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1275 Engine Rebuild


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#31 Chris.Williams

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Posted 11 January 2019 - 04:58 PM

Update:
Well it turns out the engine block I've purchased is actually a 1380, complete with (What I believe are) Omega pistons. Upon inspection of the main bearings and big end bearings that came with everything, they were stamped as standards, which makes me think the crank hasn't been machined, which has impressed me as there are no causes for concern over the journals/bearing seats, and whilst the bearings are in poor condition from being out of the engine and not protected properly, they have no signs of scoring or sufficient damage, so thinking of continuing with standard bearings and not machining the crank where it isn't necessary. 
 
In terms of the parts I'm thinking of using to rebuild this engine, I'm still only after a fast road setup at relatively low cost, and I do plan on making upgrades in time as funds come available for elements which can be swapped out while the engine is in use. In terms of the components I'm thinking of upgrading now, I was considering an uprated oil pump and maybe a fast road cam, then beyond that I currently have a simplex timing assembly and have been researching on the benefits of upgrading to duplex, but I'm a little uncertain on whether to stick with simplex and tensioner, duplex and tensioner, or just duplex. If anyone has any recommendations for additional or alternative components then I'm welcome to suggestions  :proud:

Do you have any pictures of this new block?

#32 Cooperman

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Posted 11 January 2019 - 05:36 PM

Before you spend money on rebuilding a 1380 you need to be sure that the bores are not worn. If they are it can be very expensive or even impossible to bore further or to bore and install special sleeves.
Many consider 1380 to be the limit for over-boring because the cylinder walls are getting thin and no two blocks are identical. Some blocks will go bigger or take sleeves, but others will not.

#33 Will96

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Posted 11 January 2019 - 10:52 PM

Currently don't have any pictures as I'm out of town, but again the cylinders didn't seem all too bad, the apparently the engine hadn't been run for long after being bored before it was "taken out of action" when I get back I'll post some pics. I need to check that the cylinders are correctly offset, which I suppose is the make or break of the project and forgot to do up until now and now been added to my list.

#34 Fastorq

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Posted 12 January 2019 - 09:01 AM

Sounds like you have struck lucky with the second hand block you bought and got more for your money than just the crank.
Totally agree with Cooperman tho
I've bought parts at budget prices before thinking I had just got a windfall only to find the real reason they were being unloaded!
Be really careful with things that are not immediately obvious as mentioned above ... Particularly wear patterns , machining accuracy, cracks etc.

Hope everything is OK.
Regds
DavidR

#35 Will96

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Posted 12 January 2019 - 10:08 AM

Thanks David. Couldn't agree more the fact that it's different from what it was advertised has made me very cautious when going into this. Currently looking into machine shops that do chemical dipping but before that I might get them to accurately measure everything rather than my own judgment with a set of verniers.

#36 Cooperman

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Posted 12 January 2019 - 11:13 AM

The big problem with the 1380 is that when a further re-bore is needed it either means another block or expensive machining. You can't get a standard sleeve to fit a 1380, so special sleeves have to be made and fitted. You can usually get back to 1275 with special sleeves, but bear in mind that the cylinder walls are a bit thin at 1380 and a further bore to press-fit the sleeves can see the cutting tool break through the wall into the water jacket.

 

The best thing to do at this stage might be to try to find a 1275 block and re-bore it with new 21253 pistons. Only re-ring the 1380 if there is absolutely no measurable wear in the bores and the bore diameter is within tolerances. To do otherwise could be a waste of your hard-earned cash.



#37 Will96

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Posted 12 January 2019 - 02:54 PM

Funny you should say that, I originally set out with a 1275 block I already had and was thinking of machining, the purchase of this 1380 happened as it was advertised as a +60 (the fact it's not has made me rather cautious) but yeah, if this "new" block isn't all it's cracked up to be, it's still running a standard crank which is the main reason I bought it. So there are back up plans

#38 Cooperman

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Posted 12 January 2019 - 11:33 PM

If I had bought a block advertised as +0.060 (i.e. 1330 cc), I would be very p****d off if I found it was over-bored to 1380. In fact, I would want my money back.

A 1330 will take the original-type standard sleeves to take it back to 1275 and these are easy for a machine shop to fit and relatively low-cost.






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