4-port to 6-port question
 

Hey everyone! I'm working on my '74 REPU (still) and have a question regarding injection to carb conversion. In a previous thread regarding a transmission question I had I discovered, thanks to you all, that I could perform the conversion. The engine I'm working on is a 6-port out of a 91 RX-7. I found a gentleman on craigslist selling a 4-port intake manifold and Weber carb and he said that he would be willing to drill out the manifold so it would work on my 6-port. I found a guide online with instructions on how that is done, but is it a good idea? He is offering to sell me the carb and modified manifold for $250, which is much better than the ~$1000 I would get them for brand new elsewhere, so I want to jump on it if it will work. The guy selling it seems very knowledgeable and it's not that I don't trust his word, but rather that I trust you all. I have attached the pictures he sent me below.

One other question. This REPU had a 20R in it when it was purchased and was missing the original motor mounts. I have since removed the shoddy 20R mounts I and am exploring my options on new ones. The mount locations on this motor are really low on the motor and may not work. I do, however, have a spare 12A lying around. Will the front cover that has the motor mount bracket on a 12A fit on a 13B? It looks like it will, but I'd like to avoid a runaround if anyone knows for sure.

Again, thanks for the advice! You guys are wonderful.

More pictures.

Yes a 4 port can be done into a 6 port if there's enough meat on the intake to longate the ports. If he knows what he's doing then let him have at it. I've seen 6 port intake made into a 4 port with better results. As far as the front cover yes they're interchangeable between the 12A and 13B. Good luck on your build. Post up some before and after pics.

Thanks for the info! I think I'm going to start a new thread to document the process. It will be lengthy, but it'll be nice to keep track ^_^

Cheers!

just another pair of eyes looking at the situation (if it's not already too late) ...

while i agree you should jump on the manifold and carbie for $250, i happen to think you should look into other means of adapting to your 6 port engine than modifying the manifold if he's doing what i think he's going to do (port the manifold to the general shape of the 6-port like how one would do with a siamesed 4-port). my thinking is if you happen to want to go with a more old-school setup in the future, you can't un-port the manifold. again, this is just how i see it.