Early Hemi oil pan and pumps - need some input

Okay, I could use some feedback regarding oil pumps and oil pans for an early Chrysler.

Here's the low-down...

I've got an extended bell 331 that is going to need an oil pump and a pan. I have a rear sump pan and oil pump, and I have a center sump and oil pump to match. The center sump seems to hold a couple courts more (truck application).

I have no objection to the stock oil system in Hemis. I think Chrysler had it right from the get-go, however I will be running the oil diverter to make sure all the oil goes through the filter. I was thinking a standard stock oil pump would be just fine, but it doesn't seem like anyone sells stock type, only the 318/340 "upgrades". The engine itself will run high compression pistons, a pretty decent cam, and just the other things needed to balance all that out. Just a nice warmed up street motor.

Any reason to go with the higher flowing pump? I'm not seeing why I really need to, but maybe someone can tell me otherwise. Since the oil system is as important as it is, I would almost rather go new or buy a rebuilt stock pump.

So, with the info above...

1) stock pump or higher flowing?
2) if stock pump, should I just rebuild what I have or is that risky?
3) rear sump or center higher capacity sump? (if the center sump pan will even bolt up, haven't tried)

Any input and information would be appreciated!

Thanks guys!

 

I asked Bob Walker this question about oil pumps (stock vs 340). He said "Why mess with it? They're better. That's why I sell em." I didn't want to argue with him. He seemed so damn sure

 

I put a center sump pan on my current 331 project. A 340 HV pump pushes 3.5% more oil than a NEW OEM pump, & a standard volume pump a little less than a NEW OEM pump. The catch is there are no new OEM pumps available, just rebuilt. The rebuilt ones, evidently, don't have the erosion in the pump body fixed so they don't flow @ full original rate. By using the 340 HV pump you might get an actual increase of up to 30% over the rebuilt pump according to Doc Fromader. The guy who put an early Chr hemi in the engine challenge said he's been drag racing it with a standard volume 340 pump w/o any problems. If the higher cap pan fits your car, I'd use it.

 

If you decide to use a 340 pump with the adaptor, beware of problems, with the oil pump shaft binding because of collar that fits into the rear main. It doesn't allow for the pump flange to mate with the adaptor flange. The collar needs to be sanded on the top so the flanges will mate..Also, the oil pump shaft, where it tappers needs to be radius-ed. The 90 degree angle at the tapper makes the shaft weak. (I've broken one).
I went through all this..
Duane

 

Is increasing the oil flow really a good IDEA though?? If it's increasing the flow 30% then that means it's increasing the flow to the rockers 30% as well. Is that such a good idea? Can the heads get rid of that amount of oil fast enough through those small holes in either corner without being opened up?

Bob is super knowledgable and I tend to agree with what he says. I want to do my research and know WHY and WHEN it's good or not good to do this "upgrade".

George, with your center pan, did you use the stock pickup tube and screen and just adapt it to the 340 HV pump? How did you handle that? Seems like the center sump would be the way to go since I have it and it's in super good condition as well.

 

These are the type of concerns I have with mating something that's not OEM to this engine. I did the intermediate shaft change for the distributor so I could have more distributor options and it was not a simple task, like they made it out to be. That's irritating when proper instructions, tips, warnings, etc. are not given.

I guess I like the stock stuff for these reasons. I need a dependable engine, that's top priority.

 

Here are pictures of the pumo shaft fractured in half..
Duane

 

Hello Again..Your right the intermediate shaft..Another thing, when I corrected the oil pump problem, intermediate shaft was to long and had to get a shorter one, because my distributor wouldn't set flush on the block.. HHH has two sizes..
Duane.

 

What did Bob say about what happened to this?

 

The stock Hemi pump is a 'gyrotor' style pump, and is more than up to the job.

All I did to mine was put in the stiffer spring that Hot Heads sells, cleaned the inside of the pump thoroughly, installed a new O-ring that I got from a local bearing supply, thoroughly lubed everything with assembly lube, and put it back together. I primed it with the tool Hot Heads sells before firing the engine for the first time. I've got several thousand HARD miles on my car and it makes 60 lbs of oil pressure on the highway, and falls to about 30 when hot at idle.

I also use the little bypass Hot Heads sells, and a modern (remote) full-flow oil filter.

There aren't any mysteries inside an early Hemi oil pump....they are super simple and you should be able to visually tell if something is too worn to re-use.

If the stock pump held up to all the abuse early Hemis were put through during the fueler days, why would you think it needs to be changed?

 

This is EXACTLY what I was thinking! The center-sump pump I have looks just fine, operates smoothly, and is clean as a whistle. I saw the spring conversion and wondered about that. $10 item and I also have the remote filter and planned on using the diverter. The engine is actually going to be very similar to what you've got setup, so this is a good comparison for me. Thanks for chiming in!

 

I could have run either in my digger - I chose a slightly modified stock pump. If you're wondering what did I modify??? Not the pressure! - I just didn't see the need to fiddle with that - time will tell. What I did do was to minimally debur each gear - set the end clearance as well as make a new integral pump cover/pickup. Normally I wouldn't fiddle with the cover, but for the digger I didn't want to risk a pickup ever coming off.

I don't see anything wrong with that HV 340 pump either - but I have known people to have issues with it. You ABSOLUTELY MUST check the shaft engagement - last guy I knew to use one didn't and had the shaft tang snap off after a couple thousand miles - reason was it had very little engagement from the get go.

Most guys run the HV340 pump simply because THAT'S the easy to get pump - nowadays and it's a darn GOOD pump. Makes sense - just check it out closely if that's the route you decide to take.

BTW - I run the diverter as well (homemade because I was pressed for time - otherwise the HH one is a deal) I also run a vintage Milodon 90 deg adapter - those are said to be an area of concern as they apparently can be restrictive - not the one I'm running though - it's heavily massaged.

 

SCOOTER,

What BASS has said here is about EXACTALLY what is in my DeSoto and i to have No Problems running a stock pump.

Mine runs 55-60 lbs all the time & idles about 30 lbs also.

Funny thing is when i ordered my 340 conversion pump from Hot Heads they told me the ONLY reason they make that conversion is because you can "GET" 340 pumps anywhere.

If you can get your hands on a 340 pump & take it apart you will see there is no difference inside a 340 pump than a Hemi Pump.

A Hemi pump has a FLOATING pick up which meens no Starvation, Which i encountered with my 340 conversion due to the pick up sucking at the REAR of the pick up ... LAME !

Hot Heads also tried to tell me Low deck & High Deck DeSoto's take the SAME Pump ... They DO NOT take the same pump !

Told me i had a Bastard Block, Well i have SEVERAL 330's and they all take the same pump ... They told me there was NO WAY.

Well, High Deck DeSoto's, Dodge & 392 have a Different pump than Early ones ..... Makes me think they dont do there Homework !

I would use your Rear Sump pan, Unless you have a FULL LENGTH Industrial Pan, Send the Pump To EGGE machine for re-build & use the Floating Pick Up.

Why spend all the $$$ at Hot Heads when Tried & True MoPaR Parts are way better ?

I also watch for N.O.S. pumps for sale, Picked up 2 for my 291 off EBAY for less than $50.00 each.

Just cus they make ADAPTED parts dont meen they are better !!

 

Gotta agree with 'keep the stock pump' crowd, and not sure that more pressure is needed. Remember that it is possible to have too much of a good thing. If the oil is moving too fast through the bearings it might not be capturing enough heat....
If the stock pump is clean inside and the rotor doesn't look like it was pumping gravel then your set.
Currently, I have a few too many of the by-pass plugs on the shelf. $5 each to the first 20 or so guys that want one. Just send a PM.

.

 

I would reuse the stock pump if it is good. To me, it is not worth purchasing another pump and adapter plate, modifying the driveshaft, etc... to get a 3% increase in flow.

Before you reuse your used pump, I would give it a thorough inspection. Check the drive tang to make sure its corners aren't worn down from torsional vibrations "rattling" it in the intermediate shaft. Measure the internal clearances and make sure the machined surfaces are free from any galling/scoring. If it passes all of the checks, it is good enough for a fueler - really - many guys ran front engine rails on fuel with the stock oil pump. Do you have a service manual for the specs? If not, PM me and I'll scan the oil pump section from one of my factory service manuals.

On every one of my engines, I replace the pump pick-up screen with one that does not have a bypass hole in the center. The factory ones are designed so that if the screen gets clogged with sludge or debris, pump suction will lift the screen, exposing the open center hole. Imagine what happens next - any debris goes straight into the oil pump and if it can't be ground up by the pump, it jams up the pump... I have seen brand new oil pump pickup tubes from Mopar Performance where that center hole wasn't "sealed" to the bottom plate - big trouble waiting to happen.

Machinists say, "measure twice, cut once".
I say engine builders should "inspect twice, assemble once".

 

Got the 340 HH pick up. What they were saying isn't an increase of 30% over OEM, but a pump that is worn close to the limit to be rebuildable could see a decrease of 30% vs a NOS pump.

 

Hey this is all great news to me, I'd rather not spend money where I don't need to. 73RR you have a PM

 

The fractured oil pump shaft according to Bob Walker was my fault..I took the fractured shaft to several machinist and they all said with out the radius the shaft is weak. Also,after further investigation, the shaft had signs of pre fracture..Very expensive learning. I can't cry about it just appreciate the learning..
Duane.

 

My opinion is that more oil volume is a good idea on almost all street engines.

Engine oil pressure is determined by a few things:
1.) oil flow rate from the pump
2.) engine's restriction to oil flow
3.) oil pressure regulator

number 1 is pretty straight forward - more oil flow (volume) = more oil pressure. Oil volume is a function of pump displacement (volume per rev) and pump (engine) speed.

number 2 is primarily related to bearing clearance and oil viscosity.

number 3 is the spring-loaded piston typically within the oil pump. Its purpose is to limit oil pressure to prevent damage.

So the worst case scenario of oil pressure is a hot engine idling. Since the oil is less viscous (thin) it can escape from the bearings easily. Since the engine is idling, the pump is turning slower and pushing less volume. If you increase the oil pump volume (raise engine speed), the oil pressure rises since more oil flow has to flow past the bearings. The oil pressure will increase as long as flow increases - until the oil pressure regulator limits the oil pressure.

Now lets look at the opposite extreme - a cold engine. The oil is more viscous so it doesn't flow as well past the bearings. The oil pressure regulator must bypass some of the pump's flow (back to its inlet) to prevent excessive oil pressure. If you raise the engine speed, oil pressure still increases slightly, but that is because the pressure regulator must open even further to bypass even more oil and it can only open up so far.

One thing you can't see happening is the oil filter's bypass. Technically it is called a differential pressure valve - it opens when the pressure differential (inlet pressure minus outlet pressure) gets too high. Its purpose is to prevent damage to the oil filter or oil pump drive by allowing oil to go around the filter element when the oil is too thick to all get through. Almost all oil filters have the bypass built within the oil filter, the main exception is the racing oil filters designed specifically without a bypass. On our early chrysler hemis, that little spring-loaded ball assembly in the engine block above the oil pump is the filter differential pressure valve (remember they had a cartridge oil filter instead of a spin-on).

Actual oil pressure at the pump (and oil filter housing can) is the engine oil pressure you see on the gauge PLUS the differential pressure (pressure drop) across the oil filter.

For those last two reasons, I try not to run my engines at higher speeds until the engine (and oil) has warmed up.

The torque to turn the oil pump is dependent on the pumps displacement and the oil pressure it is pushing against. Since the oil pump drive has a certain torque limit, some engines need upgrades to survive running a higher pressure and/or volume pump. Increased oil pump drive torque means increased power required across the rpm range, so many choose to avoid the high pressure and/or high volume (HV) pumps for that reason alone.

Some race engines will need a HV pump to maintain oil pressure because of increased bearing clearances. Race engines also NEED higher oil pressure to force the oil into the bearings HARDER to prevent metal-to-metal contact at high rpm's. Remember the general rule of thumb: 10 psi per 1000 rpm?

Tired engines with loose bearings can also benefit from a HV oil pump, as the increased oil flow helps maintain oil pressure at the lower speeds.

As for the rocker assembly, its oil flow is dependent on oil pressure as well as a couple other things. All other things being equal, increasing oil pressure will increase rocker arm oil flow. Increasing oil pump volume will not change the rocker arm oiling volume - unless the oil pressure increases.

My preference on my street engines is to run a HV oil pump (when it is available) without increasing the oil pressure regulator valve spring tension.

Fortunately, the OEM Chrysler early hemi pumps were designed with plenty of volume. That is why I recommended reusing your OEM pump if it passes the thorough inspection I posted previously.

 

Scooter you can always run the 7 quart pan from mildon. They use a good stock pan and add the additional depth. It is a rear sump pan.

 

Hey Scooter, One thing you mentioned above is you have a extended bell block and want to run the diverter. I have the same set up and when I tried to install the diverter I wouldn't fit flush against the block? After having a good look at it and making a few calls it turns out early blocks do not use that diverter. All you need to do is remove the ball and spring check valve and it's now a full flow!

As for the oil pump, I bought the 340 HH pump. I had to sand the shaft to get it to fit and also talke to a friend who had one of the shafts snap due to too tight tolerances.

Hope this helps.
Geoff.

 

Interesting! Haven't heard this before. Anyone else experience this????

 

I fully agree with all that, Rick. Especially that statement...

 

Full flow right past the oil filter...

What forces the oil through the oil filter instead of taking the easier path?

In order to ensure full flow through the oil filter, you must isolate the two passages. The factory did it on some engines with a solid plug.

 

The stock pump is actually a better design from the get-go according to many articles I've read... I'd use a stock pump.

Now MY conundrum... I don't know which pump I have in my 354... I bought a 340 pump kit from HH's... part of it is on my parts shelf... my engine guy can't remember what he put in. I haven't fired the engine yet but I guess i better find out BEFORE I do....

 

There is a TON of info to read here and some really great input!!!! Thank you everyone!!!

By the way, if I remember right, my stock pump was pushing around 70 to 80 psi before I tore the engine down.

Here's the pump I speek of. (that's not rust, it's some kind grease)



Is this screen good to go or should I replace and/or modify it? (sorry for the dark picture)

 

Someone tell me about "floating pickups" as well. (no, not pickup trucks floating in a pond, or something )

 

What is stamped into the little tag on the pump? The tag might designate its a replacement pump. Do the five little screws have the "DPCD" markings on their heads? I think every 331/354/392 pump I have ever seen had those markings on the screws heads.

The "floating pickup" had the pickup screen mounted to the oilpump cover on a pivot so it can move up and down slightly. That way it stays near the bottom of the pan. The design was abandoned by 1957 with the center-sump pans, as the pickup was threaded into the pump.

As for your pickup screen, refer to my earlier post about the bypass hole lurking beneath that screen's cover strip. You can also see the floating pickup on that 1956 oil pump.

 

The earlier hemi's used a pickup that actually pivoted on the pump. It will be obvious if you have one as the rest of the pump syou can clearly see that they thread directly into the pump body. I don't think pivoted like you'd see on the race pickups where they are allowing the pickup to move front/rear to keep it moving with the sloshing oil - IIRC the factory one pivoted mainly up/down - I'd have to look at the one I have to be 100% positive.


There's nothing wrong with a stock pickup - yours looks dirty to me - I'd want to make sure it was spic and span before I'd run it - not just on the outside bu tht einside asa well. You might give it a close inspection in and out. I got rid of the pickup on my digger for a couple reasons - first I have no suspension - things tend to vibrate when you run over a bumpy road at 130+ mph. I was also hoping getting rid of it would make things like tire shake less potentially damaging as well. Pretty much an overkill thing on my part.

 

Here's some better pictures. The heads of the bolts do in fact say "DPCD". The tag is stamped "50".

I agree it's dirty and I had definitely planned on pulling it apart and making sure that all is well and replacing any seals it might need, and what not.