How thin is TOO thin?

I have some T2 side housings that have been street ported, and I want to duplicate my earlier half-bridge effort, but the ports have been opened to within 12mm of the coolant groove. Stock appears to be about 14mm, so I'd be looking at 3mm wide bridges.

That kinda worries me.

If it matters, I think I was only making the eyebrow 30-32mm high.

 

Nobody?

 

I have zero experience but I would thought that you already know seal traces pretty well.
Or do you concern about bridge cracking?

 

alternate is to cut into the rotor housing to move the BP further away from the main port opening.

 

Yeah, I'm not worried about the seal tracing so much as bridge failure.

The problem is that these are groove-in-sidehousing engines so there is very little room to go for making the eyebrow.

 

i know where the seals reside, the opening doesn't have to be fully inside the rotor housing edge. ideally you want about a 2mm wall from bridge to coolant seal wall or slightly larger.

 

My only other FC style bridge port had teeny tiny eyebrows (9/64", IIRC) and they were still within 1mm of the coolant seal groove. If I were to leave these housings with 5mm thick bridges, then I'd need some super tiny tools to make a bridge that small, and it would probably be pointless.

Eh, I'll just scrap the housings. They're kinda ported too big/late for good power anyway. Kind of a shame, since I bought the engine as a cheap way of getting a good center and rear housing, but what can you do. We thought it was a stock port.

 

What if you port into the coolant seal groove, put pins at either end in the groove so you don't suck the coolant o-ring into the intake port.

Then use Hondabond or something on the side housing to rotor housing for that little bit of contact they still have to seal them?

If you then run Sierra Pet safe at 100% in a non pressurized cooling system it should go forever without leaking coolant into the intake port.

You get to play with a more aggressive port, try something new and save some side housings!

 

or you could always scallop the rotors and get some more port timing out of it

 

I really, really don't want to compromise seal integrity. I'd be worried about it every time I see the temp gauge clock past 230 at the end of a run.

I thought about it for about five minutes. I don't want to have to worry about it.

 

What would you worry about? That it might develop a drip and you suck some coolant into the intake ports from intake vacuum?

Your engine won't care.

With the 100% Sierra in 0psi system you only get a gravity drip with a coolant leak no matter what the temp is.

Besides, I use Hondabond or Rightstuff with no issues on metal on metal no gasket on the front cover, oil pan to baffle to block, water pump and water pump to block.

I have run my engine completely out of coolant in a race (forgot to torque block drain) idled it while run group finished, drove it back down the 2+ mile course to pits, let it cool while I worked the next heat, blocked the hole with random bolt wrapped in electrical tape to fit and wedged in place, put coolant in it, drove back to hotel with no leak, got another drain plug, raced it next day and on- no issues with that motor (till it ate an EGT probe and pinched a corner seal). The no gasket Hondabond/Rightstuff seals were all fine from the temps/expansion/contraction.

Only place I had an issue with Hondabond/Rightstuff with no gasket was on the turbo oil feed. The excessive heat transfer from the turbo center section to the oil feed line caused the new stock turbo oil line to crack from expansion where the tube met its flange during repeated 4th gear tuning runs. Note, there was no leak on the housing to flange Hondabond seal.

I learned the stock gasket here is Asbestos and the bolts are SS to stop the heat transfer- I now use the Asbestos gasket even after I went to SS Swagelok fittings/tube to -AN for the oil feed.

 

or you could always scallop the rotors and get some more port timing out of it

I really really want to try this mod, but I am too cheap to get my rotating assembly balanced!

I have also heard this makes the side seal slots more prone to foreign object damage, but it would seem like the gap to the rotor housing to rotor at the bevel would make it really hard to pinch something in there to start with...

 

I can't use that stuff, it's way too expensive. It's what, $40 a gallon? That's an awful lot of money to spend on a disposable item, that WILL need replenished on a frequent basis. I go through a lot of radiators and hoses.

Another problem is freeze point. It gets cold enough here that pure ethylene glycol coolants will freeze. I can't find data on propylene glycol coolants but knowing the two chemicals' similarities gives me pause.

Another (huge) problem is operating temps. I get my best operating temps on a cooling system of pure water and Water Wetter, or a few drops of dishsoap when isn't available. The antifreeze hurts the heat transfer ability. Pure water corrodes the aluminum housings like nobody's business, though

Funny story. I use Right Stuff. The latest engine I have in the car was a GSL-SE block, straight GSL-SE everything internally, nothing fancy except for a couple 18mmx8.5mm eyebrows on the secondary ports. (More on that later) I used NAPA 18ga hookup wire for assembly like I did on the previous seven engine builds I've done. I know for a fact that i torqued the tension bolts to 23ft-lb like I always do. Anyway, I drove the car for about 500 miles this winter before it started blowing coolant. I figured it was due to the ~10f temps and the necessity of immediately putting the engine under load on a cold start because it's a half bridge and I park my car where I can't sit there for a half hour blipping the throttle to keep the plugs clear while waiting for the engine to come up to temp, combined with the wire jacketing's (lack of) elasticity.

Anyway.

Pulled the engine apart yesterday morning. None of the tension bolts had any more than maybe 5 ft-lb of torque on them. (Huh?) Inspection of the coolant seals revealed that none of the inners were burnt yet, but they were discolored. The outers, however, all showed signs that they didn't fit in the grooves and were holding the housings apart. Conclusion: The outer seals were holding the housings apart on initial assembly, and the four or five heat cycles it took for me to rack up 500 miles were what it took to compress them further and relax the tension on the tension bolts. And for those 500 miles, the only thing holding combustion gases at bay was Right Stuff.

I have two engine's worth of 2.4mm Viton and 2.0mm neoprene cord stock. I'm not going to use the wire anymore... And the bridge eyebrows are now 32mm tall, same as my first half bridge. This is either gping to work well or it's going to suck, so I'm building this engine's replacement immediately after I have this one in the car.

 

Man Peejay, I think you take the cake when it comes to the cheapest rotary rebuilder.

 

Well, when you process as many engines as I do, you have to economize somewhere

I think I may have the air filtration problem handled.

When I eventually go piston engine, I'm going to laugh in the face of anybody who says I should give rotaries a chance. I've been going full bore Sisu with rotaries.

 

this is true. one of our drivers got a ride in a 1970 boss 302 trans am replica, and he's hooked. (you actually have to DRIVE the car, and he liked that) anyways, his father in law has a mustang they wanna get rid of, so we started looking at v8 stuff, and i'm surprised at how expensive everything is, its like porsche prices. $7-8k for a crate motor? $1000 for a holley carb? $1000 headers? you could almost build a 911 engine for that, and it'll make 350hp too AND run @full throttle for a couple days straight