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Old 12-14-2019, 06:02 PM   #1
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4.3 Supercharged Chevy

Finally got my hands on a cheapo boxster. Its a pile LOL, BUT $1500 seemed about right for a strait chassis and clean title.

Now I just have to wait for the half off weekend at LKQ. I am gonna shove a 4th gen 4.3 Chevy engine in this thing with an Eaton M90 blower.

I think I'm gonna draw through an edelbrock, but I might go with a Holley. Haven't decided yet.

At anyrate, I got this thing, but now I have to go on vacation... Sucks cause I'm going to be off with the wife and not at home in my garage. :lol:



Well here is the pile... (yes I do body work too)



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Old 12-15-2019, 05:38 PM   #2
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Didn't take long. Got a nice cheapo Eaton M90.

$100 and after I get back from vacation I can get a rebuilt snout from Ebay for $300.

Rebuilt blower for $400 not too shabby.



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Old 12-15-2019, 07:12 PM   #3
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Looks like a cool project. Lots of the guys on the forum wouldn't touch a $1,500 Boxster, but at that price you've got nothing to lose and a lot of potential fun if you like playing with cars. I'm looking forward to the progress.
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Old 12-15-2019, 07:38 PM   #4
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Looks like a cool project. Lots of the guys on the forum wouldn't touch a $1,500 Boxster, but at that price you've got nothing to lose and a lot of potential fun if you like playing with cars. I'm looking forward to the progress.
2 years ago I wouldn't have either. My wife had an auto and that thing was super fun even though slower than a heard of turtles. That car's gone now its my turn.


Got a bit of inspiration off of YouTube. This guy went ham with the intercoolers. I don't think I'm gonna have to use two belts, but who knows at this point.

https://www.youtube.com/watch?v=L_FRdIjGkgg

^^^ Apparently I'm not the only idiot who wants roots noises emitting from their V6 engine.
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Old 12-15-2019, 08:54 PM   #5
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I had an M90 that I thought about blowing down into a VW VR6 with. After laying it out and looking at what it would take to do right, I passed the whole project on to someone else.



Do the M90s have a stock mounting on the 4.3, or do you have to fabricate it?
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Old 12-15-2019, 09:30 PM   #6
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100% gonna have to fab.

I was gonna just do a piece of 1/2" aluminium. Tap some holes in the top to bolt the eaton to it and bolt the bottom to match the 4.3 intake. That'll also give the ability to position the snout where I want it in-between the alternator and A/C compressor.


Accessory position is the reason why I've chosen the 96-02 chevy 4.3. The accessories on the 4.3 almost line up perfect with the accessories on the German H6 engines. So all I have to do is break out my line lock crimp tool and fab up some hoses. (that's a big fingers crossed there LOL)



As for engine building I am just going to put a healthy cam in it and some good pistons and rods. Maybe some light weight rockers for show. Nothing too spectacular; I just want about 300whp maybe 350 if I'm lucky. BUT the torque should be to die for.



One question I'm wrestling with is weather or not to buy new springs. I like the stock ride height but I don't know how much the original springs have sagged over the 20 years of life. Especially since this thing has like original struts on it (its a motor boat) so I'm sure these springs might be "sprung out". Just don't know if its worth the cash to toss in some new oem springs.
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Old 12-19-2019, 08:11 PM   #7
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I'm thinking this might be the way to go for mounting the edelbrock (I'm dead set on another eddy) on my Eaton.




The best irony I can think of... using an adaptor that is supposed to convert a carb intake manifold to a throttle body; to bolt a carb to a throttle body. LOL its perfect.


I still might weld up my own intake. Just for fun.
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Old 12-19-2019, 08:19 PM   #8
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I love engine swaps so don't take this wrong, but won't you have a huge issue with how tall the motor is? Let alone with a blower on top
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Old 12-19-2019, 08:37 PM   #9
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I love engine swaps so don't take this wrong, but won't you have a huge issue with how tall the motor is? Let alone with a blower on top
I hope so. I'm gonna build a plexiglass top. I wanna see this...thing.


I do want to do the "cayman style" hard top as well. So I don't need room for the convertible top. That whole rear trunk area is probably going to be substituted by a series of square tubing supports.

If the blower, carb yada yada are to far aft/high and I can't close the rear trunk; I might turn a pair of elbows around 120* go with a pair of SU carbs on top of the valve covers. One conveniently placed in front of each of the side intakes.
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Last edited by Qingdao; 12-19-2019 at 08:42 PM.
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Old 12-23-2019, 06:48 AM   #10
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Respect your initiative for taking on this project.....Whatever you do just keep us informed of your progress if you would please.....And good luck!
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Old 12-23-2019, 04:24 PM   #11
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Respect your initiative for taking on this project.....Whatever you do just keep us informed of your progress if you would please.....And good luck!
Well I'm trapped in a forced vacation with my wife ATM. I'm so glad to be getting back to the garage in the next few days. Then I can start mocking things up, and poking the car.


I think I am just gonna buy a $125 4.3 off ebay for starters and toss a cam in it. Not even gonna upgrade rods.

I got the blower, and I found a used eddy on ebay as well for $100. Manual choke


Honestly, for the growing crowd of IMS failure guys. I think the 4.3 is the way to go. Naturally asperated and carbed; you won't have to worry about wiring (there are electric chokes but I like to pull the nob). Its 4" shorter than an LS motor so you won't have to cut up the firewall. With a simple cam and an intake you've got almost 300#s of tourque which is more than the 3.4 Porsche engine. And they are CHEAP and plentiful; Kennedy adaptor and a bit of angle iron added to an engine/cam/carb/intake is less than a 3.4 Porsche engine.
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Old 12-23-2019, 04:50 PM   #12
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growing crowd of IMS failure guys. .
really ??????
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Old 12-29-2019, 04:02 PM   #13
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I took a crack at trying to replicate a part out of foam.


I put my M90 in a bag....



Then I covered it with great stuff...



Then I took the M90 out of the bag...



Then I filled that void with great stuff and Styrofoam...



The end result...




I took the end result out of the plug way too soon because I noticed the great stuff wasn't curing on the outer edges of the plug. I tried to drill an air hole and the bit caught the bad and made a royal mess....

I think I am on the right track but I need to use a card board box to retain the negative. I should be on my way to scoop up a 4.3 tomorrow.
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Old 12-30-2019, 02:47 PM   #14
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Well... to hell with making a foam copy. This thing is gonna fit no problem. I might have to hack the fire wall some, but not any more than you'd expect.

And OoooHMYgod does the Eaton sit perfect on top of the 4.3.








All I should have to do is hack down the back of the M90 just a hair and tig up a square bore plate. Adapt the M90 for the 4.3 LIM; drop the carb on it and call it a day.




As for the size constraints here is the skinny...




The 4.3 is 22" long from flex plate to W/P... The 2.5 Porsche is about 23 ish (I can't exactly see down in there).

The 4.3 is TALL from the bell housing up its gonna be a whopper of 12" and after about 5 inches forward of the bell housing its gonna be about 16" (cause of the carb). According to my rough estimates that puts me at about right at where the top of the rear storage bin would be. Another words this is gonna fit under the glass.... BUT JUST barely under the glass.
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Old 12-31-2019, 03:00 PM   #15
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Cut down the M90 some more. It almost sits flush on that LIM. Cool cause now all I need is a good 1/2" thick aluminum adaptor plate.





If I'm able to get the carb low enough I'll slap on my buddies old Duel fuel carb hat. How cool would that be having a duel fuel Porsche!!





I also put my vehicle make emblem on it; fits perfect.
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Old 01-04-2020, 03:12 PM   #16
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Damn waiting for pieces. I ordered a 3/4" plate for the adaptor and carb, but it won't be in till Monday. In the mean time I'm twiddling my thumbs.

I did cut out this portion of the firewall. Hoooooo boy what a smell when the grinder met the old sound deadening material. It might also be my grinder is 60 years old and ready to retire.





Do any of you guys know for sure if these are the P/S hoses? They are right behind the drivers seat. They snake under the A/C compressor.




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Old 01-20-2020, 03:47 PM   #17
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I don't really want to flood this thread with needless updates so I've stayed away for the moment. But the engine is out and for sale if anybody wants a boat anchor or coffee table. LOL

Seriously I think it might be a "re-builder". The oil filter didn't seem like it had an excess of metal shavings... IDK Doesn't matter





The Harbor Freight engine hoist which normally is quite inadequate when it comes to length did VERY well here. Just used a long chain and whola the engine is free.









Still waiting for my buddy to finish (or even start) welding my M90 so I can fit it to my 4.3 and get to rebuilding that engine.
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Old 01-21-2020, 07:56 PM   #18
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Well I hit a brick wall. Kennedy doesn't make an adaptor for a 4.3 with an aluminum oil pan for a 5 speed boxster. They wrote me and said something about the starter not having a place with the adaptor plate.

Ah poooo.

I messaged them back to see if I could use an 88-95 4.3 engine. I mean if its the aluminum oil pan that's in the way I can work around that. Shoot mild steel is easy to work with.

I don't see the difference between a 4.3 and a SBC and the difference between the LS and SBC is .400" of bellhousing spacing. So buy an LS adaptor and add .400" of spacing???


One question I do have for any high output boxsters out there; what clutch's are yall running? I'm not seeing too many aftermarket options out there. How much power can the stock clutch hold?
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Old 01-22-2020, 09:42 AM   #19
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They probably did you a favor. The five speed can barely handle the power from a 2.5/2.7. The five speed won't last that long behind the torque of a supercharged 4.3. You're much better off using a 986 or 987 6 speed.
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Old 01-22-2020, 04:42 PM   #20
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Its cause they use a proprietary starter they make in house and where they put it the starter conflicts with the aluminum oil pan.

I have a friend who, if you get on him hard enough, welds aluminum. Worst case I buy an older 4.3 and use an older block. But more than likely the oil pan is going to be custom.



So 5 speeds can't take the torque?

I have decided to tone it down a bit on the engine. No aggressive cam, light boost, stock or dish toped pistons, and only a 25 shot of nitrous at best.

I'd say 300#s on a good day.

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