j beeman

I have experience building reciprocating engines, but none with the rotary. I have been told that street porting a 13B will have the same result as installing a race cam in a reciprocating, that being increased high RPM power at the expense of low end torque. Is this true?

Also, if anyone has input on my question regarding starting a 13B that has been sitting for years, I would appreciate that answer as well. I know there is a lot of experience on this web site. I posted it in the wrong forum and didn't get any responses, maybe I will here, in the right forum. Sorry to post it again but I think it was missed. If this is rude, please let me know, I'm new to the site.

I am now the proud owner of a 13B engine that hasn't run in about 6 years. The engine was rebuilt and started with new rotor housings, rotors and practically everything replaced with no modifications, then put in storage in a friends garage waiting for that perfect project that never materialized. I now own the engine and I am lacking in rotary skills / knowledge. I have done all of the things I would have done with a recip, pull the plugs, put oil in the cylinders (OK, chambers, old terms die hard), and turned it over by hand. The engine is free and turns easily with the plugs removed. I then turned it over with the starter for about one minute and it seemed smooth and free. What concerns me is that the oil that drained out of the chambers through the spark plug holes when turning it over was slightly rust colored. If this was a recip I would start it and change the oil after running it a short time. What do you recommend that I do with this engine? Do you think it needs to be torn down and inspected, cleaned, and reassembled? Does anyone recommend just starting it up and running it? Any input from you experts is appreciated.

mar3

iTrader: (8)

Street port done all by itself would be more like sliding in a Comp Cam 268H grind into a 400+ cid V8...I wouldn't say race cam at all. That was my experience but with a 12A and the stock Nikki carburetor.

Let's see what the EFI 2dgen rotary guru's have got to say.

Mario III

diabolical1

iTrader: (3)

the average streetport gives a solid bump in power from the mid to upper ranges of the powerband. usually, it's definitely NOT akin to a race cam or race-prepped head(s). i hear many people say that it sacrifices low end, but to be honest, i don't agree with that. i've found they usually retain whatever torque they had stock in low RPM operation and a notable bump in the middle that lasts longer (maybe not the right wording). that said, i have seen streetports that were big enough to affect idle and had a much more riotous powerband.

as for your other question, it would be best to actually do a compression test and know for certain where the engine is right now, but if you're getting good, even pulses in all 6 chambers, then i'd say you could start it as is. i, personally, don't see a need to tear it apart unless you were experiencing less than free rotation or no/weak compression.


Mario, if a 268H cam is mild to medium on a 400, then you're right.

j beeman

Thanks for the replies. When I noticed that the oil coming from the chambers had a slightly rust colored tinge after turning the engine over for a while I was hesitant to start it. I am not sure what any very small particles could get caught up in and act like abrasive powder. In a piston engine it is normally just expelled through the exhaust or into the engine oil and collected in the filter. I will try starting it when the weather warms a little.

Aaron Cake

iTrader: (1)

It's kind of too bad you turned it with the starter. The little bits of rust basically are sand paper being pumped through the engine and are the result of the engine sitting in a garage without being properly stored. They may have caused damage, maybe not. Nice thing about the rotary is that you can just take a flashlight and look through the exhaust parts and see the whole bottom half of each chamber. Check for pitting, scratches, etc. It may have just been surface rust, or it may be worse. I suspect just surface rust otherwise seals would be stuck in place.

Defining the term "street port" can be a bit of an issue. Some street ports hardly effect port timing at all, while some people consider a port that causes the engine to pull 6" of vacuum and not idle below 1500 RPM to be a "street" port. In general though, most reasonable street ports end up not really effecting low end torque and vacuum all that much. You didn't mention whether the engine was a 6 port or 4 port, and when talking street ports, there are some key differences. For example, porting the secondary and aux ports in a 6 port engine almost always results in the loss of low end torque. Porting the secondaries in a 4 port engine won't, if the port is reasonable.

These two videos may help you a bit.

The first one shows disassembly of a 4 port 13B engine, from my '76 Cosmo:

http://www.youtube.com/watch?v=W1MXfs_Srs4

This second video shows a conservative port job. While it is a very different port job than would be done by most people on an RX-7, it does show how porting is done and goes into a little bit about why I ported it that way.

http://www.youtube.com/watch?v=y1Gy5sVMK3o

rotor2067

rusty looking oil is from letting engine sit around for a while.?.... ive found sparying a bit of wd40 in plug holes and turn over engine.... run for a while...change oil ect..should be okay...as long as you have good compression... also cannot use normal comperssion tester..has to be a special one for rotarys... and a small tip.. not leave engine sitting for long periods...always start it every now and again....to stop any seals ect from perishing inside... and porting motor is always good for power increase...and you cant beat the sound :-D

j beeman

Thank you for taking the time to reply Aaron.
I mistakenly said that the engine was a 13B, it is a 12A. I made the mistake because my boat engine is a 13B. I put oil in the 12A chambers and turned the engine over by hand more than 30 revolutions before trying it with the starter. the engine showed no resistance so I used the starter to be sure I would be able to do a compression test. That is when the oil came out through the spark plug holes with a little rust colored hue. If it hadn't turned freely by hand I would not have used the starter. Still, if the oil has a rust colored hue there are rust particles, albeit small, in the chambers.

On the other matter of the boat engine, I believe it is a 4 port, but I am new to rotary engines. I have a lot to learn and am trying to do so. I bought the Atkins Rotary overhaul video to familiarize myself with the internal parts and design, it helped, but there is a lot more to it than just knowing the parts and how they fit together.

Here is a photo of my boat engine, anything you can tell me about it is appreciated. I don't know what model it is.

rxtasy3

iTrader: (2)

yes u can, just have to remove the schreider valve.

Aaron Cake

iTrader: (1)

Sounds like you are OK on the rust then. As long as there isn't any obvious damage when looking through the spark plug ports or exhaust ports, and as long as it turned freely, you're probably fine.

If you can take a few more picture of that boat engine from different angles (especially spark plug side and front) then it would be helpful. Looks like an interesting piece though!

j beeman

Hi Aaron,
Here are a couple of photos of the engine. I hope you can identify it.

rxtasy3

iTrader: (2)

by the shape of the intake mounting flange it's definitely 86 or later engine but removing the intake will prove whether it's a 4 or 6 port. but it just might be a T2 engine, making it a 4 port.

aaron, i can't believe the shape those rotor housings r in. was it a low mileage engine or had it been rebuilt at one time using new housings?

j beeman

The engine was new from Rotary Power Marine in about 1997, if that helps, and I was told it was an engine that was designed to be turbocharged. I was asking about the low end torque because of it's importance in boat applications. If you can only run one gear (prop pitch) then it's always a big compromise.
I am not looking so much for top speed, because in a 15' I/O boat the rated 240 HP of the rotary is more than adequate in that department. I am told the boost is set to 7 LBS. The boat came with a 90HP Renault Gordini engine, and I later changed it to a GM 2.5 inline 4 (120HP). I want it to pull very hard from low RPM for skiing, hauling around a bunch of lardass old guys, and fast 0-60 times. I can limit the top speed by my selection of prop pitch.
I don't want anything to go wrong with this engine so I have decided to send it to a shop near me for disassembly, inspection, and reassembly. I talked to some guys at A-spec tuning and as far as I know they seem professional and knowledgeable, but I don't know much about rotary engines. It seems like the prudent thing to do since it has been sitting so long.

I realize I am asking a lot of members in this epic post, but I have another question. Have any of you heard of or used an Alpha PI042 engine management system? That is what is on this engine and it is made by a company called Webcon http://www.webcon.co.uk/ The system was supposed to be set up correctly for the engine at the factory, and it was test run, but I don't have any support for the system. I am considering changing to a Microtech, but it may be hard for a tuner to do the job on a boat.

I included a couple photos to show the size of the boat. 15' is very small. It is the smallest factory I/O boat that I am aware of. It went 50 with the 120. I built the interior, but it has to get a new one with this upgrade.

Thanks again.

Rotor_4_Life

Good thread!

Aaron Cake

iTrader: (1)

Looks like it may be a hybrid engine using TII irons and NA housings. I don't see the knock sensor port on the housings, which is why I believe they are NA. It's an odd, interesting and unique engine. Not necessarily because it is a TII engine with NA irons, but because of all the stuff that is bolted to it. The center iron makes me thing early 13B or GSL-SE though. Which would indicate earlier 13B housings.

rxtasy3

iTrader: (2)

t2 irons with early 13b housings would mean they had to deal with the extra set of O ring grooves.

j beeman

Is it good etiquette to ask about other's experiences with a shop by name on this site? I am interested to know if anyone has experience with them. They seem to be knowledgeable on rotary engines.

diabolical1

iTrader: (3)

generally speaking, there shouldn't be an issue with asking questions. i don't know if the mods want that stuff here or in the appropriate Regional forum or the Good Guy/Bad Guy forum though. tact is usually the key though.

Aaron Cake

iTrader: (1)

Of course. Which is why I make the distinction of 13B housings only being used with a GSL-SE center/end irons.