gosman

This is a true story. I kept my 1979 RX-7 for over 30 years. Only one refresh done on the 12A. Three years ago I gave the car to a retired friend of mine down the street. I knew he would not destroy the car. He proceeded to drop a 13B Bridge rotary with a 4 barrel Holley in it. Over $7000 of modifications in addition: new suspension, fuel tank, radiator, battery, wheels and tires, brakes on and on. When I gave him the car, it was not running. I only requested one thing, if you ever decide to sell it, give me first chance to buy. That day has come. But my little mild mannered Clark Kent has emerged as Superman! This is now a race car with that familiar sound of a bridge motor! Straight headers with a very limited restrictive muffler is so loud that my wife is embarrassed and my neighbors will soon have little patience for me. At 65 years old, this is not my kind of car. Many here would probably die to have this car. I am afraid that a youngster will tear this up within months and my 35 years of patiently keeping this car around will be all for naught! So I want to keep it or sell it to someone that will care for it. With few people like that out there, I most likely will get the car back for much less that my friend has put in the car. So my choices are:

1. Drive the car and know that it is no longer a day car and will be just driven occasionally putting up with the noise and rattling of the body with a high revving engine that every kid in town will smile and envy as I pass by. Neighbors will hate me and my wife will never be seen in it with me.

2. After speaking with a local Rotary shop, I can have them return the car to it's formal glory with a little more power by changing out the bridge rotors with some normal ones. Keep the housing and all the new seals. They also recommended going back to the old Nikki carburetor since the Holley is way too much carburation for this engine. But this would be some major cost to do this. But this would still give me more power than the 12A with a lot less noise. Their opinion is that the bridge will never allow a descent quite running street car.

What are your thoughts? What would you do in my case? Sell it to someone that will race it and tear it up or try and save it by giving it a new life with less noise? Knowing that I may have to put another at least $5k into it.

WANKfactor

iTrader: (1)

What a great story! It would be a shame to sell it since it sounds like you have emotional investment in the car.
Is it possible to have your spanner wielding neighbour or the rotary shop build you a nice mild 13b engine and sell the bridgey on?
If the suspension is all solid bushed and the interior is stripped out it might be a bit of a bugger to put up with cruising around.
Or maybe join a mazda club and enjoy the car on special occasions and friendly events and road rallies?
You could possibly quiet it down a bit with heavier straight-through mufflers (and more of them) with out shutting the motor down too much, and reintroducing some body deadener if it has been removed.

Some pics would be great. Sounds like a tidy little unit!

gosman

Pictures attached I hope!?

perlhaqr

So... what's a bridge rotor? Does it have something to do with avoiding compression losses / exhaust to intake contamination when the rotor is going across the ... hump, in the combustion chamber?

diabolical1

iTrader: (3)

if it were me after 30+ years with my '79 ...

i would likely keep it as is, just doing events and stuff on occasion. however, i would also have a street rotary, too. since this is your only one, if you want to drive the car often, i can appreciate being apprehensive about the noise (more so than what my neighbors would think about it), so i would likely choose choice #2 or at least a variation of it.

selling the engine as a package (Holley, exhaust and all) would make the most sense, but then it leaves you building something from scratch. that sort seems like a waste of a known good engine since you're not likely to be able to sell it for enough money to cover buying a good core and a decent build, then intake and exhaust.

on the other hand, rebuilding this engine with stock ports is a better idea since you could get a set of side housings for a few hundred (once you find them). hell, you might find a whole 12A for a few hundred if you're lucky and can take what you need and sell the rest. however, it still leaves you having to get some sort of appropriate intake.

the advice from the shop is a little misleading in the sense that you would, indeed, have to do something about replacing that Holley. however, if memory serves me, the older carb'd 13Bs used Hitachis, not Nikkis, and i don't think they will interchange without some sort of adaptation (i would need to double-check that). either way, i'm not sure how easy it would be to source a stock 13B manifold, so you'd either have to work at adapting a 12A manifold to work or look for something else. then, of course, there would be tuning to do. overall, i don't think it would be too complicated once you had the parts, but again, i don't know how easy it would be to find some of them.

you could also go about trying to "tune out" some of the bridge's signature sound and then work on muffling it while maintain a somewhat decent flow. if you look up the member Peejay, you should be able to get some good info if this interests you at all. you could probably even Megasquirt it, like he did, using most of what you already have. there are videos of his car around, so you can judge for yourself if it's too loud for you.

at the end of the day, this endeavor will be like everything else. it will come down to budget. the options are out there. find the one that fits.

diabolical1

iTrader: (3)

welcome to the board.

in the event that this is all new to you, look at this: https://www.rx7club.com/new-member-r...rimer-1039179/

i may be overstepping by answering for him, but i think that was simply a case of thinking one thing and typing another. i think he simply meant to type "housings" instead of "rotors".

gosman

The porting primer was most excellent! Perhager this should help you with your question too! Too bad I don't know what I am buying. My little fire-eater of a car is getting more popular as I read up further! I may have to list it for sale if you guys keep building it up!