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Discussion Starter #1
Hello Alfa Friends,
My '78 Spider is starting a rod tick,not loud but there.Is it
possible to just replace the rod bearings? The same tick occurred on my '74 Spider and eventually resulted in sudden rod bearing bolt failure after passing several cars at redline speed in 4th gear(Centerline dismantled that engine and showed me the damage-they sold me another engine).All advice is greatly appreciated!
Mark 303-258-7905.
 

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Well certainly it is possible to just replace the rod bearings. Heck, it's possible to just replace that one rod bearing that is making the tick.

The problem is that assuming the tick is due to excessive clearance at a rod bearing, the cause could be a worn crankshaft journal - not a bad bearing. So, just replacing the bearing shell might not solve it. Also, the tick could be coming from a loose piston-rod pin. You'd hate to disassemble the engine, replace only the rod bearings, and have the noise still there.

If you're really on a budget you could just pull the pan, measure the rod bearing clearances, and if one or more seem excessive, replace the rod bearings. But the "right" way to fix it would be to rebuild the whole bottom end.
 

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Follow Jays advice on this. Remember, nothing is ever as simple as it seems. First, take a look. Then measure and look at some other bearings. With that rod cap off, see if there is wobble in the rod across the axis of the wrist pin. If you find ANYTHING unusual, pull the engine, and fix it correctly. Just my opinion, from my own experience.
 

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You need to decipher the cause. The crankshaft on Alfas is really durable - I had a bearing spin in a race: the crankcase was damaged (aluminum melted) but the crank was fine (just polished it and replaced standard bearings). Mine (and most others) was the first intermediate bearing, with no direct lubrication. Dropped a crank plug and the rest was history.

Unless you have a gazillion miles on the car, bearings shouldn't wear out, especially just one. You will need to find the cause and fix that.

Robert
 

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rod bearing failure

Mark, Verify the issue as these post suggest. I'll add my 2 cents worth.
2 liter cranks very rarely fail. We have rebuilt a lot of them over the years. Big end bores will go out of round and start causing bearing clearence & oil pressure problems. Our experiance has told us that wrist pins will usually make a lite double tapping. Especially under decelertation, although it can be hard to hear. A stethascope works real well hear. We also use a set of electronic ears and mount them on top & bottom of the engine to verify where the noises are coming from. If it's tapping at idle then pull one spark plug at a time to nail down which cylinder it is.
Rebuild it right, rebuild it once. You be surprised how many egines we've rebuilt that were "just rebuilt". It's more than 50%!
Happy hunting, Jo
 

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Discussion Starter #6
Thank You! Jay, Gordon, Robert and Jo for your Understanding Advice. The head came off a'79 engine I bought from Centerline,the '78 head was shot and Autotecnika(Ron Pederson) decided to do an oversize valve job on the virgin head off the '79 for the '78,after other repairs and getting road ready, that 'tick' started to show up.The '78 block has 118K+mi.,the '79 block(sitting in my garage)has 68K,original mi. Friendly Advice indicates that the '79 block should be rebuilt(Alfa West?) and refitted to it's now modified original head( I will put the rev counter gear into the '79 block)?
Mark
 
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