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Old 01-25-2015, 04:29 PM   #5
Bjj_junkie
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Join Date: Jun 2014
Location: Miami beach Florida
Posts: 16
Re: general help on 250 to 305 swap

Quote:
Originally Posted by mechanicalman View Post
I assume this is a 2WD.

Did you buy this combo because you wanted BOTH the auto trans and the V8? There are issues with both in terms of installation, however you could do one or the other without doing both no problem. IMO the engine is easier than the trans, both are complicated.

I believe the engine cradle is the same, however the 6cyl perches, I have read, will locate the engine farther back than the small block V8's were originally. I have read that they do give enough clearance for a small distributor but get either tight or actually hit the firewall if you use the larger HEI; the V8's came from the factory with smaller points distributors; I expect the 305 has an HEI. I have read the V8 perches are different than the inline 6 perches. I have also read conflicting reports so there it is clear as mud.

To complicate the installation, I assume you will be using the accessories on the 305 and that would likely be the longer water pump. That will put the alternator on the passenger side as opposed to the driver's side, as long as the wire reach then no problem. If you have A/C, then the compressor would be on the driver's side as opposed to the factory passenger side, so you would need the appropriate A/C hoses to reach across the engine bay.

If you are going to run a floor shifter for the automatic, that un-complicates things a bit. If you are going to run a factory steering column with automatic shifter, you have to stick to a factory configuration assure the trans is in the right position to line up with the pivot bracket on the frame. I have read there are two different positions for the bracket as long as it's in one of them. You will also need an automatic trans rear cross-member.

You will also need to remove the cross-member that holds the rear engine mounts to the bell housing. I'd recommend while the engine is out to use a big air hammer with a hardened chisel to remove the forged rivets. You can also cut them off with a torch or a die grinder then pound them out with a round flat chisel. Or, use a sazall and cut as close to the frame as you can but to me that looks ghetto.

If you still have points on the 6, you will need to replace the resister wire from the fuse block to the coil with a 12ga wire to the HEI.

And then there is the driveshaft length issue.

I expect there may be some way to start at the driveshaft and work your way forward to avoid having to alter the length of the driveshaft, but I'm not sure. Maybe someone that actually knows will chime in and un-complicate this for you.

If you don't mind a little trial and error, you could get the auto trans cross-member, drop the engine/trans in with the driveshaft you have now first see if you have distributor clearance at the firewall then see if the trans linkage bracket lines up or it it will line up in the alternate position then if all looks well drill the holes in the frame for the trans crossmember if they are not there already. Then holding up the engine with a floor jack (2x8 chunk protecting the oilpan), line up the engine perches and/or replace them as necessary. Then use the appropriate fan shroud to accommodate your fan and extra water pump length, or change the fan to fit the shroud after the depth issue is addressed, factory fan shroud can be shortened if necessary.

And, you will need a new radiator and trans cooler lines. Oh, and hopefully your new steering column or shifter assembly will come with the proper backup light and neutral safety switch.

You will need a new exhaust system to fit the 305 manifolds.

I'm sure there are yet more details, but I cannot recall them all.
thank you, yea ill be doing a floor shifter and the person i bought the engine from included the exhaust system and radiator.
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