403 swap

[my85gp]

Well I picked up a 79 403 to replace the 305 in my 84 cutlass and was curious about a few changes I might need to make since a few of you guys have probably done this. Will the 403 oil pan work? Also I need to replace the clutch fan but the one I got from the wreckers was off a 307 (thinking it might work) and the bolt holes dont line up. Now I can either just go get the proper fan one off a 403, drill holes in the mount on the input shaft of the 307 fan, or just go get a flex fan. Was wondering what your guys thoughts about flex fans are and if i even need a clutch fan. I just know cooling is key with a 403. Damn, I should copyright that last sentence.

Thanks guys

 

[Blake442]

Oil pan will be fine.

I've never been a fan of flex fans and would recommend getting the proper fan/clutch combo.

 

[my85gp]

Ya Ill probably go get a proper 403 fan. Also I have the th400 that came with the engine, and apparently I need to have the driveshaft shortened but dont know how Id go about doing that, or what length it would be. Your car is awesome to Blake

 

[Blake442]

Thanks! 8)

If you swap to a TH400, you'll need a new slip yoke and you'll need to take about 1/2" to 3/4" out of the driveshaft. There are several places around town that can do this for you.

I had mine shortened 3/4" (even though I only asked for 1/2") and rebalanced for $90.

 

[Blake442]

The best thing is to measure it on your car to be sure...

Put the slip yoke into the trans all the way, and pull it out about 1".

Then measure from the center of the U-joint back to where the center of the u-joint sits on the rear end.

 

[joe_padavano]

Well I picked up a 79 403 to replace the 305 in my 84 cutlass

If the existing engine is really a 305 Chevy, then you will need everything off a 307 Cutlass - motor mounts, frame mounts, accessory brackets, water pump, starter, etc. The 403 and 307 are externally identical, so just install this using everything from a 307. Be aware that Olds used three different length water pumps and the accessory brackets and pulleys must match the pump length. Also, be sure to reinstall the two spacers between the PS pump bracket and the block or your belts will never align.

 

[my85gp]

the motor was complete when I gotit. it came with all the accessories(ps pump, starter, etc). What you said about the 307 and 403 being the same might not be totally true, because I got a ps pump off a 307 and it didnt fit, the cap would hit that aluminum alternator bracket coming off the block, so I had to go get a pump off a 403. Basically all I need is the frame mounts. Im going to get some pictures tonight and hopefully figure out how to post them on here.