i was looking at some under driving pulleys and a high flow cat both equal out to about 200bucks for both.think i would get at least 20hp from the 2??

 

maybe at the motor....but not at the wheels. Do you have headers yet?
Them and a nice muffler...you will be hooked up.

 

I used to have underdrive pulleys but with my stereo system running, a/c and headlights, the power use to surge when coming to a stop and at idle. Dash used to dim also and I have a 400 amp alternator. I took them back off. The extra few hp from them was not worth it.

 

well i already have a flowmaster muffler,headers will come whenever i get some more extra dough..but i can get the underdrive pulleys for like 50 bucks so i guess that would be worth it right..

 

id say about 5hp at the wheels. i have them on mine, i have dimming prob at a light with lights on etc as well.

dont waste ur money on the cat... u'll get more from intake mods or exaust headers/catback. where are u getting a highflow cat for 150$??? i get them at car shows for 50$ 3" highflow cats.

 

i mean i could take out the cat and run a pipe there to replace it but idk...so that only 53 bucks for 5 whp not that bad if i just delete the cat.

how good is flow tech headers, i can get the header and Y-pipe included for under 300 bucks from summit.

also been looking at the slp runners...

 

flowtech is junk everyone says so pretty much

if you want cheap go with hedman or edelbrock

i've got edelbrock shortys and there flanges arents very thick nor is the tubing but, mine work quite well sealed perfectly fine so on....

as for 5whp maybe you'll gain that by removing the cat but, i doubt it... Unless plugged even if so thats not enough to feel it.

best investment would be to buy a standard abrasives porting kit and a cone shaped 6 inch carbide burr.

fully port your tpi setup and heads and you're looking at well over 30hp that you will actually feel for less than 100$

well 200$ if you count having to regasket then engine

 

as he said, u could put a pipe in for the cat but it would affect much if its not blocked. it will change the exhaust not slightly too i think. i heard flow tech is not so good but ive put the edelbrocks on my 87 305tpi and they went in good, not that bad for there price. i think the SLP's etc are wayyyy to expensive. they all work the same basically. i would say edelbrock or headman as well.

the porting would be great but the runners would have to be upgraded since u cant port the stock runners. SLPs are good if u can port well and portmatch the plenum to the runners. the heads/intake porting can be expensive but can be done for 200$ if u kno how to port. i wouldnt recomend u porting anything like that unless u kno what your doing and have done it before. if u end up porting everything u can def see 30hp but at the expense of alot of downtime, since all that porting is gona take a long time. porting the intake etc would be more beneficial if u port them to the aftermarket runners. u cant really hog to much outa the plenum/base if u have to match them to the stock runners.

most HP will be exhaust/intake. catback before headers since u dont want the bottleneck to be at the end of the exhaust. u have to do the catback when u do the headers and not the headers before the catback. after that, stock vortec heads with a TPI vortec base will net 50hp over stock. even more with aftermarket runners and porting etc... this is with stock cam.

stock 350tpi 225hp
full exhaust will net 25hp a the wheels.thats like 250hp at the motor now
vortec heads/vortec TPI baseplate 50hp.... now 305 at the motor
runners, porting to base/plenum etc...320hp at the motor.
1.6 roller rockers and custom chip...330-340hp at the motor

 

well the cat been on there since 88 and i already took all the mission control sh*t off anyway,so im going replace with a pipe.

i mean i just thought about this,way buy cheap header when u know u going to regret it down the long run.mine as well save up and get the good stuff the first and be done with it right?..

well i never did any porting and i dont know what to do so i leave it at that..i only make like 330 every 2weeks all i have to buy is gas/insurance which the insurance isnt much 48bucks per month so..

whats a good header/y-pipe combo that will bolt up together and wont have any clearance issue??

 

i put on underdrive pullies and didnt really see much gain at the track or dyno. maybe 3-5whp. you may see a "FEW" ponies but probly will never feel it.

Thing i did notice was the motor free rev'd quicker. touch the throttle and it spun up quicker. Less rotating mass helped it rev quicker... but that doesnt mean better horsepower. Just was nice on the street, the motor jumped into power band much quicker.

 

yeah i going get the pulleys every lil bits helps so what the hell.already did the free mods,k&ns,air foil,24lb mustang injectors came with the car,flowmaster muffler.have either 3in or 2.75in pipe more like 2.75 since no 3in came factory on any 3rd gens.smog delete that's all i can think off..


my car has 2.77 gear dont understand the who gearing thing but how would it do if i change it to 3.27??

 

i've done that swap, its a noticeable gain. if you can find a 3.27 or better yet, 3.45 gear set with a good 3 series posi carrier unit, it be worth it.

 

they have a couple iroc-z at my local junkyard maybe i be lucky and find one.

 

no stock car came with anything higher than a 2.5" exhaust... and they where all crimp bent... not the best for flow. the muffler mod isnt really doing anything bc your just changing the muffler not the backpressure... muffler changes are cheap ways just to sound better. a CATBACk will help with increasing more HP/tq.

i wouldnt put anything cheap on my car either... but the SLP headers etc are insanly $$ and arent thay much diff then edelbrocks/headmans... basically ur pay for the name and that they are made outa stainless. they will all give u more power over stock... just depends on how much ur willing to pay. same thing with catbacks. all 3" kits are the same just different tones/mufflers.

rear gears are simple... the lower the number lets say 2.77 means your driveshaft make 2.77 complete full turns with every single complete turn of the wheel. stepping up to 3.23/3.42/3.73 means the driveshaft will do that many turns for every complete turn of the wheel. this is good for increased acceleration and off the line performance but limits TOP speed and increases cruzing RPMs.... that means its bad for gas mileage and highway driving.

another note... 3.27 rear gears only came in the austrailan 9bolt and was a posi carrier. used basiacally on 350tpi's bc the increased ringgear diameter could handle the power of the 350. the 9bolt posi will not fit in a 10bolt... which u prob have.stock gears ranged from 2.77/2.73/3.27/3.23/3.42

3.27 are on 9bolts
everything else is in 10bolts... 3.42's can be found in only manual 305 TPI's with the option for that gear ratio.

3.23 are a good gear for TPI;s and so are 3.42... but thats the highest i would go since the 3.73 will take u outa ur powerband wayyyy to fast.

 

he should have a 9 bolt rear being a 88 Irocz with the L98. And i thought L98's had 2.75 inch pipes? just what i heard i'm not sure

 

I love my 3.73's!!!! I wouldn't go any other for an auto!
4.10 for a manual.

People who tell you different......never had one in there car!
I'm still in 3rd gear by the end of the 1/4 mile. So I'm all good.

 

if you have high flowing base/runners and a cam, 3.73's would be great for 1/4 mile with a 26 inch tall tire. my 3.42's are a tad small for HSR on top. i cross about 500 rpms lower than i should be

 

LOL u Camaro people have it easy. I'm building a 350. (blocks already .040 over) I was going to get a Stealth ram......but it's to tall for my stock hood. Cowl hoods look great on camaros.....not so much on Trans Ams. I don't like the ram air hoods they make for 3rd gens,

 

thats disappointing for you, the HSR is such a great intake Vette guys have modded the plenum and HSR base to fit under their hoods, perhaps you could do the same?

else make a custom top plenum thats lower but wider to maintain volume?

 

yep i do have a 9bolt rear,and when i bought my muffler the inlet was 2.5OD and it side into my stock pipe with some play.so i know it either 2.75 or 3in pipe..

 

LOL....maybe ill save my $$ and try to find a hood that looks good. Theres not many out there.
Thx for ur input!!

 

these should bolt together right??

headers

http://store.summitracing.com/partde...5&autoview=sku

Y-pipe
http://store.summitracing.com/partde...5&autoview=sku

 

yep it sure would, or is suppose to.

 

aight cool be buying them both on my next pay check..umm would i have to do any hammering with these headers or it should fit perfectly around the chass.thanks for everyone input

oh one more question since it doesn't say,do those headers come with a o2 senser hole..

 

How 'big' was your stereo system??? A 400 amp alternator should power the space shuttle, shouldn't it??? Would you get any dash dimming with the stereo off? I just installed a 180 amp and haven't gotten around to verifying the pully mod's benifits. I certainly don't mind mods that only add small increments in horsepower. If we do 5 small mods with only 4hp gains, that sure adds up when your done.... Nitro

 

just what to make sure,does hedman HED-68470 header come with a O2 sensor fitting on the driver side...

 

my car was a stock 87 formula 350. stock exhaust and i got a replacement stock muffler and tail pipes. stock was 2.5 OD" crimp bends and all. i still have the walker mufflers and tailpipes, they are in good condition, i would sell it cheap as a stock replacement if anyone wants it? only had 1,000 miles on it

tenpin842.... remember u have a 305! not a 350.... your 305 doesnt even need the highflow TPI aftermarket intake. not like a 350 needs it STOCK!
your 305 is winding to the moon with that intake where your passing through the end of the track at wat....6000RPMS??? id say thats where your peak HP is cuz your intake flows more in the upper RPM's due to your lack of cubes. on a 350 a highflow TPI will max RPM at roughly 5200-5500. if your lucky.

anyone who knows anything about these cars will tell u that 3.73 just too low a gear for a TPI setup. TPI's dont make enough hp/tq at higher rpms and thats where the 3.73 puts u. on a 350TPI 3.73s are too low a gear. a better gear would be 3.42/3.23/3.27. not to mention the 3.73's totally kill your gas mileage if u even decide to drive the car on the road. with a HSR gears would be 3.42 (as stated kinda small) or 3.73. since the HSR flows enough in the upper RPM;s to support where the 3.73's put them.

i also have the ram air II hood on my 3rd gen... which looks a whole lot better on a firebird with a 84-88 front bumper cuz it was made to follow the lines. i also have the HSR which will fit fine under the additional 2" of hood clearance i got with that hood

 

yeah you will prolly get about 15 to the motor with the puleys and cats but still it is a good upgrade. i would say go for it

 

Just a question,
Does anyone know what kind of HP I should get out of removing the cat, using '91 iroc stock manifolds with the stock 3" "y" pipe and removing the entire a/c system (the only thing left in the car is the condensor (the rad like thinggy lol). It was a stock LG4 1986 Z28 4bbl.
I'm not sure if this model had a smog pump, it did however have this flap type valve on the right side manifold between it and the y pipe but nothing is hooked up to it.
And yes I know removing all that garbage and just using headers would be ideal.. but having a family of six doesnt always let you spend what you want to.

Any figures would be great.
Thanks

 

Just want to point out a slight correction so it does not confuse anyone. The 9 bolt rear end came out with 2.77, 3.08 (Rare) 3.27 and 3.45 (Stick only) gears.