main bearing question, plus rods question

[JonOfScio]

I can get .25mm over main bearings for the same price as regular ($32 at shucks)

 

Isn't .25mm over going to be better because it's just bigger? Will it fit guaranteed on my EA81? These were parts listed for EA81s anyway.

 

And aren't the reason why 1600 pistons get higher CR in an EA81 because of the rods... couldn't I use EA81 pistons and use the EA71 rods and get the same thing?

 

Thanks.

 

(you guessed it... rebuild time... mwahahahah!)

[toybuilder]

EA81 and EA82 use the same main bearings. If you get .25mm over you will have to have the crank reground. Yes, this is better. You should do it. It will cost about $60-$75 to regrind the crank.

 

I don't know about the pistons or the rods, but all EA81 and EA82 1800s use the same piston rings.

 

Good luck!

[Guest taprackready]

Just putting oversized bearings in for the sake of getting bigger bearings is kinda of a wast of time/money. If you don't need them, don't go through the hassel of haveing the crank ground to install them. You'll never know the difference anyway. A good engine will go well over 200,000 with stock parts.

 

I don't know about the 1.6 pistons. I would look in the repair manual and compare the specs on the 1.8 and 1.6 to find out if the rods are longer or the crank has a different stroke.

 

Bill

[toybuilder]

Being bigger is not what makes oversized bearings better. The advantage comes from regrinding the crank, which makes it perfectly round again.

[JonOfScio]

the reason for new bearings is because the EA81 1800 NA carbed engine I'm going to get has bad main bearings, thus, the need to replace them.

 

and if I can just get 1600 rods and not have to worry about the whole kit and kaboodle of the rods and pistons, then hey, I'd be set.

 

That plus the gasket set for the engine.

[JonOfScio]

reading back in old posts, EA81 stock is 8.7:1, EA71 in an EA81 block is about 9.0:1 and SPFI EA81 pistons are 9.5:1.

 

Because the similarity of the EA81 and EA82 pistons and rods, it's possible I could just use the EA82 pistons and/or rods, whichever it is that is bigger in size that results in the increase in CR.

[Caboobaroo]

if you're gonna use the 1600 rods, then I would also use the 1600 pistons too. The pistons are made to take the compression better than the 1800 pistons. It would be a waste of time if you decided to put the 1800 pistons on the 1600 rods. I think you'd start to run into a lot of problems. As for the bearings, I would have the crank regound just for good measure. If you end up not regriding it and you reasseble it, you have a chance that your bottom end could possibly go out on you then you'd have to tear it all back apart after you've done it once before. Trust me, I've been there, done that and no its not fun in the least bit:madder:

[TomRhere]

When you have a crank ground, the bearing size will be "undersized" by the amount the crank was ground, not oversized. If you have the block bored out, then the pistons will have to be "oversized" by the amount that you removed from the block. On the crank, if you have an engine shop check it, Mic it out, you may not have to have it ground. It may just need to be polished, just depends on it's overall condition. I've rebuilt a few engines over the years, some with rod knock being the main reason for doing so. Some of the cranks were shot and needed reground, some just needed polished up. Just my .02.......