Here is my story…. I just bought an FD a 1993 to be exact. It has 56K original miles on it. It probably has not been mechanically maintained the way it should have been, but I digress. I bought this car knowing it probably needed a motor and turbos. Here is the summary of the story; the car has low compression (40 PSI on chamber #1 and 80 PSI on chamber #2) I get 3 equal bumps for each chamber during the compression test. Some of the symptoms are as follows: (1) cold starting takes a couple more revolutions than it really should (crank it over for 4 seconds or so) (2) Hot starting takes a lot more. I have to hold the gas down like ¾” while I crank it over and then it finally starts. (Cranking for like 9 seconds) (3) Once warmed up the car will not idle below 1250 RPM without feeling very stumbly. (4) @ 1200 RPM it only pulls 10 - 11 inches of vacuum.

So here is my question. I am looking into rebuilding the motor. I have rebuilt piston motors before with much success. I know rotaries are easier that piston motors. My goal is to end up with a street ported engine and 3mm apex seals. My goal for this FD project is 400WHP (With single turbo). I am unsure however, what other internal mods are good ideas for reliability at this power output.

My main concerns with rebuilding or getting a new/rebuilt motor from a company that is already done are:
- Oil porting (how necessary is this, to what level, and what exactly is done in this process? What is the goal of oil porting?)
- Coolant porting / modification (Pretty much same questions as above).
- What about dowel pinning the block, I have heard it is unnecessary for anything under 450WHP. Myth or fact, what are your findings?
- What else should I consider as far as specialty parts to use? For example, I have been looking around and saw Hurley springed corner seals and specialty tip seals as well as side seals. How important is it to upgrade over standard 3mm tips and stock type side and corner seals? Is it really that important?

Any other info that may be floating around with people “IN the Know” about rebuilding would be greatly appreciated too.

I have searched for 10s of hours and I mostly find biased info and second hand knowledge. I am really looking for some first hand knowledge and recommendations here.

I appreciate all of the input.

 

There are several people doing/have done rebuilds recently; Mahjik, rynberg, herblenny, just to name a few. You could check out their topics on their rebuilds and ask them specifics on their process.

 

I haven't updated my rebuild thread yet, but here you go: https://www.rx7club.com/showthread.p...hlight=rebuild

In addition to the build options in the thread, my builder removed the thermal pellet for reliability. Feel free to ask me any questions.

 

In my experience -

Dowel pinning - save it for the big leagues. I would say 550hp+
Water Passages - always a good idea
Oil porting - no knowledge, (unless you are referring to the 3 window mod) I just have the upgraded pump to keep my pressures higher than stock


I've heard good and bad things regarding Hurley seals, so I wouldn't know.
I've always been a fan of the Hayes Rotary coolant seals. They are MUCH more durable than stock "rubber" bands, and are able to withstand 1500F, (where you're motor would be melted through undertray anyway)
When I rebuilt my motor, I had the rotar faces ceramic coated to help disapate heat, and I too removed my thermal pellet.

For the porting, grab the templates from Racing Beat...

Hope this helps.

 

This is great, these are tips and tricks I was hoping for.

 

Stick with the stock seals and stock parts.

If you could afford it, go with new housings.

Dowel pinning, i think its a waste unless you are going to make power and trying to acturally put it down. Otherwise, just stick with what you have.

Water passage, I think its also waste of money. Unless you are looking for that extra cooling.. but better to get an upgraded radiator.

Don't try to rebuild it yourself unless you are willing to go thru couple of motors. If not, get someone to build it for you. Someone with alot of experience..

Most important thing of all would be to make sure you get your car tuned by the right person.

 

Can it really be worth it not to do the rebuild your self? I guess you would save a lot on shipping by doing it yourself.

 

I think it's a matter of doing it yourself or doing it accurately yourself. I have never rebuilt a rotary engine, but from what I've read and learned, there are procedures that you need to follow down to the wire that would be less forgiving if skimped on an equivalent piston engine rebuild. I think the key is attention to detail which a lot of people may overlook because of time or budget restraints.

 

Who is the most reputable engine builder for the price?

 

what is the general concensus about dowel pinning a motor. is it really important for the 400whp power range?

 

There are lots out there... your best bet might be to find somebody local to you (try the regional forums). Otherwise, there is pettit, rx7store, mazda remans, etc. Search on rebuilds and you should get a better idea of what you are looking to do and who can do it for you.


Nope.

 

no, don't waste time or money on dowel pinning your motor. and stay far FAR away from any hurley engine internals, esp their apex seals. trust me, they break at the drop of a hat. Go with mazda internals, with the exception of the upgraded coolant o-rings if you must.

Instead of spending all sorts of cash on extras that arent needed, invest the cash in a good water injection setup. seriously. it will save you many blown motors.