Hi all,

Over the winter I've torn down my 86 GXL 13B 6-port, planning on rebuilding it half-bridged going with a Mazdatrix 6-port Bridgeport template. For those of you that don't know; This template slightly extends the primaries and eyebrow's the secondaries and aux's.

Here's the thing; close inspection saw all parts perfectly within factory spec for 'reuseable', i.e. no warping, no deep scarring or wear on the sideplates, good e-shaft and rotors, etc. This lead me to believe I can get away with a cheeky bridgeport, bar one thing:

The rotor housings have about 0.4 to 1.2 millimeters of chrome 'edge-chipping' over lengths of 2 to 3.5 inches along the combustion/exhaust area of the housings. The FSM says this is still in spec, and it matches the wear on the rest of the parts, BUT; I'm worried this will either/or/both significantly increase my break-in process, hurt/negate my bridgeport benefits, or cause the engine to never (properly) run at all.

Parts (re)used as per following;

- All 86 GXL engine parts from the original engine
- Stationary gears, rotor- and e-shaft bearings from the original engine
- New OE sealing kit (coolant, gas, o-rings, gaskets etc)
- Atkins 2-piece apex seals & springs
- Solid corner seals with FD springs
- Atkins side seals & springs
- New OE oil seals
- Atkins e-shaft thermowax delete kit
- Rebuilt factory mechanical OMP

I think that about sums up anything to do with the closing of the engine and it building compression etc. If there's information missing just ask.

I'm not aiming for high horsepower, I just want it to brap nicely and get me around the block a bit faster

What's your thoughts on this?

- Brian

 

No one huh?

 

The bridge port I built almost six years ago had about four times that much chrome flaking. Easily. It made 208whp on a Mustang dyno last year, after a lot of abuse.

Don't worry too much about it.

 

Sounds good.

On the same subject; I took a look at the Mazdatrix 6-port Bridgeport template even scribed it on a busted sideplate. The 'eyebrows' seem rather conservative. I can understand this as it's a product bearing their name and therefor should be fail-safe, but the eyebrows are positioned about 2mm inwards of the gas-seal groove, and there's about 8 to 10mm of 'bridge' between them and the original ports. Port-timing looks okay, but I was wondering how far I could open up the eyebrows inward towards the bridge? like, could I add another 1 or 2mm and still be safe?

Hope to hear from you

 

no one lives on this forum. we all have a life, jobs, and other priorities. u must be patient when asking questions. it might take a while for someone that can best answer them.

as for the question about the eye brow, that bridge is there to still give the apex some support and not fall into the port, so u don't want to cut that too thin. some usually port the other way, out towards the rotor housing, and even getting into the rotor housing and needing a chamfered edge, even cutting into the inner O ring groove.

 

I see that, and I wouldn't be adverse to chamfering the rotorhousing as this build will probably be their last when looking at wear, but the eyebrow as laid out by the template is already only 1 or 2 milimeters from the gas-seal groove, and the 'bridge' is as much as 8mm wide. Meanwhile I'm reading a lot of people here bringing that bridge down to 5 / 5.5 milimeters and still be safe, so whats up?

 

The Mazda Factory Race bridge ports from the Group A era had bridges that were 4.5mm wide, according to the FIA homologation paperwork.

When I make a bridge port, I do not move the original port's opening line, and I make the bridge 5mm wide.

'86-newer engines can not be bridge ported as extensively as earlier engines without compromising the coolant seal area. This is a large reason why my engine is based off of early housings. If you are willing to compromise the coolant seal, then the Turbo II or FD engines are better to start with.