Forged Internals... 3S-GT Help ease my mind.

The MR2 broke a ringland, and I bought Wiseco Pistons and Eagle Rods to replace it.
This is my first time with forged internals and I didn't realize the difference in weight. My mind is in overdrive.... I was doing this in car, so it will be a significant amount of work to get the crankshaft out, not looking to make big HP, maybe 250-300 later on. What do I do?

*3S-GTE

Don't be so harsh. Everyone got start someplace and learn.

Now finish pulling the engine and check everything. Get new bearing and whatever else it needs. Will pay off in the long run, especially if you want to keep the car.

My friend worked at Wiesco until last year. His neighbor had a turbo honda civic. Unsurprisingly it melted some pistons. He gave him a great price on forged bits and he said F that ebay is cheaper. So he bought no name forged rods and pistons. Then he did what you are doing, IE drop them in no balancing.

20 seconds after it started for the first time, and the kids revving the crap out of it.....BOOOOM. Engine came apart, and a piston and half of a rod came through the hood. My friend was out side so he walked down his driveway to find that piston still spinning in the middle of the street.

So yes, balancing is required. E36 M3 its required if you loose only a few grams off a piston, and you lost a ton of weight.

wlkelley3 wrote: Don't be so harsh. Everyone got start someplace and learn. Now finish pulling the engine and check everything. Get new bearing and whatever else it needs. Will pay off in the long run, especially if you want to keep the car.

He asked what he needs to do. It isn't being harsh if it's the truth.

I would pull the motor and send the crank, rods and pistons to get balanced first. Good luck.

I've worked on my own cars for years, this is just my first experience with forged internals. I didn't know there was such a drastic difference in weight. Didn't list that in the specifications when I got them, just Dish/Diameter/Compression.

Pretty sure you gotta drop the crank out and have it balanced, they take metal out of the counterweights to match the new piston/rod combo. You can hone the bores block in car but it's not ideal, assuming the bores measure ok and you don't need them bored out for oversize pistons. If this is a high power turbo car you'll probably want to open the rings gaps up from stock in any event too.

EDIT: Broken ring lands can be caused by too tight of a ring gap, under boost the rings get hot, expand until the ends touch, and then blow the ring land off when they grow more and grab the bore.

I'll be pulling it out this week. Its just a completely stock car for the time being, just like to really take care if my cars. Figured this would be a nice upgrade for any future power adders. Plus its the 2nd lowest production car on the MR2OC #0000075 (lowest was #0000051. Also can redo the aesthetics of the block while its out.

I know plenty of people who have installed forged pistons and rods with the motor in the car. However, it was usually on a healthy motor. I don't think having the entire rotating assembly balanced should be necessary. I would guess the cylinders probably need to be honed at least though. So pulling the motor is probably your best bet.

Oh man, I wish I knew about this. I have a built 3SGTE with wiseco pistons that I would have made you a great deal on.

Remove the block and take it to a machine shop.

Did you buy oversized pistons? what about the connecting rods, are they undersized?

It was a healthy engine until it broke a ringland in #2 cylinder. It began smoking under boost, otherwise running great. 3" stainless exhaust, HKS Sidemount, JDM ECU, 15psi she scooted pretty well. The PO swapped the car with an st165 block and a gen 2 mr2 head. Message me about that engine... May be interested for another Mr2 to swap. Dansxr2 at yahoo dot com

Dietcoke wrote: Wait, you literally thought you could just bolt them in and be done with it? What you should do is take it somewhere, and stop working on it. Ever.

Wait, you literally thought you could come on here and discourage someone from learning and working on their own car, on grm, and that that was appropriate?

What you should do is take that e36m3 somewhere else, and stop posting like this here.

dansxr2 wrote: I'll be pulling it out this week. Its just a completely stock car for the time being, just like to really take care if my cars. Figured this would be a nice upgrade for any future power adders. Plus its the 2nd lowest production car on the MR2OC #0000075 (lowest was #0000051. Also can redo the aesthetics of the block while its out.

It's a good opportunity to go through it and make it right. Check everything out and do it right while you've got it apart. Sounds like a cool car. Have fun, if you need help here, don't hesitate to ask.

Alright alright, I'm gonna weigh in on this sub conversation here, and do so as a guy that has never assembled anything more complicated than a two stroke. 1) yes we don't have to be "harsh" 2) that "harshness" could save a life, so stop with the "I'm holier than thou because I pretend to be nice to people and be positive in my life and am politically correct" crap. I probably wouldn't be standing here alive if it wasn't for 99% of people around me telling me I'm in over my head and doing so in a way that hurt my feelings.

Every once in a while something pops up that I have never heard about or even considered, but I should have known about. This is one of them, and I'm almost embarrassed to admit it. Rebalance the rotating assembly? What? Is this just a 4 cylinder thing? I've been messing with Rover V8s for years. Changed pistons many times. I understand rebalancing when the crank is offset ground for larger stroke, because you have changed the center of mass for the crank, but for a piston change. Maybe its just that the Rover crank is zero balanced and its a 8 cylinder so the 8 different rods and pistons balance each other out, and this has never come into play for me. For the record, I don't mess with 4 cylinders, so I'm in the dark here. Someone explain this to me like I'm stupid. Is this just a zero balance vs a harmonic external balance thing?

In reply to tr8todd:

Are you putting stock components back into those rovers or lightweight forged bits? Thats what we are talking here. Even in v8s its always best to balance afterwards but when you're just going back with stock components into a truck motor that wont see north of 5k theres not much reason to spend the extra bucks. But when you're trying to get the max out its best to balance. Weigh the rods, weigh each piston, try to match them all to get an even weight then you put weights on the crank to match what the piston/rod/pin combo weighs, stick he in the machine and it tells you which counter weight either needs drilling and weight removed or weight added by either adding weight by welding up stock balance blind holes or drilling and heavy slugs of metal (mallards is what old dude called them but idk the propper spelling). Ive done it on v8s that see power and or rpms and in this case i HIGHLY recommend he have it balanced.

I don't think it is possible to balance an inline engine. You can balance all of the pistons/wristpins/little ends (reciprocating assembly), you can balance all of the big ends/bearings (rotating assembly), and you can balance the crank...

But how do you balance the crank to the pistons? If all of the bobweights are the same (and they will be, see steps 1 and 2) then putting them on the crank (which is balanced, see step 3) will make no difference to the crank's imbalance. Because of the nature of an inline crank, you can't get the counterweights to "match" the bobweights. You could put a pound of lead on each counterweight or you could machine them off entirely and it would still look the same to the balancing machine.

Lots and lots of people have just thrown new forged internals into an engine and never had a lick of a problem related to the balance. If it was balanced before (we can assume that it was) and the new rods and pistons are near each other in weight (we would hope so with modern processes... got a decent scale?) then that is all you can do. If they are lighter or heavier than the old parts, yes it will affect certain forces in the crank, but there isn't really a way to measure that without cutting up a crankshaft for testing purposes. And to be honest, an insufficient/excessive counterweight issue would mainly manifest as wrecking main bearings (1, 3, and 5, with 2 and 4 looking okay) and if you're not doing that, then why worry?

Gap the rings, Plastigauge the bearings, follow torque specs religiously, and fix your tune so you don't blow through another piston. Move on with life.

You don't use bobweights on an inline engine.

I believe wiseco pistons are supposed to be +-1 gram. Not to sure about the rods though.

loaded old piston/rod was ~3.25 lb as I don't have access to a digital gram scale.

New piston without rodbearing, circle clips, and rings.

I'll go to the Post Office Tuesday and see what they weigh on a more accurate scale.

Now, I ain't a engine balancer, but IT SEEMS TO ME that I have read that a 4 cylinder engine is inherently self balanced. What you want is all the assemblies to match. If all the piston/rods are the same weight, then the motor will be balanced on a 4 cylinder. 4 cylinder motors have 2 assemblies up and 2 assemblies down. That balances itself out. You might check with a professional shop on that. I would also say that rustspec13's friend's friend that blew a motor probably was due to cheap ebay crap from China or poor assembly and not because there was any great difference in balancing. For a piston to come out like that, the big end would have to have let loose at the top of the stroke. That's not a balance problem.

As someone who has built many 4 cylinder race engines, static balance (rods & pistons) and dynamic balance ( rotating assembly ) are done separately. As was pointed out, an inline engine is inherently self balancing. My engines worked fine at up to 9000 rpm's. All static balancing was done to 1/10th gram. Pistons and rods were done separately and large and small ends were also matched.

And its out, will be taking to a machine shop this week to have it checked and rebalanced in necessary.

Dan!!!!!!

Long time!!!!

I use to build lots of 4age's and the best $$$ spent on them was to have the rotating assembly balanced. It is not that they are bad from the factory it is just that they can be made better. While you are getting things balanced have the flywheel done as well. After ever balance they all seemed to rev quicker run smoother and font seem to mind being run up past redline like the stock ones do.

I think snappy is what I would describe it as after balancing. I never used aftermarket pistons or rods. I always used OE they were more than good enough for the non boosted motors we ran and since they would get torn down ever 30 hour or track time or so for a freshening and there was never an issue. I would hone the cylinders and replace the rings.

One thing that I found important was to do a through de-burring inside the block. There are a lot of casting lines and slag over run in the castings. I would also look closely at all the sharp edges of mating surfaces and machined surfaces and make sure to radios them. The other area I would always work on was the oil drain back holes in the head and there corresponding holes in the block. These can use some extensive cleaning up. I found several blocks and heads that these return holes were partially blocked with casting over run. Probably ok for street use but would cause the head to load up with oil and cause oil starvation issues in long high speed sweeper. Non of this is difficult to do. A drill and a dermal tool and an assortment of grinding stones and a couple of hours and you are done.