hey guys i have an 85 IROC-Z now that has an all stock 305 TPI with an auto tranny and id like to put a 350 in it i know the TPI set up will bolt up but what has to be changed on it to ocomidate the bigger engine? computer? feul injecters?

get back to me guys is this a big deal to do id realy liek to keep the TPI for now so what all has to be changed with the 305 TPI intake to bolt to the 350 and run right?

im also goign to be converting this car to 5 speed and puting 373s in the rear along with headers and a full exaust upgrade.

also later on id also like to put a bigger cam in the 350 will i have to change anything computer wise or will the engien still run right with a higher lift cam.

as you can see i am very new to feul injection my last car was an 83 Z28 (92 Z28 clone) that had a 305 carbed engine in it that had a bunch doen to it. i dont know much about TPI though so hopefuly you guys can help me out a bit.

thanks in advance guys

 

come on guys i know some one can help me out with this

 

yes,the TPI setup will bolt right on w/ no problems as long as the block ur putting it on has the same head bolt angle...86 and older or 87 and newer. u will not need to change the computer for it to run,but it would help to have a 350 chip in it,but the 305 chip WILL WORK.

the fuel injectors on a 305 are 19 lb/hr and the 350 stock are 22 lb/hr...but again,the 305's will work,but wont perform as well as it would w/ the 22's.

i wouldnt put the 5 speed behind a 350 TPI if u plan to beat on it alot b/c the torque will murder the T-5 (thats my GM didnt have an option for them w/ the 350 from the factory). 3.73's w/ a stock TPI intake will blow,ull run the RPM's outta the powerband way to fast and ull be disappointed from what ive heard.

when/if u change the cam,u will have to get a chip burned to go w/ the new cam specs (lift,duration,etc.).

hope that helps

 

wouldnt i have to change the computer when i put a 350 in it also? the cam is going to be different then the 305 cam so in my eyes ud think you would also have to change it to run the 305 tpi on the 350 engine am i right or wrong here?

 

I have an 85 and I'm running a 350 with the ZZ4 cam in it and lots of other junk..... You can run the stock computer, just put an 85 Corvette chip in it. The calpak is a separate chip in the 870 computer so leave the stock 85 calpak alone. If you change gears, you need to get a calpak that is calibrated for your new gear set. If the gear ratio was a factory option, the calpak is around $20 at the dealer. The Corvette chip is around $50 at the Chevrolet dealer.

You will need the 350 knock sensor and ESC module. Don't let anyone tell you they are the same, they are not. It will run "ok" with the 305 stuff ( still have to use the 350 chip) but you will keep getting those annoying codes that leave the yellow light on in the dash.

You will also be much better off putting the 350 injectors in your car. They are cheap enough now it doesn't make much sense to take a chance on leaning out your motor and damaging it. If you are bound and determined to use the 305 injectors you will have to get an adjustable fuel pressure regulator and kick the pressure up to around 50# for it to work. BTW, that is really hard on those "old, stock" injectors and you have to constantly readjust the fuel pressure….

As far as everything working perfectly with your motor, depends on the cam. If you leave an L98 cam in the 350, which is what came in the '85 305 and Corvette 350's (86 & up 305's had the peanut cam), you will have absolutely no drivability problems. If you put a hot cam in it, you will probably have cold start problems. It will need to warm up to run right, just like a carb…..

If you have a hot cam in it, the car will run smoother with the later model computer. I gained 2.5 mpg by going to an 165 computer and it almost idles like it's stock. With a better calibrated chip it probably would. Not to mention eliminate the cold start issues.....

Another item, the 350 with the L98 cam only pulls to 4500 rpm, your 700R4 is set up to pull to 5K. You will need to swap in a Corvette governor or go with a little more cam, say the one in the 330 hp crate motor. That should make good power to 5k and still work with your engine management system well.

There will be others who will say go more radical, but this will make you the best power within the boundaries you set, i.e. Stock induction.

Use a high quality harmonic dampener. The 85 305 TPI engines have an annoying habit of spinning the outer ring on the balancer. I did it several times before I bought a Fluidamper. This screws up your timing, causes you to fail smog (or close!) and candamage engine bearings. The 6 1/4" fluidamper unit works fine on 305's, and on 350's that have lightweight pistons in them. If you are running pistons over 550 grams, I would reccomend the 7 1/4" unit.... I get to swap units today......

PS: I would also go with the 52MM TB. That eliminates that annoying lug when you hit 3rd gear using an 870 computer…..

 

He covered most of it...

If not, be aware of the mentioned years of the small block.

'85 intake will NOT bolt onto a '87 later IRON head 350. Now if it happens to have the alum Vette heads, you're good to go. However clearancing the intake to work is not hard....but probably better in the long run to find a '87 and later intake for cheap. The conversion DOES Work, but even with washers under the intakes bolts, they tend to seep oil ( very very slowly )...at least the 5 or 6 times I've done it they have...nothing to worry about really..



870 ECM will work fine, even with the 305 chip. Will it be optimal? NO....but it's not going to really hurt anything...it will get you by until you can easily rewire the 870 Harness to swap to the 165 ( the cheapest, easiest route in my opinion ).


As for the 5 speed question...it's not hard at all in a 3rd gen. Just gather all the parts ahead of time.

- Tranny ( MUST be from a 3rd gen app to work, they are tilted )
- Clutch, pressure plate, T/O bearing, pilot bearing
--Shifter
- Pedals
- Hydraulics ( Master cylinder and slave cylinder w/ hoses )
- bracket for master cylinder to mount on brake booster
- 5 speed console insert
- Torque arm mount ( some say their 700 tranny one worked, I've done 3 5 speed swaps, and had to get a 5 speed torque mount everytime, guess I"m unlucky )


It IS NOT a hard swap. Worse part by far is contorting yourself under the dash to get the old pedals out / new pedals in, etc

Take the seat out, makes it easier.


The Automatic chip WILL work with the 5 speed...but it will "hunt" at idle w/ a 870 ECM.


HTH