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GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
2/21/17 12:18 p.m.
tuna55 wrote: FYI I have not seen a very strong correlation between compression numbers and horsepower. Often, compression will be way down after a season of racing and yet power will be pretty close. Run it!

That's because compression causes most power loss at low revs. I've even heard stories of racing teams intentionally sabotaging their compression to cheat static compression tests, because at high revs it doesn't make anywhere near as much difference.

Knurled
Knurled MegaDork
2/21/17 12:36 p.m.
rslifkin wrote:
Knurled wrote: Drain the engine oil, replace with ATF, drive the snot out of it.
No no no no no! Unless that engine would be happy being run flat out with cheap 5W-20 in the crankcase, this is a quick ticket to bearing damage IMO. Plus, modern ATF isn't any better at cleaning than modern engine oil, it just happens to be a fairly thin oil which can be useful for cleaning.

Personal experience suggests differently regarding the cleaning ability.

As for oil viscosity, in the ranges we're working with it has little to do with bearing load/oil film strength. In short, if you're flowing the oil, it's going to be good enough for the bearings.

Don't tell the Internet that I like to run 5W20 in rotaries, they'll freak out Now that 0W20 and 0W15 are available over the counter I'll experiment with those too. I do run 5W40 in my Volvo but that is only to keep the oil light from coming on at idle when rallycrossing in summer. Volvo says that is acceptable, I would rather a warning light be an actual warning of a problem.

docwyte
docwyte Dork
2/21/17 12:42 p.m.

Keith, I believe his budget issues are due to paying a shop to do the labor.

For a shop to pull the head and oil pan will be a very expensive endeavor.

LanEvo
LanEvo Reader
2/21/17 1:18 p.m.
Keith Tanner wrote: The budget is just a head gasket and an oil pan gasket. It's about as complicated as a shock change, you're just opening a box and looking at the parts inside. Heck, you may not even have to pull the engine.

The way the W201 chassis is designed, you can't get to the oil pan without dropping the subframe or pulling the engine.

Moreover, let's say I do look at the rings and decide they're junk. Ok...so now what? If I can't afford to have the spare engine rebuilt, why even bother? I just need something that will run, even if it makes 1/2 power.

Keith Tanner wrote: Scammer engine builders are the worst. We've had to be the bearer of bad news a few times when we've opened up a "high end built engine" and found junkyard parts. It always turns into a he said, she said situation.

This guy had a pretty solid reputation. But he really screwed me.

docwyte wrote: Keith, I believe his budget issues are due to paying a shop to do the labor.

Exactly. I live in lower Manhattan and can't exactly tear into an engine on the corner of Fulton Street and Broadway. I've got to pay shop rates, and I'm totally tapped out. (Needless to say, my wife isn't exactly pleased with all this either!) Need to find a cheap solution to get me through a couple of races, which is all I have time/budget for this season anyway.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
2/21/17 3:27 p.m.
docwyte wrote: Keith, I believe his budget issues are due to paying a shop to do the labor. For a shop to pull the head and oil pan will be a very expensive endeavor.

Completely understood, which is why I then made comments about the actual difficulty of the job. Having to remove the subframe does make dropping the pan more difficult, but I can do a subframe swap on my Miata in about 45 minutes. This is obviously an extreme case, but it shows that we're not necessarily dealing with impossible timeframes.

If you don't have access to facilities, then you can rent them. I'm sure NY has some lift rental locations where you can pay by the hour as you wrench.

If you pull it apart and decide the rings are junk, then you can decide to save the engine or destroy it. There are currently no holes in the block. It would also probably be easier to free up stuck rings when you're holding the pistons in your hand. If you just pour stuff from the "magic fix in a bottle" aisle in NAPA down the spark plug holes, then you're leaning more towards destroy. If something does go wrong, you'll hole the block and destroy pretty much everything - including potentially your car if you're not good with driving on oiled up tires. It might seem alarmist, but it is a risk you have to acknowledge. Even if you don't pop the engine, you may end up damaging the bores.

The alternative is to play it safe. If money is an issue, racing on a sick engine might save you money in the short term but can cost you money in the long run. This is simply a decision you have to make.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
2/22/17 7:05 a.m.
LanEvo wrote:
Keith Tanner wrote: Scammer engine builders are the worst. We've had to be the bearer of bad news a few times when we've opened up a "high end built engine" and found junkyard parts. It always turns into a he said, she said situation.
This guy had a pretty solid reputation. But he really screwed me.

A familiar story to me. I'm starting to think that the worst mechanics have solid reputations.

tuna55
tuna55 MegaDork
2/22/17 7:14 a.m.
GameboyRMH wrote:
LanEvo wrote:
Keith Tanner wrote: Scammer engine builders are the worst. We've had to be the bearer of bad news a few times when we've opened up a "high end built engine" and found junkyard parts. It always turns into a he said, she said situation.
This guy had a pretty solid reputation. But he really screwed me.
A familiar story to me. I'm starting to think that the worst mechanics have solid reputations.

TunaDad paid a well known engine builder once. $14K later, he had an engine which made six passes and spit the crank out of the bottom of the block. Five pistons were hitting the combustion chambers. The engine he built in the now-free time outran that one by over a tenth.

volvoclearinghouse
volvoclearinghouse UltraDork
2/22/17 7:15 a.m.

In reply to LanEvo:

"Need to find a cheap solution to get me through a couple of races, which is all I have time/budget for this season anyway."

Sell the Merc, and buy some seat time at a LeMons/ Chump race?

RealMiniParker
RealMiniParker UberDork
2/22/17 7:22 a.m.

In reply to volvoclearinghouse:

I was just thinking along those lines.

Sit out a season, and put those entry fees toward rebuilding engine.

rslifkin
rslifkin Dork
2/22/17 8:04 a.m.

In reply to Keith Tanner:

My thought on the matter is this: if the motor runs as-is and seems healthy other than low compression, it's unlikely to blow up after soaking the rings.

Soaking them in stuff to clean them may not help anyway, depending on whether they're worn or just gummed up. But it also might help. And it also provides an answer to the "dirty or worn" question without having to tear into the motor.

Based on the success that's been reported by people with Saturns known for clogging the ring packs with oil goo, I'd say it's neither snake oil nor magic bullet, but somewhere in between.

LanEvo
LanEvo Reader
2/22/17 8:24 a.m.
volvoclearinghouse wrote: Sell the Merc, and buy some seat time at a LeMons/ Chump race?

People race for all kinds of reasons. For me, love of this particular car/platform is a major reason. I really enjoy driving it and don't really want to be in anything else right now. Think of me as a vintage racing weenie who sticks with his sputtering MG TD for no rational reason.

As for the crapcan series, I've never had much interest in them. Besides, all my friends are racing with the CCA.

RealMiniParker wrote: Sit out a season, and put those entry fees toward rebuilding engine.

Yeah, that's basically what I did for the last two seasons.

I'm not going to miss another season because of this damned engine builder.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
2/22/17 8:35 a.m.

I think an attempt to un-seize this engine while closed is worth a try. If done right it can't make things worse and could result in an engine that runs well for years with little money spent.

+1 for MMO down the spark plug holes and a first run with ATF mixed into the oil.

bentwrench
bentwrench Dork
2/22/17 8:53 a.m.

If you are racing on a budget you don't have time to not fix it right.

Fix it now before you install it.

Even if you just take it apart and scotch brite stuff and clean the piston grooves.

Once stuff grows behind the rings there is no way for it to escape so it will sit back there and bind up the rings and eat at the grooves.

LanEvo
LanEvo Reader
2/23/17 4:34 p.m.

The engine is already installed.

"Fixing it right" means paying someone to pull it, rebuild the bottom end, then reinstall it. As much as I'd like to do that, I can't afford to.

Further, It's not stuck/seized (as some people have mentioned). It runs. Just makes lower compression than it should. The more it runs, the better the compression numbers have been getting. That seems reassuring to me.

The car is actually pretty well known in the Benz W201 world. Not many Bekkers strokers running around. From what I've read, the engine wasn't driven very long after the build before running into costly CIS/KJet issues and being sold on. The guy who bought it bit off more than he could chew: he installed a ghastly Evo II body kit, took on a trans rebuild, and tried to sort the KJet himself...but failed. He parked the car for some 9 years before selling it to me.

In other words, it's not really a worn out, gunked up, high mileage engine. It's a fairly fresh engine that's sat in a Connecticut garage for close to a decade. I expect the rings are rusty.

Robbie
Robbie GRM+ Memberand UltraDork
2/23/17 4:44 p.m.

Just sent you a PM. I say give er the good ol Italian tune up. Or just stop worrying about compression. Oil pressure? If yes, then race.

minivan_racer
minivan_racer UltraDork
2/23/17 5:17 p.m.

How low are we talking anyway? Is low compression the only symptom or is there blowby?

LanEvo
LanEvo Reader
2/23/17 7:32 p.m.

Compression should be around 190 psi for a new M102 16v engine; lower limit of normal is 150. Mine was making around 90-100 per cylinder last time we checked. That was just idling in the shop and revving without any load.

My mechanic says he expects it will be better once we do a MMO soak and drive it around under load for a while.

I don't see any signs of blow-by, but I won't really know until I drive it around a little. There's a catch can, so I'll keep an eye on that. Besides oil consumption and smoking, what else should I look for?

Dr. Hess
Dr. Hess MegaDork
2/23/17 7:40 p.m.

I've never heard of checking compression numbers on a running motor.

Otherwise, oil consumption, blow by, smoking, that is about it.

daeman
daeman Dork
2/23/17 7:41 p.m.

Are you sure the compression gauge being used is accurate?

Reason I ask is that figures that low should make the thing damn near impossible to start.

LanEvo
LanEvo Reader
2/23/17 7:45 p.m.
Dr. Hess wrote: I've never heard of checking compression numbers on a running motor.

Sorry. I meant to say we checked compression after letting the engine idle for a few minutes and revving it a few times. Didn't actually drive it under load before checking compression. I understand driving under load would help to unstick the rings.

Dr. Hess
Dr. Hess MegaDork
2/23/17 8:24 p.m.

I think you just need to drive that thing and don't worry too much about it. If the compression numbers are all about the same, stop over thinking it.

Tyler H
Tyler H GRM+ Memberand UltraDork
2/23/17 8:32 p.m.

Drive the dogE36 M3 out of that thing. If it doesn't blow up, you're good. Seriously -- there has the be like 3 other guys in this hemisphere campaigning a 16V Cosworth. You can probably bum a spare off of them if something bad happens.

minivan_racer
minivan_racer UltraDork
2/23/17 9:06 p.m.
LanEvo wrote: Compression should be around 190 psi for a new M102 16v engine; lower limit of normal is 150. Mine was making around 90-100 per cylinder last time we checked. That was just idling in the shop and revving without any load. You may also want to run a oil with a decent amount of zddp in it like Mobil One extended mileage. The extra additive is supposed to help with ring wear. My mechanic says he expects it will be better once we do a MMO soak and drive it around under load for a while. I don't see any signs of blow-by, but I won't really know until I drive it around a little. There's a catch can, so I'll keep an eye on that. Besides oil consumption and smoking, what else should I look for?

That's really it, if you have low static compression but no blowby then doing the atf trick then running the dog piss out of it will probably build it up to the low side of acceptable. If you are getting a lot of blowby then I'd consider doing a re ring because the oil control ring isn't sealing.

Robbie
Robbie GRM+ Memberand UltraDork
2/23/17 9:17 p.m.

Test for blow-by:

  1. Make sure pcv is working correctly and remove oil cap while engine is idling
  2. Place hand over opening
  3. If you feel air coming out you have excessive blow by
tuna55
tuna55 MegaDork
2/24/17 6:54 a.m.

Run it!!

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