Head rebuild questions on 615 - Page 3 - PeachParts Mercedes-Benz Forum

Shortsguy1 · #31 11-12-2014, 11:41 PM

I do not believe there is much to be gained by changing out the diff on a 220D. Based on looking at engine torque curves and road load (hp vs. speed), it is my belief that MB picked the gear ratio to allow for the highest top speed possible. In other words, going away from MB's choice is likely to lower your top speed. The theoretical top speed of your car is in the low 80 mph range. If you never plan to drive that fast, then by all means change your diff. If you plan to only drive 65 or less, then a different diff will lower rpms at 65, and improve fuel economy. But if you plan to drive 70-75, I would discourage any changes.

Plus, any change to the diff will make acceleration even slower. In some places around the world, they use this as an indicator of insanity. Kidding about that.

Lucas · #32 11-13-2014, 10:19 AM

Built for comfort not for speed! Lol. I drive 62 on the freeway, even in a brand new car. In most vehicles it's really the threshold where you mpg's drop. And on a 60 mile drive it doesn't add much to your time.

So I'm trying to increase my efficiency in that range. 50 is comfortable and when you let off the throttle you don't get a lot of engine braking. 60 however, I do get significant engine braking.

A lot of it is caused by blowing my other motor. Granted it was Frankenstein with mixed parts, had the pre oil filter ripped and upside down, and went through multiple owners. The new one I got is in way better shape. I notice a drastic difference in how the oil pressure responds.

I'm a little worried about the acceleration. I have to get on the freeway to leave my house, but no on ramp. I take my time and wait for traffic to clear. Coming home there is one on ramp I always hit that's downhill and long.

I drive to town which is 5 miles away, and beyond that 30-60-120 miles (Santa Barbara-Ventura-LA). Probably more LA soon with work. So I'm preparing for that.

Not saying it's the right decision to swap my differential, but it's free and I'm already needing to remove my cv's to reboot, so it's the time to try it.

I'm gonna hate myself if I switch back.

So the question is, will 3.96 to 3.69 give me that little bit of room I need between the difference of 50 and 60 mph? I hope so.

I think most go fast type of guys think we are all insane. As gas prices rise, they will realize. When fuel was 0.99 gallon I had a car that got 10mpg. And now I'm here.

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leathermang · #33 11-13-2014, 10:27 AM

The problem with driving 62 is that other people are driving 75 and texting at the same time...

Lucas · #34 11-13-2014, 11:04 AM

It's a dangerous place out on the concrete jungle. The trick is to get in front of a semi.

Before the MB I rode a motorcycle. I would go about 75-80 to stay ahead of people but not pass too many. It was stressful.

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Lucas · #35 11-14-2014, 06:32 PM

It's getting weird in Lucas's garage again.

I decided to do a wet compression test before dumping money into a head.

I get the car warmed up. Check dry compression at suspected cylinder (#2) and got 250lbs. Put too much oil in, cranked it, I believe the oil ignited, and got 600 lbs. fortunately didn't break anything.

I pull the tester back out of injector hole. Crank on it a bit with a rag to catch the oil, not much comes out.

Test and get 400 lbs.

Decide I'm crazy, and hooked the injector back up and started the car. Ran for 20 min.

Disconnected, test dry and get 320 lbs. Test wet with 15ml oil (measured) and get 340 lbs. sounds about right. I believe this is good news that my rings are ok.

I pull #1 to see what a wet test does to a good cylinder. Get 390 lbs (battery is getting low). Add 15 ml oil and get 420 lbs.

So that all looks good.

The question of why my compression went up arises. Originally I was hoping (due to financial perspective) that this valve my be gummed up.

Maybe when that oil ignited it blew some crap off and I went from 250 lbs to 320 lbs.

I'm gonna check valve adjustment, if it's seating better I should have less clearance. If it's flush with no gap, I'll adjust, warm it up, and repeat dry and wet tests.

If not, I'm thinking I should run some type of cleaner through it. I have a half gallon of MMO. The older experienced gentlemen at the auto parts store says Lucas diesel cleaner is the best, which made me blush.

Does anyone have experience with this type of scenario? Ever get a motor from an old lady?

And once the best treatment to dump in my tank? With the way my valve seals are leaking I could put some in the oil too. 😂

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leathermang · #36 11-14-2014, 07:03 PM

Lucas, Is your life insurance paid up ?

Lucas · #37 11-14-2014, 07:15 PM

Quote:

Originally Posted by leathermang

Lucas, Is your life insurance paid up ?

Edit: Do not ignite oil in your motor to clean your valves. I got very lucky that nothing exploded. If you want to do something, put mystery oil in after the combustion stroke, re-install your injector, and turn it over as fast you can to force it up into your exhaust valve. Let it sit overnight to drain before starting.

lol. You've never ignited oil under compression? I have 15 foot leads on my remote starter trigger don't worry. I'm contemplating putting some MMO in and lighting it up.

I'm checking valve clearance hot which I'm not a fan of. However, FSM states exhaust 0.3mm cold and 0.35mm hot. If I shove hard I can get a 0.33mm in, so probably a little less.

Therefor, my gap closed up a little. Need to check it cold in the morning, and readjust.

I have MMO already, is the lucas stuff any better in the tank? Or another product?

I'll have everything for my bearings tomorrow, and I need to tackle that first. But I'm gonna do a treatement and rig my washer pump to a mister in my intake, get as many buddies as I can in, and find a hill.

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leathermang · #38 11-14-2014, 07:21 PM

If you were really ocd in the proper direction...
you would only set ... or check ... your valves when they are STONE COLD..
like overnight cold...
because of the variable in ' warmth ' and expansion you do not have a way to measure....

Lucas · #39 11-14-2014, 08:23 PM

Yeah I will. I noticed it changing as it cools. I had to check if it was closed up though. Then I realized there isn't a gigantic chunk in there.

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Lucas · #40 11-14-2014, 10:58 PM

At some point, I'll take out the laser tamp gauge and measure valve clearance difference with temp. That will be interesting.

I can publish results, but it will be application specific. Even in an original motor, there is a chance different parts will be from different batches. Due to density and specific gravity, they will all do something different. Gives you an idea which parts will fail first though, ie, softer metals.

Previous ride was a bmw bike with buckets and shims for valve clearance, removing two overhead cams for adjustment, so I get into getting it right the first time.

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t walgamuth · #41 11-15-2014, 07:42 AM

I doubt the oil combusted. YOu just filled up the combustion chamber,which is small to begin with and got a very high compression reading because of that.

Lucas · #42 11-15-2014, 11:02 AM

Good to know. I wondered about that. It acted like it fired but that could have been from the pressure. My gauge didn't have any oil in it. I'm surprised nothing broke. I'm doing bearings today, but am going to the junkyard to put together a water injection setup after. Maybe I'll get this thing cleaned up. I went with buying a Lucas brand cleaner, partly because now I have a 5.25 oz bottle I can fill with mystery oil and keep it in the car.

One option I'm weighing is setting #2 with exhaust valve open, locking the motor in gear and car blocked, adding some type of solvent, and pressurizing the cylinder with air to blow the solvent onto the valve. Of course, unbolt my exhaust and put a drain underneath. Should I be so bold as to put gas in there?

Disclaimer: Anyone reading this thread should not attempt anything I do on my accord. I will admit all this is slightly dangerous and may damage the motor, or myself. Never put gas in a diesel.

Lucas · #43 11-15-2014, 12:55 PM

I made long term build thread:

1970 220D in for the long haul

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Lucas · #44 12-09-2014, 04:56 PM

Alright please ease my cheap skate mind before I pull the trigger on the machine shop starting my new head.

I still have low compression on one cylinder. I have definite head gasket failure with coolant going missing, pressure in the radiator when cold, and oil seeping off the head.

The oil recently got a lot worse.

If head gasket failure was causing my low compression, wouldn't I have low compression on more than one cylinder?

Or could cylinder pressure go somewhere else?

I was hearing air coming out the exhaust manifold, and no bubbles in the radiator. Maybe I should double check for bubbles?

leathermang · #45 12-09-2014, 05:08 PM

Quote:

Originally Posted by Lucas

.......If head gasket failure was causing my low compression, wouldn't I have low compression on more than one cylinder?

Or could cylinder pressure go somewhere else?

I was hearing air coming out the exhaust manifold, and no bubbles in the radiator. Maybe I should double check for bubbles?

I think you have a burned exhaust valve....
pull the trigger on taking that head to a machinist....