so in the next few days were gonna make a cheap homemade exhaust system for my 85 carb12a, well i was jus wondering if backpressure is a big issue, it would be stock header and a 2.5 straightflow to a ?????straightflow muffler maybe? maybe leave a cat in there? not sure, jus lookin for a real cheap exhaust for a lil more power, advice and experience will all be appreciated, thanks (p.s. i searched and couldnt really find anything that helped, if there is a thread sry)

 

well the stock manifold on a 12a is the limiting factor, on the pro7 cars we used to run a 2.5" system, as straight as possible, going under the axle to a magnaflow straight thru can, its not that loud. if you get all the tuning right and have a healthy engine you can expect 112-116hp at the wheels.



header would add about 10+ hp, at least 125hp.



this is with a stock 12a, stock carb.



if you go over the axle you're loosing 3-5hp

 

j9fd3s.... What kind of Magnaflow? I've been looking for something that will be fairly quiet, but your setup seems to make some decent power gains too... I've got bigass 2.5" headers though, so I'/m assuming it'll be a little louder...



ANy other suggestions for mufflers? from other people? I was thinking about the Edelbrock SDT (sound Deflection Technology) since they don't have any packing for the rotary to blow out... but not sure how loud they'd be...

 

we already decided were not goin over the axle jus becuase of that factor, and im not gonna be in serious pain over a slight lose of clearance. and yea stock 12a stock carb, not gonna buy a new header cuz like i said, jus lookin for a cheap exhaust, im buildin a 10ae and this is jus my daily driver its jus 2 damn slow. on the pro7 cars did u change the header? and what do u mean tuning(on a carb that is)? sry, im a lil carb illiterate, i was hoping for boltup and go

 

pro7 you had to run the stock manifold, 84-85 one is better. the stock carb is fine, theres just a little more to be had by fine tuning the mixture a bit, its optional

 

you need something straight thru. those deflector/baffled setups arent heavy duty enough, rotary will dissassemble them .



the old school setup, is to run 2x2.5 racing beat t2 presilecers, and then your choice of rear muffler.

 

i got the big roadrace header, rb presilencer with rb muffler. The car is really close to stock sounding but it has alot more "get up and go" then it did before. u could buy a cheap used rb header on ebay (i did that). If you want more power without spending a whole lot go to the local bone yard find a j-109 and biuld your own DLDFIS. I did that too and the car starts way easier and revs smoother to. Oh yea no pops or backfire either.

 

so i put the exhaust on, we had to ghetto rig the flange to go onto the 2.5" pipe cuz the dumbass at the store sold us the wrong one and we were to lazy to go back. we left the first precat on but took off the main cat and the 2nd precat. no muffler jus the straight pipe back from there. i can tell its DEFF faster, idk if i got 20hp but 10-15 would be believable, but sadly enough i raced my buddy in his 4.3 s10 AT and he beat me. i beat him on the launch and was pullin from first til i shifted into 3rd then we were dead even (speed wise, i still had about 1 car length) then when i hit 4th and he started pullin and by the time we hit 100 he was ahead of me and i wasnt catchin up. so its time for another cheap mod anyone ran ram air on a stock 7 12a? we have an idea on how to do that and with that should be able to beat some damn s10, anymore advice will be appreciated

 

well theres more power in it, but you need a header. also you should set the timing, to 20-24 BTDC L over 4000 rpms. you also want to change the fuel filter, and make sure the ignition is working perfectly