i bought a 79 intake manny at the yard today it is noticably shorter intake runners and the middle ports are alot smaller than 84 85 but it looks easier to port than the 84 i think i paid 15 for it i got the oil cooler and tower as well. i was just wondering if there were any power improvements with the manny id assume a little more top end power.

 

well since 79-85 12a's all had 101 FWHP, i dont think you will get any newfound horsepower witht he 79 mani...

 

Easy to port,a little smoother.Probably wont increase HP, but it may shift the power slightly to a different RPM, by affecting port velocity and effeciency.

 

gregs brings up a interesting topic i think, i am new to the rotary thing but from what i have learned is that the 84 85 had better compression then the earlier wouldnt that account for better something i know higher compression piston motors make more power rx7carl has flow tested the after 79 manifolds and he was dissapointed with the flow differences in each runner to me the runners look egual to one another outside with outside and inside with inside i mean i just find it a little odd that tha horsepower didnt change with the years also since didnt the 82 have a lighter flywheel i just dont think those numbers are very accurate but maybe im bringing up an old thing.

 

oops i meant non 79 manny rx7carl has flow tested.

 

The great thing about the early manifolds is they lacked the dreaded "shutter valve" which often sticks and creates a hang during deceleration....not to mention restriction of air flow.

 

Compression ratio remained constant in the 1st gens. The early cars had lighter FW's, but heavier rotors, so that cancels out. As far as the manifold, the 79-80 has a much better plenum and less bumps and crap to interfere with the airflow. The runners arent smaller, its decieving. Look down into the 84-85 and look how the runners neck down.

 

What's the most common method for blocking the egr ports if you run a 79-80 manifold?

 

jbweld

 

Too ghetto. I take a piece of angle aluminum and bolt it to the bottom of the manifold to block that port.

 

what is my car going to do after i install a 79 manifold ported to match the gasket also what vehicles can a get a better fuel pump from than ours like any v8 carbd from the jyard would that work for a bit?

 

Do you use a temp rated sealant around the egr port area when installing? By chance- any pics around of this?

Also- an unrelated but related question- Can I use one of the vacuum ports on the manifold for a pcv valve/breather on the oil filler neck? Reason I ask is if I use my stock 85 manifold base plate/shield- I don't believe the vacuum holes match with the manifold.

 

Nah, just make it so its flush with the manifold parting surface and the stock gasket will do the rest.

Not sure on the PCV, but I think thats ok.

 

Here's a '79 manifold that I think has been ported.

 

Yup- that's been ported. I was thinking about port matching the 79 manifold that I have and use it with the sterling/carl carb on my stock 12A, but really don't know if it's worth it or not.

I've done a few searches on here before and came up with mixed results (port matching and porting intakes).

How's your intake project coming along, Carl?

 

Those primaries are over ported. Mine is at a virtual standstill. Now that mother nature has stopped ******* us around I can get back to testing.

 

You should see the engine it came off of. It's a streetported Pineapple Racing engine.



It looks like they used some Devcon in the EGR port. It's got 3B rear, R5 intermediate and Y front casings with '76-ish rotor housings and '83-'85 rotating assembly.

 

why do they block off the coolant holes to the intake???? with the plugs. and might i add YIKES what the hell happened to that engine?

 

dont hate me cuz i dont know but are the primaries the ports in the middle of the intake manny?

 

To keep the coolant from heating the manifold. I think it was a boat anchor. Oh and that porting MAY be ok for a SP. I havent tested SP's for flow yet.

Yup, primaries are the 2 center ports.

 

It was a racing engine that had a Racing Beat old style black air cleaner assembly. Somebody left it out in the rain and water simply would collect at the concave part at the center of the lid. Then it would drip down the long stud and into the carb. The carb butterflies and everything below them was ruined due to water damage. The side plates were so bad that the metal could be scraped away with a fingernail after the rust coating was removed. At least the carbon apex seals may be reusable, as well as the rotor housings. I haven't dug deep enough yet to know.

 

so how come more people dont talk about blocking off the coolant holes to manifold? can i do that on my sp 12a

 

Its not a secret subject. It comes up once in a while. Most people just dont wanna hassel with it. Sure you can. Some guys epoxy quarters over the holes. I use 20mm freeze plugs. 2 engines and only one small seep.

 

is it worth it for a daily driven 7? also should the egr port be blocked off? because i scored a race car with a atkins motor and this motor had a piece of aluminum welded and smoothed to block the egr port would it be benificial to block the coolant holes as well?

 

edit- never mind. Re-read Carls post, he already mentioned it.