m117 4.5 block measurement

[mercmad6.3]

I wouldn't bother removing the coating ,millions of cars were fitted with cast iron pistons in the era before 1950.
The squish clearance should be where you focus your attention. A clearance of .030 minimum is required and you need a used compressed head gasket and lump of plastecine on top of the piston to measure it .
A big clearance promotes preignition with todays fuel so get it as close as you can. A few years ago i built a Chevy engine and I had to remove 040 off the block decks to get the clearance closed up.
I would be using the 3.5 euro heads to take advantage of the smaller combustion chamber too.
Dont try and skim the piston crowns,they are very thin on top and any material removed will cause the pistons to heat up leading to failure.
Are the 560 rods bored for pin oiling? .If not,consider getting them drilled like a 3.5 rod for a bit of reliability.
And will the 560 oil pump fit?

[GGR]

These 4.5 pistons are scooped in the center. Shaving the top will only remove material off the perimeter. Will this create a heating problem? I'm asking because I want to stroke my early 5.0 into a 5.6 and my plan was to reuse the 5.0 pistons and shave the top of them to get a 10:1 CR.

[mercmad6.3]

The middle of the pistons is only 3.5 mm thick .I am sure it is a bit too thin to go shaving the edges of the crowns.
Get and old piston and cut it in half and see how thick they are at the edge. With oil cooling benefits of the drilled rods,the pistons are cooled when driving so the original lack of crown thickness is not a problem . I may have one here I can cut I think.

[Tony H]

Thanks for your input Ron-I appreciate it. Not sure which route I will go at this point-just stroking and using the cut-down 4.5 pistons or boring and stroking. The 5.6 rods are drilled for pin oiling just like the 4.5 ones. The dished 4.5 pistons have a 9mm dish so I will not be anywhere near the crown if I take off 5mm and it will still leave a 4mm dish+ plenty of room for valve notches. I plan on using K-jet heads because they are flat and not recessed like D-jet heads so I can get a proper squish area. The piston coating comes right off so no big deal if I end up using the 5.6 pistons. If I use 3.5 heads my CR will be too high due to the smaller combustion chamber+ I don’t want to rob my 3.5 of any parts. The K-jet heads have a very similar combustion chamber but slightly larger.
If I go the 560 piston route I will end up with the same deck height as if they were in the 560 block(whatever that was). I think there might be offset wrist pin bushings for fine tuning deck height.
I'm not trying to build a high $ race engine-I'm just trying to go for as much displacement as I can with stock parts and some machining plus I think it's kind of cool to build an engine like this.

[Tony H]

During my search for piston rings that fit the 5.6 pistons and are compatible with a iron block I came across Deves and found their 5.6 rings are cast iron alloy-the same alloy used in the iron block piston rings. So I would think they would work. Any opinion on Deves?

[bwostosh]

They have been doing rings for a long time.
Call their tech guys for advice.
I use them.

[Tony H]

Thanks Brian-I did talk to them are was told the rings will work no problem.
I keep going back and forth on how to proceed (to bore or not to bore)but I think I will get the block sonic tested to insure I can safely have it bored to 96.5mm.
Afer doing some calculations I think I will need to use 3.5 heads to get a decent CR as the 5.6 pistons have a 30cc dish.
Anyone have some 3.5 heads they want to sell? I want to keep my original 3.5 intact.

[Tony H]

Originally Posted by mercmad6.3

I wouldn't bother removing the coating ,millions of cars were fitted with cast iron pistons in the era before 1950.

Turns out I was not removing the coating, only polishing it. After doing a bit of research what Ron said makes sense. So why could I not use iron coated pistons in a iron block? It is not really iron but some kind of alloy as a hard drive magnet(the most powerfull magnet at my disposal) barely sticks to it and muriatic acid had no effect on it. I know that running alum pistons in a alum block is not good.

[GGR]

I know someone here in DC that has a complete 3.5 K-jet engine. He may be wwilling to sell the heads if you're still interested. I think the K-jet heads have deeper recesss for the injectors. I had to grind the fixing points on the D-jet intake madifold to fit the D-jet injectors on the 5.0 heads.

[cth350]

Tony,

How's the hand?

Those 3.5 heads I have need guides and milling. My machinist will do the labor for 275$ per head, presuming we supply him with Benz guides, not the after-market TRW ones. He like the Benz supplied guides because they have a better profile for than the others (better lip sealing apparently).

-CTH

[Tony H]

Hand is good-thanks. After mic'ing the block and pistons and finding them within spec I decided to just stroke and use the 92mm pistons. To get the squish area around .050” the piston projection will be a calculated value of .25” or .635mm assuming a head gasket thickness of .075” but that is a new, uncompressed gasket. Anyone know what the thickness of a used head gasket is?

[bwostosh]

Measures with digital calipers across the steel combustion chamber rings

Used measures .072-.073 both 4.5 and 6.3 head gaskets

New 4.5 gasket measures .073 also

Not much "crush" ?

Is there supposed to be?

[Tony H]

Thanks Brian. I was under the impression head gaskets "crushed" a certain amount and that amount needed to be considered when setting up the squish area.

[bwostosh]

That is strange the lack of dimensional change.

I pulled a head from a fresh valve job on a pick a part yard and my buddy looked at the head gasket (perfectly clean) said he would re-use it again.
I don't know if I would ?
The old style embossed soft steel as used on old detroit iron, really did crush.
The sandwich construction types are different.

Yes, I do save old gaskets to digitize and maybe someday
have them cut from solid soft copper on the waterjet.
As the hot rod motors have done.
( clarkcopperheadgaskets.com )
I called them and they have .073 thickness and will cut to my DXF files.

[Tony H]

When I was thinking about boring to 96.5 it would have needed custom head gaskets and I did a bit of research. Copper seemed good but also seemed prone to leakage if the head was not o-ringed. I think the MLS gaskets would be a better choice. Cometic MLS Gaskets, Multi-layer Stainless Steel Custom Head gaskets ON Sale They will make custom gaskets.
I will go with .073 as my final head gasket thickness.
From what I have read unless you are a real pro .050 is the min squish area to consider.