jutny

well i finally have access to my poor car with the blown 12a. I want to get the 13b running, so i need to modify my 12a header to fit the 13b, i reckon that i have to cut the header flange, and one of the tubes,and lengthen it by 10mm (each rotor housing is 10mm wider, so thats 5mm from each on the spacing, for a total of 10mm difference between the bolt hole spacing.

my question comes in here, i still want it to connect to the rest of my racing beat exhaust system. I have a s4 13b with a 12a front cover on it, so which tube am i gonna want to cut (i either cut the front one and lengthen it, or i cut the back one and cut 10mm out of it.

if that didnt make sense, i'm sorry, but i drew it out on paper and thats what i came up with.

anybody have experience with this type of ****?

(the plus is i have access to somebody that can weld pretty much anything, so i actually have a chance of getting something done here.

-Kurt

Rogue_Wulff

I know a guy that races a 1st gen. He normally runs a BP 4p 13b, but has a 12a for a backup engine. He swears that his 12a header, with the flange cut, can be easily flexed enough to fit either engine. Haven't tried it myself, so I cannot confirm this.

jutny

anybody else? i only have about 3 days tops to get this done, i have to get the car out of the barn, pull the 12a, make some injector block off dealies for the 13b, swap the clutch over, put the motor back in, and then also figure out this header thing.

also i'll prolly have to jerry rig the beehive onto the 13b temporarilly, cause my FMOC is on the 79 in NJ.

flight_of_pain

you cannot just flex it, but if you really feel the need to cut up a good header, then leave the rear runner alone and lengthen the front runner. this will give you a total of .5cm difference from 12a-to connecting pipe, vs 13b- to connecting pipe. i did the same thing for my 13b swap, and its really easy if you cut the runner on one of the straight sections, and cut the flange, then bolt it all to the engine, and you can tack it at the rigth length.

isaac

jutny

well i'd love to not cut up a good header, but i definately do NOT have $200 for a new header, and i havent been able to find a used one in a year or so of looking (on and off).

so you;'re saying: cut the header flange and front rotor's runner (on a straight part) and then bolt it up to the motor in 2 pieces, and tack it back together, then take it off and fully weld it up.

thats pretty much what i thought, i just wanted to make sure that the exhaust will line up, which you're saying it will, within 5mm. right?

MattG

iTrader: (2)

ok, here is that you can do. I have seen this done. You can split the header down the middle and open it wide enough to fit.

This PR guy that lives down the road did it. So I have seen first hand that it works.

81gsl12a

iTrader: (1)

^^^^ im with matty i have heard about this from a few ppl..you may need t ooblong the holes a little bit

MattG

iTrader: (2)

I dont even think Jose did that, But you could try.

Rogue_Wulff

That's what Joe done. Just split the flange, and spread it out a bit. He has swapped the 12a back in a couple times, when something goes wrong with the BP 13b. As he put it, even a stock 12a in the car, will at least get points for starting the race. Might not be anywhere near as fast, but it gets the car back on the track.
He said it takes a little effort to bolt the header up, to either engine, but it does work.

jutny

cool, i'll just cut the header flange to start with and see if i can make it fit.

chances are i'll end up cutting a primary just to do it "right" and have less mechanical stresses on things.

will post with my experiences soon.

MattG

iTrader: (2)

Id see how it works before you go cutting into the header

Siraniko

iTrader: (13)

I've done it many times. Be sure to grab a short piece of 2 1/8 connector from a partshouse (autozone pep-boys) as you will need to extend the pipe coming out from the front rotor.

jutny

awesome!

i'll get that done.

i got it started tonight with the blown 12a, and jiggered it out of its parking space in the new barn (pics as soon as i have a decent host) I warmed it up and took it out for a drive, its amazing how much fun the car still is with only 650cc's pulling strong (or not, lol).

so its parked outside now, i'll start tinkering with the motor swap tomorrow.

any of you know any more little things i'll have to do putting a s4 13b into my 12a powered car.

i already have the 12a front plate and oil pan pn the new 13b, and the RB upper bolts to the stock s4 lower mani, so thats set, other than that i THINK its just header and oil cooler, so i should be pretty much set.

2 1/8 thats good to know.

thanks.

flight_of_pain

thats exactly what im saying, i tried it first by just cutting the flange, but the exhaust ports dont line up at good angles(the are angled funny, go ahead try it) and it plays hell on your exhaust studs to try and get it on there, its better to just cut it, and make it all fit nice.

isaac