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  #1  
Old 06-26-2006, 07:39 PM
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'76 117 motor under '84 116 heads ????

Needing help from "Been there done that" types....

I blew up a customers 116 motor on Saturday. ....it let go at 5200 rpm.
Was tracing a slight tapping noise that would go away when running engine without #3 followers installed.

Threw #3 rod through the coolant jacket !
This was an engine he got me that I took apart and rebuilt, so it's down to me.
Shoulda stuck with my first gut feeling of pending problems of water damaged steel components...like rod bolts..... but they all checked clean and thicker than spec'.

Anyweather......he said he's like a 117 motor now that the 116 has broke.
I have ( two.)117 short blocks ( MPI.) of 1976/8 vintage, but the heads are gone .

Can we marry this 117 block to 116 heads ?
If not...I'll have to find a 116 block.


.

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  #2  
Old 06-26-2006, 07:57 PM
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I don't know man. The 76 is a cast iron block and the 84 is aluminum. One is a 4.5 and the other is a 3.8 or possibly 5.0. They are both CIS. You have to be sure that water jacket oppenings match up. The heads may produce different compression ratios. It will take a lot of thought. Good luck.
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Old 06-26-2006, 08:15 PM
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I've thought of this before in search of boosting compression for a 4.5 for more performance.

m116 heads WILL fit an m117. I have 3.5 heads on my 4.5.

BUT aluminum block heads ARE NOT interchangeable with cast iron block heads. They have different head bolt angles and will NOT bolt on.

Your m116 heads will probably fit on any aluminum-block m116 or m117. Be aware that 3.8 heads on a 5.6 will have much smaller valves, but much higher compression. Might be an interesting experiment. I haven't checked it out but I would imagine 4.2 heads on a 5.0 would produce something similar to the effect that the 3.5 heads did on my 4.5.
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Old 06-26-2006, 08:22 PM
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Well....ONE engine is an iron block 117, the other turned out to be an iron block 116.

The 117 block numbers are : 117 983 12 040139.

Sure does look awful close to idenmeanical though...but knowing how that goes, it prolly won't work.


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Old 06-26-2006, 08:37 PM
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Whooopppeeeeeeeeeee.....just uncovered a M-116 alloy block....!
I wonder if the 117 iron block crank will fit the 116 alloy block ?
Both engines use a bore of 92.0mm...the stroke of the 116 is 65.8mm as opposed to 85.0mm of the 117.

My machine book gives the 350/380 and 450 engine cranks, the same journal sizes. Trouble is the rods are listed as same...how can that be, without different pistons ?


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Old 06-26-2006, 08:47 PM
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You said the 116 is an '84. That'd be aluminum. The 117 at '76 was cast iron.

As I said, cast and aluminum heads are NOT interchangeable!

3.5's and 4.5's have different pistons. 4.5 pistons are flat and don't reach the deck of the block. 3.5 pistons do, and are recessed for the valves on some and have small center cutouts on the others. The major difference is the crank - a 4.5's crank has longer travel to cover the longer block.

A m117 crank will not work in a m116 block because the pistons would be pushing out WAY too far above the deck.

If you have an iron-block m117 with no heads and an iron block 3.5 with good heads, do the swap. A lot of people think the 3.5 has more power, but it's the way it's geared and actually has less torque, though about the same HP. If you put 3.5 heads on a 4.5, you get more power than US 560's had stock I believe.
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  #7  
Old 06-26-2006, 09:29 PM
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I DO have a iron block m-117 with no heads, but a m-116 iron block motor with heads..So...fit the 350 heads to the 1976 117 iron block, yes?

What do you suppose the C/R might be ? The 117 is listed as having 8.0 to 1 ratio and the 116 as 9.3 to 1 .
Book reads 116 engine heads having 15.8 mm deep combustion chambers.
117's have 17.85mm deep.....that's quite a few less cc's if the 117 pistons are flat top.

Then there's the intake manifold....the 117 has to be wider between the intakes of the cylinder heads if the 117 block is taller.....what intake did you use?

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Old 06-26-2006, 11:07 PM
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I used 3.5 heads on my 4.5. They were a straight swap. Used the m117's manifolds of course - a 3.5 has the same exhausts I believe, but a narrower intake and a smaller diameter throttle body and no idle air circuit. I measured ONE cylinder (#6) for compression after this and got 145PSI, or about 9.9:1 compression ratio. I am assuming it's 10:1 and I have some compression loss in my cylinders (it might even be more, my block has 145K on the original bottom end). It drastically increases the top-end power as well as off-the line power (which I missed at first due to a misadjusted mechanical advance I fixed last week).

Only problem might be: The 3.5 heads were for D-Jet EFI, the 4.5 block you have was a K-Jet and your setup for it (if you have it) is K-Jet. You might need to search around for the correct O-rings or whatever to secure the K-Jet injectors, I don't know the difference between them and D-Jet ones at the base.
EVERYTHING about the 3.5 heads is identical to the 4.5's except the combustion chamber. See my adventures here:

Got the 3.5 heads, think I'm good to go!
My headjob is in progress!

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