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"SMALL BLOCK OIL PUMPS CRACKING"

 
pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/26/13 06:16 PM

This is first hand information I want to pass on to all Gear Heads. We have found, on Small Block Chevy Oil Pumps, that some housings have cracked.

We think we found the cause of some housings cracking. We use Melling, Moroso, and GM Z28 oil pumps. It's not a failure of one type pump.

What We Found:
  We viewed this through out clear oil pan. We set the "Studder Box" to 6,800RPM, which is a little over Stall for a SBC with a TH400 Trans. And it was a Scary thing to see. Believe me.
  Engines that are subjected to excessive Vibration, Imbalance, or Missfire. When guys go into the water box some guys have to melt the tires. Why I don't know?
Studder Boxes, Engine not balanced correctly, and an Engine thats Missfiring.

Studders Boxes as we know cause cylinders to drop out, and cause this missfire. As I said the water box, then that same guy will stage his car, while the other guy is still in the water box. All this Missfiring is causing an engine imbalance, and shaking the oil pumps on a SBC to a "Death Rattle".

I just want to suggest that the guys that do their own engines building, have the oil pump housing checked for cracks as you would do your engine block.... Tongue

Bob  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 02/26/13 06:46 PM

wow... that must be an eye full at that rpm to view...

wonder if it would help to cryo treat the oil pump body to prevent the fracture... or just swap to one of the billet designs... similar to other race parts


i guess a high speed digital camcorder that does a thousand frames a second would not nearly be fast enough.

how much of your pan is clear???  the whole thing or just a window in the side...

do you have a variable speed strobe or perhaps a quality timing light to view the motion frozen.??

even using a separate crank trigger pickup and ignition to trigger it for dyno runs.

must be approaching the harmonic frequency of the pump and pickup..


lastly... wonder.. if one could thread some tube stock..  and drive a long pulley tap thru the oil passage where it passes thou the area that cracks then thread in the tube to reinforce the area with something different than cast iron...  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/27/13 01:14 PM

Wayne:
When Dave the dyno guy called me. We watched what a studder box does to an engine, when it causes the misfires. The Vibration the oil pump oscillates at is approx. 122 times a sec. So for every pulse the engine misses, the oil pump gets almost double that. Dave the dyno guy is going to set up a steel billet oil pump. When we get the data I'll post it.
  We actually watched the sequence with an old strobe light. From an old Connecticut State Police Cruiser Dave's father had from the early 1970's. We have a power supply that we can dial the speed of the strobe up/or down. It's very similar to hooking a timing light to the coil lead. The only difference you don't get the pulses as clear on the timing light. I hope to get some data in a week or so.....It should be interesting.
  As you know when an engine gets windowed the oil pump breaks in the process. Now we wonder if the Cast Aluminum oil pumps can't handle the studder boxes. The oil pump castings that we have seen the last year or two are really CHITTY. The castings are really too light weight. The higher dollar engines get the steel billet Moroso oil pumps. We still have guys that are on tight budgets. You Know It's a catch 22. Thanks for your imput. Confused

Bob  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 02/27/13 03:23 PM

that almost calls for a variable speed motor with a drive rod in an offset to rock a steel plate with a rear main cap and oil pump bolted to it.. to duplicate the harmonic resonance..

mounting a half circle to the deck behind the oil pump with lines to see the harmonics..

or just to do fatigue testing...

i wish that melling would create stamped spring clamps that would hold the oem and high volume oil pump pickups in the pump body..

i have tack welded them in place...

sent one off to a shop when i did not have a welder. ask them to tack weld it.. . they welded it all the way around.. with the pump complete... i tossed that pump..  tried again  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/27/13 04:42 PM

Wayne:

I have always tig welded them completly around the pick up tube.
I have seen the pick ups fall off. I read an article up vibrations
on burn outs. Per John Force: He stated that they kill one mag on
burns outs to cut down on engine vibration. I guess thats why the
Pro-Stock cars have dry sumps.
 
Bob  

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 02/27/13 06:20 PM

That's a good tip. Must be a sight to see at 6800 rpm.
I never tried to fry my tires when doing a burnout.
Some of the guys I ran against would do half track burnouts.
Waste of time and money but it put on a show and that's what
the spectators like to see.
I tried long burnouts and found no advantage in 60' or ET.
I also kept the burnout rpms down to about 4-5000 in high gear with no
stutter box and never had a problem.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/28/13 02:35 PM

Dave:
Remember the bleach burn outs. When I get back I'm going to put a steel billet
pump together, then Dave the dyno guy and I will run some tests. Who would ever think that a studder box could cause a problem like this.
  But the way they have thinned the oil pump housings out, its very probable. Its like the (chicken or the egg).
Even with the oil pumps tig welded and braced the best we know how. It's amazing! If you can picture a paint shaker, and crank it up as high as you can ever get it, it still might suprise you....How's the Project doing?

Bob  

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skyeking
I mow my lawn and find Chevys
Posts: 2738
Joined: 08/09
Posted: 03/04/13 01:02 AM

Hi Bob!!!
are you relaxing or stirring??.
Have a good one...  
skyeking

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geargrabber
V-6 Camaros rule!
Posts: 74
Joined: 07/12
Posted: 03/26/13 05:58 PM

Very interesting. I have to agree with Dave on the `spectacle` aspect of long high rev burn outs.
As far as rev limiters go, I always try to avoid hitting that on my motorcyle (the only high performance machine I currently have). I always just ...hmmm, I guess you could say `felt` that a `miss` introduced at 12,000 rpm, couldn`t be good for the engine. On the contrary though, I have been told that water sports machines (ie. wave runners etc.) hit that limiter quite often when jumping waves...?
I currently have a oil pump in my `cart` at summit..the kind that has the shaft extend beyond the gear into the cap, and a bolt on screen. Any good?
I think perhaps I should start a new thread and give a update on where I`m at as far as the `old vette` is coming along and my questions regarding head choice.  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 03/27/13 11:55 AM

Geargrabber
Crazy Dave the Dyno guy and I haven't been able to get together on running the 2nd phase of our tests. We have both been busy. Anyway we are shooting for MAY hopefully.
  It may sound like just bolt that stuff on and go at it. We want to get the correct data so we can pass it along.
  I remember running a 3/4" tube,remove the factory screeing so we still had a large enough area to do datd collection. Then we installed a Nylon Mesh over the inlet. The reason was 2 fold 1.to see if flow increased 2. to see if there were small metal particles we mixed during assembly. Grin  Cool
Please also remember when we loose and engine for test reasons,we pay for it. We have no GRANTS TO WORK FROM as a letter we received from no named person. These tests are on us.   Thanks
Grin
Bob  

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geargrabber
V-6 Camaros rule!
Posts: 74
Joined: 07/12
Posted: 03/27/13 04:59 PM

Thats a shame you could not get a grant for such a neat endeavor...you know like the Government would give to a scientist to see how many flies a frog has to eat before it gets gas...who cares about that..hehe
Yep the whole bolt it on and go aspect of this particular oil pump is a main attraction for me...the extended shaft design would apear to be more robust as well.
The only draw back with this pump is not being able to get one in standard volume. 10% more is as close to stock they are offered.  

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