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View Full Version : Kaboom: Time to Rebuild (Help Please)



JasonH
03-15-2003, 03:15 PM
After a year of hard use on the stock long-block I have finally blown a piston. I must admit that the catastrophic failure is not a huge surprise since the engine had 109,000 miles, and there were a few bad episodes of detonation during the past year of fun and experimenting at the track (one at 17+ psi of boost when the vacuum line to my wastegate snapped). I believe I must have developed a hotspot that finally let go, as the blowout happened at idle. :(

Anyhow, after considering several options (even some real crazy non-MB V8/Tranny swaps), I have decided to simply rebuild my engine, but upgrade it to produce & safely handle more power.

At this point, I know we will be doing a very light bore, adding some custom built aftermarket pistons that can handle waaay more HP than I’ll ever be dishing out, using total seal bearings, and making some needed improvements on the head. (CKlasse, I swear I’m not trying to compete with you ;)

I am hoping that some of you super-tech types (Jeff, Kleemann, etc.) can help me get some much needed information. I need to know what the stock 220 rods tolerance levels are. Can they safely handle 300hp, or will I need to use an aftermarket rod like a Crower? (CKlasse I believe you just ordered some Crowers right? You also are ordering some cams from them as well if I’m not mistaken. I may want to look at this as well. Any info on this would be much appreciated.)

In addition, what is the tolerance level of the crank itself? We are thinking that it should be fine at 300HP, but does anyone know how much HP it could safely handle?

Finally, I seem to remember someone saying that they actually had the shop manuals for w202. We could really use the information on the C220, 230, and 230K. Any chance you might be able to burn me a copy, email me PDF’s or whatever? I’d pay if necessary, but given how much this is going to put me in the hole, would prefer a gift of kindness.

TIA,
Jason

speedybenz
03-15-2003, 04:31 PM
Jason,

With a fresh piece of paper to start with I would for parts look at Forged pistons, Carillo rods, maybe Crower, new valves and valve springs. New rod and main bearings and new rings.

Look for a multi-piece steel head gasket. New head bolts or studs.

With an iron block I would also look at overboring and using larger pistons.

Plus if the crank rod journal diameters are larger than what is used on Honda's then I would have the crank rod journals offset ground to that smaller diameter both to increase the stroke but also to reduce friction.

Cams can be measured and a new grind can be deterimined based on other engine criteria. But for a Turbo motor you want ot keep duration similar but increase lift.

Jeff

JasonH
03-15-2003, 05:54 PM
Hi Jeff,

Thanks for the reply & the attempts to reach me via phone :cool:
I may call you to chat later.

While I am bummed about the breakdown, I'm also excited about the prospect of what I will have when I am done with the rebuild. This has also forced me to go off as far as building it for show as well, and doing that cosmetic stuff. I will have my valve cover, tubing, & manifolds (including the big throttle body u) all polished/repolished. Maybe some powdercoating as well.

We definatley intend to bore it... although not much. It's pretty thin between the cylinder walls as is. I can't remeber exactly how much we are taking it out, but it will still be a bit less than a 2.3L. At first we were considering dropping the compression to 9:1 like the Kompressor, but ultimately decided we will retain the 10:1.

Definately going with custom built forged pistons. Perhaps JE, but the guy doing the work has been using another brand (that eludes me at the moment) on several massive (800+HP) race cars and boats without no problems, so may go that route as they are cheaper than JE. Will also get the best rings possible.

All bearings top and bottom will be replaced with high quality "total seal" (I think is the brand name).

Still not sure about the rods though. I would really like to discover what the tolerance levels are of the stockers first. Yet I'm sure that we will find the need to replace those as well. I was thinking crower, just because CKlasse had already ordered some up, so build time may be quicker.

You throw out some interesting ideas regarding the crank. I'll have to run those thoughts by the guy doing the work.

Do you have any idea what the actual tolerance levels are for the stock rods & crank?

Any idea where I might find a multi-piece steel head gasket?

I guess the bottom line is that I want to do this right, but don't want to have to take out a second mortgage doing it ;)

Another factor is I would prefer not to have to wait 6 weeks before I'm rolling again.

Thanks,
Jason

speedybenz
03-15-2003, 06:49 PM
Jason,

I totally understand both the cost and time issues. But just a little extra of both can result in a motor that runs like a rocket and is reliable.

Cometic gaskets are who you want to talk to. Get valves that are undercut on the stems to reduce wt. Same with the pistons, before you order check the wt. and compare it to your stock pistons.

Rods cost money, but if there is any doubt get the good rods. If yours are usable and not too heavy, see about having them polished and then shot peened.

With a turbo you want Forged pistons not cast or hypertecnic (SP). The forged pistons are very tough and will stand up to minor detonation.

(This is Critical) Reduce the piston to head clearance to 0.035-0.040 inches. If you run this clearance any larger you risk poor combustion chamber burning and detonation, and any tighter you run the risk of having the piston hit the head.

Make your guy does a great job honing the bores. How the rings seal is where the power is maintained. You want a very smooth finish and you want the bores plateau honed.

Also if you reduce the cylinder head volume by milling the head, which is very good, you can then run a nice dished top piston which tend to make great power and are less prone to detonation.

The rod bearings should be set at approx. 0.0025" clearance and the crank main bearings at 0.002". But let me double check these numbers based on the crank journal diameters.

More later.

Jeff

JasonH
03-18-2003, 10:33 PM
For those interested, here are some pics of the carnage:

http://www.turbobenz.com/Ouch.htm

Enjoy :p

w202mae
03-20-2003, 12:43 AM
Did I see a crack hole in the piston :) At least the block is a solid deck design unlike the Honda. Looks like MBZ block is cast iron or cast aluminum?

Another thought, is the factory headgasket metal or carbon paper with center metal ring. I am just curious. :D

JasonH
03-24-2003, 04:00 PM
Block is cast, as far as I could tell, but I'll have to check again to be sure.

MB uses the composite head gaskets with steel rings around the pistons as stock on the C class cars. However, I am researching other options.

Jason

Under Pressure
03-25-2003, 03:34 PM
Man, you have a good attitude. If my engine popped I would be fired up. I hope Koolvin looks at this and considers running at no more than 6.5psi on the turbo'd C180.

JasonH
03-26-2003, 02:10 PM
Don't get me wrong, I was far from happy when I lost the piston. The reaction was more like @$#%, and then... :eek:

However, I'm always one to try to make lemonade out of lemons (in this case very expensive lemons) ;)

Jason