Chev piston matching game!

[ThirstyMQ]

Hi again all,

I know this may not specifically be Nissan orientated but I figure that this engine is most likely going in one, I thought I'd post it here.


The problem I'm having is that i aquired a 350 short block when I bought my MQ but since I've had the engine pulled apart, I've separated the pistons from the caps and can't remember which one is from which. They seem to be balanced or something because there are areas on the sides of the pistons that have been ground off. Same on the caps.

See photos attached.

Basically, I need to right my wrong and match the parts back together. A friend of mine suggested getting an inside micrometer and testing for roundness. Is this the only way? I've checked them all over and can't find any trace of numbering either. If weighing them is a medtod, I might have screwed that up to by de-burring them a little. I did the block (which came up brilliantly) but I thought the rods and pistons could use some too.

Anything anyone can do to help would be great.

Cheers
Lewie

[Brett S]

Uh oh Spaghettio.
Unlucky all that balancing workdown the drain prob best taking it back to a performance engine builder that knows how to balance em and let him play mix n match.

[RED60]

The inside mike prolly won't be any help. If they don't measure the same you're up for resizin anyway, so the weight bit goes out the window. If they're any good they should all mike the same. Also, equal weights of the assemblies (cap, rod, piston n gudgeon) does not mean u have the no. 1 cap on the no. 1 rod. If there are large weight difrnces between the caps, with trial and error u may get it correct or at least go close, but there are no certainties. Would whoever you got em off be able to help?

[V8Patrol]

You fuct up big time


Choices are .......

Get access to a good set of scales and play mix n match for a few hours...... and trust me the scales you'll need arent readilly available at the supermarket !

get a engine specialist to play mix n match for you ...... expensive but a lesson well learned for the future

get them RE-BALANCED.... will cost about the same as paying a specialist to play mix n match

Kingy

[ThirstyMQ]

Thanks for the help guys.

A mate of mine sat down and played the mix 'n' match game. We matched small wear marks on the rods to the caps and we 're pretty sure we've matched them all up. See the pics to see what I mean.

The photos aren't the best but if I could get better ones you would see that there are definite matching marks/gouges to work with. I guess I'll find out soon enough if we did it right or not.

Luckily, the pistons are numbered so I know whick pots they came from and we did the same for the main bearings too.

Lesson learnt.

Lewie

[V8Patrol]

You sure that these are "balanced" ??????


They look dead stock

[Brett S]

The first lot of pictures seem to have disappeared but did it not show the caps with the balancing bosses ground to differnet heights hopefully meaning balancing had been done?(im sure there is a proper name for the extra metal bit that ya grind to change balance also on little end as well)

[RED60]

I'd have to say the system you're using to match up is a bit, ummm, risky. If ya rekon ya rite, now it's time to weigh.

[ThirstyMQ]

That particular mate or mine has had extensive experience with race engines and engine building and if he's confident, so am I.

We spent a fair bit of time under my light in the shed sorting through them and there were deninite individual cherecteristics that lead us to one particular rod or cap. All the rods markings and scratches/gouges were very different from eachother so it wasn't too tricky to march them. Luckily.

Also, they fit together "like a finger in a bum" so to speak!

All in all I'm confident we've matched them all up correctly but, as I said before, I'll soon find out.

Here are the photos I posted before with the comparison between different caps and the piston balancing thingies. (I don't know what they're called either)

[Pauwolf]

Mate, I would get them resized just in case, not balanced just sized for $100 odd bucks its cheap insurance you wont even have to take the pistons off. better than a siezed motor because 2 caps were incorrect. no one can be sure the caps are correct, I have assembled my own v8 holden using the method you described only to have to pull it down and resize the rods , and grind the crank and new bearings because I spun a bearing. I have put lots of motors together, i did it for a living. I was too clever for my own good. resize them


Paul