Swap 3ac carb with 4ac compatibilty

dug320 · Post by **dug320** » Sun May 15, 2005 2:23 pm

I have been running my Tercel with a 4ac for year now. I transferred the 3ac carb onto the 4ac with no problems. I have read that putting the 4ac carb on the 4ac engine will give me better performance. A weber carb looks nice but I already have the 4ac carb.

The obvious difference between the two carbs is the 4ac has bowl vent to charcoal cannister; my 3ac does not.

The solution appears to be finding the closest vacuum diagram that includes the bowl vent with a minimum of re-working.

I am on the right track?

I have an 85 tercel 3ac. The closest schematic is form a 84-85 Corolla FWD. I see a three pronged charcoal cannister and an outer vent control valve added,; nothing else appears different.

takza · Post by **takza** » Mon May 16, 2005 4:31 am

Not quite sure what you are saying, but both my Cal '83 and a Fed '84 3AC have the carb bowl vented to the 3-outlet charcoal can thru the OVCV.

arbskynxnex · Post by **arbskynxnex** » Mon May 16, 2005 12:44 pm

I looked in the FSM and from your description you have one of the Canuck (Canada, eh) versions If you have the FSM or the Chilton's manual for the tercel it shows the diagrams for different versions, I'd look to make sure. If not let me know and I can upload the images for you. When I changed my carb over the only differences I saw were the EGR Vacuum Modulator had an extra port on it, and the carb it self had an extra vacuum port on the throttle body, I just plugged the latter and the carb hooked straight up to the tercel stock vacuum lines (including the EGR modulator) and ran just fine. You might be able to cap the vent from the bowl and see how it runs that way, personally I'd try that first since its cheaper and easier. Or you may have to rob the emission parts from a Cali or Fed tercel (shudder). If you can, take some pics of what your set up looks like.

dug320 · Post by **dug320** » Mon May 16, 2005 3:27 pm

I have both the Chilton and the Toyota Manuals. I looked through the Chilton to spot the nearest configuration.

I do have a Canuck 3ac but the 4ac came from another Canuck and I was kind of surprised that there would be a difference.

I guess I could plug the bowl vent. But it is nearing the time to tour the wrecking yards to see if there are any cars that can donate some parts so I will look for the parts in the 4ac diagram.

takza · Post by **takza** » Tue May 17, 2005 4:11 am

The only difference would be that the EVAP carb setup will have an opening to pull can vapor INTO the carb and one to VENT the bowl to the can?

Both could be plugged off....

You should only have 2 gas lines going to/from the tank.....? If so...you can't use a charcoal can.