Questions about new pistons and bearings...

[LordLo]

I'm going to rebuild my current engine which has 160 compression all a cross. No sludge build up and runs like a champ.

Question is, what size piston should I order? Or should i not even order until I have the engine a part?

The cylinder walls the last time I checked were in pretty good shape, no scrapes or pits. Should i order standard size then?

No rod knock either so should standard bearings be fine?

 

[Yellow 13]

The piston sizes are on the bottom of the block, if theres no excessive wear I'd stay stock...unless you have some extra income and high power goals.

 

[Halsupramk3]

most likely just one size up. but it is always best to order pistons after the block has been checked out. That way you will know with the info from the machine shop what size you need. also you will need to know how much metal will need to be removed from the deck and head to see what size HG you will need to retain stock compression ratio.

I ordered my ross pistons first and got the one size up (14 thou i think) and even with a 2mm HG i have 9:1 compression ratio. a little higher than i would like but usable. custom pistons could have lowered the CR with a thinner HG.

 

[aljordan]

Why the hell would you rebuild a perfectly running motor???????????

Go out and buy a JDM motor if you want to rebuild something.

 

[turbo4toy]

Why the hell would you rebuild a perfectly running motor???????????

Go out and buy a JDM motor if you want to rebuild something.

LOL..... i would agree with him unless you are planning on upgrading your motor to the point where you do need them. Spend your money on making it look better, have more power, or handle better.

You could always throw a big ass turbo on and boost till something breaks and you would have a reason to do it.

 

[LordLo]

Why the hell would you rebuild a perfectly running motor???????????

Go out and buy a JDM motor if you want to rebuild something.

I want to keep the machining cost to a minimum.

 

[NewWestSupras]

what does machining costs have to do with building a motor thats "running like a champ?" Wait for it to blow up, then rebuild it stronger. If it ain't broke, don't fix it...

 

[mattjk]

The piston sizes are on the bottom of the block, if theres no excessive wear I'd stay stock...unless you have some extra income and high power goals.

damnit! everytime I see you, I think it's Joe. :biglaugh:

 

[LordLo]

what does machining costs have to do with building a motor thats "running like a champ?" Wait for it to blow up, then rebuild it stronger. If it ain't broke, don't fix it...

When that happens, I'll probably end up having to get an overbore; something I'm trying to avoid.

 

[Clip]

but the question still remains: why fix it if it aint broke?

 

[Jetfixr757]

Correct me if i'm wrong, but the weak link in the 7MGTE is the connecting rods, with that said, a good set of H beam rods with the rest stock internals should make for a pretty good bullet proof bottom end, yes?
Jet

 

[gixxer750]

the 7mgte has quite strong connecting rods and pistons. the pistons would break first. Well, possibly the rod bolts first.

And....if you are going forged, unless you have a new block, you are going to need machine work for forged pistons. This is because the oil clearances for forged pistons are tighter than stock pistons. If you don't machine and get standard, they are probably going to slap thier asses off.

 

[LordLo]

but the question still remains: why fix it if it aint broke?

Fine! I'll go with a t70 turbo instead. :evil2:

 

[starscream5000]

What are you power goals? If it's under 450-500 and the car is "running like a champ", just make sure everything is tightened to spec, bearings are good, HG and block/deck surfaces flat and smooth, oil pump and water pump are ok, and maybe a few other small things that need to be checked on (oil squirters cleaned).

 

[aljordan]

I want to keep the machining cost to a minimum.

The cost of boring a motor is problee $10-$30 a hole. They are still going to hone it, cut the rods, deck the block, cut the head, line hone the mains, polish the crank, ect.

You'd save a hundred bucks.. if that.

I say keep it together man. Put that money into a savings account to earn you more money. When you need to do a rebuild, take that money and and do it up.

 

[bigaaron]

Most 7m engines with any kind of milage on them will have a taper in the cylinder walls, if you put new pistons and rings in an old block without boring it you are just throwing your money away.

 

[bowsercake]

What if he is just replacing the bearings and rings? The engine can't be in that bad of shape, but still. If the engine is already out, why not replace the bearings, rings, and upgrade to ARPs so that the engine lasts even longer?

 

[bigaaron]

What if he is just replacing the bearings and rings? The engine can't be in that bad of shape, but still. If the engine is already out, why not replace the bearings, rings, and upgrade to ARPs so that the engine lasts even longer?

Exactly, do it right and do it once.

 

[starscream5000]

Agreed .

 

[LordLo]

Thing is my engine has a stock hg with arps. Runs strong, but I'm sure with any type of increased boost it'll blow. I've been running 10-15 psi daily for the past 6 months.

I was going to just replace the HG with a metal one, but if I'm going to go through all that trouble of pulling out the top end and having the block decked... I might as well just rebuild the whole thing since it'll be out.

Just my thought.