camuman

a thread came up and it is being posted that built motors, IE ones with aftermarket pistons and rods, rings etc will not last longer then an oem motor. since we can not agree on the life of an oem motor, lets just put a ceiling at 100k miles relatively trouble free.

please, if you have a built bottom end just post up your mileage on the motor since the build.

heres the thread where this all started.

https://www.s2ki.com/forums/index.php?act=P...4606&p=15260989

i personally think a correctly built, correctly tuned aftermarket internals motor can last just as long. hell, my buddy has a built bottomend in his accord and he has been daily driving it for over a year now, i think he has atleast 20k on the rebuild.

anyone else?

rob!

A properly built motor can last as long as OEM especially since a good engine builder will make all the clearances dead on. The problem is that people with a built motor tend to beat the piss out of them because.. A: Its built and B: its built for a reason aka the stock one didnt hold up.

When you know you have an oem motor and you are pushing a ton of power out of it you have that in the back of your head and you tend to take it easy on the car.

AlexS2200

This is going to be an interesting thread.

s2k_bb

https://www.s2ki.com/forums/index.php?act=P...4606&p=15260989

That's what I don't understand either. jzz30 is just stating that


"aftermarket forged pistons wear out faster than oem. and im not saying they will wear out in 20k miles. it is dependent on usage but it probably wont last 100k that an oem piston would easily go "


but he never explains why.

Think about it this way... if both an OEM engine and Build engine are driven the same way, it would make no difference right? As long as it was built correctly.

jzz30 says "aftermarket forged pistons wear out faster than oem." but never supports it, or where he got the idea from. I'm really interested on the subject also.



If a car is built with beefed up components for boost/power/reliability/etc, shouldn't it be able to handle the rigors of the daily commute every day too?

as long as you change your fluids regularly, I don't think you have a problem of hitting 100k with a beefed up engine.



The only way though if it's some ridiculous 2.5L F22C stroker kit pushing 1000HP @45psi or something to that extent. That's definitely not going to last 100K miles. Most race teams rebuild every few runs or so if your up to that level. Unless you have a bullet proof 2JZ that can handle 500hp+ stock

But if it's a mildly built 350-400hp F22C with reliability mods, it should be no problem for reliable everyday driving.


Any opinions?

DeadZero

Also Having Stronger more STURDY PARTS. That alone should be able to make a rebuilt motor more efficient and longer lasting.

Sellout

There's one reason that a built motor won't last as long as a stock motor, all else being equal. Forged pistons. They expand more than cast pistons, generally. Some are worse than others, it depends on the silicon content.

Because they expand more, you have to run a looser piston-wall clearance. In extreme cases, with forged pistons that have very little silicon, the tolerance has to be so loose that you could actually reach in and move the piston back and forth in the cylinder. I've seen some that were so loose you would wonder how the piston rings manage to stay in the grooves.

Start up a forged motor with low silicon pistons and you get piston slap. The piston is rocking back and forth in the cylinder until it warms up enough to expand fully and stop beating up the cylinder walls. There's just no way that a motor with pistons like that can possibly last as long as a cast motor...

PowerAdder

^ (example) 03/04 cobras come stock with forged pistons/rods. there are many over 100k miles boosted to hell and back with no problems.

Chris@NLM

Anyone who builds a motor with piston to wall clearance that is so big the piston can bounce back and forth in the cylinder shouldn't be building a motor. Sometimes people build race motors with bigger clearance but never extreme enough to be bouncing around. A piston with little silicone content will have a smaller expanding rate and wouldn't need as much clearance not more clearance. There are plenty of cars out there that come with forged internals from the factory including the s2000. Forged parts do not wear more faster then cast, thats just not true. We have built motors that have lasted way over 50k and are still going. There is no reason why a built motor with a moderate power level cant last 100k.

73Zero

I'm definitely subscribing to this topic, as I've contemplated getting my engine built by one of the reputable builders here (Laskey, InlinePro, etc)...but I've always been concerned about the reliability and longevity of a built motor. While I've seen good (and bad) stories pop up from time to time about built motors, I've never really seen a post stating (and substantiating) the longevity of their motor.

This topic will certainly be interesting to read.

Sellout

If you read my post again you'll see that there's nothing I said that is incorrect. There is one reason that a race motor wouldnt last as long as a production motor, and that reason is the expansion rate of the pistons used in a race motor. There are people using pistons in street cars that really have no business there.

I also noted that some pistons are worse than others, depending on the silicon content. Look it up yourself if you have to. The forged pistons used in production cars like the S2000 and Mustangs are a high silicon content piston designed specifically to reduce the expansion rate so they don't have to run such extreme tolerances. There is a drawback to these though, they're not nearly as strong as a low silicon forged piston. They're more brittle. They're easier to break. Certainly they're stronger than a typical cast piston, but that isn't really saying much, is it?

I didn't mean to imply that all forged pistons have ridiculous expansion rates. Clearly there are some that don't, and those ones can last damn near forever. My point was only to show an example of one thing that can make a built motor not last as long as a production motor. That one thing is low silicon forged pistons. Build a motor with this type of piston in it and you'll be lucky if it makes it past the 40k mile mark.

As for pistons bouncing back and forth. Ever heard of piston slap? It's not a term I just made up...