CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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Hello everyone! I am a new member and need some help with my iroc. I have an 1985 iroc, L69, 5 speed. I am doing some upgrades on the 305 H.O. , headers ,intake, carb, etc. and have run into a snag. I replaced the factory comp. controlled q-jet w/ a Holley 4150, 570cfm w/ elect. choke. I now realize that since this carb is non comp. controlled, that I also need to change the distributor to a vacum canister HEI. My question is what to do w/ the ECM and sensors. Do I leave ECM unpluged or does the ECM also contol non emission components, such as elec. fan and elec. choke? If anyone can help, I sure would appreciate it!
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The ECM doesn't control anything else. You can pull it all out without cutting anything.
Unless your car has the in-tank electric fuel pump. Which it might, if it was a factory L69. You'll have to do something to get that pump operating.
BTW, if that 570 CFM Holley is a Street Avenger (or any vacuum secondary type), that's not the right thing to be using with a T5. A 600 double pumper would be much, much better.
Thanks for the reply! When I checked the RPO code, it did show the car having the L69, but I don't think I have an in tank fuel pump. I pulled a manual fuel pump when I rebuilt the motor. I thought about the double pumper for manual trans., but I read somewhere that a vac. sec. would work just fine. Have you run or heard about problems using this set-up? Also, I have a green wire that ran to the elect choke. Can I still install this wire to the new carb and also how does the electric fan get control? Does the ECM have anything to do with both? Thanks!
The L69 had both the engine mounted mechanical and in-tank electric. Better check again.
The vacuum secondary is about the worst carb possible to use with a T5. Unless you never plan on "aggressive" driving.
The radiator fan is controlled via a thermal switch in the passenger side head. It grounds a relay circuit, which turns on the radiator fan. For the carb'd cars, the ECM was not involved in running the radiator fan.
You can use the electric choke wire on the new carb.
BTW, this isn't legal from an emissions standpoint.
Hey 57kid, I checked th wires going to the back. I have a black (grounded), pink and a brownish-orange. Would these be for sending unit only, or can you tell if they are for in-tank pump also?
I probably be driving the car like granny, but I'll try the carb for now and see what happens.
As far as the the fan switch, I do have dark-green wire on each side of the engine bay. The one on driver side has a spade type connector. The one on the pass side has a plug in type. Can you id these for me?
And no, we do not have emission testing in Florida. I remember those days of long lines. What a mess!
The pass side sensor should be for the fan. It will be in the head and is easily mistaken for the KS which sits in the block below it with a similar connector.
There should be a fan relay on the firewall near the booster. It should look similar to the fuel pump relay that you've likely got. The fuel pump relay will also pull a signal from an oil pressure switch (two wire) at the china wall near the dist (usually teed off the same line that feeds the single wire oil pressure guage).
__________________ "A man who voluntarily drives a car like that and still manages to maintain such impervious confidence that it will faithfully start the next time he turns that key is an encouragement for us all to take greater risks in life."
Hey, thanks for the help! I think I have a better idea of what to do now. All the members and third gen owners are lucky to have a sight like this one. Hopefully I can help somone in th future. Very much appreciated!
