Lando

Good morning guys. I hope you didn't work 2 hard on the stangs last night lol. So I have a brand new 306 crate motor carburated with a Holley HP600cfm. What's a good idle ratio? And wot? On idle I'm in red zone at about 15 and high 14s and would hesitate to go 17s. thats where i start ****ting my pants. I got a couple wot and caught 10.9 and 11.3 also at 2500 it stays at around 12.5 - 13... Very new to running carb so advice and instructions on carb tunning are more than welcome. Thank you guys. Sorry for all the numbers.

Lando

Should add that car doesn't hesitate at all and has power all across the band. Very small hesitation when you start rolling. It's an auto e303 cam. Edelbrock rpm intake. Gt40 x heads high flow pump. Fuel 255lhp. Msd Steel gear dist.

skunk21

whats your base idle? and do you have a vac gauge handy?

hi5.0

I'm just curious about your fuel (pump?) numbers? Sounds like a bit much to push through a mild carbed engine combo even with a good fuel pressure regulator/return system. Lots of good info on out on the 'net regarding EFI to carb conversions and tuning.

Lando

Thanks, 255lph pump. Return system and all was doing just great with a 351w that was pushing close to 600horses. So I'm assuming my problem is tunning and timing.

Lando

Don't have a vac gauge but could get one. Idle set at 900rpms and yesterday idle air/fuel was reading 15.4 and around there.

skunk21

adjust your misture screws until you get the highest vacuum reading ( stop adjusting when you see you are at the highest vac reading and further adjustment doesn't change the readings ). readjust your idle it's going to change. make sure the engine is warm first. give this a shot. plenty of people running efi tank with return system/ regulator on carb conversions. FP should be in the 5-7psi range 4.5 would be about the lowest.

Lando

Trying this tomorrow! Thanks a lot skunk21. Might bother ya later tomorrow! Lol

cdynaco

Yeah back in the day I never heard of A/F ratio. That all came with ECU's, hypereutectic pistons and powdered metal rods. lol

We'd just bring the idle down as low as possible, then tweak the air screw back and forth (rich to lean) so as to achieve the highest rpm at that idle. Then bring the idle screw back to normal. Of course this changes a bit from summer to fall to winter.

As for the main jets, one of my books said its best to check the plugs after driving up a long mild grade where you are under moderate acceleration (because checking them after idling much would probably show richer [dark or black] than it is vs actually running on the main jets). Then pull over, pull a plug, and look for that nice tan color.

That was the extent of A/F ratio! lol

onebadvert

Just fyi if your a/f gauge isn't a wideband its not gonna be fully accurate. So being just a hair off I wouldn't sweat to much. I would more importantly keep a good eye on your plugs to make sure they aren't getting to black. And just like cydnaco says its best to read the plugs after a good pull.
I use a wideband. I want to eventually use a super charger so it will come in handy for me.

Lando

Thanks guys, finally I got to play with the carb last night, my plugs are fine. I am reading 9psi fuel. I warmed it up and played with the carb screws and got it at around 13-14 a/f idle and stays in good mix at wot. It sounds way better, checked plugs again after clean and looking great. Very happy... Definitely thank you guys... Might get the buffing job done today... Quit my job so yeah lots of free hours for a while...

skunk21