Cleaning pistons and rods

[phi22b@ck]

Ok,

I have an L28 that has been _OCOMPLETELY_ dismantled. The block is at the machine shop getting tanked and miced.

If it comes back within spec for the bores, what should I soak the piston/rod assembly in to dlean all of the carbon off? I remember hearing something about using some special brush for cleaning them but it has slipped my mind at this point.

Also -- if the pistons that came out are within spec, and look OK what are the gains (oustside of oversizing) for getting new pistons and pins? I am definitely doing all the bearings, rings, and rod bolts already, but dont know if I should plan on getting new pistons...

Thanks!

p

[2ManyZs]

Guess you could have just taken them into the machine shop and had them cleaned along with the block.....

I've used Berkibile 2+2 Instant Gum Cutter, works pretty good. Get it most auto parts stores. That and a brush should clean them up pretty good. Ask the machine shop, there should be something you can use instead of an aerosol solvent that will work just as well, in fact they may even sell it themselves.

Only thing that would prevent you from using the old pistons is the ring grooves, or large nicks in the piston tops. Check the ring side gap with the new rings, use a feeler gauge and check the gap on the top and bottom of the ring where it sits in the groove to see if the piston groove is within spec. Not sure the spec at the moment but it's probably around here somewhere......This is not the ring end gap, it's the ring gap on the top and bottom as the ring sits in the groove. Of course, the end gap is not critical until you are ready to put the pistons back into the block.

[Mudge]

Scotch brite pads should clean up the piston tops pretty nicely, and wont scuff 'em up like a wire brush

[Ben]

If everything measures up ok, there is no real benefit to spending the $$$ for new slugs, except for the fact that you can say that they are new.

I bought my un-touched L28E engine with 220,000 km on the clock, tore it down, had it honed & put fresh 'consumables' through it (rings bearings, gallery plugs etc).

It's done 300,000 km's now and 70,000 of them have been with the T3 forcing things through a little harder than stock...

This engine is a N42 combo (8.39:1 compression) running 6psi boost & producing ~220BHP. It is fed good fuel (98RON), synthetic oil (Mobil 1 every 5,000km), Genuine coolant & clean air (Finer filter) & I expect it to last a long time yet.

Long live stock pistons

[phi22b@ck]

2Many -- that would imply proper prior planning... something I am rarely guilty of...

Thanks to all for the help!

p

[Mudge]

So long as everything checks out with the F54 block I have, I'm not even going to hone it, I'm going to use a glaze breaker and just refresh it.

The engine has about 175k on it, and if it is TRUE that the longevity is good then there should be zero problem in doing so, so long as the engine I have was well kept. This has been done to American V8s with more than 200k just fine, and I know of a Miata with a turbo that is over 220k miles on the stock bottom, so I dont believe that a rebuild is in order every 100k

So, hopefully this will be a nice budget setup when I'm through

[phi22b@ck]

My goal is to trim as many costs as possible on my racing engine build -- this is for a backup motor. I am really cheating the reaper by not replacing EVERYTHING, but since I just want to scoot around the track for a while with a beefy suspension and at least a semi-purring engine. I can wait a few seasons before I do a FULL build....

2many -- I know I know -- not enough money to do it right the first time, but there is always enough to do it again... Inevitably the right way is replacing everything, but that can be done later :+)

[2ManyZs]

No reason to spend big bucks on a back up motor, a buddy of mine ended up using the original engine as a back up for a race, got third place that weekend. The motor was the original one in the 73 (my first Z) that I sold him so he could go racing. It had over 150K on it.

I would just do a bearing, ring and gasket set. I would however, at least do a "home" honing on the cylinders so you get a better seal on the new rings. If you spend money on new rings, you might as well at least get all your money's worth out of them.

[phi22b@ck]

What about crankshaft and rod assembly balancing? Would you do that on a basvkup? (I was thinking after schools I would switch them and start a tear down on the "old" motor").

p

[2ManyZs]

If this one is going to end up being your "school, spare" motor the only thing I would do is have the crank checked for straightness, and if needed polish the journals. When you re-assemble it, be sure to "plastigauge" the bearings to make sure your tolerances are in spec.

New rings and bearings, new oil pump, maybe a water pump and a gasket set would be about it. Perhaps you might want to go ahead and put a new timing chain and tensioner, just so it doesn't need to be done for a while and you should get a few years out of it.

I'd spend more time on the head and valves since you could use it later on the "race" engine. You might end up needing a spare head more than a spare block (hopefully) so it might be better to go ahead and do one head now, and do the other one later when you do your second engine.

[Mudge]

I have heard 2 things so far, one person found that thier internals were within .3 grams of each other in balance, and someone else said I think they were as much as 4 grams apart?

2 very different experiences... I myself would love to balance the internals but that remains to be see, I'd also like to polish the rods, but again thats all time and money and I dont know what will ultimately happen, although I'm not in a rush.

All those little things "I wanna do this/that" do start to add up though...

[Ben]

4 grams - I wish!!!

I've just fited new OEM 1st OS pistons (flat-tops) to the original L24 that belongs in my '73 & there was 6 grams between the lightest & heaviest _rod_.

I ended up weighing all parts & then matching up to get the best balance (some bolts were 8-grams, others were 9-grams). Then I removed material from the rod only.

Instead of removing all flashing & then balancing, I just removed the flashing as balancing. Afterall, this was simply an excercise in improvement, not necessarily precision....

The final balance was within 1-gram, not bad for a home effort!

(150-grit belt sander & 450-grit wet-n-dry).

Apparently the Datsun stuff was well balanced from the factory. So consider the tolerances on less advanced engines...