yerkonoku

iTrader: (2)

hey there, I just bought an Evo 8 with a knocking engine, chick ran it low on oil I think and started knocking and died.(car and motor have 76k) Should I attempt to rebuild it or just say screw it and throw a long block into it? Just need some advice from the experts. thanks in advance, and the engine didn't throw a rod it just knocked. If anyone has a longblock Evo 8/9 motor I have cash... But also need to know if mine is worth rebuilding.

HyperHoHo1

I would have it taken apart first and examined to see what the damages are. It is better to have it rebuilt than to buy a used long block so you know everything was done right. The last thing you want to do is to buy a used engine to find out it has an issue(s) with it.

MechTech

Agreed. If you have the cash and plan on building something or buying a built motor do it but if your just lookin to get on the road or have other plans take it apart first and attempt to find the knock that will tell you which route to take.

yerkonoku

iTrader: (2)

Hm, okay well I kinda wanted to build it a little bit nothing to insane I am just not sure if the rod knock would effect the life of the engine in the long run... I don't want to build it and drive it 20k and have it explode again =O

fre

iTrader: (4)

As long as the wear parts are replaced/block properly machined, I wouldn't think rod knocking would have any ill effect on the block/head (replace crank, pistons, rods). I am pretty sure a long block will cost you more $ than rebuilding the one you have and it wouldn't even be as strong of an engine. Now the downside to built engines is that they tend to have shorter lifespans as the clearances are not usually as tight as factory and the pistons are usually forged for strength so that wears out your cylinders faster than cast. If this is a daily driver then you might want to consider a used stocker. If you can live with an engine that will last maybe 70-80k max then build it up. Of course, you can probably try to rebuild your engine to last slightly longer (use cast pistons), but even then, the clearances will probably still be looser than stock. I would be curious to know how long the longest lived built engine has gone so far and what components were used.

4RETECH

iTrader: (86)

^^^ huh???

A big advantage with forged pistons is they generally result in a more ductile material, with the effect being the piston can take a higher level of detonation before failing. As far as I am concerned, this is not such a huge bonus as you engine should be tuned not to detonate in the first place, LOL

OP: tear it apart if you have time. A shop can determine if it's a rod or not. You could always buy a built engine.

I did mine at 209K,wiseco/eagles, arp head and main studs too for my DD Evo.

fre

iTrader: (4)

Well, I am unsure of the power limits for cast pistons, but the problem is that when making large amounts of power, detonation is part of the deal. You get a little bad gas or the conditions are just right and your tune is close enough to the edge, you can see some detonation. This is the nature of making big power, so that is why I would steer clear of cast pistons for high power applications (600+).

Even at my power level, I am taking a risk (~530whp). Obviously if you tune conservatively enough and never get bad gas or never run your car in a situation where it might knock then you should be fine with a cast piston. I am taking the risk right now and haven't had an issue yet, but I plan to upgrade to the 3586 which will put me pretty high up there ~600 I am thinking, so then the forged piston is worth the peace of mind.

So the bottom line is you can have a piston that will allow tighter clearances, but will be more brittle and keep your power goals in check or you go with the more flexible, stronger piston that will require looser clearances, but allow you to crank the wick up without being paranoid of going boom.

Now with regards to the OP, he can probably stick with cast pistons because his power goals are not too high up there.

cmspaz

iTrader: (1)

After my last rebuilt spun bearing block, I won't do it again. New (or removed running) block or bust.

Had a partial blockage in an oil passage persist through the hot tank, spun a balance shaft bearing at 2k on the motor after said blockage shifted and fully blocked the passage.