I have a 79 that has a bad side seal. I do have two spare engines, an FB 12a and a 6port 13b from a GSL-SE. Both spare engines are without intake manifolds or exhaust manifolds. Of course the test was done with the engines being cold.

FB 12a
F 100 / R 75

13B
F 115 / R100

The test was done with a traditional tester with Schrader valve removed. The 12a would be cheaper for me to install, assuming I can use the stock thermal reactor system with the FB engine. The 13b will have me figuring out exhaust and a carb. A main point to say is the 79 is dead stock, and I do not want to do anything that can not be reversed back to original. I'm leaning to using the 13b to get me going and rebuild the SA 12a when finances are better. Th 13b is destined to be installed in a '80 that is currently under the knife. So, what would you do?

 

I don't think the thermal reactor will work with the FB block. How bad is the side seal issue on the 79 currently? You could go with a RB header/street port exhaust and use the FB engine as long as that rear compression number isn't a harbinger of things to come. Then you could still use the 79 carb.

 

I am expecting terror when I tear the 79 engine apart. It smoked heavy above 4000 rpm or so. I have been looking for a RB exhaust, but nothing fits into the current budget. Buying a new exhaust is almost the same price as a rebuild kit. So I would look at a rebuild firs as I mentioned. the car is stock.

T G, it looks like you believe the 12a's compression is not worth writing home about, but still may have some service life left. Just keep the AAA membership current. I do have the 12a exhaust manifold and maybe I can connect the stock manifold into the existing "catback" for less than a perfect description of the muffler.

 

In France, FB had thermal reactors, not catalysers, so I think it could work with the FB 12A.
To my knowledge, the two exhaust are interchangeable, just mounting points further down the line can be different.

 

You could look at getting a used RB header and using that 12A with the header connected to the existing exhaust. Or maybe an FB exhaust manifold and some minor fab work to connect to the existing exhaust.

 

Than you for the repies,

It seems the plan of action is to purchase the Racing Beat header (16008) that connects to the heat exchanger. I will replace the heat exchanger with the mini pre-scilencer when budget allows. I will use the SA manifold and carb on the FB engine, blocking off the center irons air injection port, of course. I am leaning at keeping the points ignition system to keep the integrity of the electrical system in check. Anything that is done must be able to be undone. So no splicing into wiring. The thermal reactor and related parts will be boxed and stored until it would be desirable for me to reinstall.

 

Sounds like a plan. Good luck with it.

 

The harness that goes from the coils to distributor isn't part of the body harness. You can remove the SA one and keep it safe and just replace with a 1981-1985 one.