apitts73

while my 3.0L motor is getting rebuilt by LR as we speak......

i have a stock 2.5L block w/ very nice cylinders and 2 full short blocks( both w/ cracked cylinders) to work from.
never rebuilt a motor before, this is the first!

its just for back up...already went threw 3 motors in 4yrs....i think i finally learned that tuning is so so important.
so i think its a good idea to have an extra motor lying around with my track record!!

so...can i just take 4 pistons/rods/crank from one of the blown motors and put them in the good block?
i dont really want to have the good block honed....very nice cylinder walls.
can i put new rings on the old pistons in the good block without honing....i heard its not a good idea to use new rings in an old cylinder(not honed)??
as for the crank...it should be ok....i think it only has 80k on it...and i will just pull it out of the blown motor and put it into the good block(checking clearances first).
i have a stock head and cam that will need to be freshened up...probably get LR to do it.
i do have a friend that has built a few v8 motors and he says he will come over any time i need help.

any input would be greatly appreciated.

adam

Mighty Shilling

Buy a rebuild kit, send the good block out for machining to clean it up and make sure it's true, do the same with the pistons and con rods, and go nuts. Its fun and you get a nice sense of pride saying you built it.

Reimu

All I feel is terror that I may have messed up somewhere

Mighty Shilling

That'll go away after a few thousand miles...

azbanks

What's the worst that can happen, you blow up another motor?

blown 944

If the tolerance group is the same between the block you have and the pistons you have then I'd just clean the block well and go to town. Honestly theses engines are easy to build but have a couple specialty things to deal with.

apitts73

ya...im not too scared!!

just want to do it the best that i can with what i have to work with.

what are the couple specialty things to deal with?

what about the rings....new rings on the old pistons?

i guess when i get the block cleaned...get the pistons cleaned too? or take the pistons out of the broken motor, put new rings on and go?

thanks again for the input.
adam

FRporscheman

First of all you need to check the tolerance group of the blocks (and the pistons). On the block deck, near the oil galleys, there is a stamp. Either 0, 1, or 2. There is also a stamp on the top of each piston, same thing, either 0, 1, or 2. You must match tolerance groups between the block and the pistons. Or, if you are honing the block, you need to measure it and see if honing will keep you in the tolerance group or bump you to the next one. All this data is in the FWSM.

You could slap new rings on used pistons and stick them into your clean block (assuming tol groups match) and just go... but you're taking a chance. Sometimes it works, sometimes the rings never seat and you eat oil forever. I say if you DGAF and you just want to put some lego parts together with your spare time, and never really use the engine, then fine, go for it. But if you want to actually use the motor, or have it as a dependable backup, then have one of your messed up blocks honed and rebuild it.

There is always the DIY cylinder lapping that Honda DustR did over on pelican forums. Basically you use a honing tool, felt, and sunnen compound to recondition your already-smooth cylinders, which makes them ready for new rings.

Just my 2 cents. Good luck whatever you do!

apitts73

ill check the tolerance for the pistons and block today...will also look into honing the cylinders of the good block.
thanks,
adam

blown 944

I personally have not had any issues just cleaning the block. I have seen a couple others done without honing and have good results in both leakdown and compression. These blocks don't seem to wear like cast iron blocks do.

My .02

doabarrelroll

I would let a machine shop handle all the small tolerance stuff, i.e. main and rod bearing installation, re-ringing, installing crankshaft. Basically, get the short block back assembled and then assemble the rest yourself.

That's what I did at least.

minho78

How much did that cost you?

FRporscheman

I really think bearings and rings are handle-able, as long as you measure. IMHO the only trick is cylinder conditioning.

I myself did put together one engine without touching the (perfect) cylinders, and it makes perfect compression and eats little oil (thank God), but I do feel I got lucky.

apitts73

i checked the 2 broken blocks/pistons and they are both #1 tolerance...and the good block is a #2.
what are the differences....size?

can i check the piston tolerance/fit...and how do i do that?

i have done a few top ends by myself so far....would like to try a bottom end now!!

i put 1 of the pistons into a cylinder of the good block and it was tight....only put the bottom of the piston into the cylinder...rings are still on.....

how tight should it be?

also...the crank...will it fit a #2 tolerance group if its from a #1 block?

thanks for the help...i really want to try this!!

adam

apitts73

also....
FRporscheman....what is the FWSM?

adam