13b rew engine over heat rebuild or new engine?
 

Hi I'm new to the rotary game. I just bought an Fd rx7 the previous owner told me that he blew a coolant hose and he drove it home for about 2.5 miles. It has compression in both rotors but smoke and over heat when in boost. So I'm guessing the o ring seals is blown. I'm going to rebuild the motor but I'm affair the housing is warp. How else do they warp? Can I deck them flat again?

Not a builder, but there are a lot of things to check for spec while the engine is apart for new coolant seals. Acceptable specs are set out in the Factory Service Manual. It really depends on how over-heated it was.
You can't "deck" housings. Shot housings are characterized by a lot of flaking chrome, cracks around the trailing plug hole and/or grooves from seals.
You CAN have the irons (side plates) re-surfaced up to a point.

welcome to the board. :)

this is my opinion, so i want that up front. of all the engines i've pulled apart over the years, i would guess maybe 3 to 4 of them were badly overheated and aside for a smoky smell to them, none of them really showed consistent characteristics. in other words, there was no commonality in them. one had spun bearings, one had messed up housings, but not two, or three ... that sort of thing.

anyway, to sort of expand on what Sgtblue said here: the very fact that the engine still starts and otherwise functions, leads me to believe/speculate that it was not as bad as it could have been. it sounds (like you said) more like a blown coolant seal. it doesn't mean damage hasn't been done, but i suspect the hard parts are probably salvageable. obviously, that means nothing until you see for yourself.

that said, i would recommend only trying to re-use the hard parts (rotating assembly and housings) if they're in spec. pay close attention to the e-shaft and bearings. rotor housings can warp if they get hot enough and, no, decking is not a realistic option for them. just replace them if there is any question. the side housings can show what i can only describe as "burn marks" or "charring" on the sealing surface.

don't bother with the seals. just toss them. my limited experience has shown they can get very brittle (especially the side and corner seals) in overheated engines. actually this was a commonality. i did have to deal with brittle seals in more than one overheated engine, but i've seen them in engines that didn't overheat (to my knowledge) as well.

That is some good information! I torn it apart and the housings Mike out fine .0017 total. It did not shrink. I haven't indicate the irons but they did show shadows of the rotor but I can not feel any ridges. Bearing and e shalf also looked decent.
https://cimg6.ibsrv.net/gimg/www.rx7...1fffe5512.jpeg
So I guess the engine is rebuildable.
https://cimg3.ibsrv.net/gimg/www.rx7...97411ce57.jpeg


https://cimg7.ibsrv.net/gimg/www.rx7...c576977ff.jpeg


https://cimg1.ibsrv.net/gimg/www.rx7...d80517aed.jpeg

Pm'ed and texted

That one iron looks pretty nasty.