Car won't rev past 4,500 rpms
 

I finally got my 79 RX-7 running this weekend (big thanks to drozhenbane) and I got to take it out on its maiden voyage. I put in the carb I got from drozhenbane and it fired right up. My problem is that the car won't rev past 4,500 rpms. It has a new fuel filter and the fuel seems to be flowing fine. Anyone have any ideas on why my car won't rev?

Also, while taking my car on its first joyride, I discovered that I had no brakes. Come to find out, there is hole in the brake line where it goes over the rear diff. Is that a special line I need to replace, or should any auto parts store have what I need?

Thanks.

Sounds like bad cats.......

I had the same problem.......

Take them off and use a impact hammer or a long socket extention and break all that shit out of there.......

Try not to breathe the dust .

Jay
1984 FB

I will have to try that when I go home. Just out of curiosity, why would the cats keep me from revving? Too much backpressure?

also, check the timming

Buy a cat replacement pipe. Probably the best $100 you'll spend.

It is possible. Also, make sure that you're not running hot after taking it out. Might be (tho, just guessing, sorry :( ) the cats. Course, also after a good run I've noticed others having problems of catalytics just glowing red. Also, like Red87TII said, it could be the timing as well. Let us know how it goes with the troubleshooting.

I'm gonna place my money on clogged jets. Over the years you will build up a varnish on the jets that will restrict fuel flow. If the carb has not been torndown/rebuilt recently I'd start considering it...

Does the enigne make a specific noise when it hits 4500? Some people have experienced a sound that is described as beans rattling in a can. This will tell you that the timing is off. Sounds like cats is what it is to me though. Your car doesnt have "cats" exactly but they do the same thing. Besy bet is to drop them, jam a big stick into them and get all that shit out of there. Even if it doesnt help your rpm problem, it will give you more power which always equals more fun lol.

I didn't notice a rattle, but the car was so loud, there very well could have been. It would hit 4,500 and simply wouldn't go any higher. Should be interesting gutting the "cats" on my 79 with the nice rusty bolts on the underside of the car.

'79s don't have catalytic converters.

I know, but they have a system that acts like a cat, though it doesn't work as well.

I agree - or stuck secondaries. In any case, carb problem.

my secondaries were stuck shut but I could still bring it up to redline (slowly). does it feel sluggish when accelerating?

as for your brakes, I think you can just buy one from an auto parts store and bend it yourself, but Im not sure if the threads will line up. anybody else?

Well, duh. The point I was trying to make is that neither the thermal reactor or the heat exchanger have the type of internal structure that can get clogged like a catalytic converter so you can pretty much rule that out.

I'm thinking that it sounds like your secondaries aren't opening and you're going into a high-vacuum condition.

The SA exhaust system can plug up. I just had one in my shop recently. The termal reactor and what looks like a cat were blocking the exhaust flow. Engine woul not go past 5k on the street and took forever to get there in 1st gear.

A set of headers and drilling a hole in the cat with a hole saw solved the problem, along with a carb rebuild. The is no media or honeycomb in the SA's that you can drill or beat out like the FB's.

Did the thermal reactor rattle when you took it off?

Didn't look at it that closely. The owner opted for a set of headers I had in the shop and the rest of the parts went to the recycler. The secondary side pipe that runs along the main exhaust pipe was broken in half right where it came off of the engine. I figured either the reactor or psuedo cat was plugged as there was very little exhaust pressure coming out of the tail pipe. This was the first SA I have worked on and could find very little info on it.

Why are you calling the heat exchanger a "pseudo cat"? All it does is heat up air from the airpump. The reason that I asked if the thermal reactor rattles is that sometimes the inner chamber can break up, causing an obstruction in the exhaust.

Hey,
Its good to see that carb got her running! I guess I should have sent you a letter with the carb, but I forgot.....Sorry :) ....The carb itself came of a running engine, it ran great at the time, that was over a year ago. It had been sitting on my parts rack since then. In South Dakota, we have a large amount of moisture in the air during the summer, and it is very possible that the secondaries have rusted/Corroded shut. The primary jets alone shouldnt let it rev up much past 4500 if at all. The secondaries are supposed to kick in by then! On the passenger side of the carb, there is a roundish metal assembly. It has a vaccuum Diagphram inside it. This unit leads to a metal lever down lower, that attaches to a linkage that engages your secondaries. Try to manually push this metal lever in, if it is stuck, spray some WD-40 on it, and use an air hose to "Splash" it around. Keep doing this until the lever moves freely. Remember this is controlled by engine vaccum so it needs to move pretty freely in order to function properly. Another option is modifying the carb for "Mechanical" Secondaries, I would ask rx-7 carl, or sterling about this route, as I dont have alot of experience with modifying the NIKKI. On my Black one, I attached a cable from the metal lever to the opposing side of the throttle linkage to manually engage my secondaries when at 1/3 throttle! THAT WAS A BLAST! A little touchy, but fun no less. Heres a pic of the metal unit I am talking about. Good luck I am subscribing to this thread to follow your progress.....
http://www.geocities.com/drozhenbanes/vacsecondary.jpg

Hi -
I'm new here - I have a '83 that had a clogged cat and thats exactly how the car acted - when I hit 4.5k rpm it was like I hit a wall - my mechanic friend checked the cat and 2 of the 3 chambers were clogged - he broke that stuff up and solved it solved the problem. Unfortunately I believe the back pressure did a number on the apex seals b/c the car started smoking alot more at that point - also b4 we broke up the innards of the cat my mechanic replaced it with a nonfactory replacement and within 2 weeks the problem came back - apparently the aftermarket cats can't take the heat generated and the insides melted and then clogged again. I'm not saying your 79 has the same problem - just thought I share my experience. Oh yeah - after the cat was "cleared" whatever performance was lost due to less compression was offset by having in effect a clear pipe.
Good Luck!

Is there any way to test if my exhaust is clogged without tearing everything off?

Because I couldn't remember what the thing was called. :uh: 'Pseudo cat' was the best description I could think of.

I was aware of the possible breakup and plugging in the thermal reactor, that's why we went with the headers. Worked out well in the long run, most of his exhaust was falling apart.

THansenite, did you solve the problem? I have a FB (GSL-SE) with a very similar problem. It is all stock, 83K miles and will not rev past 3K after it warms up. I replaced the fuel filter and cleaned the mesh filter going to the stock fuel pump. Looking for a fix. Thanks.

Last time THansenite logged on was 2016.