Balancing rods/pins/pistons - 3 new 1 old :(

[mm289]

As per my post above on the case, I am about to re-assemble this 1600TP engine. Its just a temporary build to get me through the summer so not trying to spend many $'s.

Engine came to me having had a broken piston in its past, so have split case, thoroughly cleaned, polished crank and about to assemble with new mains, rod and cam bearings.

Engine came with 3 of the original (new) pistons, not sure what they are (pics below if anyone recognises them ) and one old Mahle.



The Mahle one also has the rod and pin that came with it not the same rod and pin as the other three

As it was fitted to the engine (which also had a turbo on it at the time - since removed ) the Mahle assembly (no.4) is 26g heavier than the lightest and 17g heavier than the heaviest of the other assemblies.

By moving pins, rods and pistons about I can get a total variance of 8g and if I did a bit of machining on the piston/rod of the heaviest assembly I could get that down to 4g. (the biggest weight discrepancy is the pin, the Mahle set is 12g heavier than the others).

So question is - is it ok to mix 'n match rods and pistons and pins like this to get close to balanced - doesn't need to be a racer so happy with 4-5g but 26g sounds a bit excessive!

Cheers,

MM

[Phil69]

5 grams is VW's spec.
I would check your deck hight's and do a compression test before running the motor but I can't see why there would be a big problem.

[mm289]

Yeh, that's what I figured thanks

If I could find out what make the pistons are I might be able to track down a matching one but I don't recognise the markings at all

Cheers,

MM

[sideshow]

If I could find out what make the pistons are I might be able to track down a matching one but I don't recognise the markings at all

Have you considered posting pictures of the top and side skirt?

[Marc]

Nothing at all wrong with juggling wrist pins (provided their dimensions are the same, of course). I keep a couple of coffee cans full of them just for this purpose. Although 8g is within allowable limits for a stocker, it would be nice if you could get them just a little closer, say within 5g. Failing that, put the closest-matched pairs across from each other (1&3, 2&4). If the oddball piston is less worn (judging by the top ring groove wear and overall appearance) have it end up on #3...if it's the worst of the lot, as seems likely here, put it on #2.
For a low-budget project like this I wouldn't have any qualms about narrowing and/or shortening the piston skirts a little on the heaviest piston(s), either - most "high-performance" pistons come with shorter skirts than those on the cast stockers, so it's not hard to rationalize some judicious whittlin'.

[mm289]

Thanks guys, will put it back together now,

Will get some pics of sides and crown on tonight.

Cheers,

MM

[mm289]

Couple more pics of the pistons I'm trying to ID



Cheers,

MM