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My 4.3L V8 swap

143K views 541 replies 63 participants last post by  Turdo2 
#1 · (Edited by Moderator)
I guess i will begin by saying Hello to the SLK community.. i've been sitting in the corner over here watching everyone else for quite sometime, and now i finally have something meaningful to post about. I usually am working on everyone else vehicles and until recently haven't had much time to do my own stuff. but its been building up, and now i have something truly special to work on.

anyways, last July, my SLK230 became my second car. its been my daily for almost 4 years and has been remarkably reliable... until last fall a head gasket started to leak externally, the A/C quit working and the car has slowly felt more and more lazy and tired. still, this car has been there when i needed it most, and I wanted to do something to bring it back up to snuff. since then i've been looking at the Kleeman Supercharger kit but couldn't bring myself to spending nearly a grand on the kit for what i would call "so-so" performance gains.

so about 3 weeks ago i was browsing Craigslist and found a 4.3 V8 from a CLK. it came with the ECU, transmission and harnass - which basically is everything mechanically. i haven't really thought about putting a V8 in the ole girl, but after doing a little bit of research and parts comparisons, i began to realize that this is feasible.



on to the build! i spent a couple of weeks freshening up the V8, as you'll see in the pictures i did a little painting and cleaning.

Currently i'm one week in on the build. last Saturday i pulled the old unit and was able to test fit the V8 and found the first problem was that the SLK A/C lines wouldnt fit around the exhaust of the V8, requiring me to use the lines that came with the V8. the second, and biggest issue, was that the steering box was severely in the way!



at this point, i pulled it back out and started to think about solutions.
 

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#2 · (Edited by Moderator)
day 2..

so update number 2.

i removed the A/C compressor, lines and Left exhaust manifold and decided to do another test fit.



after looking at the V6 exhaust manifolds, it looks as though they have a curl near the back of the manifold that looks like it may avoid the steering box.. then i found an image of a crossfire engine bay and noticed that the steering boxes on those (as well as SLK320's) was about 2" lower on the car. I believe in 1999, the SLK only had the 4 cylinder and i believe this is why they had yet to lower the steering box which is why i'm having a clearance issue.

at this point i realized that the V6 manifold that i bought to modify to fit the V8 wouldn't fit either, unless the box was moved.
 

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#3 · (Edited by Moderator)
day 3

so an update as of tonight 2/23.. i got the trans back in the car. i'm using the V8 trans for 2 reasons. 1: the bolt pattern on the bell housing is different between the 230 and 430, and 2: the 230 trans was feeling very lazy and shifted hard when cold. This saturday i will be grabbing the rack & pinion from an E320 and am going to fab some brackets and attach it to the car. this should solve the last of the interference issues i have. people who have swapped V8's into V6 cars or Crossfires need not do this as the steering box is mounted lower down on the frame rail.

so now that i have some time, i'll clear the air on a few details because someone may want to know this. My SLK is a 1999 with the sport package and AMG wheels. the engine came from a 1999 CLK430, and it had 150,XXX miles and i got to see it run and even do a burnout before the engine was pulled from the car. the car had been T-boned. i was able to grab the engine/trans/ecu for $350. i have compression checked the engine, as well as used a scope to check everything out internally. to be honest, ive never seen such clean cylinder walls on a used engine! i also believe in "If it aint broke, dont fix it" which is why i didn't do a complete rebuild. i painted the valve covers red in homage to the red "kompressor" strip on the old engine. note: i had to make custom engine mounts that may not be required on SLK's that came with the V6... the V8 mounts were 3" too wide, and 2" too far back. i'll take a picture next time i'm in the shop.

the 4.3 is a good engine to try this swap on for a couple of reasons. the first is that it isn't an extreme amount of HP, and i can make sure that nothing gets torn up prematurely. the second is because it shares underpinnings with the 500 and 55 engines, which may come at a later time. the third is that the 4.3 has a lower compression ratio than the N/A 500 engine, which may play well later on down the line with a Kompressor upgrade. don't quote me on that!

until next time. have another picture:
 

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#9 ·
I wish I could do that kind of engineering. I'm stuck with thinking in the box, which is hard enough for me...:surprise:
Or hunting scwewey wabbits:grin: You can do anything you want if you have the time and patience to do the research that goes along with it (plenty of info and support out there). There is a solution to any problem, that is part of the challenge and it is greatly satisfying when you find the solution. For me its a matter of motivation or how interested I am in something, if its there I'll go for it successful or not.
 
#8 ·
Y):hb: Awesome, gonna be my favorite channel! Nothing like a mechanically inclined individual with ball bearings of stainless steel to take on a beast project>:D. Your inspiration to create beast from beauty is surely to be an infectious thought for me. This looks to be a fairly reasonable and relatively inexpensive project, hope it turns out really well. May just find me an old beauty to transform, preferably an R171 body.
 
#10 ·
This conversion has been in the back of my mind for ages , it should make for a good little car , I'm guessing a 320 would be an easier starting point but you already had the 230 so that's the way it goes . The steering rack conversion should improve the car a lot regardless of the engine swap !
I'm ok with the stripping out , fabricating mounts and re fitting but electrics have always been my problem, I just can't get my head around them . When I swapped rover v8 engines into a couple of older fords there were only ever a few wires to swap about to get it to fire up , invariably twisted together and taped up :surprise: I wouldn't know where to start with a modern wiring harness , sensors and ecu .
I'll watch this thread with interest .
Good luck
 
#12 ·
so, back in my thinking box

and I'm thinking that you will have to uprate the front springs a bit,and probably the shockers as well. that luvli V8 and gearbox has to weigh a fair bit more than the 230 kit you took out. and you'll probably need a bigger radiator, as all those extra horses are going to warm things up a bit under the bonnet. and then you might want to do up the brakes as well.

what's the extra weight factor you are lookng at?:nerd:

P.S, I don't fancy doing 16 sparking plugs on that with my back.:wink:
 
#13 ·
and I'm thinking that you will have to uprate the front springs a bit,and probably the shockers as well. that luvli V8 and gearbox has to weigh a fair bit more than the 230 kit you took out. and you'll probably need a bigger radiator, as all those extra horses are going to warm things up a bit under the bonnet. and then you might want to do up the brakes as well.

what's the extra weight factor you are lookng at?:nerd:

P.S, I don't fancy doing 16 sparking plugs on that with my back.:wink:
i dont ever fancy buying 16 spark plugs :surprise:

i'm estimating it will be about 100 lbs extra. max. there are a couple of things to consider as far as weight goes. the first being the 2.3 is smaller, yet it had a supercharger bolted to it, as well as all the piping, and the 2.3 is also a steel block compared to the 4.3 being aluminum. i'm saving some weight by removing the intercooler and replacing the old rolling ball steering setup with a normal rack and pinion. that rolling ball gearbox has to weigh 25 lbs alone!

as far as cooling goes, a supercharged engine requires a good amount of cooling capacity. it also looks as if the intercooler covers roughly 40% of the radiator, and not having that heat exchange in front of the radiator will definitely improve airflow. at this point, i'm going to run it with the current radiator and see how it handles daily driving, and maybe even some autocross in the hot Kansas summer.
 
#14 ·
there must be some fancy equation we can invoke

to work out the cooling issues ,if they ever become issues, but in the meantime an easy stab at it would be to compare the sizes of the two respective rads. I'll bet there isn't much difference. another thing would be water pump delivery rates. If the pump rates are similar, then I'd guess the rad qualities will be similar and the heat output would be similar as well.

I definitely tip my hat to you Sir. and the chap at benzworld who put a V12 6.0 in his r107.:grin:
 
#16 · (Edited by Moderator)
Update: 2/25/17:

Thank you everyone for the kind words!

didn't get much done on the SLK today unfortunately. I was planning on grabbing a steering rack this morning, but got tied up with a close friend who needed help rescuing a couple of '65 Chrysler 300's. fortunately LKQ wrecking yards are open on Sunday so I will go pull one first thing tomorrow (sunday the 25th). the car i will be pulling it from is a 2001 E430, but the LKQ in Wichita has 3 more E320's and an S430 if I need anything pressing. Unfortunately this E430 is missing the key, otherwise i would grab the ECU/immobilizer/key from it and have my electronics figured out. this could still be an option if someone knows if i can have new keys programmed to the ECU and immobilizer. It would be the new style "key" where its just a piece of plastic that you put inside of your ignition hole (clean thoughts), maybe someone has some experience having those keys made?

from what I've researched, i will also need an E430 diff with the correct ratio or the ECU will put the car in safe mode when it detects that the vehicle speed isnt matching what it thinks the speed should be (based on pre-programmed gear ratio calculations).

so after i get the steering rack and engine in, i'm an ECU/immobilizer/key and Diff away from having a nearly-factory running SLK430. R):burnout: (anyone have a parts car???)

how about some pictures:

did some cleaning


one of the 300's
 

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#17 · (Edited by Moderator)
back to the exhaust..... real quick!

so as far as the exhaust goes, I did a fit up of the V6 manifolds I ordered. IT STILL HIT THE STEERING BOX!!! :soap: the engine was about 1.5" lower than before, but the box was keeping it from leaning back. My thought is that i would of cut the V8 one in half and welded the front half of it onto the rear 2 of the V6 manifold, however, with the rack and pinion steering i wont need the up-sweep in the back of the manifold for clearance. I like that it has the O2 bung in it but that isn't necessary. the upstream O2 bungs can be welded in further down stream as long as they are before the cats. It also looks like the V8 manifold will flow better.



i found my immobilizer (passenger foot well)
 

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#33 · (Edited by Moderator)
it looks like a still-shot from a health and safety at work film.:nerd:
if that's a 430, why not snag the rad as well, in case you need it later.
Thought about it.... the lower middle has a gouge that scares me... however it does not seem to be leaking. I took a couple of pictures of the ends of the radiator in proportion to the engine because i forgot my tape measure. i have yet to compare it to the SLK. it looks like the physical ends of the evaporative section are the same width as the engine + manifolds.

 

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#23 ·
Excellent project and kudos for carrying-out this challenging project. Please keep the photos coming, and if possible 'a nice video' of the completion to hear and see this wonderful transformation of your SLK....:tu:
 
#24 · (Edited by Moderator)
update 2/28/17

The first hour or so of work last night involved locating the steering rack and seeing how it clears with the engine in place. I learned a couple of things.

1. In order to clear the engine, the steering rack would have to mount so low that the inner tie rod knuckle interferes with the lower control arm... it looks like i will be torching a channel into them and then bracing them with some extra steel.

2. since this is the first time the engine has been in without hitting the steering box, it finally sat low enough to take note on how the exhaust will have to run.... and it's not pretty. i will need to modify the manifolds to fit around a couple of bulges that are currently in the fire wall. this will involve me cutting off the current flange, and probably adding on a 10" section of pinched pipe. this will put the flange down along side the transmission.

3. after the fab work is complete, the steering rack will need to be installed from under the car, and will also require the removal of the lower control arms and the 2 cross-braces. this isn't a big deal as I should never have to replace the steering rack.

I was pretty overwhelmed and discouraged after the fit up... the project went from one problem to three!.. So i did the only thing i know what to do in these scenarios; cracked open a cold one and decided to take my anger out with the grinder. what resulted turned out to match up really well and i believe it will look nearly factory when i get it all welded in.



using cardboard for templates.


now.... to get through this day at work... and on to more fabbing! :tazz:
 

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#29 ·
This reminds me of the days my friend told me to put a 3000cc V6 into a Ford Escort back in the mid 70's. I thought, why not? Should bolt straight in, right? Ended up having to cut a chunk out of the engine sump, fabricate the engine mounts, adaptor plate to mount the engine to the ZF 5 speed gearbox, cut and shut the prop shaft with 2 different ends to mate with the ZF gearbox and the Lotus Cortina back axle, fabricate brackets to hold the back axle in place with extended 'U bolts', fabricate handbrake bracket to get it to work due to the axle and cables came from a Ford Lotus Cortina, get a complete exhaust from the headers back because of the limited space available, not to mention having to upgrade the suspension and brakes etc. Did all this in my front garden (Which went down well with the neighbours, lol) except for towing the car away to get the exhaust made...I have to admit that I had several 'cold ones' but when the car was finished, it was definitely worth all the aches and pains....Good luck and you're making fantastic progress...:smile:
 
#30 · (Edited by Moderator)
3/1/17

I beefed up a few welds and sprayed a little paint. the welds are a little ugly but the penetration is good (clean thoughts..) I will definitely be taking the control arms to a fab shop as i am not confident enough to weld anything over 1/8" mild steel, especially something as important as a control arm.

Today i found a good deal on an ECU, immobilizer, key and door lock from an E430. i chose this over other MB products (ML, S) because i have access to a scrap yard E430, and two other E320's. i will need to grab the interior harness from one of those cars and will most likely see if i can start the engine with all the wiring outside of the car before i figure out how to route everything.

so, whats next?
1. this weekend i'll remove the control arms and have them ready to be modified for steering rack clearance next week. :smile:
2. hopefully i can have the engine in full time after this week. the only thing keeping me from this is the inability to wiggle the exhaust manifolds in and out - they still need some work. :laugh:
3. need to figure out adapters for the tie rod ends :nerd:
4. small amount of clearance in firewall for steering shaft
5. need to think of a good way to seal off the steering shaft hole - the old grommet was split and explains why i could never seal the cab up from dust.
6. exhaust manifolds...... TBD :|
7. dash wires from E430 ... (this weekend??)
8. hoses and wiring.

pics!

yes, i know the yellow is off... the color on the lid is definitely not the same
 

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