All Big Six ARP Main Studs/Oil pump clearance

Relates to all big sixes

THE FRENCHTOWN FLYER

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1366 passes roughly 341 miles at full throttle... with periodic pauses it must be noted...
Even including burnouts and driving to and from the pits its probably less than 500 WOT miles. But that kind of cyclical operation is far more stressful than say, running an Indy 500 race, stabilized at WOT.
 
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alwill923

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I am putting my 1965 240 together with ARP main cap studs and new oil pump (just finished oil pump installation yesterday). This is how I solved the problem right or wrong I am not taking it apart.

I cut the stud down in a lathe on the nut end (fine thread). I put a very slight taper on the top of the nut (about 15 degrees) to remove the flat but did not go far enough to shorten the nut. Left the washer off, used ARP thread lubricant and torqued nut to the recommended 80 ft-lbs.

My thinking is the nut has the same thread engagement and a bolt does not have a washer. I am not building a race motor so it should be fine. Actually I had the engine running like this for a while.

I was thinking about milling the cap down (only where the nut and washer goes) to allow the nut and washer to be used but not sure if it would weaken the cap. That being said all that would have to be removed from the cap is the thickness of the washer.

anyway done! If you do not have access to a lathe it could be done by grinding BUT do not let it get hot!
 

alwill923

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Took some pictures
 

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THE FRENCHTOWN FLYER

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I never broke a crank - forged or cast.
But I did discover a crack in a forged crank (#6 rod journal - the usual place of origin) I acquired used with unknown history. It may have been cracked when I installed it or on its way to cracking with the additional hours I put on it. Since then I did the usual machining upgrades to my forged cranks - undercut rod journals, chamfered oil holes, extended snout keyways, balancing, etc. and have not broken the crank, but I did break two main caps.
Covid has reduced the amount of racing I did this year but my Frenchtown Family Truckster has upwards of 1400 passes on it with a cast crank shifting it between 5000 and 5500 RPM.
My altered in my avatar gets shifted at around 7000 RPM with occasional - Duh! Oops! - neutral or burnout overspeed to 7800 - 9000. I would not trust a cast crank to stand up to that kind of abuse for very long.
I think for 99% of the engine builds discussed on this forum a cast crank would do just fine. Unless you're a belts-AND-suspenders kinda guy I would not pursue a forged unit.
In my street intended builds I use cast cranks, except for my Willys coupe that has a hand-me-down racing engine in it.

I don't use main studs.
 

THE FRENCHTOWN FLYER

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I was thinking about milling the cap down (only where the nut and washer goes) to allow the nut and washer to be used but not sure if it would weaken the cap. That being said all that would have to be removed from the cap is the thickness of the washer.
That will work. The caps typically break at the peak of the arch.

For a typical turbo application I think the logical order of progression of likely engine failures will be:

1. head gasket
2. cylinder wall
3. rod
4. main cap
5. crank

assuming metal timing gears and later hypereutectic pistons.
 
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CNC-Dude

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This issue does come up quite often on both the small and big 6's. I actually thought someone was going to do a sticky on it for future references. This is a common issue, but easily resolved by grinding the threads flush with the top of the stud, but not limited to just that, but also could include relieving the oil pump body as well. All of these solutions are normal and also are required in other Ford engines that by design use a bolt on pick- up tube where the pump also comes into close proximity to the crankshaft. Just expect it's not a screw them in and done operation like most other engines. But I think it defeats the purpose to buy the studs and then swap out one or two for bolts because of a minor issue that's easily solved. This is the essence of hotrodding, so don't get discouraged, but get creative....
 
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I wanted to share the problem and fix of running ARP main studs and the new standard flow melling pump clearance problem. The main studs in the ARP kit were too high for oil pump clearance and the oil pick up tube didn't have threads to grab. I called ARP and got two
Bolts sent to me (reference pics for part numbers). I used a felpro gasket as they were much thicker and used a small die grinder to take some material off the oil pump (hopefully not enough to cause it to fail. Im going to the hardware store to get 2 washers and a new nut for the pickup as the old one is not the right threads. Hope this helps someone
Why is the stud longer in position main cap five? My bolts came with one like that too.
 

CNC-Dude

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The longer one goes to the location where the pickup tube bolts to. Depends on which oil pan/ pickup tube combo you are running so that will determine its location.
 
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