2 questions about TPI 85 iroc
 

i have a 1985 iroc z, 305 TPI, 700 r4 trans (auto). my first question is, can i put a 52mm throttle body in it without changing anything else? my second is, can i put an edelbrock tpi intake manifold in without changing anything? lastly, i hear people talk about "built" transmissions. i was wondering what i could do to "build" my transmission a little more. thanks. Ryan.

Neither the throttle body nor the intake manifold should require any changes to anything else.

Your first mods should be better flowing exhaust. A bigger throttle body and better intake manifold won't help at this point. K & N air filters will help you get more air in, but you won't be near the flow limits of the stock throttle body.

Do even bother with the 52mm TB or intake manifolds for now. I would concintrate more on Exhaust and Headers for now. The 305 TPI does flow enough air stock so u wont need that extra stuff. If u want more air to the engine get some K&N filters, Gut the MAF screens, and cut the air boxes out. U should notice a difference with that.
Dont wasnt ur money on junk that u dont need for a 305. its not worth it.
Headers, Exhaust, Cam, AFPR, along with the air mods I listed above should serve that 305 TPI good. If u need more power u could do some Heads and stuff like that.
U wont get much faster then high 13s with a 305 TPI. If u want to go fast get a 350. But if u want to keep the 305 TPI dont expect to be getting into the 12s without spending alot of $$$$.

I have the same engine and im trying to get into the high 14s with it a 4400ft above.
Good luck.

Cragg is right. The LT4 came with the same size throttle body as your 305, and I've seen guys run slower 1/4s by putting a 52 on to a stock LT4. There's absolutely no way you'll get ANY benefit from it.

I wouldn't cut your MAF screens either. The MAF can flow way over 500 cfm with the screens in place, which is more than your 305 will ever need. In fact, the computer can only recognize around 4XX cfm of airflow anyway, so giving it the capability of more isn't helping. The 85 MAF screens are a huge pain in the *** to cut too. The 86+ MAFs are constructed differently and their screens are easy to remove. I cut them out on my 85 and found absolutely no benefit.

As for the TPI parts, all that crap will fit but you won't really find a big improvement from any of it. Like Cragg said, start with exhaust. Unfortunately, you have basically no choices. The 85 uses the 4-bolt cat instead of the newer style, so none of the 86+ exhausts will fit without modification. The only exhaust I could find for my 85 was a 2.5" dynomax. On a 305 that will be plenty of exhaust though.

When I order my exhuast I am going to get the 1986 and up stuff and eliminate the cat. If eliminating the cat when u live in illegal then buy a high flow slip fit one. The 1986 and up stuff is better because u have more to chose from and sometimes it cheaper. And its a hell of a lot easier to find.

Pepperdad have u been to the track with ur car yet. Does it have any mods done to it. And what kinda options do u have on the car.

Thanks

Reply
 

i put in a fast chip and cut out my MAF screens. i also have k&n's, and i removed the backseats. i've never been to the track but i've raced dozens of people on the street. i've lost a few but i beat a mustang notchback, eclipse, seR, and a few other moderately fast cars. i have one more question, when i shift from park to drive or reverse, or any gear from park, my car jolts very rough and can be noticed from within the car. what can i do to stop or weaken this? thanks. Ryan

mine does the same thing when I put it into drive. It seems to settle down if u let the car sit for 15 seconds, and the RPM settle down to around 500RPM. Mines good to go after that.
Well let us know what u get some 1/4 mile times with ur car.
In ur origional post u asked about buliding up ur transmission. The best thing to do is get a shift kit (Transgo Shift Kit) and get a corvette servo, That should make ur shifts a whole lot faster and harder.

The 86 & older 700R4s are notorious for that. That's a big reason why they were redesigned in 87. All of the old ones bang into gear like that.

Reply
 

thanks for the help. i'll soon put your advice to use. i have a question about what craigg said about cutting off the bottom of airboxes. should i cut just below the slices in the housing or farther down? and if i do that, can i still put an slp cold air induction on? thanks. Ryan.

One of my buddies with a 1985 IROC went down to the local performance shop and was going to order and SLP cold air induction. We know the guys so there nice and give us advice and good deals. Well they told him that the SLP kit was a waste of his money and they he would get the same results or even better results from gutting the air boxes.

What other mods do u have planned for ur car.

underdrive pullyes, lighter driveshaft/water pump, hooker headders and cat back, edelbrock TPI intake, t.b. bypass, still thinking on slp cold air, gutting maf fins, and that's all i can think of right now. i'm trying to get the most out of the 305, then i'm going to sell it and go bigger. Ryan

how do you gut the airboxes? cut off right underneath the air slits?

cut it all out!
 

take off your air cleaner assembly and pull out your air filters anything below that cut out.
the peice that the air cleaner assembly bolts to can be unbolted and removed to make it easier.i used a Dremal to cut it out on my 85 Z.