Decision time for repair of 2.2 stroked to 2.4

[swade]

Folks,

As I posted on the technical forum, while driving on Tuesday I noticed a rod knock above 3000-3500 RPM and shut down the motor. I knew that the engine had to be torn down to investigate. I found that one of the aluminum plugs in the drilled passageways of the crankshaft had come out. The connecting rod on #1 cylinder was about half way through its bearing shell. I feel pretty lucky that I heard this and shut down prior to something coming through the case.

Before I removed the engine, engine still warm I did a compresson test.
Cylinder
1. 195
2. 202
3. 210
4. 206
5. 209
6. 205
The engine pulls very well (at least before I took it apart), I was pretty pleased with the compression results, I do not own a leak down tester so I don't have data from that.

Engine: 35,000 miles on rebuild
6210154 which is a 71 E 2.2 case engine with MFI but running PMO's.
Pistons:
Mahle 84V51 RO2H no damage
Cylinders:
Mahle 84Z0 no damage
Head:
911 104306 no damage
Rod:
911 103 105
Crank:
D597887, number on OD of one web, I dont see any other numbers on the crank. How do I determine what crank it is? PO claimed it is a 2.4 crank and cylinders are 2.4 84mm bore.

Main bearing journals are in fair shape and measure at the low end of their 0.50 under tolerances at 56.74mm
Rod bearing journals are in fair shape (except for #1) and measure at the high end of their 0.25 under tolerances at 51.74mm. #1 measures 51.74 across the web but 51.60 in line with the piston, well below the tolerance for 0.25 under but leaving enough meat for a 0.50 under solution.

See photos below to see #1 journal, question.. is this the way to go or should I source a new crank. To use this crank it would have to be ground/hardened/magnafluxed and balanced. Would this event at #1 automaticly reject this crank?

After deciding what to do about the crankshaft I have to think about the magnesium 3R case. All the studs are there, no rust, no sign of pulling out, and the spigots are fine. There are no piston squirting nozzels in this case. I do not plan on hot rodding this engine, I was very satisfied with the way it drove, do I need to remachine the case?

The #1 connecting rod is discolored at the big bearing end, the other rods I will have reconditioned but this one I am sure will be replaced.

The cam looks good visually, the heads look fine and the compression readings were very good. The engine does not smoke even on start up and does not burn oil. I am hoping that I do not have to do much top end work on this other than gaskets etc. Comments welcome.

I appreciate everyone that has read this far and welcome comments and suggestions. I will post my progress. I travel a lot so the repair will take a while, it will not get finished this summer but maybe a few drives before they start salting again in the late fall.

Wade

[HawgRyder]

First thing I would do is "ring" the crank.
This is easy...just hold the crank dangling on your fingertips...strike one of the counterweights with a metal object (wrench) and listen to the sound it makes.
If it "rings" it probably has no cracks....if it sounds like a sour "boink" it probably DOES have cracks.
This will tell you very quickly if the crank is worth th trouble of sending to the machine shop (will save you $$ at the shop).
After that....decision time for the rest of the rebuild.
Bob

[Steve@Rennsport]

Originally Posted by swade

See photos below to see #1 journal, question.. is this the way to go or should I source a new crank. To use this crank it would have to be ground/hardened/magnafluxed and balanced. Would this event at #1 automaticly reject this crank?

I would replace that crank with a good, standard one. These are not difficult to find nor expensive.

After deciding what to do about the crankshaft I have to think about the magnesium 3R case. All the studs are there, no rust, no sign of pulling out, and the spigots are fine. There are no piston squirting nozzels in this case. I do not plan on hot rodding this engine, I was very satisfied with the way it drove, do I need to remachine the case?

Mag cases change shape when they are disassembled and in most cases, the crank doesn't turn easily when reassembled the same way unless the case is machined. I would have the parting lines machined and main bearing saddles bored back to standard so you avoid using the dreadfully expensive and difficult to get OS bearings.

The #1 connecting rod is discolored at the big bearing end, the other rods I will have reconditioned but this one I am sure will be replaced.

Make certain that the replacement is weight-matched to the others.

[Flat6pac]

Its easier to buy a whole set of rods than try to match one into the 5.
Bruce

[swade]

Thanks for the response. Sure wish that plug had stayed in. More questions to follow, thank you for your advise and help.

W