gchu

I have an 88 Iroc Convertible with a 305 TPI Auto - so it's got the detuned 195 HP engine in it. I am planning on doing some engine work on it this winter to get it ready for the summer so I was wondering what would be the easiest (i.e. cheapest) way to get about 250HP (at the crank) from it?

I'm not looking to go much over that as I'm worried about the rest of the drivetrain holding up - so I want to keep it around 250HP. I'm not looking to race it so I'm not looking for a super motor. Just something with a little more juice. I figured 250HP would be safe as the stock 350 TPI in 92 put out around 245 HP.

I am already planning on installing headers with a dual cat/exhaust setup - I do not think this alone would get me to 250HP - right?

What else should I go after? I want to keep the 305 engine so going to a 350 is not an option. Can I install the cam from a 305 TPI with a manual transmission (that combo is rated at 225HP)? I know I'll probably have to get a new/custom chip as well. If the stock cam from the 305 TPI with auto is not the answer, what cam do you recommend?

I'm looking for some detailed answers, preferable with manufacturer and PN if you have it.

rezinn

New camshaft and exhaust could do it, a custom chip would be nice. Cam and exhaust are probably the two worst parts of your engine for performance as is. An LT1 camshaft would do nicely, and they are plentiful and available cheap. A good tune up could help, best to make sure everything is running perfectly if you want it to make the most power it can.

vwdave

GM High-Tech Performance has a 305 TPI project car you might be interested in. They went from 191, to 221hp. (To the wheels)

Dynomax headers and catback
Homemade cold air kit with K&N cone
SLP runners (Untouched IIRC)
Jet Pulleys (which made like, 7hp to the wheels by themselfs)
Comp cam springs and Rocker arms. ($180 version)
TPIS FP Regulator
FastChip

Thats all the engine bolt-ons they have done. If you get a LT1/LT4 cam you would be MAYBE at 230-235. Also depends on if your upper and lower intakes become a restriction. But if your doing a cam, those have got to come off anyway, so maybe you would like to do some homemade porting. That would probably get you there.

thinslice

Are you sure about the LT1/lt4 cam? that sounds like alot of cam for a 305.

vwdave

Alot of the TBI guys are running them.

I would get prom burning too, that alone is worth something, and you will probably need it to get everything to run peachy in your car.

cronsformula350

Yeah with headers and cat back expect at least 20 more hp, possibly as much as 30 with a good cam, call comp cams, cam help for a cam they would recommend for your type of build up, and I don't know if better runners would be worth the money, in gmhightechperformance, they picked up 5 hp on a 305, more is possible with a cam, so they may be worth it. I would also recommend removing the baffles from your air lid, and using k&n's or some type of free flowing aftermarket air filter, and removing your screens from your maf. Also advancing your timing, is good for up to twenty more ponies. Porting your intake base and plenum would help though, and leave your stock tb, its more than enough, but a airfoil from tpi will make it smoother and help mileage somewhat, check on my site with the mods I did and see how much mileage I got. Also a set of underdrive pulleys would be worth it, they picked up 17 hp and 13 lb ft with a set of street ones from JET performance, which is worth the price of less than 130$ for the pair of pullies. So yes you can pull 250 off pretty easily. Why do you think that your motor puts out less hp, you motor LB9 was supposed to put out 215 hp, and 295 lb-ft of torque according to my article on 88 fbodies, in my HPP magazine.

So even though its a 305 it has potential, but the 350 has alot more potential, but a 305 can have some ***** with a tpi, since the tpi intake was originally designed for a 305, it can push a 305 further, than a 350.

http://www.cardomain.com/id/cronsformula

gchu

Thanks for the tip on GM High Tech Performance - I didn't even realize that magazine was out there. I just checked out their tech link on their website and it looks like their project blue thunder is very similar to what I'm looking for - although they have a 5 speed in their 305 TPI and I have the auto.

Cronsformula350 - according the the tech link on thirdgen.org, the Auto 305 TPI only has 195 HP vs. 215 with Manual - I think the only difference (besides the chip) was the cam. That's why I thought about swapping cams and a new cip.

Anyway, it sounds like I should be able to hit 250 HP from headers/exhaust, adjustable fuel pressure regulator and cam.

I'm not sure about the Comp Cam Springs and rocker unless it makes sense to do it the same time as the cam - or would I get better results from just doing the springs and rocker and leaving the stock cam?

I'm also a little hesitant to do the Jet Pulley as I believe these are underdrive pulleys - since I do a lot of stop and go driving, I would be worried about getting enough charge

I'm planning on installing a 89+ Dual Cat setup so I'll be using the SLP w/AIR headers, 2 stock cats (I need to keep it emissions legal), and a flowmaster cat back system.

So what cam should I use with a dual cat system?

Thanks everyone for the info so far!

vwdave

You dont HAVE to get rockers, I am running the stock stamped 1.5's on mine, but you have to remove and readjust the rockers anyway, less work in the long run.

March makes a pulley set that keeps the alternator turning at the proper speed.

Honestly, the best cam for the money is a LT1 cam. Most of the LT1 guys who swap out their cams will sell them to you for cheap, and they are a nice upgrade from your current cam.

Also, spend a little extra money and get a 95+ S10 4.3 torque converter. I got a rebuild one for $90 and its roughly a 2000-2400 stall. I personally love it on my car, and I am pushing more power than you are.

People make mistakes of getting something too big for them. You wanna shock people AND have a fast car? A few well chosen mods will make almost any car scream.

cronsformula350

Yeah you are right, manual version was rated at 215, auto at 190. I would recommend the Flowmaster catback, it makes the engine sound alot better, and will make others wonder if your car was a 350 or a 305, sometimes its hard to tell.

Also how many miles are on your engine? If you do decide to swap the cam, talk to the guys at comp cams tech help line, they can set you up with a k kit, that has the new cam, bearing lube, lifters, and pushrods, timing chain, and some instructions, for a few hundred bucks, this would turn your 305, into a competant performer. As for running roller rockers, you could use them, they help reduce alot of friction and according to john lingenfelter, the average oil temp difference just by running roller rockers is 10-15* cooler than with stamped steel type. Roller rockers have alot more consistant lift than stamped rockers also, so even if you don't buy roller rockers, opt for a set of comp cams steel rocker arms. Yes the adjustable fuel pressure regulator helps too, only a few hp on the top end, but up to 15 in the midrange and low end.

I don't think you would have to worry about charging even if you run the underdrive pulleys I have the ASP racing setup on myne, and it uses a crank pulley with 51% underdrive, and a alt pulley with 23% underdrive, so the alt. is spinning 74% slower than from the factory! MY pullies are great, and made a huge difference with mileage and torque, hp, everything, theres alot less drag with them on the motor, makes alot of sense, and they were only I 130$, had to be custom made, because they don't stock them, but they still sell them. www.aspracing.com

This is the crank pulley on my motor now, look at your factory one compared to this:

gchu

cronsformula350 - I have 145K on my car, but the engine was supposedly rebuilt at 100K - I bought it about 4 months ago. It has a very slow drip coming from the oil pressure switch/rear oil pan area of the engine. I figured I would need to have it rebuilt again and thought I would get some mods in at the same time.

I had thought about dropping in a 335 stroker kit, but decided against it since I really wasn't looking for that much more power (TPI 335 had done a nice build up with all stock TPI setup and wound up with near 300 HP). I was really just looking for about 250 HP, which got me to thinking about installing headers and swapping out the cam when I got it rebuilt. Figured this was cheaper than the $600 it would cost for the stroker kit - since I would need to the exhaust either way.

Of course, if I can get the oil leak fixed them tearing apart the engine, I would just do the headers and the Crane Cam rocker arm and spring mod that GM High Tech Performance did. Since I will be paying someone to do all the work, it will be very driven by cost.

Anyone have any recommendation on a good performance shop in the Philadelphia/Lancaster Area (my zip code is 19438).

vwdave

My oil pressure sensor leaks too.

There is a 99% chance you DONT need a rebuild. A external oil leak is just that, probably a seal or soemthing went bad, depending on where it is.

redtail2624

GM high tech didnt pick up 7 HP with the jet pulleys but rather 17 HP yes 17 that not a misprint.They checked the #'s several times and got the same 17 hp from just the jet pulleys and yes that to the ground.bvery good idea if you ask me.

cronsformula350

I know thats what I put, 17 hp, and it is a great gain for the money, if you think about it. Most people will spend ten dollars for every 1 more hp, so 17 for under 130$ is pretty good, which would also say that my more radical race set from asp would have a much greater gain, maybe when I get my car dyno tested after the motor build up, I'll try the stockers again, and see how large of a diff there is, I noticed a huge difference after I put them on though, car had way more torque, and accelerated much faster than before.

vwdave

I have never heard a car getting 17hp from pulleys. If they did, people on here would be going nuts over them. (17hp for $170?)

Must have had some bad accessorys or something.

cronsformula350

the gain was on the dyno, checked several times, no bs, in gm hightech.

vwdave

I have that issue too. Just something tells me there is more to it than just that.

cronsformula350

It is also possible that, they will also give you a better gain with other parts. Some times the sum of the parts are greater than the individual ones, so with the headers, catback, and runners, they may have helped more. But I know that a 305 doesn't make as much torque as a 350, so naturally they would probably help unleash more power on that motor, than on a 350, but when I put on my asp racing underdrive pulleys, I felt a huge difference.

Compare this to your stock crank pulley:

vwdave

Dammit, I know that. *Smack*

91RS5speed

Im pretty sure the 17hp was from pullies, runners, and maybe sopmthing else.

1bad91Z

iTrader: (1)

That 17hp was probably an intentional misprint so the magazine could get the pullies for free!

83ho86tpi

My 305 has a Chip, headers, no cat,adjustable fuelpressure, 9inch long k&n air filter, gutted maf sensor, airfoil and flomaster exhaust. All this on a stock 86 tpi block with 127k miles on it. Id say im close to where you want to be. Id do the mods on everything but thr 305. If you want to do mods on a engine later, get a 350. You might as well put $ into parts you will keep. And if you have to spend $ on rebuilding your motor, or want to go for internal engine changes, go with a 350 or more cubes, not a 305. You will get better results per $ with the larger engine. Just my 2 cents worth.

cronsformula350

What you said is very true, and makes lots of sense. The only thing is that, for some people swapping an engine is just not an option for many reasons, like time, experience with that kind of job, energy, and effort capable of putting into a car, its just not for everyone. And a healthy 305 can still take damn near all the ricers out there anyhow.

pecha

hey guys I am looking for the same goal as gchu
I am putting a L98 cam instead of my peanut cam so my question is:
Do I have to change the chip to have it running? Or will it just help but is NOT necessary (I'm on a budget)?

PHAT89TA

anybody know the websites to get the jet pulley kit

no1kicker

I have a set of march pulleys and they make a very noticable difference especially on the highway.

5SIZ

I only use an underdrive crank pully, still use the stock alt ulley because i wouldnt want to get any voltage drop.

i have a V-belt setup so all o needed was to get custom belt from any auto store, took a while ot get the right ones but itwas a sinch.

i would definatly recommend underdirve pulleys, but the price to performance ratio..get full roller rockers first, proform has 1.6 full self aligning rollerrockers for 170 w/ free shipping.

ans thats if you have center bolt valve covers, thereeven cheaper iyou have a pre 87! like 130 or something lol.
Oh I have 190,000 miles on my motor.