Project: Iron block 5.6 - Page 3 - PeachParts Mercedes-Benz Forum

Tony H · #31 11-18-2012, 12:29 AM

The last thing I need to hear right now is twin cam heads might fit a 4.5 block-I will never get my project finished:-) I have thought of seeing if 5.6 heads would fit a 4.5 block since they have larger ports and intake valves but they also have larger combustion chambers. If I had some flat top 5.6 pistons instead of the USA ones with the 30cc dish I might put more effort into checking it out. Even with 3.5 heads I will have about 9:0-1 cr after head gasket volume is considered. I could have the combustion chambers welded up on some 5.6 heads to increase the CR but the idea of my project is to build a engine with commonly available parts.

Quote:

Originally Posted by mercmad6.3

I have seen a alloy 380 engine with 3.5 iron block heads. Great performance too, but there are two bolts which are different so it wasn't really a bolt on fit. A set of 5.0 or 420 heads would work and work well because of the large (huge) port pockets.
The m119 is just a m117 with twin cam heads and a lot of bottom end parts interchange .
So..how about a 3.5 or 4.5 block with M119 heads....?

Re head gaskets, on my old Chrysler hemi (354 Cu.in with 13-1 compression) I had a set of solid copper gaskets made by cutting with a laser cutter. Very simple too, they simply used an old gasket set to get the coordinates and then cut the gaskets .It took about 1 hour and from memory was around $100.

Frank Reiner · #32 11-18-2012, 01:31 PM

Tony H.:

Please recall the head gasket pics that you posted. There are five bolt holes that are slightly relocated for the aluminum block engines (the third row up from the lower edge of the head). That relocation is the result of those five bolts being angled by 1deg.,52min. from perpendicular to the block surface.
Those are also the bolts that pass thru and hold down the cam towers. There appears to be sufficient metal (in the heads of the aluminum block engines) available to re-drill those five holes at 90 deg. to match the iron blocks, if one were of a mind to do so.

Why were those bolts relocated? To shift the stress distribution at the top edge of the cylinder bore, in an effort to minimize distortion of the bore caused by tightening the bolts.

Tony H · #33 11-18-2012, 11:59 PM

Thanks Frank-that's good info. I keep drifting off to thinking about trying to use 5.6 heads but I need to stick to my original plan of a simple to build engine. If I use alum block heads then my 3.5-4.5 accessories won’t fit (alternator, PS pump, etc.) and it starts to turn into a weird, hybrid engine instead of an iron block engine.
I have thought about porting my 3.5 heads to the same profile as the 5.6 heads. I will see how ambitious I get. I can always pull the heads later for work if I choose.

Frank Reiner · #34 11-19-2012, 05:05 PM

Tony H.:

Re: Pistons
Were I doing your engine project (I'm doing an uprated M116/420), I would be looking at pistons from the Ford 292 Y-block. They are flat top w/o valve notches. Std. bore 95.25, comp. height 44.70 (remove .040-.045"), piston pin .912" (steel sleeve in rod + OE style bronze bushing). Cast are available for under $250 for 8 with rings, forged for approx. $620. for 8 with custom crowns. If you were to determine that you have a considerable amount of wall thickness, oversizes are available; the limit would be the head gasket bore.

Tony H · #35 11-21-2012, 12:30 AM

I had calculated the CR around 9.0:1 but I plugged my numbers into several different CR calculators on the net and got about 9.88:1. Not sure where I went wrong. Maybe someone can check my results. Here are the specs
bore=96.5
stroke=94.8
head gasket thickness=1.24mm (.049")
deck height assumed 0
piston dish volume 30cc
combustion chamber volume 39cc with 3.5 heads
Thanks

Frank Reiner · #36 11-21-2012, 11:25 AM

Tony H.:

Using your volumes and gasket thickness, I get a total chamber volume of 78.16cc. Swept volume is 693.4. These yield a CR of 9.87.
If you add 4-5cc for clearance volume above the top ring and valve notches, the CR becomes 9.34. Etc., etc.

Head chamber volumes for the 116/117 aluminum engines are 44.75 and 55.8cc respectively.

I should think that the valve sizes of the 3.5 heads would be the limiting component, as well as the flow area around the valves that is associated with the small chamber.

Tony H · #37 11-22-2012, 10:03 AM

The 3.5 intake valves are only 2 mm smaller than 5.6 valves and the exhaust valves are the same so it shouldn't be too bad. There are no valve notches since the piston dish serves as the notch. the 3.5 heads really don't look that bad-here is a side by side comparison to a 4.5 head. It really creates a very compact combustion chamber with the piston being part of the
combustion chamber.

Tomguy · #38 11-22-2012, 10:59 AM

Tony, have you done a flow comparison between a 5.6 head & a 3.5 head? I'll bet the 5.6 head flows at least 20% more.

Tony H · #39 03-06-2013, 05:18 PM

Block went to the machine shop for boring today. The machinist is boing it tight so I can assemble the bottom end and check the deck height then it will go back for final honing and decking if necessary for the proper squish area. I will wait until the rods are back from being rebuilt to check since the rod length can change slightly when the big ends are resized. Hopefully my cylinders will not be the thickness of tin cans when I get it back! they are
.25" so they should be .167 after boring-still plenty thick.

Tony H · #40 04-18-2013, 03:20 PM

Got the rods back from being rebuilt (magged, resized, checked for straightness, side beams polished, static balanced, pin bushings checked)
The shop that did the work(A BMW tuning shop in So Cal) said they were the best stock rods he had seen in terms of strength and straightness. He said he wished BMW rods were this good. Block is being bored today. Should be able to assemble the bottom end without rings to check deck height this weekend.

Tony H · #41 05-15-2013, 12:23 AM

Finally got the block back from the machine shop today. Not much time to do anything with it other than put a piston in one of the cylinders to see how it fits. The machinist honed it tight (The piston was very snug) so I could more accurately measure the deck height without the piston rocking in the bore then back for final honing/decking if necessary to achieve .040" squish clearance. Hopefully this weekend I will have time to assemble the bottom end without rings to see where I am on deck height. Just feeling through the coolant passages I could barely discern any difference in cylinder wall thickness-it’s still plenty thick. My machinist thought it was not worth sonic testing due to the substantial remaining thickness. Pics to come.

vandor · #42 05-15-2013, 12:34 AM

What compression will that squish clearance give?

Csaba

Tony H · #43 05-15-2013, 05:40 PM

I have calculated a static CR of 10.0:1. That is using 3.5 heads and assuming a squish clearance of .040". There might be a small additional volume due to the fact the head gasket fire ring is larger than the cylinder bore. If I use K-jet 4.5 heads the CR is 9.25.1.

Frank Reiner · #44 05-15-2013, 07:37 PM

Tony H,

When you cite a squish clearance of .040, is that .040 below the block deck, or .040 below the head surface?

If it's .040 below the head, and the gasket is .045 (for example), then the piston will be .005 proud of the block.

Tony H · #45 05-15-2013, 11:49 PM

I think I will be looking for .009" out of the hole assuming head gasket thickness of .049".