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Old 08-13-2011, 07:59 AM
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Hot Heads oil pump failures

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. I've don that on past engines to extend the duration between rebuilds and itís 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 (itís 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 couldnít 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 Iíve talked with who has actually put some hard miles on their hemis feels like I do. Their stuff isnít 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.



Thereís 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 wasnít 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, wasnít 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.

Last edited by DeSoto; 08-13-2011 at 08:07 AM.
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Old 08-13-2011, 08:33 AM
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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. I've don that on past engines to extend the duration between rebuilds and itís worked fine.


Ten under bearing would not turn on a standard crank. Max clearance is about
.003.

Add .010 and it is too tight.

Maybe you mean .001 or one thousands under?
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Old 08-13-2011, 09:39 AM
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Quote:
Originally Posted by bnun12
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. I've don that on past engines to extend the duration between rebuilds and itís worked fine.


Ten under bearing would not turn on a standard crank. Max clearance is about
.003.

Add .010 and it is too tight.

Maybe you mean .001 or one thousands under?

No, the crank was already 0.010" undersized. I just threw in a complete fresh set of bearings since I had one rod already out to get at the piston.
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Old 08-13-2011, 10:02 AM
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I've had the same issue with Melling pumps.
Most of the engines I build are for racing so I remove the standard bolts and install bolts to accept safety wire. Mosy people just use Locktite, but I prefer safety wire on stuff that really matters.
I am used to seeing the crank and the remains of the bearing and rod burned and black when the rod lets go from lack of oil pressure. It looks like it was the failure of a rod bolt or a rod, right at the notch for the head of the rod bolt.
Did you hear any knocking before it failed?
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Old 08-13-2011, 10:26 AM
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Quote:
Originally Posted by lmsport
I've had the same issue with Melling pumps.
Most of the engines I build are for racing so I remove the standard bolts and install bolts to accept safety wire. Mosy people just use Locktite, but I prefer safety wire on stuff that really matters.
I am used to seeing the crank and the remains of the bearing and rod burned and black when the rod lets go from lack of oil pressure. It looks like it was the failure of a rod bolt or a rod, right at the notch for the head of the rod bolt.
Did you hear any knocking before it failed?

No knocking, no rapping, just a bang. All of the rod bolts are broken either at the base of the threads or at the base of the head. Two of the bolts are still in the caps (well, part of the cap, there isn't an intact cap in there) holding a piece of the rod but they're bent close to the point of breaking.

The engine, for the most part just loafs along at - 2900 where the speed limit is 70 and around 2700 where the speed limit is 65 - or less all the way to Louisville from Mass but once I got into the steep hills, the vacuum would bleed off and on this paryicular hill, it was wel down in the single digits. I was pulling a pretty steep grade in a 4500+ pound car with a lot of momentum at 62 mph in spite of the grade.

I've seen blackened cranks too but everyone I encountered was the result of PROLONGED oil starvation, not sudden oil starvation under severe load.

You can run an engine for a long time w/o any oil in the pan, just don't put a load on it while you're doing it.
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Old 08-13-2011, 10:57 AM
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It would be interesting to know how may failures they've had with this setup. I know I've used their 340 conversions twice with no problems. However, in neither of them has that many miles on it at this point.

If there is an inherent problem with them, I'm sure Bob would acknowledge it. However, if he's trying to survive like so many other small businesses these days, maybe not. Frankly, I'm surprised at his reaction to your complaint since my dealings with him have always been good. I've been to his place a couple times and he's always been more than receptive and helpful. But.... those were better days.

Most people who build an early hemi aren't going to drive it as much as you do Skip so I suppose there is a good possibility of an inherent problem with the their pump design. I know this is the second pump you've had problems with, I just haven't heard of anyone else having that kind of problem before. Sure would like to know if it was maybe a bad batch or if they're all that way.

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Old 08-13-2011, 11:36 AM
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Sorry to play devil's advocate here, but the fact that you simply kept on driving your car with an oil pressure problem is just plain stupid. Instead of getting an expensive tow home ($500-$750) with a running/driving car, you now have a 10x more expensive engine rebuild. You are blaming your engine failure on a faulty oil pump, when the gauges were staring you in the face for hundreds of miles telling you what was going on inside.

It doesn't matter what kind of motor the oil pump is in. Just because it's a HEMI doesn't mean it needs to be extra hardened or made of special materials. The pump sees the oil side through the pickup, and pushes it through the feed side through the block. If your clearances are too tight on the engine side, that can stress the pump. If you run too thick of an oil, you can stress the pump. You said you put new bearings in the motor. Did you check the thrust? As far as having a hardened shaft, is there an outbreak of broken shafts that aren't hardened? I'm not a HEMI guy so some clarification there would help me to understand.
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Old 08-13-2011, 05:11 PM
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Quote:
Originally Posted by joelster
Sorry to play devil's advocate here, but the fact that you simply kept on driving your car with an oil pressure problem is just plain stupid. Instead of getting an expensive tow home ($500-$750) with a running/driving car, you now have a 10x more expensive engine rebuild. You are blaming your engine failure on a faulty oil pump, when the gauges were staring you in the face for hundreds of miles telling you what was going on inside.

It doesn't matter what kind of motor the oil pump is in. Just because it's a HEMI doesn't mean it needs to be extra hardened or made of special materials. The pump sees the oil side through the pickup, and pushes it through the feed side through the block. If your clearances are too tight on the engine side, that can stress the pump. If you run too thick of an oil, you can stress the pump. You said you put new bearings in the motor. Did you check the thrust? As far as having a hardened shaft, is there an outbreak of broken shafts that aren't hardened? I'm not a HEMI guy so some clarification there would help me to understand.

It's pretty obvios you didn't go look at the other discussions because you'd see that these points have already been addressed.

As for the low oil pressure (25 psi on the highway), I ran the engine at or near that presure (with a stock pump) for years so there was no reason to be concerned.

The pump shaft drive tang is just that, a tang. Click on the picture and open it up. This pump only has 35,000 miles on it and the tabg is about ready to break off bacause a soft chrome moly shaft was used instead of a heat treated shaft. It's basic metalurgy here. He's selling defective parts but, since his customer base is mostly "occasional drivers" he never sees any come backs.

Go read the other referenced posts to see all the documented problems with this pump.
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Old 08-14-2011, 07:37 AM
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This is what you said right here:

Quote:
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.
You WATCHED it drop 10lbs, and then you KEPT ON DRIVING. You adjusted the cruise control to compensate. Not too smart.

You said earlier that you had to go to a high volume oil pump because a stock pump can't get you the pressures you like to see. That is called excessive bearing tolerances. If the machine work is top-notch and clearances are checked and within spec, a high-volume oil pump should not be needed.

My car has a stock shortblock with new bearings and everything is well within spec. Stock oil pump with 100,000+ miles on it. Oil pressure hits 80lbs on a cold startup, at a hot idle it settles to 25-30lbs.
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Old 08-14-2011, 09:11 AM
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i've read about high volume oil pumps draining out the pan quickly in some applications... not 100% sure that's true or not. i dont plan on going with anything but milidon.. as long as it'll take care of my needs.


how far was this exit??? you had 15 psi?? i read where you said 25.. and that it dropped 10 psi. did you get ready to shut it down?? or did you drive a few miles to the next exit??? why not go with a hardened shaft for the pump??

i ask questions mainly because i'm not sure on a lot... and maybe myself and/or some one can learn from yyour experience.
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Old 08-14-2011, 09:14 AM
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561 mile tow is a lot cheaper than a 997 mile tow

Yea, I tried to make it to the exit ramp 2 miles away because Iíd just passed the sign for the US 40 exit.

The engine has 93,000 miles on it and had 60,000-ish when I put the high volume pump in BECAUSE I COULDN'T GET AN UNSCORED PUMP HOUSING TO THROW ANOTHER REBUILD KIT INTO. NEW pumps weren't available back then.

This is the third short block in the car with 257,000 miles on the clock. Same cam, heads and pistons. I know what it'll take for oil pressure and I know it'll go over 100,000 miles with only 30 psi because that's all I had for the duration on the second short block with the best pump I could find and two fresh rebuild kits.

Midway through the service life of the 2 previous short blocks I replaced the bearings and pump innards.

The Hot Heads pump was defective, plain and simple. I

knew the bearing clearances were within tolerance because they were all new and Plastigaged within tolerance, A bit on the wide side but still within tolerance. Aside from being all banged up, thereís no sign of excessive wear on the bearings, either. There was adequate lubrication until the oil pump failed altogether and the front rods clamped onto the crank with a vengeance. Two rod bolts snapped at the base of the threads. Two more snapped at the base of the heads and the last two are still intact in chunks of the rod/cap assy. Thatís indicative of a seizure complicated by the mass of the vehicle in motion trying to keep the crank spinning (the car scales out at 3860 and with me and my luggage in there, itís well over 2 tons.)
If this were a free-running engine, it would have stopped just like your lawn mower when it hits a rock but it wasnít. There were terrific strains on the rod bolts when the bearings seized and that twisted the caps right off.

The ONLY drawback to this whole situation is that I won't make it to a couple of events before winter with this car. I'd planned on junking the block and crank at the end of September anyway as it was worn out. Iíll just have to drive my other hot rod like I did when the tire shredded and took out the rear of the car.

I already have a new set of pistons to build a new short block this winter. A few of the ring lands are on the verge of needing shims and that's why I pulled the engine apart to send a piston to Ross for measurements. I wasn't planning on re-using either the block or the crank. The block has cylinder wear and the crank would need to be turned again. I already have the fresh block and crank.

HOWEVER, if the Hot Heads oil pump hadn't leaked since just after I'd put it in, I might still be driving it with 45 to 50 psi, hot, like the old Hot Heads pump I took out (the one with the worn out shaft)

My point is not about the tow. If I'd played it safe like you, I'd have had a much bigger tow bill. As it was, I got well over 400 miles under my belt before I had to have it towed.
My point is that ALL of you with Hot Heads oil pumps had better WAKE UP or you'll wind up with problems down the road.



The ONLY priority for me, this summer, was getting the car to MoPar country at the Nats as it's only one of three that's made every one since the beginning in '76. Everything else was inconsequential.

But, if you want to argue the point, go ahead. If you think pointing fingers is going to make everyone elseís Hot Heads pump suddenly heal themselves, more power to ya.

Me? I would rather save someone the hassle of having to haul their motor back to the builder and pay through the nose to get the necessary repairs done. I only pay for the machining and assemble my own engines because I've learned to not trust most "builders" because they usually make mistakes and won't stand behind them afterwards.
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Old 08-14-2011, 09:20 AM
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if it was me... i'd do the repairs myself....

but i like building crap all the time...


depending on what the pressure was... i probably still would have pulled over, investigated... and decided if i was ab;e to fix it from there.. but at the same time.. i have fam almost everywhere on the east coast... so i always have a spot to put my truck if need be.
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Old 08-14-2011, 11:03 AM
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Just so you guys will know Skip is one of the most knowledgeable people in the country when it comes to early hemis. He's been building and running early hemis in his '34 for at lest 30 years that I'm aware of and probably longer than that if the truth be known. He doesn't like to blow his own horn so that's why I'll do it. He just doesn't build a car and then let it sit. He drives them! Mass to Ky every year and I know he's driven it to the salt flats several times too.

I'm not going to second guess his decision to keep driving when the oil pressure dropped. That was his decision based on having at least minimum oil pressure for cruise rpm, which he had. My interest is the HotHeads pump. I don't know if this was an isolated case or if it is indicative of a systemic problem with the pumps. Either way, I thank Skip for bringing this to our attention. Those of us who run early hemis need to be aware of this kind of stuff.

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Old 08-14-2011, 02:36 PM
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It's 47 years and three short blocks in the '34 and 3 years before that with a '55 DeSoto in a '39 Dodge pick-up.

I just finished pulling the rest of the engine apart this afternoon.

In addition to the three rods visible Monday night, I found another one half broken once I got the windage tray down. #5 had a busted bolt and twisted cap. the other bolt was still there holding the cap. Another couple of revs an it'd have come apart as well.

All of the bearings on the still-intact rods as well as the 5 main bearings all show preliminary signs of galling. The crank shows no signs of having been subjected to prolonged excessive heat or lack of lubrication (it's not blue)
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Old 12-24-2011, 01:00 PM
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thanks for the info,,,sorry to hear about your troubles
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