Hot Heads high volume oil pump warning.

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This past spring I pulled my hemi down so that I could send a piston out to Ross so that they could measure it and make me a duplicate set.
Since I had to re-ring that piston, I figures a quick hone and ring job wouldn't hurt as the engine had been together for 93,000 miles.

I had to drop the Hot Heads modified Mellings 340 high volume pump in order to get at the rear connecting rods and when I pulled it down, this is what I found.



The pump has about 35,000 miles on it.

Since I wasn't planning on putting that many miles on before I tore the engine down for a rebuild, I replaced it with another of their pumps as it would, most likely, provide more oil than a stocker on an engine with 93,000 miles on it. I even threw in a fresh set of ten under bearings. (the crank had been turned 0.010"/0.010") I've don that on past engines to extend the duration between rebuilds and it's worked fine.

So, now I have an engine with a fresh set of rings and bearings and a new oil pump. Everything should be fine.

WRONG!

When the engine got hot, the oil pressure dropped off a bit more than I was accustomed to but I attributed the heating to the rings being tight. I dropped the break-in oil and put in my usual 15-40 Shell Rotella and a bottle of ZDDP+ and the pressure came back up.
The engine temperature began to drop back to normal. Now, normal for that engine for the past 15 years or so has been 160 down the highway, 180 in city traffic or on 90+ degree days. The engine was running on the thermostat all the time until the rings broke in then it came back to the 160 on the highway.

Well over half way to the nationals (it's a 1000 mile one way trip for me) the oil pressure started to drop again but it stabilized around 40-45 psi from the normal 50-ish psi on the highway. Just outside of Charleston, WV, it dropped again, this time to 25 psi. It stayed at 25 psi for the remainder of my trip to Louisville and on the way home until I jus crossed over the VW-MD border on I-68.

The reason I went to the high volume pump in the first place was because the stock pump only could muster 25-30 psi when the oil got really hot and, before I changed the intake manifold to a vented type (open between the intake runners), heat was getting trapped between the manifold and valley cover and the engine always ran on the thermostat. The new manifold allowed the air to cool the aluminum valley cover and better dissipate the heat and I wound up having to put a bug screen on the radiator to get the engine to run hotter.

Anyway, while I was in the bar Monday night at the Crowne Plaza in Louisville , I was introduced to the Walkers (Hot Heads) by one of their suppliers who happens to be a close friend of mine. I related the tale of the original oil pump and mentioned the fact that the shafts should have been hardened and his wife insisted, more than once, that they were. Bob Walker corrected her and said that they, in fact, were not hardened. She, however, insisted that they ship one or more a day and have never had any issues with them.
If you doubt that claim, as I do, here are a couple of links to discussions about the quality of their pumps.
http://www.jalopyjournal.com/forum/s...t=98959&page=4
http://www.jalopyjournal.com/forum/s...d.php?t=615310
In my parting statement ( I couldn't take any more of her incessant chatter about their high quality) I mentioned that their lack of complaints must be due to the fact that their customers are all trailer queens. Everyone I've talked with who has actually put some hard miles on their hemis feels like I do. Their stuff isn't up to the task.

About 10 miles into WVI noticed the oil pressure drop almost 10 psi then fluctuate so I knocked the cruise control down from 65 to just over 60 to get the engine down to 2500 rpm and I headed for the next exit. I was right at the ramp when the front three rods seized the crank and the caps twisted right off with 4500 + pounds of rolling hot rod trying to keep the crankshaft spinning.

$2200 and 12 hours later, the car was in my garage and I went out Monday night and struggled to get the pan off and this is what I found.


   


There's a bolt missing in the oil pump cover. I found it in the bottom of the pan and went looking to see where it had come from.

Hot Heads disassembles brand new Mellings pumps, presses out the hardened Allen-socket pump drive shaft and presses in a chrome molly shaft of his own manufacture. Hus shaft is not hardened, hence the issues with the first pump.

Just after I got the oil pan down, a friend showed up and we decided to check the torque on the rest of the oil pump bolts. The readings we got with an old pointer-type torque wrench were 20+, 10-ish, 5-ish and TWO foot pounds.

The missing bolt is near the output side of the pump. When the oil was thick, the pressure was at the factory setting of 65 psi. Once it got warm and the oil thinned out, it squirted out the gap. The pump cover sits below the oil level so there wasn't any issue with sucking air, either. When I was pulling the steep hills in Western Maryland and eastern West Virginia, I was getting the oil petty hot and the pump, simply, wasn't up to the task.

You might want to think twice about putting that Hot Heads modified Mellings 340 high volume oil pump in your hemi if you intend on actually driving the car. If your intention is just to build a killer engine and haul it around in a trailer all the time, well then go for it. You can probably afford the rebuild expense if you already can afford the trailer and fuel costs

[enjenjo]

Not to defend Hot Heads, I have had similar wear on the shaft of Mellings high volume pumps on Buicks too. That's no excuse for leaving the pump cover bolts loose though. I solved the problem on the Buicks by using a factory 401 Buick pump shaft as a replacement.

[wayne petty]

i wonder if it would not be easier to have a manufacturer like ARP create new intermediate shafts to be pressed and pinned into the hemi gear that are longer and have a hex to work with the melling 340 pump...


i have a question..  has anybody checked the clearance between the flat on the top of the new pump shaft and the factory style intermediate shaft?? that kinda looked like it might have excessive clearance..

one more question.. is there a guide like a small block chevy has to align the pump and the intermediate shaft ends.. so they are not offset?? or are they captured in a tube in the block to keep them aligned properly...  i know it uses a bronze bushing under the gear like all other mopars..


i was looking at other intermediate shafts with a hex.. and wonder.. if the hex ends are stronger being machined or if a manufacturer like ARP could hot head the shaft to create the proper hex shape...

just ideas from the sidelines..

[Crosley.In.AZ]

Sure looks like a heat treat process is needed or not performed correctly.

Keep in mind that heat treating moves the metal around. You would not beleive the processes we go through to manufacture a simple input shaft for a C4 transmission.

Our heat treating processes we use are now in a vacuum chamber.

Hot heads may even look at Cyrogenic treatment as an option

[jaybee]

Hard to imagine you're the only one ever to have a problem and you had two bad pumps in a row.  Hope they're stand up about it but your conversation with the owners doesn't point that direction.