mrcivic69

iTrader: (1)

Hello everyone,

Its been a long time sense I visited the site and happy to be back. I have finally got to a place in life I can finish off my project 7. I have owned a 1985 RX-7 GSL for about 10 years and it has been sitting for the last few years because of lack of money and other real life problems.

But like I said now is the time finally to finish it. I never was thinking about doing engine work but now that I am settled I am thinking that why not make it amazing.

I have been doing lots of reading and searching on the web to learn more about porting. I get the general idea of it and think I want to give it a go. I am leaning towards a bridge port job but I am not sure how hard that is to do for a first timer.

I am about average at wrench turning and think I can pull it off. I have looked up some templates and don't really know which is best. And for the exhaust port job I never see anything called "bridge port" just "street" or "race" so I dont know what matches a bridge port job.

Basically I have alot of odds and ends and questions but I think maybe that is enough for now. If anybody has any tips or advice I am open to everything. And if anybody has "work in progress" pictures that would be the best.

Thank you in advance... And glad to come back to Club RX-7!!!

Opeth1stgen

iTrader: (3)

So your leaning towards a Bridgeport, is porting easy? I think so, with the right tools, patience, and a steady hand its possible to make a nice port. Racing beat is a good place to start for templates, there BP template is conservative and still gets the job done, for exhasut go with a race port, BP engines need to breath. Search the forum and you will find many threads dealing with bridgeport engines. But I must say a BP is not for everyone, starting from a stop there is very little torque so stop and go driving is horrible, only till about 4000 rpms does the engine start to wake up and above 5000, massive acceleration! and in order to get the most out of a BP many things must be done to support the high rpm's the engine is capable of. I included a picture of a bridgeport I did using the Racing Beat template. hope this helps.

bahlorm

Quick question, you have to pretty much take apart the engine to port it correct?

cfamilyfix

iTrader: (15)

^yeah you can only port a motor when it is apart

mrcivic69

iTrader: (1)

First of all thank you for your tips and input.

I am leaning towards bridgeport but I do plan on driving the car on the street mostly and many some track/autocross. I know the bridgeport has bad low end power but I live in a smaller city so there is not lots of stop and traffic.

I am wondering though when you say you need other to do other things to support bridgeporting. I am guessing you mean like bigger carb and that type of stuff???

I guess the biggest reason why I would like to try bridgeporting is that I have a fear of tearing it all apart and say do a streetport then put it back together and be alittle disappointed with the small increase. Oh and I do like the lumpy idle LOL.

Thanks for your advice so far and I hope to learn some more about porting.

P.S. That is a VERY nice bridgeport you did!!!

Opeth1stgen

iTrader: (3)

Yes, a bigger carb is needed weber 48 ida is what I use, but I meant supporting the high rpm's a bridgeport will be doing, its good to have the engine balanced and rotors clearanced, hardened stationary gears, competition bearings are a very good thing to add, All of these details depend on what your goals are. search the 1st gen forum for bridgeport and you'll find alot of good info (use advanced search) also mazdatrix sells a video about porting thats pretty good.

mrcivic69

iTrader: (1)

Wow thanks for the input on beefing up the internals.

As a first timer I really never thought about that stuff. It does make alot of sense though and is starting to seem like maybe a bridge port might be alittle too much for basically a street car.

I don't know alot about a street port like how much better it is then stock but I just figure bridge port would be a very nice jump. I guess I am alittle tossed up about which way to go as I don't have many stories to go with.

I have seen some nice street ports and I know they are still very good on the street. I just dont know if the power gain will be "worth the time" Do you have any advice or thoughts of street vs bridge???

P.S. I will be ordering the Mazdatrix porting and the rebuild DVD they offer. It looks good and any info I learn is a bonus.

Thanks again!!

DriveFast7

iTrader: (1)

The full bridgeport kicks and bucks under light throttle (cruising) at and below 4000rpms. I wouldn't drive on on the street. What you could do is a short bridgeport. Make it half the length of the pic posted earlier on this thread. The closing half. That way it won't open so early and cause exhaust gas dilution.

A streetport will give about 20% more hp in and of itself.

Here's a nice mild streetport. Closes 3mm later than the Racing Beat template.

mrcivic69

iTrader: (1)

Hello Brad...

Thank you for the input. The street port is the safe route I think but at 20% it is a small gain. I didn't really know about the bucking and all that at crusing speed with the bridge port. Very good information to have.

Now you said I can do is a short bridge (I take it that is half bridge) and shorten it on the closing half. Now this might seem like a dumb question but is that the half where it gets narrower?? Like just make the bridge stop shot of the original port??

Once again this is my first time I will be porting or rebuilding and any info is a life saver (plus money saver) so I thank everybody for their help.

P.S. Do you know the typical % gain of a half bridge, and full bridge just for giggles??

DriveFast7

iTrader: (1)

A half bridge is when you bridge port 2 of the 4 intake ports. Since 2/4 = .5 = half that's where the term came from. What I was talking about is a 'short bridgeport' and you shorten it on the opening part, or the bottom part. And only port the later part which is closing end of the intake cycle.

For % gains, you'll have to look around for it.

mrcivic69

iTrader: (1)

Thanks Brad for the explaination on what was a half bridge. I would have never figured that one out. Don't know the
pros of doing it that way but sounds like it would un-balnce things... but idk im a rookie.

As for a short bridge port that might be a happy medium from street to bridge. I do plan to drive on the street and
might get tired of the bucking while cruising.

So if your looking at a standard port your saying that the smaller narrower part of the port is the opening and
begining... meaning the rotor is spinning couter clockwise while looking at it like in your picture?

Sorry for so many questions.. I am fairly new at all the insides of rotary.

Thank you for your time EVERYONE!!