TH425 adapter

[magilla]

My Karmann Ghia project utilizes the drivetrain from a 1970 Oldsmobile Toronado GT (455cid with a TH425 transmission). Of late, I've been torn between building the 455 or swapping it out for an all-aluminum LS-style motor, as I'm rethinking how I want to proportion the weight bias fore and aft - and using an all-aluminum motor would help. The Olds 455 only weighs about 50-lbs. more than a smallblock Chevy, and I am planning on going with Edelbrock aluminum heads & intake, so that will help in reducing weight. The other factor I have to reconsider is using the Toronado drive axles - compared to 'Vette halfshafts/uprights/calipers, etc., these puppies are heavy. The biggest obstacle I'm facing in going to an LS-style motor (or any motor) is the adapter plate to mate it to the TH425. Has anyone ever heard of the TH425 being used with a different engine, or anyone making adapter plates for oddball engine/tranny combos?

[shep]

might contact these guys see if they have something. http://www.kennedyeng.com/
Here is their Toronado adapters http://www.kennedyeng.com/other.htm

[b-man]

I don't think you'd need to use anything other than a common BOP to Chevy trans adapter plate, the bellhousing pattern on the TH425 is BOP (Buick/Olds/Pontiac):

http://www.summitracing.com/parts/TCI-230000/

http://www.summitracing.com/parts/TRD-0060/

After that all you should need would be a flexplate that's compatible with the LSX engine to GM TH400 or TH350 trans, pretty sure those are also offered by a few different suppliers. This might require the use of a crankshaft to flexplate spacer, there's one pictured here:

http://www.crateenginedepot.com/Pres...lates-C19.aspx

More GM flywheels and flexplates to look through:

http://www.bulkpart.com/Merchant2/me...ory_Code=FLYgm

Perhaps someone familiar with the correct flexplate required and whether or not a spacer is needed will chime in.

Hope this helps.

[magilla]

Thanks, guys. I'd talked to Kennedy Engineering a few years ago, Brad, but they told me they didn't make any adapters for the Chevy 502/502 cratemotor that I was contemplating at the time, so I didn't consider them after that; however, it does look like their adapter kit for the TH425-to-Chevy V8 might hold some promise. It looks like I'll be using the 455 for a while, though; at least until I can get everything lined up for a complete, donor LS2. The 455 isn't really such a bad deal, what with it pulling 400hp/500fpt in stock configuration; and, it is a unique drivetrain for the project. In talking to Mondello, this motor is a good candidate for reliably making over 600hp. It is just that I'd really like to remove as much ass-weight as possible. To help balance front/rear weight bias, the original design plans were to increase frontend tube diameters, fab a heavy-walled fuelcell, front-mounted batteries (two), etc.; however, things have a way of morphing in other directions, which is why I'm seriously contemplating changing out the motor, lighten up the rear subframe, and utilizing C5 driveaxle components to reduce weight, instead of making the front half of the car heavier.