the 86 is about ready for an upgrade in exhaust breathing.right now it has the stock pre cat manifolds and y-pipe and flowmaster cat back.my question is,how much hp/tq will i be missing out on by swapping the manifolds for a pair of 1 5/8"shorty headers with a y pipe as opposed to rebuilding the whole exhaust (it's in great shape)around a pair of full length headers?also will the difference in exhaust pipe length (aparrently made necessary by the '86's torque arm)make a difference with the full length setup?

I looked at your signature. To be honest I would'nt do anything else to the car until you get rid of the open 2.73 gears

believe me roger thats first on the list!saving for some 3.55s.just planning the header swap.i'm hearing 1-2tenths difference between the shorties and full length.does that sound about right?

I thought you'd get some good responses on this question....I'd be very interested to know some comparison data myself. Here is a link to an article I found awhile back...keep in mind it was written by the owner of a company that specializes in block huggers and shorty headers (nice ones, I might add!)

http://www.sandersonheaders.com/letsgettech3.htm

I agree with Roger69 - I bet 3.73 gears and posi would be worth darn near half a second when compared to an open 2.73 rear.

But to answer your question, shorty headers are fine IMO, they will typically have a slightly higher power band than full length headers with the same primary diameter though. There are a lot of 1-1/2" primary shorty headers for your car, just make sure you get something with 1-5/8" tubes.

thanks for the replies bpos and eric!
higher band huh eric?i had it in my head that the band would be lower.thats cool.i just found a 3.73 posi diff and gears from a 98 z for a killer price,any chance of swappin them into my housing?i know i'd need axles at least

Originally posted by Eric68:
I agree with Roger69 - I bet 3.73 gears and posi would be worth darn near half a second when compared to an open 2.73 rear.

But to answer your question, shorty headers are fine IMO, they will typically have a slightly higher power band than full length headers with the same primary diameter though. There are a lot of 1-1/2" primary shorty headers for your car, just make sure you get something with 1-5/8" tubes. I can second that (no pun int.). I was running a 15.3-15.4 with my lame 327 3.08 + open rear. I upgraded to 3.73 + eaton posi (1000bucks) and literally took .7 seconds off my time without any other changes. I actaully had the same amount of traction off the line (more torque @ wheels, but more traction.) hope that helps!

Yes. In general, larger shorter primary tubes = higher / narrower RPM band while smaller longer tubes = lower / wider RPM band.

Not too sure what gears will fit what in the 3rd - 4th gen cars. I thought they were all 10 bolt 7.5" sets? You might try to look up Freddy aka Big Gear head - use the search feature for his posts. He is out of Kentucky I believe not sure how far away though - might be worth a trip to his shop if you are in Columbus.

Shorty headers will usually make about the same peak HP as longtubes, but the long
tubes will make more mid range power (better peak TQ), the shorty headers will make
less mid range.

geeze eric,i havent seen big gear head on here since i re-signed up(used to be bgn4chng)!is he still posting here?seems to me the big differences in the two setups are;the '86 rear has 26 or 28 spline axles while the '98's are 30 spline.also from what i can gather the '98 rear may be 2-4"wider.i have not measured one yet though.
as for the headers;having a fairly stock bottom end and the split pattern 274xe and original heads (for now),not to mention the fairly wide ratio 700r4,it seems to me i'd want to build all the midrange torque i can!after all isn't it torque that wins races?this would seem to make the long tubes the logical choice in the long run.
thanks as always for all the opinions guys,and keep 'em coming graemlins/thumbsup.gif

It all depends on what you can fit...and on what your target is. If it's a street car, that only runs to about 6000 rpm, and is usually in the 2000-4000 rpm range, you want long (like 30-32") tubes, smaller collectors (2 1/2-2 3/4 inches)and small diameter, equal length primaries (1 5/8). For higher rpm (like 7000) and more specifically race duty, you're going to want shorter (24", maybe), larger diameter (1 3/4 - maybe even 1 7/8) primaries with larger diameter collectors (3, 3 1/2). And there's the whole continuum in between, depending on how you want to tune it. Shorties are a compromise between what'll fit easily, and something that flows a lot better than stock manifolds - but they're not in any sense "tuned". They're way too short, and they're not generally equal length anyway.

If shorties are all you can fit...use 'em. They beat the hell out of stock manifolds, though you're probably giving up 10-20 hp (wild ass guess), and lose some bottom end torque. If you've got room, and the clearance is not a major issue (full length headers to to hang down quite a bit - that's why lots of them end up crunched half shut), and emissions issues are not an issue, use full, equal length headers, and do what you have to to make the rest of the exhaust fit, until it needs replacement. Makes more sense than buying headers twice "because the exhaust system's in good shape".

For your typical 300-400hp street car, 1 5/8 x 30-32 inch primaries, with a 2 1/2-2 3/4 inch collector and 2 1/4 to 2 1/2 inch dual exhaust system is going to be optimum. More toward the shorter/larger diameter end of that spectrum for 400hp, and the longer, smaller diameter end for 300hp. Much over 400hp, and you might want to step up to 1 3/4" primaries - closer to 28" long, and a 2 3/4 to 3" collector. Most aftermarket headers are not really tuned, either. They're designed around a particular diameter, and made to fit. They may be equal length and they may not, and they're usually shorter than optimal.

Even if you're going to buy mass-produced, the $10-20 Headers by Ed (www.headersbyed.com, I think) charges for their design info packet is good background for header design...if you can take the rather overblown, propagandist tone with a grain of salt. Very good advice...just a little gassy. And if you get the urge, building your own headers is kind of fun (and sometimes frustrating, time-consuming, and LOTS of practice welding). Buying aftermarket is easier, and more practical...building is for psychos that think they need to do everything themselves (or put engines where they don't belong). :D

Have fun!