percedes - PeachParts Mercedes-Benz Forum

larry perkins · #1 08-14-2007, 07:07 PM

ok guys,are you ready for this.
some years ago my co,perkins scale corp,redesigned a toledo scale and we had to rename it so it got called a perledo.
now i have to rename a mercedes engine,according to my calculations i now am making a 3.283 liter engine ,this is a 3.5 liter with 3.5 crank,3.5 rods and a 3.0 piston. the complete objective was to prove that a 3.5 engine block could be saved and have replacable sleeves which should give it a life span far beyond mine. mercedes says you have to replace the block when wear limits are exceeded.
so i was thinking percedes would be a start,what do you think?make suggestions.
larry perkins lou ky 103 old cars.
ps did i come close to calculating the displacement right?

#2 08-14-2007, 08:59 PM

You will have to actually measure it.

sixto · #3 08-14-2007, 10:11 PM

Do the 3.0 and 3.5 pistons have the same crown height (wrist pin centerline to top of piston)? If not you'll either have insufficient compression or send the piston through the head.

Sixto
87 300D

sixto · #4 08-14-2007, 10:14 PM

The 3.5 rod has more swing than the 3.0 rod. Make sure it doesn't smack the tighter 3.0 bore in the 90* A/BTDC zone.

t walgamuth · #5 08-14-2007, 10:17 PM

displacement sounds about right. it ought to be a torquey thing!

Best of luck.

I wondered what you were headed for with all your ruminating on the 3.5 motor.

Tom W

#6 08-14-2007, 10:20 PM

Make sure the 3.0 pistons weigh the same as the 3.5 pistons, I doubt they do. If they don't then engine will vibrate itself apart.

deerefanatic · #7 08-14-2007, 10:43 PM

Why? As long as all 6 are the same weight, they should balance out? Light weight forged pistons are a common aftermarket performance product for g@ssers...

#8 08-14-2007, 11:08 PM

The crankshaft has counterweights to offset an exact piston and rod weight.

deerefanatic · #9 08-14-2007, 11:30 PM

Hmm...... maybe hafta have a weld shop ad some weight to em.....

larry perkins · #10 08-15-2007, 07:26 AM

in ref to the rod and piston weight,i should have made a note for the exact weight while rebuilding some of the earlier 3.5 engines but i know for sure that the replacement rods sold by mercedes do weigh more than the origional benders. i will post exact weights of both rods later.will also weigh both pistons and post(87mm and 89mm)
its a good point,i havent had any of the 4 that i have completed at red line but at the normal running range(1800 rpm for me they really run smooth)just kidding,we all need a chuckle. they are smooth though.
keep the suggestions coming.
larry perkins

t walgamuth · #11 08-15-2007, 07:40 AM

I was of the opinion that the counterweights mainly balance the crank unto itself. The weight of the rods and pistons balance each other, mainly, I think, and they want to be the same weight too.

I matched the pistons on my fifty one caddy using a paint scale and the drill press at my favorite machinist's shop. You just take the lightest piston and remove material on the others til they match. There is a place on the piston for it.

I don't know though, not being an expert on the subject. I will ask my favorite machinist.

Tom W

vstech · #12 08-15-2007, 08:51 AM

t, yes all the piston/rod combo's need to be balanced, but that is so the counterweights they bolt onto each throw can be the same for balancing. the crank is balanced so the entire reciprocating weight is equal. that is throw with piston and rod to counterweight.

vstech · #13 08-15-2007, 08:55 AM

I don't think this engine can be built... what are you going to do? put 3.0 sleves into a 3.5 block? or are you putting 3.5 crank/rod into a 3.0 block with 3.0 piston? it does not sound plausible. I will be amazed if MB created a motor that can swap these parts.

vstech · #14 08-15-2007, 08:56 AM

oh, and if it works...
how about...
Merkedes?

larry perkins · #15 08-15-2007, 10:09 AM

tom, yep been doing the research on the 3.5,one of the reasons i was trying to get a donor block that wasnt useable was to experiment on and not possible trash one that could possible be used again.
couldnt get any one who was interested enough to donate of charge a reasonable amt.
i am waiting on a counter bore bit so if anyone has a old block give me a shout.
larry perkins lou ky