The Stovebolt Site Forums The Shop Area The HiPo Shop 51 GMC engine swap moving up 60 years...

302 jimmy out - vortec 4200 going in...with turbo

Not mine but an interesting swap to follow.

The number of parts to do the swap are a lot better than earlier on.

you might want to check out vortec 4200

I still love looking at the 4200 in early rides.

Is there someone still building flywheels for the guys that like shifting?

I think so.

Do you still have the trannie adapters that you fabricated.

I actually have a WC T5 collecting dust.

I found this old link you had on Inliners

http://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=68018

Have a better solution - an adapter plate - then you use a 250/292/SBC bell housing so all the existing clutch linkages work. The plate is 3/8" thick.

bell housing adapter plate

That's definately something to thik about. I saw Rover did something similar over at the 4200 forum.

With your adapter plate, I'm assuming you would need a flywheel/flexplate extension, right?

Does the starter mesh up right or does it need modified?

The plate certainly opens up what can be ran behind the 4200. SM420, Muncie, TH350, etc...

You might need to space the pilot bearing back a 1/4" or so, otherwise with a manual trans, bolt the flywheel from Jerry W. up with the clutch and good to go.

For a PG/TH200/350/400/700 you need a spacer for the t/c snout and they are available now. Also have extra long dowel pins.

For the starter, use one of 2 ways:

- modify the bell housing to clear the starter nose like Gary Hart did on the GMC. If you do this then you can use the stock starter.

or

- purchase the starter adapter from Steve Pohill that bolts onto a tilton starter - this is the no cut/weld solution.

I'm using this adapter with the tilton starter and it works well.

The 4200 is about 180 to 200# lighter then a 250 and I'm guess here 250 # lighter then the 235/261. No idea how heavy a 270/302 jimmy is..

The pre '06 engines are 275 HP SAE net and with a little bit of work with a good tune you can get another 15-20 HP out of them.

Even stock its doubling the power of the 235 and then some.

Not done yet are the frame side engine mounts.

If truck has a stock frame under it - then the stock pan needs a minor tweak to work or notch the cross member. Have a look at Gary's pan.

I'm looking at some iron bellhousings from early V8's. They'll allow me to locate the engine/trans in the factrory location. It looks like I'd have to go with the Polhill starter setup. I can't feasible see cutting and welding an iron housing.

Pohill starter starter

Gary's been working the TIG... intake and exhaust getting close to done.. Turbos not far off....