I just took a 74 13b apart. 3b plates and the old school MAZDA font rotorhousings. The plates have been mildly streetported. Since the intake runners on the plates are small, how much if any should I increase the intake ports? It's for my REPU with 4.625 rear gears that is for fun - secondary transportation and weekend stuff.

The straight edge lines up with the bottom of the tension bolt for reference.

Is the corrosion by the water seal a problem? And, can it be lapped out?

 

Can a S4 or S5 Turbo exhaust sleeve be pressed into this rotor housing? Where would I get one and what can be done to make it stay in? Has anyone gotten a hight temp adhesive to work or do you weld it in?

What should be done to the exhaust port to improve it? Should I port downwards and round the bottom? How much should the exhaust be ported to best match up with the intake ports?





No exhaust sleeve! Where can I find a replacement and which ones fit? How to keep it in?

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those sleeves have roll pins that hole them in. funny tho, my 74 13b has tall intake ports in the center housing. urs might be 76? do those rotor housing have the blocking plugs in them? i have them in mine.

 

It may be 76, dunno. I thought the 74-75 REPU had the smaller runners, and 74-75 cars the larger ones. I have the blocking plugs installed in the pics.

 

It's actually good that the exhaust sleeves are out. They are quite small on '74-'75 housings. I'd recommend squaring up the closing edge and redoing the 2mm 45° bevel.

The intermediate plate is a true '74-'75 3B casting. Don't let others tell you otherwise.

I like the look of the intake ports. They look very well done. There is even a little smoothing near the end for the side seal to remain healthy. I'd say leave them unless you know exactly what port size you want, and the matching carb etc. But why go bigger? They look really good.

 

i agree. except the sleeve is fine, the later engines are too big by the time they get to the header flange.

AZ rotary rockets makes sleeves, maybe they have something that would fit?

 

Any more input on the intake ports? Should I port them out some more?

 

i wouldn't.. another milimeter here or there isn't going to make a difference

 

Well I bought the Racing Beat Streetport template and marked it on the intermediate plate. Per the template, I can go up 3.5m to 5.0mm and back .89 to 1.4mm. And curve the bottom a bit.

Anyone know if the 3B plates can take that much grinding?

And the intermediate plate can be lapped with 3 thou to spare!!

 

Plates are getting the Racing Beat streetport now. Unfortunately the intermediate plate had only 3 thou of wear left on it, wasn't worth doing it's 2 ports only to have it last one rebuild.

So I had to dip into my brand spaking new intermediate plate supply.

 

Brand spankin new, eh? I hate you....

Ports look good, but I'm no expert. Good luck with the build!


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Brad, I'm running the 1/2sp-1/2bp in the widebody w/o the sleeves. Others have done the same with no issues. I would fill the exhaust port holes with lab metal. Pricey, but it's about the only material that will hold up to the heat.

Drivefast. The best way to tell if you have more material to port is stick your thumb in the intake port and the fore finger in the port itself. When you get down to 1/8", stop.

 

hell ya 74 housings!! I'm still waiting for mine, wow and those are the 74 13b plates too

 

someone else is porting it, i figured out it would cost me more for the tools, time, purchasing / disassembling / practicing on junk housings than to have someone else do it right the first time.

the exhaust sleeves greatly reduce transmission of heat from exhaust gases to the coolant. when i accellerated full tilt i saw the coolant go up in temps very, very quickly. quicker than any other rotormotor i've owned which all had the sleeves. including the previous motor in the same REPU. the sleeves are made of iconel, real good stuff for exhaust. the grand-am daytona prototypes use it for their entire exhaust system!!!!

so new rotorhousings getting streetported too. had to dip into my new parts bin more than i wanted to, but it'll last longer and make MORE POWER. AND BETTER GAS MILEAGE.

yeah, all 3 plates are 74 3b. i pickled the intermediate plate in case i need it in the future. especially if california makes me smog a 74 truck anytime again (it has the coolant port on top to heat up some smog part). every few years the politicians here think about removing the pre-1976 smog exemption. plus good usable 12a used plates are getting hard to find.

it's also getting the bigger 17.5mm oil pump (hardened gearset), 4 new bearings, ALL new seals, and i can shim the regulators more to get some tasty oil pressure. the motor should really hummmmmm when it's all done.

And Dupli color has high temp engine paint that'll match my truck. Even called Racing Green Hunter.

 

Had it all ported to Racing Beat template specs. Here are pics of the front plate, the shop fixed the port cleanup job done by another place, and used RB streetport template per my request. Enlarged the runners too.

Lapped. I'm wet sanding the plates with wd-40, 600grit, very light pressure, and a 2x4 as my sanding block.. How do I know when to stop sanding and put er in the parts washer? How do I know when all the lapping compound is removed?

Anyone know of a cheap easy to get rust inhibitor for a water based parts-washer running one part Simple Green to 9 parts hot water? I don't want my irons to rust in the parts washer.

 

If the parts stay submerged in the water based solvent, they shouldn't rust. The less time in the, the less chance of it happening. Once you're done cleaning them, wash them with dish soap, rinse with cold water, pop in a warm oven to dry out the cast iron, spray down with WD-40 when dry.

 

Thanks trochoid, they did rust some while submerged. I tried the dish soap too, afterwards it flashed rusted pretty quick. So next time I sprayed the plate with Metal Ready and scrubbed em with green Scotchbrite before and after taking it out of the parts washer and that did the trick.

Also sprayed Metal Ready down all the coolant and oil passages to get rust out of there too.

Oven helped dry them too.

 

my PP is all new too, it really runs good, its worth doing.

i also shimmed a regulator, i forget how much, i think i doubled what RB says for the front regulator and then a little bit, with 20-50 it does 100+ psi on the stock gauge