CF2: 2.0 TS Engine, no3 big end knock HELP! - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 13-04-10 Thread Starter
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CF2: 2.0 TS Engine, no3 big end knock HELP!

Im after some advice from experience engine builders.

Here is the progress thread on the 145 forum should you be interested:
Langers: Alfa Romeo 145 Facelift Rosso Red - Alfa Romeo 145 - 146 Forum

Number 3 big end started to knock. As you can see, its only just taken the coating off the shells and just started to score them. Also, as you can see that number 3 crank journal has marked, however, I can only just feel very very small groves on it when running my nails (which are very fine) across the journal.

Do you think i would get away with wet & drying the crank a small amount with VERY FINE paper and a new set of standard shells? Im after some advice from experience engine builders. I just want to get this engine running again, it doesnt have to rev to 7k and sing, but run to be driven gently and a couple of hundred miles... at least for me to sell the car as a runner and advise on the bottom end.

Here are the pics...
Engine Bottom End pictures by undersealer - Photobucket
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My advice would be no. What is critical is the clearance between the big end journal and the shell as this is what allows the thin hydro-dymanic layer of oil to form and it is upon this film that the journal 'floats' when rotating. For this film to be preserved requires the journal (and shell) to be smooth, parallel, round, with the correct clearance which generally is around the 0.0005" to 0.002" range. Knocking means that the film is being destroyed and metal to metal contact ocurring, due to one or more of these factors being incorrect. Sanding enough to remove the scoring (even light scoring) will remove a significant layer of metal given the fine tolerances required with shell bearing clearances and further increase the clearance. It won't do anything for concentricity, straightness, etc either. So it won't fix the knock and may make it worse.

Darryl in New Zealand

Last edited by KiwiAlfa156; 15-04-10 at 03:13.
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I was hoping that the crank would have been OK. As soon as a removed the bottom of the rod i knew that it wouldnt have been as straight forward. I dont really want to pull the crank out as i want a quick turn around on the car. I might just do as planned, sort all the niggly problems and flog it as requiring a new bottom end.
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Quote:
Originally Posted by langers View Post
I was hoping that the crank would have been OK. As soon as a removed the bottom of the rod i knew that it wouldnt have been as straight forward. I dont really want to pull the crank out as i want a quick turn around on the car. I might just do as planned, sort all the niggly problems and flog it as requiring a new bottom end.
You are not going to get more than a few hundred quid though are you if you sell as is..


It will probably be cheaper to get the crank ground and some shells fitted, as you could then sell it for the full asking price.
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That is as bad as I've seen. You have options but none of them will be easy and/or cheap.
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hahaha i have seen worse on my old engine before i got it rebuilt! I will try and find you guys some pictures!
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Yep - your car is worth nothing with a noisy bottom end - either surce a second hand engine or get the crank reground, abuot £ 90 if you do not need main bearings, new thrust washers - about £ 10.00 from memory and over size shell about £ 40.00 + a load of time
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I think im going to try and get away with keeping the engine in the car and slide the gear box accross, i dont have access to an engine crane at home and i have no space in the workshop.
I will look at either a) Changine the crank or b) grinding the crank.
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Once it starts to knock the only course of action is a regrind and new shells!

I would advise against changing the crank unless its brand new with the correct shells! Best bet is get the crank out and have big end and main bearings reground, new shells and thrust washers.
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Ah finally some pictures mate. Yes I'm with everyone else on this. Regrind and a set of oversized shells. Should be ok on the hardening front though as its not too deep!
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a regrind and oversized shells you should get change from £100...
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