Mx3 B6D bottom with a 323 GT B6T head?

Icedawg · Post by **Icedawg** » November 26th, 2007, 12:50 am

As the title says, does anyone have experience with mating a 94-96 MX-3 B6D DOHC bottom end with the head, intake and turbo manifold of the 88-89 323 GT DOHC B6T engine? I know the compression differs, with 9 for the B6D and 7.9 for the B6T. Do the other parts mate up properly? Will the higher compression run with the B6T engine management system and mechanical retardation of the distributer?

Josh · Post by **Josh** » November 26th, 2007, 9:32 am

NO, the DE has two extra oil ports that run alond the exhaust side of the block. the Miata and 323 B6's dont have thies oil passages. so if you are dead set on making them work you have to block them off. so like taping the holes and finding some sort of plug. you are better off swaping the whole motor. also the intak manafolds are different. and with the B6T mani you have to mod your hood.

remember the DE Head on boost will make about 20 more whp than the turbo head. the ports are alot bigger.

Icedawg · Post by **Icedawg** » November 26th, 2007, 10:03 am

The whole assembly is in a Festiva, and the intake off the B6T fits under the hood. Since I wish to swap the head from the B6T onto the MX3 B6D bottom I would use the B6T intake and exhaust manifolds too. So that should make the intake mani work right? But your news about the oil galleys is disappointing.

As for the 20 hp more, that sounds interesting but I would have thought that had something to do with the higher compression ratio as well as the head design. Is that so?

Josh · Post by **Josh** » November 27th, 2007, 9:29 am

Icedawg wrote:The whole assembly is in a Festiva, and the intake off the B6T fits under the hood. Since I wish to swap the head from the B6T onto the MX3 B6D bottom I would use the B6T intake and exhaust manifolds too. So that should make the intake mani work right? But your news about the oil galleys is disappointing.

As for the 20 hp more, that sounds interesting but I would have thought that had something to do with the higher compression ratio as well as the head design. Is that so?

if its in a Festiva you shouldent have a problem then with clearance. you could swap the pistons to another B6 block. go cheep and only swap rings and ring berrings. the DE head in comparrison to a B6T head, the intake and exhaust ports are almost 1" bigger in diameter. this is where you gain your power.

Icedawg · Post by **Icedawg** » November 27th, 2007, 10:20 am

Thanks Josh
A friend managed a search that found this set of answers as well, which confirms your comments about the oil passages. But if these passages are for oil return (no pressure) as the thread says, then it seems that using the B6T head gasket should be enough to plug them off.
<http>http://www.mazda323performance.com/foru ... php?t=7225

I am trying to go real cheap, and just use the Mx3 bottom end block straight into the Festiva, instead of the worn out B6T block. That means no piston swap, so I am using the 9.0 compression instead of the 7.9 of the B6T. The B6DE block was rebuilt at some point, but I do not have it apart yet to see what shape it is in. I am planning to keep the B6T head, intake and exhaust mani's so that I can still use the B6T ecu and the well known wiring swap with the Festiva. If I use the B6DE head with its distributer then I get into a need for a piggyback or standalone ecu controller, mondo tuning, and an unknown wiring crossover with the Festiva.