4.3 Supercharged Chevy

[Qingdao]

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?

[itsnotanova]

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.

[Qingdao]

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.

[itsnotanova]

Originally Posted by Qingdao

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.

I'm guessing you're a chevy guy? The audi/porsche 5 speed is like a T5 and the 986/987 6 speed is like a T56 in terms of power it can take. What you're doing is like connecting a SBC 350 to a T5. Sure it might work, but it won't last if you try doing any kind of aggressive driving. You're kind of limited to power with the 4.3 cast crank but even in stock form I think it's too much for the boxster 5 speed

[Qingdao]

Originally Posted by itsnotanova

I'm guessing you're a chevy guy? The audi/porsche 5 speed is like a T5 and the 986/987 6 speed is like a T56 in terms of power it can take. What you're doing is like connecting a SBC 350 to a T5. Sure it might work, but it won't last if you try doing any kind of aggressive driving. You're kind of limited to power with the 4.3 cast crank but even in stock form I think it's too much for the boxster 5 speed

Never really was a Chevy guy, but working in a shop for almost a decade now I respect their engines. Everything else about GM is garbage, but there engines are nothing to shake a stick at.


Hmm.. It just costs so much to swap that trans. Other than the longer shift cables, does it require different axles?

I think I'm going to try the 5 speed for now and then later on swap over to the 6 speed when it breaks. I mean I have a 5 speed now. Why not have some fun and break it. \m/

[itsnotanova]

Originally Posted by Qingdao

Hmm.. It just costs so much to swap that trans. Other than the longer shift cables, does it require different axles?

I think I'm going to try the 5 speed for now and then later on swap over to the 6 speed when it breaks. I mean I have a 5 speed now. Why not have some fun and break it. \m/

Axles, uprights, calipers, transmission mounts and somewhat the aluminum belly pan but that can be modified easily. That's if you go with a 986 6 speed. A 987 6 speed requires modifying axles too

[Qingdao]

Waiting for Kennedy...

I started working on the subframe. I figure I don't need the engine in place to start on that.

The plan is to run two of these square tubings from the cross member by the bellhousing strait forward and then bolt them to the under body of the car (with a substantial backing plate of course).

Then to give it some more strength I am going to run a bar from where the aluminum skid things on either side of the body and attach that bar to the two running the length of the car.

These are the bolt holes that will secure the subframe to the body. I inserted some steel pipe to give the square stock some "anti-squanch" power. The backing plate I am going to put inside the car (under the seats) will have two M12 bolts welded in place. In my head it should be easy to bolt this subframe up, but its just in my head atm.









On a side note I sold my M96 at a whopping 580#s. I was just looking for a cheap replacement engine when I went with the 4.3; I didn't expect to loose almost 150 pounds of weight.

[maytag]

Originally Posted by Qingdao

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.

I'm all for creativity, and even mods just for the sake of modding.

But I gotta ask, gently; if the goal is 300.... that's a poop-ton of work for 300..... so,.... why?
I mean.... I've done my share of gm v-6 stuff... mostly 3.8's (wasn't the 4.3 the truck motor?) And I get the fascination with turbos on 'em.... but otherwise?

It just seems like SO MUCH WORK for a 10% hp increase over a Porsche 3.2 that bolts right in.
?
Respectfully, of course.

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[Qingdao]

Originally Posted by maytag

I'm all for creativity, and even mods just for the sake of modding.

But I gotta ask, gently; if the goal is 300.... that's a poop-ton of work for 300..... so,.... why?
I mean.... I've done my share of gm v-6 stuff... mostly 3.8's (wasn't the 4.3 the truck motor?) And I get the fascination with turbos on 'em.... but otherwise?

It just seems like SO MUCH WORK for a 10% hp increase over a Porsche 3.2 that bolts right in.
?
Respectfully, of course.

Sent from my SM-G970U using Tapatalk

I can understand confusion. LOL

Most of this work is for the blower right behind my head. Just want the VEEEEE sound. Addition of power is a side effect. I'm a strange one.

I'm toning it back to about 300 because I don't want to spend more than I paid for the car on a transmission. At least not right away. … Who knows in a few years once I get the body and suspension the way I want them I might re-visit the trans and engine output. Typical Chevy problems; engine's got more potential than any trans can handle.

Work yeah, but have you priced a 3.2 lately? If I went to the larger tranny and pumped up the 4.3 to a respectable output I'd still be paying less than swapping the engine alone. (side note after the clutch/adaptor purchase I'm in $3500 car purchase included)

Another reason for the 4.3 is I got one when I bought my garbage scow of a pickup truck. I'm about 100% certain it has jumped timing, and it still runs (I just advanced the distributer so it only pings a little). Well 2 years of driving essentially broken and it keeps ticking gives me the impression that its a VERY robust and well built engine. What better engine to put in a car that is less than easy to access the engine?

I am reminded of building my RX 5 years back. The trans always is the compromise area. I had to limit my output on that engine too. But like then I want the engine noises from the blower now; at that time I wanted the wooosh noises from a turbo, the power increase is a side effect.

[maytag]

Originally Posted by Qingdao

Most of this work is for the blower right behind my head. Just want the VEEEEE sound. Addition of power is a side effect. I'm a strange one.

Actually, that makes total and complete sense to me... maybe I'm strange in the same way, but I fully support all sorts of machinations for the right sound...

Carry -on!

And yes, the 6-spd has different axle flanges. I'm told that they can be swapped over though. Also a different input shaft, so clutch would need to be changed as well. (Disc only, if you start with the right clutch)



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[Qingdao]

This is the level of crazy I am at.

That's my dually RX7. LOL


https://www.youtube.com/watch?v=FjH_e1V_PYc

^^^ this is my inspiration for the mid engined blown car.