Inliners International Forums General Discussion Engines GMC engine swap

Hello everyone,i have a 47 chev fleetmaster 4 door sedan RIGHT HAND DRIVE, with a 216, i cann"t get a 261 here but are still looking,so have found a 270 gmc six form a 57 pick up,I would like to know if anyone could give me a few tips on fitting this to my 47.It will have the pickup gear box with it as well, should i try and use it or stick to the one i have got,Lastly can i buy hop up parts for gmc engines, manifolds etc, any help would be great. sincerly Martin

out of cal. bill fisher's gmc speed manual.

40-48 chevy to install a gmc.

remove entire front-end sheet metal assemably. remove chev.engine and transmission. add extensions to motor mounts,install gmc. move radiator forward 1 1/2 " by modiffying bottom gravel shield to clear. on 42 amd later the cowl by the top of the radiator should also be cut for clearance. reinstall body work.

also he says to use chevy front motor mounts at the rear. they are stronger then the rear mounts. you have to drill the brackets to take the 7/16" bolts.

buy the drawling in the book for the extenstions. you need 2 pices of steel 1"x 3/8"x 2 1/2". on the 1" face you come in 1/2" from one end and drill and tap one 3/8-24 hole. from that hole you move 1 1/2" and drill a 25/64 hole.

now for that little bit of work you get 54 more cubic inches and a better oiling system then the 216. even in stock form the 270 is way ahead of the 216. and yes there are a lot of hop up parts for the 270.

as for the transmission if you want a floor shift i would go with the truck if it is a 3 speed. if it is the truck 4 speed i would not use it.

Dear Martin;

Yes; go with the 270 as 261s are really rare these days.

The 1948 transmission was designed for the 216" engine (85 Hp.) & won't hold up under the added torque etc.

Truck 4 speeds of that era were 3 speeds with a "granny" first gear which was extra low for carrying heavy loads. Avoid them as Bob suggested. The GMC 3 speed would be okay but might be hard to find parts for.

That engine for that car, with a 'late model' P/U T & D (5 speed) would be a great combo.

Patrick's has all the 'speed' equipment you'll want.

Good luck.

In the day, when Bill Fisher published his instructions, one would mount a GMC 270 or 302 but preserve the stock Chevrolet drivetrain--transmission, torque tube, and differential--which would necessitate moving the radiator forward. From inside the car, everything would appear to be stock. Even someone lifting the hood might not realize that the engine had been changed--until he noticed that the radiator did not look quite right.

If now you choose to use a later four- or five-speed transmission and open driveline, you can retain the radiator in its stock position, use the stock Chevrolet front motor mount, cut the firewall slightly, and reposition everything from the flywheel back--which you will have to do with the later transmission in any case. A '48-'51 Chevrolet pickup bellhousing will facilitate this choice. This is what we have done with the 302 in my 1952 two-door. You want the 1937-'40 Chevrolet water pump. With the stock vibration damper, you should be able to mount and drive the fan, generator, and water pump, while clearing the radiator. If you use a Fluidamper or some other kind, you may have clearance problems.

God's Peace to you.

d
Inliner #1450

As Don mentions, if you go with the '57 tranny, you will need to change to an open driveline as well. 48-59 truck housings can all be used, but the 48-53 versions have better mounts.

Also at issue is are you staying with 6 volts or changing to 12 volts? Reason being that if you decide to retain the original driveline, the Chevy flywheel will not work on the GMC, and the '57 flywheel is for a 12 volt system which has a different number of teeth on it from the 6 volt setup, so you won't be able to use the '47 Chevy starter with the '57 GMC flywheel. You would need to look for a '54 or earlier GMC flywheel in order to stay with the 6 volt starter. Just make sure it has the right number of bolts. If the outside diameters of the two flywheels are the same, you may be able to have a machine shop press off the tooth rings and switch them, should you not be able to find the right flywheel.

If you don't hot dog it, the stock drivetrain will work fine, but upgrading to a newer open driveline is best.

Thanks for all your replies i will digest this info and get back to you all once i get started on the swap.I have ordered a parts cataloge from Particks today.A local guy here has recently fitted a 292 six to a 34 chev roadster it has a 6/71 blower bolted direct to the crank, check it out at nzrodder@petrolhead.co.nz,

Hi, I have located a 261, from a NZ 1960 Pontiac has a three speed with it,Its done 83000ml and was overhauled a few thousand miles ago.I will use this instead of the 270gmc.I got a cataloge from Patricks ,What would be the better dual inlet , fenton or Offy? I will also need a filter are the beehive the better type to get, your opinions would be aprecaited. thanks Martin