DOHC B6 Information

[TWFodor]

Charlie, do you know how much of the head can be shaved before causing issues with compression/valve clearance, etc? The head on my xr2 has some gouges in it and needs to be resurfaced. I just don't know how much it will affect the compression. I believe they will need to take off between 5-7 thousandths, but I don't know for sure.

Ouch. Right on the compression ring.

[FestYboy]

Any reduction in chamber volume will increase compression. .0050" isn't all that much, you will still be under 9.0:1.

Personally I'm a big fan of high compression turbos though (10:1+)

[Advancedynamix]

My head is shaved .020" on Pedro. Anything under .010" won't make much difference as long as the head has not been decked before. I strongly recommend a cometic gasket and ARP studs.
If more than .010" needs to come off, you will want adjustable cam sprockets to make up the difference in cam timing (or do the slotted idler cheat trick).

[FoMoCoMotion]

Finally put my "stroker" B5-ZE back in today only to have a massive oil leak at what appears to be the rear main seal - Most of the rebuild kit I used was for a 92 Miata since I was using the Miata crank, rods & pistons. Do you think the rear main seal between the 1.5L Crank and the 1.6L crank could be different??? Man I dread pulling it back out just to replace a seal. But with most of my projects it takes me 3 tries to get anything right LOL :banghead:

[reddragon]

Camshafts. All the engines share Intake Camshafts, but the exhaust camshafts vary from Automatic transmission, manual transmission and Turbocharged. From my personal testing, I do not recommend using an automatic exhaust camshaft in a B6t, especially in a Festiva. The slight improvement in low end isn't noticeable in such a light car and the auto cam chokes the engine at higher RPM and can promote detonation under higher than factory boost levels.

I'll have my camshafts out this week to replace valve stem seals. I was thinking of switching my exhaust camshaft (engine is from an auto, late model B6D) for a B6T exhaust camshaft. Just realised that this probably isn't going to work, as my exhaust camshaft drives the distributor.

As the B6T intake camshaft drives the distributor, can it be used as an exhaust camshaft in the later B6D? If yes, do you think it's worthwhile swapping them over, as opposed to just keeping the B6D automatic exhaust camshaft?

[RED121]

Any info of how a b6t from a tx3 laser would go into a mazds 121 db bubble?

[xXxEpicxXx]

https://www.amazon.com/Protege-Perfo.../dp/B00JA1BNL0 i know people have cut the flange from a honda header and welded a b6 flange my question is would this header work for the same? its cheap and i think it would be a could try.. just seeing if anyone has used this type of header on the b6d swap

[reddragon]

Any info of how a b6t from a tx3 laser would go into a mazds 121 db bubble?

Should be much the same as 121 da or festiva wa. Have a read through some of the garage build threads. Motor will need to be shifted forward to clear brake booster.
What gearbox you using will probably determine how you go about things.

[parrainx]

My ‘91 might be toast, so i’m looking for a Capri to grab B6D out of.

I think everything is pretty well covered here, but i want to confirm few things.

Will capri’s ecu plug into the festiva harness? I’d like to run capri injectors and i’m guessing they will be better controlled with capri’s ecu.

Will be mating it to stock festiva transmission. When buying a new clutch do i get one for festiva or capri?

Thank you

[shorestiva]

Capri ecu will not plug into a festiva harness. Run all the festiva fuel injection stuff including the injectors. Use the clutch and flywheel for the transmission you're using. People are having good luck with the exedy clutch kit.

Sent from my SCH-I545 using Tapatalk

[Sleeper]

If you ran a B6D on the festiva engine wiring and ECU. Could you add a turbo at low boost ( 4-5psi ) if you added larger injectors?

[Dragonhealer]

It won't run well with larger injectors on stock engine management. For low boost, the easy way out is a rising rate fuel pressure regulator. Like the one Gready (sp) used in their Miata 1600 turbo kit.

[Sleeper]

It won't run well with larger injectors on stock engine management. For low boost, the easy way out is a rising rate fuel pressure regulator. Like the one Gready (sp) used in their Miata 1600 turbo kit.

Thanks for the reply! Would a stock festiva fuel pump be able to keep up with a low boost B6D? And how much boost do you think a B6D running on a festiva ECU could handle with a rising rate fuel pressure regulator? obviously running B6T with its electronics and ECU is a much better option. But i love the simplicity of a B6D on festiva electronics. I would imagine that a B6D with its higher compression rate @ 5psi should produce as much power or more than a completely stock B6T running at the factory 7ish psi...

[william]

From what I've seen the festiva and xr2 pump are the same part number and rocket man has tested to stock xr2 pump at 19 lbs of boost so I say your gunna be fine at 5 psi boost .

[Dragonhealer]

The fuel pump is fine if stall pressure is still over 85psi.
The B61P (B6D in 90-93 Miata USD) is 9.4:1CR and can run 5psi boost with a high quality rising rate regulator. More and you will be doing it over again and could have done a B6T for the effort of doing it twice!
Use 1.85 inch (2" if that is all you can get) exhaust pipe from turbo to cat (or expansion chamber) and 2.25 inch pipe and muffler post cat. The expansion chamber is important when not on boost if you are not running a cat.
91 octane minimum, don't get happy with the timing, don't cruise more than 30 seconds at boost. (Don't ask me how I know)

Keep in mind the XR2 uses boost more effectively due to the low CR, and has knock sensing....