...and what a wonderful resource this place is! Here I was thinking I was all alone in my desire to mod the bejesus out of my 305 TBI. If anyone's interested, here's a little background of me and my car... and what I plan to do to her.

She's a 1988 Iroc-Z that I bought new in '88. She's been driven by three other people, besides myself, in the past 16 years, but she didn't like it ...and it hurt me even more She kinda looks like that grey Camaro in the ThirdGen.org picture at the top of the page (only much more beautiful ofcourse She was the first car I ever had and will also be around long after the rest are gone.

Anyway, I have nothing done to my baby right now, but am planning MAJOR street-oriented modifications over the next few weeks. My plans include a new rear-end (posi 3.42); port and polish job on the heads (which I'll do myself); an open element air cleaner (because they're so beautiful); a hotter cam; headers; Edelbrock TBI intake manifold, 3" exhaust with no cats and a high-flow muffler. I'm getting a ported throttle body unit and bigger injectors with a higher pressure fuel pump as well. I want to stick with the stock stall speed, and have a operating power range from idle to about 5500 rpm. And today I decided that I'll be doing my own chip programming as I have easy access to PROM burners.

Most of this stuff is on the way (I've thrown a few thousand bucks at my beautiful baby over the past couple of weeks - and she's worth every penny and more).

But I'm very open to suggestions on how to port the swirly heads, camshaft selection and injector size I'll need ...and PROM issues.

One question I have is what kind of cam durations and injector sizes have people managed to get working well on this kind of engine?

Any suggestions?

By the way, I'm glad to be here

 

Welcome to the boards, i found this place about 3 years ago right as i bought my first camaro. it's been tons of help and fun over the last 3 years.

now onto specifics, if it were me i would try and find a set of either 081 casting heads, from a 305 TPI, or a set of the alum. 350 TPI i believe both are the same CC size as the 305 TBI, i know the 081's are but not sure of the others. they flow much better from the factory and will port much better. they can be had for a few hundred bucks or less depending on how lucky you get, check ebay. now for a cam, many people here have gone with an LT1 cam, however i'm sure someone will say go bigger, that's up to you on how wicked you want. it's a pretty decent cam and will give you nice power gains and used can be had for like 70 bucks. injector size, i'm not really sure, maybe 68# or 75#. i would also buy a new fuel pump the walboro pump, which one has slipped me so i cant say which, somebody will know. also have you upgraded the suspension? new springs, shocks, Sub Frame Connectors(a must), Strut Tower Brace, Panhard bar, Wonderbar, all things you may want to consider.

 

Yeah I'd also recommend picking up a set of 305 TPI heads and porting them. The swirl port TBI heads don't give much gains even when ported, they're a lost cause. Go with either 55pph or 65pph injectors with a better pump. If you're getting a bigger throttle body make sure you bore out the Edelbrock intake along with it. You could also look at the Holley TBI intake which already has 2" bores or a carb intake with a TBI adapter, all viable options.

You're definitely on the right track though and good to see you'll be burning your own proms that will definitely help you. I'd say if you can burn your own to go with a bigger cam than an LT1. I'd look at maybe a ZZ4, still can get it cheap and its a pretty hot cam in a 305.

 

Can I use 454 injectors (75 #) and back the fuel pressure down to get the appropriate flow rate?

I was talking to the guys at Turbo City and they told me not to get 454 injectors because I'd never get the car to idle clean? They told me to get 68 # injectors instead, but backing the pressure down to 10.75 should give me 68 # out of the 454 injectors. So what's the difference? Will the 454 injectors fit in the Rochester 220 injector pods?

--
Casey

 

Yeah, the 75's will fit. If you really want them you can certainly use them and back off the fuel pressure like you say. Just make sure you figure out the right BPW constant to put into the Prom when you are tuning it. Other than that it should be fine with those injectors.

 

If your getting into prom burning you can just adjust for the bigger injectors in the chip with out messing with the fuel pressure. This will all make sense when you really start getting into prom burning and see how these ecm's work. I suggest getting started on the prom stuff now before all the mods that way you can learn on a already semi tuned car, I say semi tuned becuase there is a lot to be had out of these things stock.

I suggest skipping the TBI intakes unless you want it just for an easy bolt on. You'll make more power with a carberuted intake and an adapter. Then you'll be all set up for when you really start turning up the wick. I've always had good luck with the performer RPM intake, there is a guy on here that even got it to clear the stock hood pretty easily. Like the other guys said don't mess with the stock heads, not worth it. You should be able to pick up a used set of 305 heads for a little bit of nothing. If I were you I would put off internal mods and just save up for a cheap 350. Easier, cheaper, and more power for the buck.

 

Welcome to the boards. It is a HUGE asset for me!!! I have to disagree on this though, the performer TBI is great. It has the same plenum depth as the performer rpm manifolds, the runners are modeled after the performer carb manifold, and the bores are centered. So unless you have another reason why it will make less power, the performer tbi will work great.

 

Definelty welcome to the boards! I always like hearing from new people on one of my forums The "Search" button will be one of your biggest assets here. TGO has become one of the highest rated Specific Interest sights on the net. I didn't know didly squat about cars in general, let alone Thirdgens, before I came here, and no I think I can hold my own perdy dang well!

Bruce (90RS305)

 

The other reason for that might be because they sell their 68# for twice the price of their other ones. But be careful when looking for 75# injectors because I tried the same thing and followed all of the p/n's that everybody said and I'm sitting on 90# injectors. But like they said, if you're burning your own PROMs, it won't make much of a difference.

As everybody else has said, forget the stock heads. Someone at Chevy should have been fired for even concieving these things.

I'll also post another vote for the Edelbrock TBI intake. I've had mine bored out to 2" to accompany my bigger throttle body.

Before you dive head on into your 305, how many miles are on her? And two, what type of posi are you looking at getting?

 

Thanks for the welcome everyone.

Gunny, she's got about 70000 miles, but she really was babied and maintained well. No winter driving, regular oil changes, etc. I can't even find rust on her. In fact, I only changed the stock muffler last year. Other than what would be called regular maintenance, she needed one new headlight about 5 years ago. She even has the original wiper blades. She's still got the same kick she had when I drove her home 16 years ago. My friend calls her the "time machine" because he said getting in her is like stepping back to 1988 THIS CAR WILL LIVE FOREVER!!

I picked up a used, stock 7.625 posi. Ordered it a little while ago - the guy swears it's in "excellent condition". I've heard the stock rigs were fairly weak ...I guess I'll find out.

--
Casey

 

I guess I was more or less comparing the Performer line of intakes to the RPM line. In that respect your looking at 10-15 hp more out of the rpm.

 

I don't want to seem dense or anything, but is it really that "simple" to just account for the 75 # injectors on a 305 with PROM tuning? (Of course, I realize that it would probably take a bit of experimenting.) I'm leary of running into problems with the big injectors because their duty cycle would have to be kept so low at idle (although I guess idling speed could be bumped up within reason). Has anybody here gotten the 75 lbers to run good on a 305?

 

Anything you could possibly want to know, someone has probably tried or is working on right now. This is a great and very helpful community for people of all budget and skill levels. I hope you will enjoy this site and your thirdgen as much as I have.

P.S. Any major modding or questions you feel I may be able to help you with, feel free to pm me or email me. GooD LucK.

 

RSCamaroGuy92, you're very kind. I've enjoyed this site already - it's given me a HUGE boost in knowledge (especially when it comes to PROM stuff - I'll have her screaming like a banshee in no time). As far as the baby herself is concerned, she's given me more pleasure than I could ever re-pay her for. Perhaps this summer's upgrades are a start

--
Casey