see it much anymore..(I have seen a mechanical fuel pump hooked up to a valve cover?? I cant imagine that helps much but hey what do I know??)

Kevin Johnson

Goose wrote
Another thing to think about is running a vacuum pump on the crankcase. This makes it more difficult to entrain air in the first place. It also allows you to safely run lighter tension rings which in turn reduces parasitic drag.

This brings a question to mind.. Old school drag racing, we used to run a breather line from one of the valve covers to the exhaust behind the header.. This actually imparted a bit of vacum to the crankcase and helped.. But I dont see it much anymore..(I have seen a mechanical fuel pump hooked up to a valve cover?? I cant imagine that helps much but hey what do I know??)

It is the same idea and it works for an engine under full throttle. It is not a consistent enough vacuum level, however, for the lighter tension rings. The speed and mass of the exhaust flow under partial throttle is not enough to induce a good Bernoulli effect. David Vizard talks about this in one of his books.

EDIT: fuel pump mod -- lots of times this is hidden. It increases the flow rate of the pump. Well -- I should say you "can" hook it up to a vacuum source to increase flow rate. When I first read your post it sounded like they were doing the extractor and fuel pump at the same time.

If they are using a fuel pump to evacuate the block -- might work. Talked to a few builders using the aux pumps from diesel engines and from the GMC SUVs (also BMWs). They will apparently draw down an LS6 10". Longevity is an issue because they are not intended for an oil vapor rich environment.

I was told there is a diesel engined Toyota in Europe with a vacuum pump built into the alternator -- there's your trick setup. 😉

Goose

We used the header hookup on a A/econo-rail 402 chevy bb in an old retired slingshot dragster chassis, (wow what a handfull!) Great big tall slicks on both sides of your head and the narrowed 9" rear differential was part of the Seat pan..(I swear really !) with a 2 speed powerglide.. put in drive point it at the far end and pull the trigger, 8 seconds later you found out how it all turnd out..If you opened your helmet and heard harp music or smelled sulphur burning, things had not gone well.