forged 5e/4e help

[yaristurbo]

so basically engine was stripped and checked to check everything and make sure all is good then possibly sold, as there was a lot of piston slap.

while checking the clyinders it appears that 1 is bigger than the rest, so now im thinking block is scrap and to forge a 4e

are the pistons the same 74.5mm, assuming I can get the block rebored to suit? will get new rods to suit.

thanks

[AdamB]

Is this engine still on the stock cylinders? Then yeah I would always advise going oversized on the pistons so that you have a fresh bore thats well within tolerence, if sticking to the 74mm bore then it can be hard and will be quite a sloppy bore.

If its a 4E then I would go with the 75mm pistons to help bump the compression ratio up as theres only so much you can do with head skimming before you run into piston-valve contact. If its a 5E stick with a 74.5mm piston because if something happens to the block you can oversized again without scrapping a rare block.

[yaristurbo]

its 74.5 now to my knowledge so you would recommend building it and trying it?

I don't want to scrap the block if all else fails then I could bore to a 75mm?

thanks bud

[AdamB]

If its the bore then I would just go with the 75mm piston and get it rebored to suit mate, would save scrapping the block.

You won't need to touch the rods mate, just use the ones that came out the engine originally assuming they are forged ones? As long as a bearings never spun you'll be fine to reuse them

[yaristurbo]

yeh theyre fine they are massive tho very tight fit to get down the bore. whats the best way to measure a cylinder?

[AdamB]

What brand are they mate?

Best way is to use an internal micrometer to measure internal diameters.

[yaristurbo]

PEC rods

the reason we think it is because the tool that you use to make sure a cylinder hasn't gone oval showed different measurements on 3 and 4, they might be within spec but the rod is tight in cly3 and still tight in cly4 but easier to insert, if that makes any sense

[AdamB]

Thats worrying mate, that would normally indicate to me that the bores previously haven't been bored at a true 90 degree angle to the crankshaft centreline, and normally you would have a tapering bore where say for example the bottom of the bore is larger than the top or vice versa, which may well be the reason as to why you have different bore diameters and tight rod clearences.

Edited December 26, 2013 by AdamB

[yaristurbo]

I know bud im devastated to say the least

[AdamB]

The only thing I can really suggest is taking the block to the engineers and get them to check the angle of the bores relative to the crank because if you go for a rebore again and the bore is off centre, you may well end up increasing the angle its off centre by.

Its not really something you hear of very often, but thats not to say it can't happen.

Edited December 26, 2013 by AdamB