So let me start off by giving you some information about the car. I have an 85 gs rx7. The car has a 2nd gen turbo block with 2nd gen N/A rotating assembly. The engine was pulled from my buddies running 2nd gen car and the car ran absolutely AMAZING! Since then I have added a stock turbo and changed the front cover of the motor to a 1st gen front cover so I could mount it into my car properly. I am also using the original 12a transmission in the car.

So now the problem... When I go to start the car the vehicle shakes like CRAZY! It seems very violent. From what I have read and from the people I have talked to everyone keeps telling me that it sounds like the counter weights are either wrong or off balance. Sadly I forget what flywheel I am using. It has to be either the 12a one or a 2nd gen N/A flywheel. When I changed the front cover I didn't touch the oil pump or anything else is there anyway I could have messed something up in there? Anyone have any ideas??? Also what would the differences be between a 2nd gen flywheel and a 1st gen? Any help would help me a lot so don't be afraid to comment! Thanks guys!

 

Firstly... You're gonna find out what pre-detonation is in a hurry if you crank up the boost.

You need the second gen flywheel to properly counter balence the FC engine.

Did you swap the front counter weight? If you did I'd stop running the engine untill you check the throw out.

 

Do not worry I plan on running very low boost! The front counter weight was never touched only the front cover was taken off. Anyway the front weight could have gotten messed up while taling off the front cover? Like if it spun or moved or anything. Also I don't remember what flywheel was put on the motor. For some reason I really believe it was the 2nd gen flywheel that was left on the car. If I pull the trans off can I tell by looking at the flywheel if its a 2nd gen or a 1st gen an if so how do I tell? Also if the front counter weight was off how do I set it back to where it should be?

 

The 12A has a smaller clutch disc than the 13B.

I don't see how it would be possible to spin the c weight or the flywheel around and not know it. The engine wouldn't re-assymble without the keyway in place.


Shaking like mad for other reasons though???

 

I have no idea the. I did notice when you rev it up a little it seems to smooth out a little bit. Still shakes like crazy but it definitely smooths out a little bit. Anything else that would make it shake like crazy? I checked the flywheel today and it didn't look bent or anything.

 

well what condition are the motormounts in? not sayin thats the problem but inspect them anyway. take a pribar to them and see if the motor lifts up off them. have you taken it on the road yet? how does it perform then? smooth as silk? if so you might just have a bad idle. are all your vacuum lines intact or deleted? my sisters cars engine looked like it wanted to jump out of the engine bay before i adjusted and set the carb, you could have a similar issue.

like the more experienced members already told you, be careful running it if its got counter weight issues. that could spell disaster on the rotating assy.

 

The car is now fuel injected so the carb is not the issue. I am missing a couple vacuum lines but this thing is shaking like CRAZY. It really seems to be like it's out of balance. The motor mounts are not in the best shape but they are not horrible either . I have not bad a chance to actually drive the car because I'm afraid if its a counter weight issue I would really mess something up.

 

I had an engine do this in 2007 because the pickups were wired backwards on my distributor. Not to say this is your issue, but howd you set up the ignition for the swap?

 

Did you reinstall the front pulley in the same orientation as it came off? And did you turn the engine while the pulley was off? I would check your timing.

 

I am currently running 2nd gen ignition system. Coils, sensor, and everything. It is possible the motor spun accidentally while the pulley was off . I remember having trouble finding TDC because the marks on my pulley were all messed up. Is it possible that timing is just super out of wack?

 

You need to find tdc then make sure the timing mark matches. All 83.5-91 na flywheels take the same clutch.

 

but do not all balance to the same rotors!

 

So a lot of work and testing was done today. This morning I pulled the transmission off the car to see what was going on with the fly wheel situation. I was happy and sad to find out that the correct flywheel was on the car. Also the whole back section of the motor looked good. Everything was in order and the key was in and everything. I also played around with the timing a little bit and the car was off a little bit ( maybe a degree or two ) but when I set it back to the "stock" position nothing changed. I did notice through this whole process that the engine and transmission mounts are pretty much non existent. Is it possible that the mounts are just so bad that it causes the whole thing to SHAKE like crazy? Tomorrow I am going to a family gathering so I will not be able to work on the car but I will definitely be back at it on Monday. I plan on closing off some of the lose vacuum lines that are just laying around and hopefully that will solve the problem. If not I have to take off the front cover to drill and weld a fitting on for the oil return anyway so I will take a look at the front stack and make sure everything looks okay inside. If you guys can think of anything else ANY help is greatly appreciated! Also I will try to post a video to show you guys what is going on. Thanks!

 

I think you're on the right track. Vac leaks are going to cause the thing to run rough, and bad mounts will amplify all that associated movement.

A few degrees of timing difference won't make much difference at idle. I was more afraid that you had put the pulley on sideways or upside down and what you were seeing as TDC was actually 90 or 180 degrees. You said that the motor smooths out when you rev it which I don't think would happen if it was that far off.

 

Yeah it definitely smooths out when you rev it up a little bit. I eliminated a lot of variables today so hopefully it wont be too much longer until the problem is figured out. I just want to start the car as few times as possible until we figure the problem out in case it is some type of internal issue going on. Hopefully soon we can figure all this crap out!

 

Sorry for the delay in the response guys a lot has been going on. But the good news is I fixed the problem!!!! Apparently when I put the front cover on before I guess I didn't put the front key in all the way and the front counter weight was just spinning free. No damage was done and the car is now running great! All that is left is a tune and I will be joining the turbo first gen club!!! Thanks for all the help guys!

 

What part of Pa are you in?

 

Im right near north east philadelphia