Clutch and bellhousing suggestions needed for 4.3 swap

Can anyone tell me if the clutch disc I have between my 225 and SM420 will work with the 4.3 I am going to bolt to the 420? I am almost positive I'll have to get a new pressure plate which sucks but if someone can tell me otherwise, that would be great.

Also, I'd like to put a hydraulic clutch in as part of this swap. Does anyone know of a 90 degree Chev. bellhousing that would have a provision for a slave cylinder built in? Someone told me to check late model Camaros though I believe the engine/trans mate with each other15 degrees off center on those (the trans is pointed towards the drive a little). Chevy trucks maybe? Any ideas? Thanks as always!

 

Before you buy a pressure plate. See if it will fit on the 4.3 flywheel. It might work. As for the bellhousing try full size Chevy pickups with the 4.3. I think someone said it had the mount for the slave cylinder.

 

Late model Chev Truck, or believe it or not Astro-Van's had manual transmissions with the provision you seek. They had an easily set up hydraulic slave mounted externally and a master that is easily converted to any flat firewall. That's what I used on the Race Jeep. Worked out quite well. You need to know which bellhousing and especially which flywheel you are using to determine if your existing disc will work. There were 4 flywheels used behind 4.3's, just like other Chev motors. 153 tooth which is a smaller diameter, and 168 tooth which is larger diameter. The 168 tooth requires a larger bellhousing and different starter than the 153 tooth. Also, clutch sizes were different. Most S-10's, etc. used the smaller flywheel so they could make the bellhousing contours smaller so they could make the transmission tunnel smaller. That covers two of the flywheels. The other difference is whether it's internal balanced or external balanced. Starting in mid year '86 when they went to a one-piece rear main seal, they also changed the balance of the motor from internal balance to external balance, similar to the old small block 400's. They also reduced the diameter of the crank bolt pattern where the flywheel bolts to. You have to get the right flywheel for your motor or it won't bolt up. The good news is they did the same to the V-8's in the same year and they interchange! So if you need a flywheel, you can get one for a V-8 for your year of motor and it will work fine! The balance is the same by the way. Hope I didn't confuse the issue too much but I went through all this while building the new 4.3 for the race Jeep and again for Davea's 2a project. Davea was actually the one that got me the part #'s for both so we could compare. Nickmil.

 

Thank you Nick! As always, your answer exceeded my expectations. And hearing that you did the same thing (with success!) I want to do is good to hear as well. Thanks again!

Oops, just one more thing- would the bigger one be better to use because of the added weight? Either way, to keep it simple, I know I'm restricted to whatever was used that year. Have you experimented with both sizes? I imagine the heavier one would be nice for crawling and the lighter one good for racing but I'd like to hear your actual experience. Thanks again!!!

 

The heavier one is better for trail running. It's not a huge difference between the two but I'd go the larger one. Not just because of weight but also because it allows you to use a larger clutch, and they tend to be a little easier to crank over due to the added leverage of the starter against the larger diameter flywheel.

I'm actually running the larger flywheel myself for some of these reasons. Mine is a billet Centerforce, but a stock one would work just fine for the vast majority. Stock ones are a lot cheaper too! Nickmil.

 

Thanks again Nick! Junkyarding I will go!

 

If you don't find the hydro clutch bellhousing you need, Novak sells a kit to retro fit a standard bellhousing to hydraulic. Comes with clutch fork slave cylinder and mounting bracket hose etc.. Pretty nice setup although I don't have it all hooked up yet.

 

Would anyone know if a factory 4.3L V6 bellhousing would work with an SM420? That bell already has all of the hydro components built into it. I just don't know if the tranny will bolt up or if the hole for the bearing retainer is the right size....

 

Ooops. Just re-read Nick's info. Sorry about that.