2003 vs 1994 blocks
 

Looking at building a forged short block for my car. Have a lead on a 94 block for a decent price. With all the covid delays in parts and machine work, I am thinking about building a block so I can just swap out the top end. Can I use a 94 block with the 2003 top end and externals?

Thanks
Paul

I have a 94 block w/ a VVT head. Hardest solution is trying to plumb the oil lines for the VVT actuator. Factory is a hardline and banjo bolts, but 94 block doesnt have this drilled unless you have the machine shop do it. My buddy and I made a 4an line that is adapted through fittings into the block that then runs up to the vvt actuator. no clue whether its enough supply/pressure to run the vvt as i'm still on an MS2.

2003 block has better thrust washers and the mbsp
1994 block has an oil feed on the exhaust side that can be used for the turbo.

I think emillio said someplace that the average cylinder wall thickness was better on NB2 blocks.

Mazda installed a higher flow oil pump in the NB2 for VVT.

The VVT hardline connects to the oil pressure sensor/switch port, which to my knowledge is present on all BP blocks, no drilling required.

Sorry I must be mistaken, it's been a while since we built this setup. Couldnt remember why we couldn't use the factory hard line but i knew there was some sort of reason.

I replace my factory hard lines with -4an lines on all my cars. Mostly because I find it less cumbersome. If you are using FM LS coil brackets you also have to move to a AN line.

The hard line should work on the lower year blocks. I know I have done it before in the past.

I think the pressure port is tapped 1/8 BSPT on a non VVT block, and 1/8" BSPP otherwise. The first one is tapered, the second one is not. You should be able to tap out a tapered thread to a straight thread and then use sealing washers like the factory did.

https://www.mcmaster.com/bspp-taps/p...type~straight/

The second port in the VVT feed line is 1/8 BSPT and would take the oil pressure switch or the 1.6 pressure sensor.

The pump, thrust washers, and MBSP would be reason to wait for a VVT bottom end, IMO.

Ah that is why we didn't run it, it hits the fab9 LS coil pack.

I take it no issues with the 4an line feeding VVT then? We did it on a whim but neither of us have tried turning the VVT on yet due to a myriad of reasons.

FM directions call for the change. I assumed they made sure it was fine. Overall as far as I know though I have not had any issues in the last 8 or 9 years.