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  #106  
Old 01-21-2018, 06:47 PM
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sorry so long to respond. I'm not that educated about turbocharging so I can't comment on the cams but I think I have seen a post or 2 on some forum somewhere about someone that turbocharged a 4.5. Early in my project I did some research on having pistons made and then looked for some off the shelf ones that were close enough to work. The closest I got were Buick Grand National pistons-they are about 97mm, close to the correct compression height (take off about .09" off the top to set the quench)but you would need custom rod small end bushings because the Buick pins are smaller-or machine the pistons for floating pins and use the Mercedes pins. They are actually ideal but for me it was easier to use the 5.6 pistons.
https://www.summitracing.com/nv/parts/slp-l2481f30/overview/?cm_mmc=pla-google-_-shopping-_-srese1-_-speed-pro
I would be happy if mine made 300HP-I don't think the heads are good for any more with the 1.75"/1.5" valves.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #107  
Old 01-21-2018, 10:20 PM
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Close to correct compression height for 5.0 or 5.6 stroke?
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  #108  
Old 01-22-2018, 12:35 AM
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5.6 stroke 94.8mm. I just did a little checking and the machine work to fit the Buick pistons to the Mercedes rods would be pretty expensive-rods rebuilt and rebushed with custom bushings. I'm going to take my chances with the 5.6 pistons.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #109  
Old 01-22-2018, 01:07 AM
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I just found these actually.
https://www.summitracing.com/parts/SLP-H522CP30

23.850 mm press fit pins. so a small bore to press the mercedes 24mm(Right?) pins

47.17mm(1.855) comp height
154.5 rod
+42.5 (half of 4.5/5.0L stroke)
_______
= 244.17 deck is 245 stock
+ .83 mm
___________
=245 deck

.83mm(.0326") under deck height. taking .030 off the deck is no problem for the intake i don't think. how about cam timing? but they are hypereutectic not forged. 200 for 6 of them so 270 for 8. meh. not sure its worth it. plus who knows what they cc at.
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  #110  
Old 01-23-2018, 09:54 PM
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just looking through some info and noticed that the m117 iron blocks have 52mm big end and 26 mm small end rods. Is that right? m119 and alloy m117 have 48mm and 24mm pin? i just had the crazy idea to run m119.960(tall deck CIS) flat top 48.5 compression height pistons and bottom end in a 4.5 block. what would compression ratio be? i guess valve cuts would be needed and maybe i could run 100ll avgas if its crazy high. I have a m119.960 with 4000 miles and a bad block deck surface. just a thought.
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  #111  
Old 01-25-2018, 11:20 PM
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I think with no dish the CR would be very high. If you were going to the expense of boring (it's a 3 stage process due to the large increase in bore to prevent distortion) you might want custom pistons. I went through 3 engines to get 8 good "1" size pistons and they still need the tops machined to get the correct compression height since the iron block is slightly shorter than the alum block.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #112  
Old 01-25-2018, 11:32 PM
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i did a little poking around and it would be like 12.66-1 figuring a 46cc head, 98mm headgasket bore( i assume its as big as the largest piston available)at .048 compressed thickness with -.5 deck height. if i could run e85 with kjet maybe but i dont think thats practical. turbo charging makes more sense really. or just convert to a rack and pinioin and put a m119 in it. Ugh, too many ideas and options.
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  #113  
Old 01-26-2018, 12:39 AM
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I'm sure you guys noticed that those Buick pistons come in sets of 6, so you'd need to get 2 sets. Or buy 4 sets and have enough for 3 V8s :-)
My cost is around $500 to have 4 custom pistons made, so likely 8 of them would be ~$1000.
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  #114  
Old 10-11-2018, 02:18 AM
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just revisiting some power increase ideas. my 450slc drift car is great. i beat the snot out of the stock 4.5 and haven't had any failures. i had a head gasket oil leak from the outside at one of the galleys i guess. swapped for a fresher long block while i had it out changing the clutch disc.i just pulled a 560 ex manifold and was shocked by how much bigger the ports are. so i started thinking about 5.6 heads ion the iron block again. bigger chamber is no good so im wondering about 4.2 heads. they have the same size intake valve but larger ex valve than stock 4.5 heads. im guessing the 5.6 inntake valve wont clear the 92mm bore. i want to know if they have smaller chambers than the 5.6 heads. i want to rebuild and port a set of heads this winter so im trying to start with the best option. i have 3.5 3.8 4.5 d and kjet and 5.6. i still have the turbo idea so thats why the 3.5 makes me think twice because of too high compression. i want to stick with a stock bottom end so if i do scatter it hopefully the heads are ok.

listen to the 4.5 with straight 2.25 pipes sing!!

https://www.youtube.com/watch?v=NjvNVXF8LsY
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  #115  
Old 10-11-2018, 12:19 PM
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I struggled and changed my mind many times on the cylinder head choice for my project. I obtained several different sets of heads(3.5, K-jet 4.5, 5.6) to study their compatibility and benefits. for me using the 4.5 K-jet heads makes the most sense for a basically stock engine. Even though the 5.6 heads can be made to fit it deviates too much from my original concept and the large chambers will net a low CR. I even considered having larger seats installed in the 4.5 heads but decided not worth the $$. One upgrade I am making is using the later 9mm stem exhaust valves. The later exhaust valve guides will fit the 4.5 heads and the valve head can be ground to the same diameter and margin of the original. There is no additional cost when rebuilding the head and the smaller stem should allow "some" additional flow.
Also if you use 3.5 heads you will have to use mechanical cams. I wanted to use hydraulic cams as I don't care for the extra maintenance and noisy valvetrain. I think the "easiest" way to increase power would be to stroke your 4.5 with a 5.6 crank and rods and have the piston tops machined for the proper height. that would provide a 5.0L engine with a higher CR. Your cylinders would need to be in good shape as the longer stroke will put the rings about 5mm higher in the cylinder so any taper would not be good. That was my original idea. But once I discovered the 4.5 block could be bored to 96.5mm I went with that.
I looked and noticed this thread is 6 years old. I may start making some progress again once we finish relocating. Presently parts of my coupe are in 3 locations.
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Last edited by Tony H; 10-11-2018 at 12:44 PM.
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  #116  
Old 10-13-2018, 03:38 AM
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The 5.0 long stroke doesn't make sense for my application. The long stroke small bore lends itself to lower rpm and I need power up top. I'm turning the 4.5 as high as 6700 rpm. It's using all the head can offer as far as I can tell. Ive thought of boreing and building a 5.0 liter iron block for better stroke bore ratio than a 5.6. I would rather give up a little power overall to have the heads let a smaller displacement engine rev higher. It's necessary drifting because I can't usuly grab another gear mid turn if I run out of rpm. I'm also a fan of the iron block durability. I was running really hot one event and I'm pretty sure it would have done bad things to an alloy bore engine. I'm going with the 5.6 cams and porting at least.
The 4.5 heads exhaust ports are so much smaller my idea of throwing the 5.6 manifolds on now would hurt flow I'm pretty sure plus they barely have the flange to seal. Looking at 4.2 heads there is an extra hump in there and smaller chamber around the smaller intake valve to increase compression over 5.6 heads.
So as far as fitting the alloy block heads what is involved? Is it just one of the cam stand /head bolts is off by .125"? Is it the one with the dowel pin around it or not? Would you redrill the head and stand or just the head and run iron block cam stands?
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  #117  
Old 10-13-2018, 08:49 PM
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It's mostly matching the coolant/oil passages (they are slightly offset) and redrilling the 5 long cam tower bolt holes in the head. The 5 aluminum block long cam tower bolts are slightly angled with respect of the block so they won't thread in. if you lay an aluminum block head gasket on the iron block you will see the difference. I think the cam towers will work without modification but insure the towers match the cams (there are 2 configurations)
The locating pins and the rest of the head bolts in the block match up with the alu block
heads.
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1971 280SE 3.5 Coupe(soon to be 5.6)
European Version
Manual transmission
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  #118  
Old Today, 02:04 AM
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have you ever looked at using 5.0 heads? im oping they have a smaller chamber. did you ever check if there is intake valve clearance for the large 5.0/5.6 valves in a 92mm bore?


(EDIT) just went through epc and the US 5.0 runs small 46.10mm intake valve seats like everthing (including 3.5/4.5) else but the larger exhaust at 42.1(3.5/4.5 40.10) like a 5.6. a 4.2 runs the same valves in a 92 mm bore so that will work. 5.6 has a 47.5 intake valve seat. 5.0 also runs the same cams as a euro 4.2. high power euro 5.0 has big valves like all 5.6. but all the 4.2 and 5.0 run the same cams. interesting. 4.2 say 232ps 5.0 265ps 5.6 300ps euro.

now i just looked and all 5.6 including ece 300ps engine and 242ps us engines run the same cams! so all the power differences have to be compression ratio. very interesting.

so still need to know if you ever checked clearance on the 5.6 head on a 92 mm bore.
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Last edited by rwd4evr; Today at 02:54 AM.
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