LB9Formula89

So I currently own an 89 firebird formula with a 305 TPI setup. It has dual cats and so far the only modifications made have been done to the exhaust. It has headers, a flowmaster muffler, and 3 inch pipes. other than that nothing much has been done to the car. I was just hoping you guys could possibly give me your opinions on what I should do to it next. Any thoughts are greatly appreciated.

sailtexas186548

iTrader: (2)

my next step would be high flow cold air intake, then a cam and customs tune (not mail order).

PhoenixFirebird

iTrader: (2)

Here's what I would do (and am doing in the coming months). Swap out the 305 for a 350.

If you're opposed to an entire engine swap, and want to slightly mod the 305 you have, that's perfectly fine. I would keep mine this winter if I didn't already have a free 350 sitting in the garage. So, if you don't go 350, here's what I would do:

Basic (for the most part. Tuning takes a bit to learn, but it's fairly straightforward)
- 180 degree thermostat
- Custom chip tunes through Moates tuning equipment
- Remove the air filter metal canister, and put an open K&N air filter on the end

More involved
- New rear gear, 3.42s are the best compromise for TPI. 3.73s and you wind the motor too high too fast, and 3.23s you take longer to get into the powerband.
- 2500 or so stall converter
- Lt1 cam. Cheap, wonderful cam for a 305, almost nothing else needed for this cam swap

Involved to the point of "swapping to a 350 requires the same work/money"
- Upgraded heads (read: aftermarket), 175-180cc are plenty. OR port a set of stock heads, which will unlock some power, but not nearly as much as aftermarket heads out of the box
- Bigger cam than an Lt1. With this you have to be careful, as a lot more is involved. You better be ready to tune if you go with a decent cam
- Ported or Ported/Siamesed: stock plenum, aftermarket runners, aftermarket base intake

Do NOT port your TPI intake/runners/plenum without upgrading heads and a cam first! It is an absolute waste without those upgrades. It actually slows the car down. The long-tube runner setup is not the bottleneck of a 305. The heads and cam are. I'll give an example. Previously 305 was running low 15s, a few high 14s. I wanted to be solidly in the 14s, so I put ported and siamesed SLP runners and an Edelbrock intake on. The result was a new best of 15.53 since the swap. That's half a second SLOWER with aftermarket parts! The ported/siamesed parts shift the powerband upwards, something the heads and cam aren't meant for stock. The combination I put on my car wants to be revved to 6000. As I'm sure you know, the 700R4 shifts about 4900-5000. I lost a lot of my low end torque (2.1x 60' -> 2.2x/2.3x 60'), just to shift in the middle of my powerband. Manual shifting at 5500 helps somewhat, but there isn't enough to make up for the lost low end.

But, if you aren't opposed to doing a motor swap, definitely look into a 350. Cheap blocks, many many many matching parts from 305 to 350, and the cost is probably about the same. But think of what you can do with those extra 45 cubes. Food for thought.

LB9Formula89

Well thank you very much. I also love your car, PhoenixFirebird! That's pretty much the same car I have!

TTOP350

iTrader: (8)

Something is wrong if you slowed down after you ported your stuff... (my guess is the 2.73 gear and your stock 305 chip)
For giggles I stuffed in a 30k mile tpi 305 once. I went 13.9s in my car, it had a old GM zz2 cam, mildly ported SLP runners and ported edelbrock base, 373 gear, slp shift kit and V6 converter, SLP CAI and headers catback. And a few of my tricks that people on here say wont work.. bald street tires..
Use a 350s car chip or timing table..

PhoenixFirebird

iTrader: (2)

Well, my aftermarket TPI components are siamesed (base & runners both), so I'm sure that has a much bigger impact on things than just porting. Although, I don't feel the TPI system is the choke point on 305s. On 350s, sure, but TPI was designed for a 305. I'm of the opinion that you would see more of a gain with opening up the heads and upping the cam, before porting the TPI components.

Thanks LB9, I absolutely love my bird! Since I bought it in April, I've only seen one other Formula. Seen quite a few GTA's, but Formula's seem to be quite rare (around here anyways).

TTOP350

iTrader: (8)

You still should see a gain and not lose that much time.. maybe it was making a lil more power and spun? Timining set properly?

Doing all the work you did to the runners/ intake wont kill your bottom end power that much.
Orginal SLPs used to have runners that were opened up all the way thru on one pair each side. These made power and had "2 distinct torque peaks" as SLP said in their adds. These made power on 305s and 350s.
SLP have sold about 4 diff versions of their runners.
This is one of the earliest sets.

APACHE JOHN

If got that same set. But mine now are opened all the way up thru and thru.........

PhoenixFirebird

iTrader: (2)

I apologize, I am severely mistaken. I've finally put all the pieces together as to why I lost so much time. When I put my ported/siamesed pieces on, I reset my TPS. I adjusted it to .54 base, but the WOT reading was 4.86, enough to throw a high TPS code. This disabled my PE mode at WOT, so I wasn't getting the proper timing and fuel additions. First time with my Wideband installed, I was running 15.3 AFR at WOT! Anyway, before I fixed my TPS, I had already put my stock parts back on. So, I have no credible data at this point lol.