Twisted ARP Oil Pump Shaft...

Well...I finally got the pan dropped enough to get the oil pump out and change the broken oil pump shaft. If you can see...the top end was twisted...and the bottom end that fits in the pump was sheared cleanly off. This all happened because the cam sprocket moved slightly, shearing the cam alignment dowel pin, and causing all 8 exhaust valves to kiss the pistons.

Will be getting the new cam machined for a 7/16 bolt, and double pinning the gear with chromoly pins before it goes in.

Will be running this cam for the rest of the season, and changing it out over the winter.

 

Only twisted a little.

 

Lol...only about $1400 worth

And honestly...I'm pretty happy that that's all it was...

 

If I had your money I wouldn't worry about it either. LOL

 

HAH...that's a good one lol! If there's another one of those incidents...I'll park it for the season lol (well...intentionally anyway ). And if I had your money...I'd burn mine just to watch the pretty smoke lol. Obviously...once you lay eyes on my car, you'll know that's true

 

I used to have some money....until I started hanging out with that Ky. crowd in July.

 

i wonder why

 

could you explain why it twisted/broke?

 

Apparently the bolt holding the timing gear on the cam loosened slightly, and the dowel pin sheared off. This allowed the gear to move just a bit...and all 8 exhaust valves kissed the pistons. Bent all exhaust valves, all exhaust pushrods, broke one rocker arm fulcrum, and sheared/twisted the oil pump shaft.

The cam bolt now has RED loctite on it...and a hardened pin. It will be double pinned in the future, and machined for a 7/16 bolt instead of the 3/8 in there now.

Not looking to revisit this issue ever again...

 

wouldn't the...oil pump...need to have locked up to twist/break the shaft?
the dist. drives the pump...cam out of time wouldn't change anything there or am I looking at this all wrong?
just seeing if there is more that needs to be checked...

...:Handshake...

 

I suspect that when the cam stopped turning briefly when the pistons hit...the inertia simply sheared the oil pump shaft. I have checked the cam, and it does not appear to be damaged, nor do the unbroken roller rockers. I am ordering a new set of those anyway though...just using the current ones until they arrive. Roller lifters appear to be fine as well. Checked oil pump...and it spins freely, and was new before the incident. Also checked distributor end to make sure it wasn't stripped any. Replaced valve springs, valves, pushrods, cam dowel, and oil pump shaft. Not much left to check or replace lol...but thank you for the input...it always helps to have someone else thinking about things that you may have overlooked.

 

just my opinion on the matter here.. but drilling out the cams snout and removing that much material might not (would even go so far as to say..will not) make it any stronger. If that was sore spot for design on these things.. then oversizing the retaing bolt would be done by all who grind them. Would be like going with too large an oversized rod bolt as you just reduce the shoulder materials cross section.. and end up weaking it in the end.

I've done this Ford stuff for enough years myself.. and been around even more that have done it for even longer.. and an after market chrome moly cam bolt(which will usually allow more torque/preload as well) with a decent hardened pin being sucured with red loctite is all that's ever been required for anything short of a full effort motor running huge spring pressures/rpm. Even many of those race setups don't monkey around with what you are doing here.

Also.. if you look around at the other engines like BOP's(especially racing engines) cam snout/dowel/key/retaining bolt design.. they don't need dual pins either.

Simple fact of the matter is that a loose bolt is the cause there.. and even if you had dual pins.. something would have likely failed anyways. I wouldn't even be surprised if two pins could sheer under that same scenario as the slight slop and wobble created by a loose retaing bolt stresses them in ways they were not designed for. Consider yourself lucky you didn't snap the cams snout completely off as that happens more than you may know in loose bolt scenarios like yours.

But.. I really do understand the overkill mentality and try to emulate that whenever possible myself. But having said that.. I would never take that much material out of an already too small of a snout like that one. Good ARP bolt.. dowel.. and hi-temp loctite will eliminate that variable completely without the need to reengineer basic architecture that many much more capable motors are using by the thousands.

Just my dirty penny on the matter and good luck with it all however you end up going on the mods there.

 

When I say loose...I don't mean the bolt was finger tight...I mean that it merely loosened some from it's 45 lb torque requirement. It was still tight when I removed it...it had just loosened enough to allow the gear to move some. With the spring pressure, 220/580, it apparently just puts too much pressure on the smaller bolt. With the 7/16...the torque goes up to 75 lbs...and makes for more holding force.

Just what I've been told from some pretty serious Ford engine builders. The pins they use are from the Danny B gear drive guys.

Will probably just order the cam with those mods when I get it...engine builder locally orders them like that from the manufacturers pretty frequently. He sends them the cam gear and they drill it as well. They charge for it of course...but everything is aligned properly.

It may be overkill...but a few bucks more for some peace of mind is well worth it to me. I've wasted money on numerous less practical things in my lifetime

I'm already a little gun shy about taking it upstairs now as it is lol...

With the way that I work...I simply don't have time to be fooling with the car all the time. I'd rather spend some money to make it as bullet-proof as I can...and then when I have the time, load it on the trailer and head to the track...without having to worry about it...

 

oh..ok.. I misinterpreted "loose" then. lol

and yeah.. I hear ya about cheap insurance. I was just pointing out what seemed to be obvious to me based on what most mfgrs are currently selling, was all.

I'd be really curious to know about others experiences using an oversized bolt on the cam snout too. Maybe you can over stress the snout with too much torque?

Not trying to put a future scare in the back of your mind.. just curious more than anything. Good luck with it all.

 

The main guy I was speaking with about it, is a Ford Dealership owner, and he and his brother supply the parts and build numerous 4.50 and faster (1/8th mile) engines. Although they do more big block stuff, he assured me that it would work equally well on my SBF cam with no issues. He says since they went this route...they've never had a failure since...which is what I'm looking for

He also agrees that it's overkill...but he knows my attitude towards my car, and my racing...and he said if I want to fix it and forget it...then that's the way I want to go. I replied "you da man!"

lol