hi everyone,
i recently bought a 87 Iroc with a Auto 305TPI and i've been wondering what are the best mods to break into the mid 14's... From what i searched up the LT1 cam would be a good/cheap replacement for the peanut cam, and some exhaust...
but as for what else im not sure? thanks

 

Pick up a pair of K&N's, and cut off the bottoms of your airboxes underneath the lip that seats the filter.

Do you have headers? If not, get those.

Get an airfoil (used) off ebay.

The k&n/!airbox mod should make a difference. (50 bucks?)
Headers will without a doubt make a difference. (250 bucks?)
The airfoil has been proven to allow around 12cfm more air to move through stock throttle body. (30-50 bucks?)

 

i got an 89 iroc 305tpi runnin 14.27@97
my mods are

K+N
tpis air foil
gutted air boxs
bypassed coolant line threw tb
reinforced slp 1le lower control arms
reinforced slp 1le rear panhard rod
3.43 gears
auston posi rbiult w/ moson parts
modified MAF
msd gm blaster coil
ngk irdium plugs
msd 8.5mm super conductor wires
dual 2.25" cat (gonna go to single 3" cat)
3" mid pipe waker m bent
quiet flow muffler from napa(donna be replaced with a flowmaster soon)
2.5"tips walker m bent
tpis lvl 2 prom
ls1 3" drive shaftmonroes bp alternator 135/55amp
edelbrock victorpump
monroes 55/135 amp alternator
monroes bp starter

these are what i have


i wanna hit the 13's with the
edlbrock headers
random tech 3" high flow cat
then
lt4 cam + 2400 b+M tq converter


btw look at the lt4 cam
ur current cam is .384/.402
the l4 cam is .448/.452 i think not a kick in the rear cam, but it get the job done w/o takin the chance of damagin anything. until u rebiuld u don't want any hot cams. the lt1 cam would also be good, but take a look at the lt4

 

I have a 91' Z28, 305 of course, I have stock motor and heads, I relocated IAT sensor, cut out air box, air foil, MSD 6al box, flowtech headers and y-pipe, no cat conv., flowmaster muffler, Taylor plug wires, and a 100HP shot of the HAHA gas. With the stock 2.73 gears I was running 14.01, I put in some richmond 3.73's and haven't run it since. I am looking at some easy 13 second passes. Over the winter I am performing some other easy mods. In my opinion the Nitrous kit was the best thing to bolt on. You can easilly spend well over the price of the NOS kit with other bolt ons and not get the same performance. The best thing is I get close to stock fuel mileage and drivability.

 

As they say, get exhaust--headers and catback, as well as a good cold air setup. Then get a cam--look at the HOT cam if you have a roller block, otherwise I have an excellent cam in mine (non-roller) with similar specs. You'll also want a better TC. Don't worry about airfoil or TB unless you find them very cheap. With cam you'll want a custom chip and AFPR no doubt.

That should leave you happy for a while. You'll probably want to look at suspension then, and upgrade rear LCAs, panhard bar, etc to get that power to the ground. Also gears. 3.73s a must w/ the automatic.

Just my 2 cents

MILT

Oh, BTW, if interested, email me. I may have a used set of 1-5/8" SLP headers and y-pipe for sale...

 

Does anyone have pictures of a cut-out airbox? I am a little confused on what your supposed to cut.

 

Don't forget about weight. The less weight your engine has to move, the more efficient it's power output will be. The hood can be changed to fiberglass, as well as some parts under the hood you can get in aluminum. Remove the smog crap if there are no emissions where you live. Remove your A/C if you don't mind sweating in the summer. I also have my rear seat, spare tire and jack off the car. When I put in my headers it should make a considerable difference due to their lighter weight and better efficiency at flowing exhaust gas.

 

A good chip will help. I picked up ~.5 sec and 3 mph with a SLP chip for 5 speed it also came with a nice 5500 rpm limiter programed in too.

 

3.73s are not a very good idea on a stock TPI

 

i really like my 3.43 gears there not to low where u can't get a good 60' time..
get (good wires,plugs,cap nad rotor, coil) look at msd and hypertech 150-250

next get a good catback, like flowmaster 375
then get headers edlbrock makes good headers and good fit. for under 400
some cheap mods are
air foil 45-70
pulleys 90-120
afpr 60-90
K+N's 50-60
and get a set of lower control arms, they will get rid of that wheel hop problem

 

I think 3.73s would go fine with a stock TPI setup--after a cam of course. I know a few people that run them, and are quite happy. That is only my humble opinion...

Skip the weight reduction crap--that's for serious racers. With the money you'd waste on a fiberglass hood and repaint, you could be well on your way to a nice set of heads. Also, you have to decide on functionality as well...i.e. do you want to forgo the comforts of A/C (providing it works) for 1/2 HP? Also, removing the spare is probably good for another 1/4HP, but is it worth being stranded somewhere? Yes blah blah blah it's free power that also helps weight transfer, but not always the smartest mods for a regularly driven car.

MILT

 

As far as the gears go I think that 3.73's are the way to go! I still have a great rpm at highway speed (not screeming for the heavens). It also wasn't much of a fuel milage sacrafice. The best part is it sure has alot of that seat of the pants take off. So don't fear the gears on a stock TPI, they will be great!

 

I would also have to say I agree with MILT use your brain, If it might be needed later on along the line leave it alone. You can still be fast with A/C, stock body parts, and a handy spare tire. I think it is great being able to go to the track and not sweating your ***** off on the way there. I would only go to the extremes if you were planning on making a full fledge race car out of it.

 

i am currently working on upgrading my 305tpi and while its almost all stock now..this is a list of my car mods when it will be done...
Stage 1
flowmaster exhaust
k&n filters
throttle body airfoil
adjustable fuel pressure regulator
msd blaster ignition coil
Stage 2
edelbrock TES headers
camshaft (maybe LT1 or LT4 dunno yet)
some valvetrain upgrades
ported plenum
transgo shift kit
3.73 rear gears
custom PROM
Stage 3
edelbrock hi flow tpi baseplate and runners
world 305 torquer heads
holley 52mm throttle body
subframe connectors
strut tower brace
aluminum driveshaft
and plenty of other assorted stuff i missed...i am not a car expert at all but ive heard my planned setup is pretty good and will hopefully get me 300 rear wheel hp

 

GET HEADS! It makes a huge difference. Also a chip, free flowing exhaust, and GEARS! If you got just that you would probly be a second or two faster than what u are right now.

 

I thought the airfoil was only for the L98? Everytime I see one on a web site it says it's only for a 5.7L engine. What's up with that.

 

u need one for a 48mm throttle body, i think theyre all the same, i got mine from thunderracing...
edit- they are the same

 

So I should be able to use one for my stock 305TPI? If so that's not a bad idea.

 

Yes.

 

An airfoil is an airfoil--5.7s will fit 5.0s. I my opinion, wait until you find a cheap one on ebay. The performance gains aren't worth the full retail price.

If I were doing it all again, I would probably do it in this order:

1) K&N filter/cold air intake setup
2) Headers and catback
3) Ignition setup (only if stock stuff needs replacing/upgrading)
3) SFCs (if you have t-tops--they make a dramatic difference. If it's a hardtop car, wait)
4) TRY to save for cam, heads, and TPI upgrades (runners/base, AFPR) do it all at once if possible
5) 3.73 gears
6) TC and cooler
7) Driveshaft
8) Other susp stuff
9) Bolt-ons like TB, airfoil, pulleys, etc

I have found that with the TPI setup (SLP runners, stock base and plenum), along with stock heads, would pull to 6000rpm and 13.9 times (w/ 48 mm TB and stock catback, A/C and AIR intact, but a nice cam). So, on a 305, upgraded heads and TPI pieces aren't "necessary" to go fast, but they definitely won't hurt!

Have fun!

MILT

 

Actually I was thinking about everything in the order you are talking about.

1) K&N filter/cold air intake setup
2) Headers and catback
3) Ignition setup (My stock stuff is on it's way out.)
3) SFCs (if you have t-tops--they make a dramatic difference. If it's a hardtop car, wait)
4) TRY to save for cam, heads, and TPI upgrades (runners/base, AFPR) do it all at once if possible
5) 3.73 gears
6) TC and cooler
7) Driveshaft
8) Other susp stuff
9) Bolt-ons like TB, airfoil, pulleys, etc

 

3.73s are not a great choice for a stock TPI because it will put you in the upper RPMs and out of the TPI power band. 3.42s would be a better choice IMO. if you want a cheap air foil, look on www.slponline.com they have the cheapest one around.

the things that are most important:

make sure everything is in tune

if it a T-top car get SFC right away (important even w/ a hard top)

full exhaust headers to catback

k&ns and gutted air boxes

get rid of the peanut cam LT1 cam is a good choice on a 305

SLP airfoil

3.42 gears... 2.73s suck

port you intake

AFPR

suspension mods

well that should get you started anyways..... thats what i would do anyways.

 

Hello,

If I could also ask a couple questions. I am in the process of putting my car back together after putting on a set of Vortec Heads and I was planning on putting on a set of Hooker headers I had laying around.

My question is, would it be ok for me to put these on? It looks like I will lose ALOT of stuff that attaches or works along with the exaust man.

I noticed a set of eddlebrock headers on summitracing that appear to have all of the stock attachments.

Should I go this route or will bypassing all of that emissions stuff pose a problem?

Also, could someone please post a pic. of what the cut-out box looks like. I have the K&N Filter and have removed the screens.

Thanks for the imput.

Mike (FireChicken)

PS. This is all for a 305.

 

Here you go..someone elses pic,but mine looks exactly the same...

 

Jeez! Just drop in the tq converter and on a good night you'll be crackin' the 13's.

 

First off, are you sure these are 3rd gen headers?

Second, I dont think FL is doing emissions NOW, but if you yank it all out and they add emissions later you'll be hurtin'.

Now if you know someone 'in the business' then I'd go ahead and pull out the air pump/air tubes.

 

go no higher then 3.42's for gears. TB foil is not worth much.. dont worry, get some KN cause u need air filters, better go get the best flowing ones... Free mods: cut the boxes like the pic says, and port the plenum. I finished porting mine, and they look nice, i gotta swap it on the car when i get home. Deff get some headers and cat back( i sugest hooker cause its the best flowing then any other, and IMO the best sounding) if u need a cat, a 3in hi flow will flow very well... look for heads and a cam later.. start cheap, and work u way up... its hard for 305 heads cause of the smaller chamber.. dont go above 60cc chamber, or u will lose compression... a good head, that isnt vortec, is the aluminum vette heads... if u can find a good pair and have them port them and get a valve job, u would be set for a nice set up.. a lt4 cam is mostly for upper rpm, so it will be killed by the tpi set up. i know comp cams make some nice cams for TPI... and while ur at it.. throw some 1.6 rr's on... and u should be fine... im sure someone is gunna come in here and spoil the fun 305 talk by saying u should swap in a 350.. .but if u wana keep the 305, good for u... there is a lot to be done to the 305... keep the 305 alive!!

 

I don't think anyone suggested the LT4HOT cam... The regular LT4 cam specs are as follows:

GM 203 210 .446 .449 .476 .479 115

Not much bigger than the LT1.

 

I recently finished putting my car back together with ported s/ heads, ported plenum and base, tpis runners, lt4hot cam, edelbrock headers,3in dynomax catback w/ ultraflo muffler, walbro 307 fuel pump. I took the car to the dyno with the stock chip and codes 34 and 36 in the computer. It made 20 more horse and 10 ftlbs more than without the hedas and cam. I now have a custom chip and replaced the bad maf relays no more codes and the car pulls alot harder from 4500- 5500. I hope to get back to the dyno in the next week or so.

 

I disagree with bigals87z28 about getting no higher than 3.42's for gears. I recomend 3.73's. They are the best compromise between top end and quickness. I can still cruise on the highway at pretty low rpm's at like 100. If you go higher than 3.73's you will probably lose some top end speed but you car will take off extremely fast. Gears are one of the best mods you can do to a camaro. It makes it a whole different car.

 

I agree 3.73 are great if you don't already have 3.23 or 3.42, My car with 245/45/16 @ 1:1(4th) ratio goes through the traps at ~4700-4900rpm @ 93 mph. This means with 245/50/16 would be closre to 4900-5200rpm or about 96 mph(this is good from low 14's)

This just gives your a rpm vs. hp range. my TPI goes through the traps at 4600 rpm ww/ 3.42 gears.(guess)\\

I say 3.73 are perfect for a TPI engine since it will make peak hp at 4500-4800 rpm, and high 13's are all that you can get out of stock TPI intake anyways NA.

 

I am one of the firmest believers of the 3.73's also. If you put in 3.42's you won't be that thrilled with the results. I think there the best for the TPI 305! I guess its like beating a dead horse too many of you think 3.42's are the ticket. Have any of you guys with the 3.42's tried the 3.73's?

 

there are a lot of guys that had 3.73's and have swapped to 3.42's and found better times... and not all had 305's!

 

I've read the posts about if your ignition is in good shape, leave it alone for now. I disagree. Specifically concerning plug wires.

I bought my car new in 88, and in 89 we started autocrossing it. I put an Accell cap and rotor on it, air foil, and cat back. The next thing I put on was a set of good Jacob's plug wires. Other than the cat back ,the Jacob's wires were one of the most noticable things I did to the car. My wife was out of town on business when I put the new wires on, and when she got back in the car a few days later, she started it and came into the shop and asked me what I had done to the car. She said it just felt "stronger".

Anyway that was 14 years ago and the jacobs wires are still going strong. They still have almost zero resitance when I checked them, so I swear by the Jacob's wires. They are one of the first mods I'd do to any car that I wanted perfoemance out of.

With a 147k mile 305 tpi 5spd car and the mods listed above, I just pulled a 204.3 hp on the chassis dyno. There were 350 tpi cars that pulled less than my 305.

 

Definitely port your plenum to knock down the EGR walls (if you don't have a dremel or die grinder, you can get a "rotary file bit" from a hardware store that works in a power drill, I did a couple plenums like that. Works fine...) You might also shim your fuel pressure regulator with something like a quarter. Bumps the psi up about 4-5 psi which is what most people end up adding in with a $50 AFPR... Worth the 25 cents to shim it... That and the plenum porting made a noticeable difference on my 86, did them both at once. Then I would definitely hit the cam, that made a massive difference on the 86 (went with a 204/214 @.050, .420/.442 cam). Then get the headers, I went with Edelbrock TES and that's another nice gain. The little 305 TPI auto (I have 3.42s in there too) runs really strong for a 305. Of course it gets bitch slapped by my 87Z but oh well...

 

Has anyone done an Lt1 cam swap? Do you need to change the chip?

 

I doubt you'd "need" to change the chip, but you'd run better w/ a custom one...check on the TBI board--they're always swapping in LT1 cams.

To the original poster: Opinions are like *******s, everybody has one!!! If you have crappy gears (e.g. numerically lower than 3.23) consider replacing them with 3.42s or 3.73s. Either way you'll feel like you're driving a new car. If you have a drum rear, look for a used 89-02 disc rear, you'll often get a rear with the ratio you want with disc brakes for less than the cost of having new gears installed.

Search the boards for gear ratios, cam recommendations, etc. Do as much research as you can b/f buying. Also, decide whether you want this as a fun car, or if you're seriously trying to go fast. If you're more towards the latter, I'll be the jerk and say you may not want to waste $$$ on 305-specific parts (like heads) if you are going to swap in a 350 or larger later...

Oh, about the ignition: I figured I wouldn't stress an upgrade unless you needed it. There's no sense if you recently replaced those items. You won't see a big difference over stock-grade parts, especially when you're motor hasn't been modded. The more high performance the engine, the more powerful and reliable you want the ignition...

I would go larger than the LT1 cam if I were you...the LT4 is a little larger--a better choice IMO. The cam in my 305 is a Comp Cam: 210/220 .500/.510 LS114. It's lots of fun.

 

I would go a little bigger in the cam department except where I live they test for emissions. I don't want to go to crazy and end up having to change it out later on. That damn govt. takes away all of our fun!

 

I have and 87 GTA and im looking to spend some money to make my car faster its a new Jasper 305 engine with some mods my mods are
-SLP cold air
-Air Foil
-SLP Runners
-SLP exhaust
-Chip(dont know what kind)
-AFPR
-Ported and polished plenum
-Modified MAF
-TB coolant bypass

Im defintaly getting headers, but i dont know what to get after that, im thinking a cam and gear drive to replace the timing chain.
Any suggestions on what I should do next
thanks

 

if you bought a new engine why a 305?!

 

I dont know why i did , i dont have a good answer for that i definatly regret it. I dont plan on making this car sick fast when i graduate from college im planning on getting and ls1 and making that my real project

 

What are you're goals (price/ET) or what do you consider fast? If you consider high 13's fast then the 305 and stock heads should be alright to reach your goal.

 

I want to get like mid 12 that would be really good, but i dont know what to do to get there. im willing to spend about $3000 this summer on it.

 

thanks for all the responces guys i really appriciate it
My biggest concern so far is if a LT1/ZZ4 cam will run well and produce some reasonble gains with the stock prom? thanks

 

if you want to do that cost effectivley w/ a 305, you are going to need to spray some NO2 IMO

 

Speaking of No2, what would be the most you would spray JUST to notice a difference. Keep in mind a higher milage vehicle, but runs PERFECT, and besides some simple bolt ons-Vortec Heads, Headers, Air Foil, K&N, chip, etc, it is pretty stock. Also, I do not know if it makes a difference, but I have a 2500 stall and really sup'd up tranny (Best buy so far! Bought for $1200 on ebay)

I am really leaning twords spray even though I have always been against it. But as the previous post said, it may be the only way to REALY wake up a 305.

I am also a believer to keep the 305's alive. I would much rather have a 305 and pull on a 350 then the other way around. Of course, I would like to hang with a Cadillac or GTP though :-P

My best time in my wifes GTP is 14.1 and I got 24 mpg getting to and from the track. Its hard for me to convince her to spend all this money to try and catch her 6cyl

 

well just to be safe... i wouldnt do more than 50 or a 75 shot on a stock internal motor

 

It will be hard for u to get to low 14s in Calgary because we are so high above sea level. I have an 85 IROC with a 305 TPI, and I ran a best of 16.1@85 when corrected to sea level thats 15.35@90. I ran that completly stock so u should run around the same. If u get to around 15.3 at Race City that would be good for low to mid 14s at Sea level.

 

i was just about to ask about this on the theoretical racing board! thanks!
Do you know if turbo/supercharged cars are as badly effected by the altitude?

 

They wont work as well as they would at sea level but other then that u just have to tune them to run at higher altitude.