onepointone

is it possible to put 3mm seals in a 12a? what about if it were to be street ported? does that even make a differece in the seals if its ported or not? i wouldnt think so. what all is required with making the 3mm seals fit in the rotors? would it be a HUGH amount of moeny, could it be done without taking it to a shop?


im looking into another 12a to get, port, build up, and swap into my car.. i want to make it pretty stong too so it will last..

diabolical1

iTrader: (3)

i might be wrong, but don't all Gen I engines have 3mm seals?

i'm pretty sure they are. streetport does not matter as long you keep the RPMs below 8500. anything higher will require seals of a different material or the 1 piece carbon seals. hope this answers your question.

REVHED

All single dizzy engines prior to 1986 had 3mm apex seals.

Even if that weren't the case, converting from 2mm to 3mm on an n/a application would be a waste of time. 2mm seals actually perform better and the only reason it's done is to 'supposedly' provide more margin for error against detonation.

Project84

And if you wanted to put 3mm seals in a 86+ N/A rotor, you would have to mill out the groove for the apex seals. Its pretty precise, and has to be done in a shop unless you have to machine to do it. I saw a pic of a rotor on the machine this weekend, but I can't find it and I have to go to work now.

peejay

Yerp... If you have a '74-85 12A (single distributor) then it already has 3mm seals. If you have a '71-73 12A (twin dizzy) then it has 5mm carbon seals, as well as double side seals. (GOOD LUCK finding replacement parts!)

No 12As came with 2mm seals, unfortunately.

REVHED

That's probably just a typo but twin dizzy seals are actually 6mm carbon.

onepointone

thanks... couple more things i know.

reason i ask is because im going to do a project 12a. plan is to buy a running 12a. buy new seals, port it.. and im looking for other stuff to do internally. is there anything else that would be worth the time and money? keep in mind i dont have a huge budget, but im not looking for it to be done for awhile.

diabolical1

iTrader: (3)

well ...
it all comes down to the budget you set for yourself. but i believe the best advice that would do you justice is to take your time and build the motor slowly! focus on relaibility as well as power, because it doesn't make sense to build something that's going to tear itself apart. when i say do it slow, i'm not talking about the assembly process, because that's really the easy part.
what i mean, is take your time to inspect and measure the specs on your rotors. take the time to disassmble every part that you can, then clean and lubricate it meticulously. use NEW seals and springs as long as you can afford it (if not, focus on the apex seals and the rotor O-rings) use an SE oil pump and either space (or upgrade) your oil pressure regulator. get the side housings lapped, if you have doubts about the rotor housings, then toss 'em and get better ones. that's the kind of thing i mean ...

onepointone

i was actually looking into apex seals, even if they arent absoultly needed. o-rings? thats getting written down, i guess ill just make a list, price things out, ect.

i found apex seals for around $30 a peice, anyone know of somewhere cheaper to get them from?

-SE oil pump

ill probably stay with a stock nikki.
what do you mean get side housings lapped? i know what they are, just dont know what you mean by 'lapped'. sorry if its a stupid question, but i know the basics, and most of the other stuff, but still picking up stuff here and there. im assuming you just mean smoothed out?

i know this was a debate, but would a lightweight flywheel be a good add-on? what about water pump? stock? alt?

what about removing emmissions and air pump? i was this to be economic, but quick at the same time. im also definately keeping a/c because it gets hot as hell during summer in virginia.

while im at it, should i go to a electric fan? i mean, this can take as long as needed, just so its done right. any help would be greatly appreciated

diabolical1

iTrader: (3)

before you start anything, research would be a great idea. get one of those exploded diagrams of the engine, and make a list of the parts (the different seals and such) then list what each of them do ...

anyway, yeah, at very minimum, apex and oil seals should be NEW. 30 bucks for each apex seal sounds good to me ... i remember paying something, like, 42 bucks for them, but i honestly don't remember if that was for the last 12A or 13B i built. (i'm tempted to say it was the 13B)
lapping??? ... well, i get it done by someone else, so i may be wrong on the explanation ... but from how it was explained to me, it's basically making the side housing surfaces even (like new) so as to promote even seal wear, and better sealing. hopesully, someone else that knows more, and can explain it better, will chime in here.
the SE oil pump is great mod for a 12A, that's why i recommended it.
lightweight flywheel is a great idea, just get it before you assemble the engine, that way you can have the whole rotating assembly balanced.
new water pump - always!
as far as emissions go, i've never believed that streetport 12A's would pass emissions tests, but i was corrected in another thread - so that's up to you.

REVHED

Lapping is just machining the side housings to remove the wear marks left by the seals and get it back to a flat surface. Some people actually say not to do it if there's only minor wear as you lose the nitriding. I always have it done though.

diabolical1

iTrader: (3)

just like to add to that thing about streetports and emissions because it's too late to edit. like i said, i never thought it would pass emissions, but someone said they had one that did ... however, i'm sure they were not running a header and exhaust system, which i would strongly recommend for ANY ported motor.

onepointone

i really appreciate this..

header and exhaust will already be done (its in the works now, engine is next) i dont have to worry about smog here in va.. so thast cool. my dad mentioned picking up a porting template, he did a 12a motor about 10 years ago by eye, and said he thinks it would of been alot better with a porting template. ill probably pick one up off of someone that doesnt have a need for theirs anymroe, ive seen them go for about 30-40 bucks. every mod im going to do, will be done before the engine goes in, so i wont have to take it out again, minus intake manifold and carb (i dont want to shell out money for that quite yet)

what about new lightweight rotors? i think $400 a piece? worth it? im not sure... probably not.. what about rotor housings? figuring the old ones shape?

peejay

Just start off with a '83-85 engine. They already have rotors that are just as light as the coveted '89-up 13B rotors.