mvd72786

I just picked up a project car ('89 IROC-Z 305 TBI). The last guy who owned it had planned on converting it from EFI to carburated... not really my first choice but the more I thought about it the more I'd like to try it, plus he had already purchased the intake manifold and distributor required to do it, and gave them to me for free when i bought the car. I know next to nothing about camaros and I'm hoping to learn a lot while working on it.. and hopefully from this forum too. I'd like to get some advice on which carb to purchase, I think I'm going with Edelbrock since they are supposedly simple and good for beginners who dont know too much (me). Im going with 600cfm... should I get a 1400 (with EGR) or 1406 (without)? Also what type/size air cleaner should i use?

bigbird89

iTrader: (1)

I just did a similar conversion myself, and learned alot from it. The 600 should be good. The egr will depend more on the intake manifold than the carb. I discovered that an egr doesn't fit with an edelbrock intake and carb, so I'm getting a blockoff plate. You can also get a spacer to make the egr fit. Keep in mind it won't be emissions legal with or without the egr since you are converting to a carburetor. You will also need the right bracket for the trans cable, as well as a tcc lockup switch. (assuming it's automatic). The stock air cleaner should work, as well as any drop base type aftermarket aircleaner.

Do a search on this and you will find a lot more info. Good Luck!

mvd72786

hey thanks a lot for the reply, i appreciate the help. however, the car is a manual... and it actually is not a stock manual either. as far as the intake goes, i have not seen it yet. I am getting the car and parts on friday, so I will know more then. do you have any additional advice with the manual? Also... what should i do in order to still be able to drive the car, register it, etc if it won't be emissions legal?

five7kid

iTrader: (14)

The Edelbrock is a poor choice with a manual transmission. A Holley-type double pumper would be much better.

Everything else being stock, you aren't going to gain much going to carb, and you will lose economy and won't be emissions legal anymore. Overall, you'd be better off just keeping the TBI.

mvd72786

I understand that, but the guy I bought it from has basically all of the required parts (carb intake manifold, distributor, etc) for the conversion, and he also told me that theres a problem with the ECM... mostly because of bad wiring from the previous owner, so rather than fix all of that, I'd like to try and convert it, and get rid of the computer control altogether. I'm not at all concerned with economy, this car will be purely for fun.
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I will look into a holley double pumper though, thanks

FueledSoul

iTrader: (18)

went carb never looked back....

mvd72786

any recommendations Fueled Soul?

mvd72786

I decided to go with a Holley double pumper... 650 cfm with manual choke. With the dual feed, do i need to adjust the fuel supply to higher pressure? right now I am planning on using a mallory 4309 regulator on my fuel line. Any advice?

five7kid

iTrader: (14)

A 650 is too big for an otherwise stock 305. 600 would be more than enough.

You don't need more pressure with dual feed. You need just enough pressure to keep fuel going to the fuel bowls, but not so much that the float needle & seat can't shut off flow when the bowls are full.

mvd72786

I see.. i have heard different reports about how big (650cfm or not) to use... in your opinion, will a 650 harm or make it more difficult for me to get this 305 operational?

bigbird89

iTrader: (1)

I'm also curious as to why the Edelbrock is not as good for a manual trans. I don't know much about carbs, and I also did the conversion because my emmissions/wiring was all hacked up by the previous owner. I got a great deal on a rebuilt Edelbrock, and future plans include converting to manual. I know the holley is overall a better carb, but what specifically makes it better for a manual vs. automatic?

Thanks!

mvd72786

If I use an intake that is supposed to fit up to 1986 heads, will it still fit on my 89 heads with any type of easy modification? I just cant seem to find a carb intake that will fit on an 89... any advice?

five7kid

iTrader: (14)

The main problem with a 650 is it will detract from part-throttle operation without helping with WOT. Unless you do heads, cam, and full exhaust, there is no way a TBI 305 can use even 600 CFM.

The problem with an Edelbrock carb and T5 transmission is the Performer is what is called a "demand-based secondary" carb. Speed shifting a T5 (shifting without letting off the throttle) is sure death to the poor transmission, even with a 305. When you let off the throttle during a WOT shift with a Performer, the secondaries close, which closes the air valve. When you go back to WOT in the next gear, the secondary throttle valves will open, but the opening of the air valve will be delayed, causing a drop in power after each shift. A mechanical secondary carb like Holley double pumpers or Demon dual squirters will respond immediately to the accelerator pedal input.

The problem is even worse with a vacuum secondary Holley or Demon, because not only is the secondary opening delayed each shift, the secondary closing is delayed during the shift, which basically makes it a speed shift event even though you've let off the throttle. T5's won't deal with that well at all.

Now, with regard to an '87-up intake manifold, I'm not going to give you a fish, I'm going to teach you how to fish. Go to www.summitracing.com, click on "Departments" under "Shop" on the left side of the page. Then click on "Air & Fuel Delivery", "Intake Manifolds", "Intake Manifolds, Carbureted", "Chevrolet", "1987", "5.0L/305", "Dual Plane", "Stock Configuration", "4-barrel spreadbore", "Idle-5500". I've done everything for you but pull the fish out of the water, hopefully you can take it from there. And do it yourself next time.

mvd72786

5-kid... thank you for the help... and the input. I did end up going with a holley double pumper by the way too

bigbird89

iTrader: (1)

That's great info. You definitely are a wealth of information. When I finally get around to swapping a t-5, I'll remember to go with a double pumper as well!

mvd72786

What about EGR... if I have an intake with EGR, but my Holley carb does not, how should I block off the EGR on the intake, and is that the correct thing to do?

five7kid

iTrader: (14)

You can use EGR with a Holley if you have the vacuum fitting available. Or, you can just block it off for non-emissions applications.

mvd72786

I'm sorry to seem ignorant... but what do you mean by having the vaccuum fitting available? I was under the impression that this holley carb does not have EGR.. could you explain how I would do this?

This is my first time, so I'm a little lost. I'd appreciate any help you could give me, thanks.

mvd72786

I have an 89 IROC with a 305 TBI... i'm switching to carb. I am removing the ECM and wiring. I took the ECM out, and i've removed the loom on almost all of its wiring in the engine bay. I also cut the ECM harness off to help pull the wires through, working my way across the bay. I have noticed that some of the wires do not go directly across to one place, a few of them split off, and go not only across to somewhere on the driver's side, but also forward as well. So far I have left these intact, but can i remove them? One in particular is a tan/white wire for example. One or two of these wires also tie in to the group of wires that go to the fan, which i assume is power for it. What can i do about that? Thanks in advance for all of your help.