I've looked at the Houston threads. They are all old. I haven't been able to find any of the tuners mentioned in the old threads.

My son just purchased a 1983 RX7 with a 12a Bridgeport. I don't even know what that means! lol. He is in over his head. The car is popping at idle and dies. He can't keep it running. when it does run, the high end seems fine--so he says.

It has a Holley 4 bbl carb, uses NGK plugs that don't appear to be fouled. He says the air to fule reading is 16-17.

He is NOT a mechanic (neither am I) but he wants to learn.

Is there anyone local that can help out an 18 year old that is very frustrated?

Let me know. PM me here or email at stevehookem64@gmail.com

Post here too for others to find new info!

 

Well, first off, thats a pretty advanced rotary topic to start with as your first rotary, a bridgeport. What
this is, is a very modified engine in his RX7. He probably needs to talk to whoever sold it to him to gain
some insights on how it worked for the previous owner and how its working now.

Bridgeports are tricky for experienced rotary mechanics to get running well. Sounds like its running
way lean at those numbers.

I would suggest he get on here himself and start by explaining and showing us what he has.

 

+1 and pics...and a video if can keep running long enough to see/hear it run.

 

I'll tell him to get in here. Thanks!

 

Any idea what a 12a Bridgeport vacuum reading at idle should be? On an actual vacuum gauge, not his in car gauge? I don't know if it is accurate.

 

It will be very erratic and low, nature of the beast. Each one is different. There is no standard because
it depends on who cut the ports and how they were done.

 

Yeah, that's what I was afraid of. The engine was built in California and installed here. Only has 20K miles on it.

 

Where is here?

 

@t_g_farrell The mechanic today told him that the front compression is 80, rear chamber is 60 and that he thought it was bad seals. Any idea if there is a standard compression reading for a full Bridgeport 12a?

Here is Houston, TX by the previous owner.

 

First off, welcome to the forum, and the crazy world we live in!

Secondly - If those compression numbers are accurate, then they are low.

I would question the validity of the numbers though because you cannot use a standard piston compression tester on a rotary in the same way as you would on a piston engine - because the rotary has 3 chambers per rotor, as opposed to just one on a piston engine. There are specially made compression testers for rotaries, but you can also get a general idea of the engines health using a piston one, if you know what you're looking at.

You have to hold the valve open (on the tester) and look at how consistent the pulses are (they will typically be lower than the "real" compression number). If you leave the valve closed and crank the engine, it will give you a higher number, but it would only indicate the highest chambers compression figure. Assuming that overall number is 90 or higher, and the 3 pulses are fairly even then chances are the engine is ok. Higher is better of course.

If the mechanic looking at his car knows rotaries and did the test correctly, then the numbers you have are too low to run reliably and smoothly - then again bridgeports aren't smooth at low rpm's anyway! As stated above though, if possible you should speak to the person who built the engine. There is no one "standard" bridge port template, so they could have done any number of things when putting the engine together.

 

Thanks! I'm sure it was done with a piston compression tester. The mechanic does know rotary engines and was actually an RX7 owner himself for years. Not sure if he compensated as you say but he said that the main issue he saw was a 25psi difference between the two compression chambers. Even if his numbers were off on the compression, the difference is still too high.

Am I thinking about that correctly?

 

Yeah the two rotors should be pretty close otherwise you'll have a hell of a time getting it to run very well. I think the advice given earlier about having your son join here and start posting pics/videos/details about his car is the best idea. Even if he doesn't have much experience with working on things, the knowledge on this site is second to none!

Also - while I have many years of experience working on these cars, my bridgeport knowledge is limited at best but others will be able to help!

 

Thats what I've been saying. Same here, not a BP expert but there are others that are
that may chime in. Doing this with you as a go between just makes it harder to for
everyone.

Your thinking is correct, but it could be a stuck side seal as well.