Duke901

I have a 1985 IROC with the tpi 305, i know that it already comes with the better cam, but i want more power. i dont want to add a 350. I just want to know the best heads, cam, headers and intake to make my 305 able to hold its own. And if i change the cam and heads would i have to burn a new chip or prom, or could i make some good power by keeping the old cam and using the new heads,headers, and intake, and would i beable to use the stock chip with them.

THANK YOU
MIKE

P.S I want this to beable to run atleast 13 sec 1/4

Jim85IROC

iTrader: (2)

That car is going to turn into a money pit if you want it to run 13s with the stock 305. Unless you just get some sort of rush from having a fast 305, you're going to find that the cheapest way to hit 13s and still have some semblance of reliability is to put a 350 in.

But... if you're headstrung on having the 305, start with the basics like headers & exhaust. The 85 already has a decent cam. The runners & base will become a restriction once you start making a little more horsepower, but upgrading those can get expensive unless you buy used stuff.

But... the big problem with the 85 is the computer. It's just plain stupid. It's slow, and has very little processing power. You can burn chips for it, but you're not going to have the tunability that the newer ECMs have. That's why I swapped to a 165 ECM and harness out of an 87 IROC. My IROC ran pig-rich with the 350 because the computer couldn't figure out what to do.

Your other choice is always Nitrous, which is the only way that thing will run 13s affordably on the 305. Just don't expect it to do it for long. I would guess that you'll probably need at least a 150 shot to run 13s.

tpi_roc

I say step #1 is ditch that computer like Jim I too have an 85 and I knew the pains of the 870. Ditch it for the 165 or more prefferably the 730 (speed density computer from 90-92).

From there plan to change and work on EVERYTHING for 13's from a 305, and really your only aftermarket head option (short of vette aluminums) are S/R torquers from WP, and they're not that great at all.


Or you can just start gutting the car and trying to strip as much weight as possible, get that thing down to 3,200 lbs

Duke901

Well, could i keep the stock cam and just add the new intake and runners and headers and make some ok power. But would that make the computer go nuts, or could i get a cam that would work with the computer and add all the other stuff i said before and be ok with the ECM.
THANKS

tpi_roc

I ran the stock ecm with quite a few changes to the car...


but after the cam it started to knock and if you're not prepaired to burn proms there's no way to lower timing, thats why the ECM is one of the first things that should be changed.

Ed Maher

Tee hee....imagine when i do it with a basically stock 305 in the heaviest thirdgen off the line

Perry93TransAm

Actually those WP torquer 305 heads are a very good start, but do not leave them unported. have a good port (mainly bowls ) done to them and have some very high flowing same size valves (manly race flows) added. this will support upwards of 300 horsies. now that you have the heads taken care of put full exhaust on it, I'm talking headers and cat-back and a highflow cat if the law requires it,if not ditch the cat, now add that beter computer and harness, as said it will run so rich youll choke all the mosquitos in three counties with the gas fumes. The stock cam will work to a point but to run 13s (high or low, what is your goal?) youll need more duration. Port the plenum add a intake filter system that is unrestrictive (the stock 85 is one of the worst) the throttle body should be fine I wouldnt go to a 52. Maybe add an airfoil and call it good. After you get it tuned add a stall of around 3000 to 3500, and some higher gears , say 3.42s or a little higher, stickies, weight reduction and launch that sucker like theres no tomorrow. The weight reduction will probably help more than youd imagine. I would start by removing all unneccesary weight at the track, like the jack and spare, the front swaybar and links, underhood insulation,fiberglass hood, aluminum driveshaft and rear brake drums (if equipped), smogpump and lines (unless required by your state). rear seat and seat belts (to the rear not the front), if possible relocate the battery to the rear and get a lightweght one for the track. Just remember every 100#s you shed from the car is 1 tenth of a second in the 1/4 so 10 pounds is a 1/100th (if everything remains consistant). Traction and your first 60 feet will be very important to good times, the difference between a low 14 and a high 14 with 250hp is the first 60 feet. if you blow in a 2.4 dont expect to hit your goal , aim for 1.8s and 1.7s launching hard. I do this regularly with the stock suspention minus the front swaybar and drag stickies (M/T sportsman pros).A good fuel pump is a must as well.
Perry

Jim85IROC

iTrader: (2)

Now compare the cost of that buildup to a 13-second 350 buildup and decide how bad you really want that 305.

Ed Maher

I bet my (damn near) 13 second 305 cost less than your 16 second 350 ROFLMAO, sorry jim, had to do it

Perry93TransAm

Actually if you keep your bottom end pretty well stock the price is the same, heads for a SBC are heads, SR torquers are cheap by comparison. The gasket set would be the same, the bearings, same the only thing that would require a different part# is the pistons and rings. Now granted the 350 with the same peices will make propertionally more power.
Perry

Poppa Chubby

Ouch. That's gotta hurt!

Zepher

iTrader: (1)

I did this to my 305,


and got this out of it,


Oh, I had a Crane Cams PowerMax 2050 in there as well.

Jim85IROC

iTrader: (2)

Touche'