[MANTECH]

I'm a only a recent owner of an 1983 GTV6, but it has been one of my favourite cars since it has come out. At most I was thinking about doing a 3.0 conversion to the car because it just seems like the right thing to do, and I'm sure Alfa may have gone that way had the car continued in production. Not that I want to start any grudge matches with the Porsche 944 guys, but there is a local owner of a 1987 Porsche 944 Turbo with an LS1conversion done to it. The conversion was done professionally and the car undoubtedly is a monster on the street and track. It turns out that the LS1 motor is actually lighter than the porsche 3.0 litre.

I've done a lot of reading on Alfa GTV6 engine swaps, and have heard about 300 plus HP in some cars. The Porche fellow tells me that the transaxle in the GTV6 has no where near the strength of the the 944 Turbo transaxle.
I'm just curious as to what horsepower and torque the GTV6 transaxle is rated for and if anyone has actually tried an LS1 swap in a GTV6. I know the C5 corvettes have a similar set up as the GTV6, i.e. engine in front, some tye of torque tube, and rear transaxle.

Just to make it perfectly clear, I love the sound of my Alfa the way it is now, as it is the way I remember it. I'm just more curious as to how strong our transaxles are and what expense would be involved to upgrade it.

 

[alfettaparts]

Like this?
This has a 9" rear end.

 

[MANTECH]

C5 DRIVETRAIN WITH REAR TRANSAXLE

http://www.fpartssalvage.com/images/IMG_2260.JPG

 

[Greg Gordon]

The GTV6 transaxle can handle about 400 flywheel horsepower is everything is perfect. I think in the real world 350 flywheel horsepower is a more realistic safe limit.

Greg,
Silicone Hose Kits
OKinjectors

 

[slyalfa]

I would think the torq of a big v8 would snap the box coming off idle. it is torq not bhp that snaps the things and a 5 to 8L v8 had a ton of torq vs a 3L
I think a vett box would be the way to go. I have wanted one even for the v6
but they seem super hard to get unless you want the v8 to go with it. and the cost is too high

 

[Hamish]

I think Slyalfa is on the right track, it's the high torque of a big engine, or highly boosted smaller engine, that will break drivetrain parts.

If you were to go down the path of an LS1 conversion, the complete corvette drivetrain as per mantech's link would be the best approach. It would of course be an immense amount of work, and very very expensive if you have to pay someone to do it for you.

I think a worked 3 litre, or turbo/supercharged 2.5 would be the more sensible option, and stay within the limits of the factory parts, not to mention keep the car a GTV6.

 

[alfaparticle]

Bill Simms is on the ABB. He succesfully autocrossed a supercharged Milano until he destroyed the transaxle. He knows what the limits are. He has probably posted about it. Do a search.

 

[Greg Gordon]

I think Bill had it up near 330rwhp towards the end of it's development. It was a very fast car and in Bill's words made his Z06 Corvette seem slow!

It held up for a few seasons but ultimately suffered a total failure and lock up which caused a crash and the destruction of the car. This failure point is in harmony with the limits found by Barry H. in South Africa and others. I seriously doubt there is a GTV6/Milano transaxle out there with more that 350rwhp.

Keep in mind, Bill's transaxle was well prepped and was about the best you could do with the stock transaxle.

Greg,
Silicone Hose Kits
OKinjectors

 

[Alfar7]

Transaxles

The later Verde/Plat cases are quite robust. Bill`s application, and his driving in the autocross`s was extremely abusive to the entire drivetrain. The only "failure" was stripping the inner teeth from the LSD unit after a couple of years, and required only replacing the insides of the LSD carrier. With full throttle tire smoking starts and hard turns under power with nearly 350 lbFt torque is more than is reasonable to expect long life.

I`ve built similar TAs which are in Porsche 908 (8 cyl porsche racecars) in Australia, and Land Rover/Buick/Olds Aluminum V8 hot rods (England) and have no reports of problems.

I have a TA built for my GTR which is being modified to fit a Montreal or LS1 in place of the V612V that was plugged in it while building the chassis originally. I`m not worried about the TA, or the capacity of the 5.5 inch triple disk clutch and flywheel to handle the torque of the LS1.

However do not think that any of the Alfa factory clutch assemblies, or the unmodified LSD units will take the power of any motor above 200 HP. They won`t.

 

[la_strega_nera]

908's in australia with alfa transaxles? really - interesting - are there any pics?

 

[Alfar7]

Australian 908 with Alfa TA

908's in australia with alfa transaxles? really - interesting - are there any pics?

The owner of the car is John Moyes, Forestville NSW 2087 If he sent pics I can`t find them...

The Supercharged Aluminum V8 Street rod is owned by Christian Mühlbauer in Germany, not England as previously stated....Here`s pics

 

[Greg Gordon]

That street rod is very nice. I like how they used the Alfa's rear suspension. The engine appears to be a Buick/Rover/Triumph etc. 3.5 liter V8 designed in the 50's. It's a super cool engine and period correct for an old school hot rod. However it's hardly a powerhouse by modern standards. It's pretty comparable to an Alfa V6 in power. It's certainly no LS1.

Greg

 

[desmo veloce]

Old school

That street rod is very nice. I like how they used the Alfa's rear suspension. The engine appears to be a Buick/Rover/Triumph etc. 3.5 liter V8 designed in the 50's. It's a super cool engine and period correct for an old school hot rod. However it's hardly a powerhouse by modern standards. It's pretty comparable to an Alfa V6 in power. It's certainly no LS1.

Greg

The Buick/Olds/Rover/Triumph V8 can be bored and stroked to 5.0 liters. It was tuned to 330 HP in the 90's for the TVR Griffith (5.0 OE application). Without knowing more about this specific motor, I don't think we can rule out LSx power levels (400+ HP).

I think that being extremely traction limited would help the transaxle in this car to live. This is very different from tire smoking auto-cross starts on wide Hoosiers in a Milano. I also think a babied transaxle in a high HP street application would probably last a long time.

Richard-

You mentioned that you are thinking of putting an LS1 into your RJR coupe project. What do you do to help these transaxles to live with 400+ ft/lbs of torque? Conventional wisdom says 350 ft/lbs is the limit.

~Chris

 

[Greg Gordon]

The Buick/Olds/Rover/Triumph V8 can be bored and stroked to 5.0 liters. It was tuned to 330 HP in the 90's for the TVR Griffith (5.0 OE application). Without knowing more about this specific motor, I don't think we can rules out LSx power levels (400+ HP).
~Chris

We can't rule it out, but I think it's highly unlikely. That engine in stock 3.5 liter form was lucky to make Alfa 2.5 levels of power (it usually had less). That supercharger is an old design Eaton M90. Almost all OEM applications with that supercharger had 210-230hp. I can see from the pulleys that it's not spinning nearly fast for LS1 levels of power. I think it's far more likely this is a low to medium boost engine comparable to a supercharged Alfa 3.0.

Greg

 

[desmo veloce]

amazing

Greg-

You know too dang much! I can't eyeball a SC setup and make an educated guess at the engine internals! I thought it could be a highly modified motor disguised by some flat black paint...

You are also right that in the 60's these engines stock made less power than even a 2.5 Alfa V6. They are lighter, however.

You da man.

~Chris

 

[Greg Gordon]

Thanks! I must confess I can't do it purely from memory, there are charts in my book.

It sort of works out like this: Looking at the pulley I would say it has a drive ratio of about 2:1. With that drive ratio the supercharger will give a 3.5 about 8-10 psi. In other words, 50%-70% more than a stock engine. A stock Buick/Triumph/Rover 3.5 has around 150 horsepower so this is probably about a 250 horsepower engine. With the headers, some internal work, good engine management etc. it might be 300hp or a little more, but it's still not going to give LS1 power.

Now it could be one of those big displacement 5.0 conversions I hear about. However if that was the case with that supercharger drive ratio it would only have about 3 pounds of boost, which would defeat the point of all that work.

My point here is that it's more likely comparable in power to a hot Alfa V6 rather than a hot LS1.

If someone will make the transaxle hold up to true LS1 power it will probably be Richard, and I hope he does it, but right now I don't see it happening.

Greg

 

[desmo veloce]

Greg-

IIRC, the fuel injected TR8 we got in the US was 135 HP. Same as the Rover 3500 Sedan of the same vintage (SD1 in Europe, I think...).

I see how you think. I just don't know enough about supercharger specs to know airflow at different drive ratios. I will be sure to keep my mouth shut next time.



Chris

 

[Greg Gordon]

Keep speaking up, that's how we make progress here, and I have been wrong a number of times, like everyone else.

Here are some pictures of broken Alfa transaxle pinion gears. Both were destroyed by a 2.5 V6, not even a supercharged 3.0. There is no good way around this problem with the stock V6 transaxle. Yes, certain years and drive ratios are better, there are cryo and shot peening treatments which can help, but ultimately there just isn't enough metal to handle more than 350rwhp, and even that's really pushing it.


Greg

 

[desmo veloce]

Manufacturing defect?

Greg-

I think I remember reading about these in a post you made at GTV6.com. Someone there (Kevin from SA?) broke some too and had his tested. There was a defect caused by oxygen present during heat treatment, IIRC.

Have you seen these types of failures across many years of transaxles, or were both of these from 82-83?

~Chris

 

[Greg Gordon]

These two were in mine, both were 1983 pinions. The year issue has been discussed, and I do think there was an issue with the 1982-1983 pinions gears. However at higher levels of power they have broken in other years as well. Not to mention other parts of the transaxle failing. All the evidence I have points to the gearbox not being able to handle over 350rwhp, with less being a good idea.

Greg