Comment by tmh88j
5 years ago
Nice! What engine did you build?
>The distance between a crank bearing or rod bearing is less than 2 thousandths on modern engines. A small amount of oil in that tiny space is all that keeps your engine from having metal on metal seizure.
The BMW S65 and S85 engines are prime examples of what happens when the wrong tolerances are chosen. I can't think of another engine family where rod bearings are considered a maintenance item.
I built an LSX (Aftermarket GM) iron block engine (V8 LS) for a CTS V. I had to get some very precise tools (Have to measure to 10,000ths) or they were useless for bearing clearances and verifying cylinder diameters. My cylinders were 4.155 bore, and the bearing clearances were around 1.8 thousandths. Forged pistons, rods and crank.
I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the work so I did a lot of research and did it all myself. I appreciate someone asking because my friends and software dev co workers aren't interested :)
Yes you are right as far as LS engine builders there's loads. I could have ordered a crate engine from Texas Speed and been done with it. And yes for hours of my time spent vs hours of money saved I lost a ton of money. But all it takes is one very small mistake to make an engine short lived with these exacting tolerances. I'd rather blame myself than deal with someone kicking the blame back. It was also a personal satisfaction thing.
My wife's engine had an issue and it was the middle of winter so I said whatever let's just have a shop fix it. In the process they "flushed the transmission" and it failed 4 days after we got the car back. Of course they stonewalled us and I can't prove they broke it. So I ordered a late model wreck transmission and replaced it and 3 years later still running strong.
But I then decided that I would never be in that position again where someone could tell me it wasn't their problem and get me aggravated. With this engine I built it from raw parts. I had the block machined, and I had the tools to verify.
It was certainly not worth my time, but as you said I love working on cars too.
I have a buddy that is adamant about not flushing transmissions if you dont have a issue because he think its guaranteed to have an issue after, from his experience. lol
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>I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the work so I did a lot of research and did it all myself
I love working on cars so I totally get wanting to do that, but why didn't you trust someone else to do the work? There are probably more reputable LS builders across the US than any other engine family.
It sounds like he wanted some very precise work done. Quality in the blue collar trades has gone to nil in the last decade. And if you do find someone that is very detailed and "by the book" level of quality, you are going to pay 3X the normal labor rate. For instance, this is a performance transmission shop [0] that regularly takes apart "precision" rebuilt transmissions only to find they were not done right at all.
[0] https://youtu.be/aI5iO2YSHMs
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It helps that they are abundant (in the hundreds of millions units produced), have been in use for decades (since the mid-50s), and are simple to work on (as evidence by the OP randomly learning to machine one).
As cool as 2-atom thick plasma transfer wire arc cylinder liners are, that's not something which will ever be available to a layman.
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17-18 thou here on my LS6 on the rods. 23-24 on the mains. I'd like to see tighter on the mains, but not sure if its worth ordering another set of bearings and using 1/2 of them to tighten up 1/2 a thou like i did on the rods.
what amazes me is the cam lifts we're running these days. I'm running .646"/.649". In the 90s .500" was big for a street motor, and only full blown race motors were running whats normal now.
Damn, dropping a new engine in a CTS V? What year? NA? How much power are you shooting for? The CTS V is definitely one of my favorite cars, I'd love to own one one day, but the ones with the manual trans hold their value pretty well :)
It was and still will be supercharged. It was 650 crank Hp, and will be over 800 conservatively . and its manual ;)
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Very cool. Although I own an LS, I've never touched an LS. The Sloppy Mechanics guy is impressive though.
Since a short block is mostly just a short block, I'll be interested in seeing if LS heads/intake manifold/headers takes off in the SBC community.
Huh? What do you mean "takes off". Do you mean do we build LS motors now instead of gen1/2 SBCs then yes.
If you mean "do the LSx heads drop onto a gen1/2 SBC", then no, not at all. only thing common between them is the cylinder spacing. The LS uses 4 bolts per cylinder like a ford, instead of 5 like the SBC, the firing order is different, the valve layout is different (ports are symmetric vs mirrored), etc.
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Why did you go iron block for your build? Is it that your were afraid you cracked the block again? How did you do that in the first place. Are you running any boost on this engine?
I'm running 14 lbs boost yes. And yes it was piece of mind that it's much harder to crack and unlike the aluminum block I can bore it more than 5-10 thou if it needed it again. Downside is 100lbs more but this is in a 4200lb car so whatever
Any race or high power engine, especially those that rev quite high will need rebuild - not just in bottom end but often with piston rings and valves as well.
You don't really hear about those other engines much because their buyers understand that a race engine needs more maintenance than any other road car.
Also, not beating on the engine until oil has warmed up to temp will elongate the bearing lifespan quite a bit. I have a friend with E60 6mt S85 that has factory bearings at 110k mi and has perfect oil analysis results.
The S65 and S85 are road car engines, not racecar engines. They're also hardly BMW's highest performing motors. Even Dinan built engines don't suffer from that problem.
They're meant to be dual duty. There aren't any road car engines I'm aware of that use individual throttle bodies or 12+ compression without direct injection.
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> Also, not beating on the engine until oil has warmed up to temp will elongate the bearing lifespan quite a bit.
I am curious if there is proof to this. I've always felt the same way. I know in the "old days" with iron pistons, if you you simply started up a cold motor and and drove it hard without a warm up period, the pistons would expand quicker than the block and would start to scour the walls and/or lock up.
But other than that, the only other "proof" I have is from people in high school that like clock work at 3:30 everyday, would smoke tires leaving the parking lot everyday. They seemed to go through motors every 6 months. I'm talking knocking bearings and lifters cracked in half. I've never gotten rough with anything I own until after a 20 minute "warm up" and all has been well (so far).
It wasn't so much locking up or anything but cast vs. forged.
Subaru EJ motors munch through rod bearings quite happily.
What are the indicators that replacing them is neigh?
In my experience with these, when I've heard the first indicator to do it, the damage is done. Standard regular maintenance hasn't identified the issue in advance. I'd be curious to see whether long term monitoring of particulates in oil can make an help though.
I thought once you replaced the crappy OEM bearings you were all set on these engines. I guess it is not the case?