Quick overview of my project. I got my self a $500 beater 93' 300se and and am turuning it into my thrashmobile, tire melting, drift thing... Becuase race car.
I'm in the middle of a serious rebuild/overhaul, im gonna keep this engine long after the shell itself is gone.
Im boring out the engine cuz more displacement = more unicorns.
this leads me to my current dilehma, oversized pistons. I can have pistons made my a very reputable shop near by, but before I commit to ~$250 ea I want to see if i can find any that will work. I've seen that certain Honda parts can work, ie. con rods.
But im having trouble finding pistons themselfs. Anyone know where i can source pistons?
Thanks!

You do not want to bore it out. It just leads to headgasket problems. If you want more displacement then get a 3.6 crank and stroke it. But leave the bore.

hm, ok. I still need to source a new set of pistons that will lower the compression for the turbo. Do you know of anything off the top of your head that will drop in? I've been combing through this forum looking but haven't had any luck yet.
Also I am well aware of the m104 head gasket issues and was thinking of going with a copper or MLS head gasket

I use CP pistons. I have a profile on them but they are not cheap. So no I do not know of any thing else. There was a guy talking about honda rods or something a while back but that is not my thing. You could also have the stock pistons machined for lower compression. But I would go with forged pistons if you are planning on a lot of boost. But you could gap the rings and if your tune was good make 500+hp on stock pistons. Kind of depends on your goals. But everything behind the engine will be toast in short order.

Thanks man. What do the CP pistons typically run you? I have a fairly large budget for this build so custom parts are not out of the question. The pistons I have are toast, parts played ping pong when the last guy tried to replace the head gasket before I got it. So i'm looking for somethig durable, my plan is to overbuild the engine and then run something 3/4 its potential so that I dont have to rebuild it for a while.

I would have to double check. It has been a long time since I ordered a set. But I think it is around 250 each. For the pistons with rings and pins. No coatings.

I'm In the same boat. I found a diesel crank and spare M104 block for cheap. My plan was to use the honda H22a rods that were mentioned in this thread http://www.peachparts.com/shopforum/performance-paddock/284473-useful-3-2l-m104-specs-using-honda-connecting-rods-6.html.

The gist of what I got from the thread is that the stock rods were too long from all the M104 blocks (Besides the C36 clearly). A member posted saying with this set up on stock piston that you would have piston knock caused by a high rod angle. This was due to the rod pin insertion position on the piston. Supposedly the insertion point needs to be raised. he came to this conclusion because on the C36 pistons it is raised to the point of touching the first ring.

I never saw a definitive answer on how to build one. I still want to know can I run the H22a rods with stock designed forged pistons? and will my compression ration be 8.8/1 like the OP of that thread stated?

The reason I want to do this is because I planned on building my M104 and having finding this crank for less than 100 and a spare block the same time was very convenient. I would want the crank balanced and knife edged. My goal is to rev to 8500-9000 if possible on boost. My goal would be a reliable 600whp compound turbo setup up with a flat torque curve

I can't find any cams besides these Mercedes 2,8 - 3,2 6Zyl. 24 V ( M 104 ) /Auslass Sportnockenwelle - dbilas dynamic Which aren't very aggressive.

What crank did you find? Unless it is a 3.5l diesel for the stroke there is no advantage. They all shared cranks. There are a few different strokes. The 3.0l, 3.2l, and 2.8l. But they are all the same strength.
As far as other pistons and rods that fit that thread was the only one anyone around here has tried anything like that. And if your goal is to drop compression by a shorter rod then you will run into issues hitting the crank. etc. etc. Just get custom lower compression pistons.
And as ar as spinning to those rpms you have a lot of work ahead of you. The platform is capable of it but you are not going to do it on a budget. I know a guy that does bonneville with one and he has over 250k tied up in a n/a m104 to run those rpms for just a couple of minutes at a time.
THe head will choke big time well before that and it requires major machining and custom part up the wazoo to make it breath at those rpms and oiling becomes a huge issue. Shorter stroke, etc. etc. etc. Pretty much you name it and you can not spin it that fast stock.

Awesome! Thanks for the reply whipplem104!!! Yeah its a 3.5, I'm still yanking it off at the salvage yard. Pulling the crank with the engine in the car is a *****, but I'm getting it done..


I think with mild head work and cams with forced induction, it should flow fine to 8500;

I had my G35 (vQ35HR) Sedan running a extremely flat torque curve from 3500-8200 Stock Cams Custom Gt35 kit.
I know it's a totally different motor, but 8500 seems very doable on a twin cam straight 6.

Now as for the piston and rod set up. You are saying not to run H22 rods. I should stick to stock rod length? I thought someone posted something about rod angle issues and possible causing piston slap... I could be wrong though. You believe running stock length rods with just low compression pistons would be fine? How would I calculate compression ratio with a stroked motor...

This is the thread I'm talking about.
http://www.peachparts.com/shopforum/performance-paddock/284473-useful-3-2l-m104-specs-using-honda-connecting-rods.html

The OP says running H22 rod with stock 280 Pistons would put him at a 8.8 CR. was there and issue with doing that. Isn't the reasoning for milling the crank to clear the pistons?


Thanks for the advice

I'm just gonna build this motor on the side. I found it randomly after reading that thread and though I should scoop it. I'm getting a m104.998 block with a blown head

I'm Freshening up the wagon so Ive been taking videos and pictures of the "build"
https://www.youtube.com/watch?v=wvAI1odluRE

I am saying if you want to run those kinds of rpms you better do your home work. You are taking a already long stroke engine and making it a longer stroke and then wanting to rev it to the moon. And on top of that wanting to throw some boost on it.
And as far as the head goes. It is not going to flow at those high rpms. It will choke out and also you will have to go solid lifters because they will definitely not work. Valve springs most likely.
Look at the lift and duration on these motors. They are relatively mild lift. And not much can be done without dumping a lot of money into the head. Really around 10-10.5mm of lift is it before valve springs, lifter buckets, and the head has to be machined for clearance. etc etc. etc. After a drop in Camshaft is maxed out the next step is around 7-10k. I have talked to several machine shops and cam companies about all of this. YOu can also find flow data on the heads. I think some of it is posted on this forum.
Do not get me wrong I am not saying your power and rpm goals are impossible. Just I would go about it differently. Well maybe the combination is impossible. But I would use a short stroke 2.8 motor and boost that. I think that 600hp is probably around 20-30 psi of boost and your limiting factor is going to be getting the air through the head at high rpms.
You still have to have the crank modified and bearings and oil supply and control to spin those rpms. Electric water pump most likely. The list goes on.

whipplem104, do you know how much hp stock rods can handle? i'm getting some CP pistons made and want to match a set of high quality rods to them, but if the stock rods will work ill leave them.

I do not know the safe limits for sure but I would say probably around 600 lb/ft of torque. But I do not know for sure. I have been making over 500lb/ft for years with no problem and low end torque is what will wipe them out. High rpm will also destroy them but separate issues.

Thanks man. This build is not gonna run crazy high rpm, it will be very close to stock so i doubt I will have any problems.

Whipplem104, again I'm calling for some of your experience! What do you use for valve springs with a performance top end build? I have been scouring the interned and so far ordered 2 sets of springs that wont work.

Thanks

Stock springs.
They are good enough for anything you are going to throw at it. Again if you hit a problem with the valve springs then you have already passed the point of caring about cost.