Effin' unbelievable: Crank interference

69427

The Artist formerly known as Turbo84
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Mar 30, 2008
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Clinging to my guns and religion in KCMO.
Well, just got the cam in and (was) getting ready to check the piston to valve clearance, but something just didn't look right at the back of the engine. I thought I'm probably just being paranoid, given all the headache this engine has been so far, but to check I slowly turned the crank around a ways until bingo. Dammit!

IM001437.jpg

The rear counterweight is hitting the rear cam cover. It's not a whole lot, but still enough to stop things solid when I'm turning it with a half inch ratchet.

Given that the assembly is already balanced, I don't want to grind any clearance on the counterweight, and there's not a lot to grind off on the cover plate, but I gotta do what I gotta do.

The previous engine was a piece of cake to assemble, was damn durable, and ran like stink. This engine has been a PITA from the start. The only thing that keeps me going on the assembly of this engine is the idea that if it was easy, anybody could do it. I was going to sell the old shortblock (it's only got about 5000 miles on it) to recoup some of my expenses on this engine, but I'm starting to feel a bit sentimental about what a good engine it was.

Well, now that I've vented a bit, it's back to the garage and see what I have to do to the cover to gain some clearance.

Edit: Well, I went over and looked at the rear of the old engine and noticed that it had a very minimal rear counterweight. If I had transplanted the guts out of the old engine (as I initially planned until I thought it wasteful to bore out brand new sleeves to 30 over), the crank would have cleared with an inch or inch and a half clearance. So, I guess I'll give the crank manufacturer a call tomorrow to ask why they designed the crank this way. It would easily clear the old style freeze plug in the cam bore, but not this protruding cap setup.
 
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Just a thought, but do you need that cap on the cam, is in because of the cam? What about going to the standard plug? That way you could get the clearance you need and none of the balanced assmebly is effected. And you don't have to take much apart to do the fix either.
 
Just mill 1/2 the cap down, and call it a day. The front thrust bearing does the work, so it just plugs the hole, right?
 
Looks like you have to remove material from the bolt too.... you're right, if it was easy anybody could do it :thumbs:
 
Just mill 1/2 the cap down, and call it a day. The front thrust bearing does the work, so it just plugs the hole, right?

That's the game plan. I just wish I didn't have to mill the area that has one of the retaining screws. Fortunately there's an o-ring in the cap, but hopefully I can still tighten it enough to keep it square to prevent any oil leaks there.

Fortunately it's in an area only I (and a thousand forum members :crap: ) will ever see. ;)
 
Well, I called the crank manufacturer and asked them what was the deal with the bigass rear counterweight. Essentially the deal is they can't know ahead of time what piston/rod combo customers are going to use, so they supply enough counterweight in case, hell, if someone wants to run cast iron pistons or sumthin. :idea: That may explain why there's some decent balancing holes in the crank when I got it back from the shop.
The guy said as long as I've got .050" clearance between the counterweight and nearby stuff I should be fine. I machined .080 off the cover for a first try, and then installed it for a trial fit. Looks like I've got .045" clearance to the crank at the moment. I'll take a touch more off tomorrow and then I should be good to go.

Oh, yeah, I forgot. I still have to grind down the head of the screw yet. I'm hoping I still have enough depth left in the top of the screw for the hex wrench to fit into for tightening.
 
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Oh, yeah, I forgot. I still have to grind down the head of the screw yet. I'm hoping I still have enough depth left in the top of the screw for the hex wrench to fit into for tightening.

Can you drill the countersunk hole deeper so that the head sits lower below the surface ? That might provide the little bit of extra engagement for the wrench... looks like an allen head bolt (inside hex) ???
 
Oh, yeah, I forgot. I still have to grind down the head of the screw yet. I'm hoping I still have enough depth left in the top of the screw for the hex wrench to fit into for tightening.

Can you drill the countersunk hole deeper so that the head sits lower below the surface ? That might provide the little bit of extra engagement for the wrench... looks like an allen head bolt (inside hex) ???

That's my backup plan. I can't drill too far because I'm worried about the aluminum ear cracking under torque, or having the screw bottom out against the block and not applying pressure against the cap.

Just gonna play it by ear and see what works.
 
That's my backup plan. I can't drill too far because I'm worried about the aluminum ear cracking under torque, or having the screw bottom out against the block and not applying pressure against the cap.

Just gonna play it by ear and see what works.

do you have a small lathe (or know someone who does) ?? Cut under the head of the bolt..... and shorten the bolt to compensate for the amount it sits deeper in the hole so that it does not bottom out in the hole....
yours, sincerely,
McGyver
:smash::smash:
 

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