I have a new project with a 80s ford 302 in it.. it came with a 2150 2bbl on top of a 4bbl weiand intake using an adapter, original 80s duraspark box, original 80s duraspark dizzy ( which had a busted vacuum canister on it.) I pulled off the smog pump, put vacuum port covers over the 2 vacuum towers unused on the back. replaced the 2150 ( it was not any good ) with a Summit Racing Carburetor. replaced the distributor with a new Duraspark distributor not a reman. new plugs gapped to 45 I had an MSD streetfire box .. so im using that. problem I'm having is when I set Idle down to around 700 or so.. it purrs fine.. put it in gear .. ( ford C6) it will almost immediately fizzle and die. Set curb idles up to 1100 put it in gear and it is perfectly normal and happy. Timing is set to between 12 and 15-- it seems very happy there. I am told by a few some motors just want to idle high just let it be.. but to me.. its wrong. My old f100 with a 302 idles like a champ at about 700 curb idle and doesn't really drop much when put in gear.. just the sound changes a bit. ( no tach ) I have set the idles mixture screws using a vacuum gauge to achieve around 20 on vacuum holds steady. What adjustments should I do to get this thing to idle correctly in and out of gear. The summit carb is Just a Holley carb with a different bowl design. uses all holley tuning parts. Summit tech recommended changing a power valve down to 6.5 ... but im not sure that is right.. but im not carb guru.. It runs smooth as silk and pretty responsive.. it is a 500cfm unit with annular boosters. floats set to the middle. thanks. appreciate any advice other than rip off the carb and put on another one. lol. too many folks have great success with this one..
Check vacuum ports, and then check them again. Just thinking out loud you losing about 25 Hp with that C-6, if you are not running above 500 Hp it's and overkill. C-4 is plenty capable.
I'm no expert, but it sounds like a timing and/or mixture adjustment, unless there's some weird thing going on with the torque converter or transmission.
Set idle mixture screws to highest idle lower idle using the throttle screw and repeat. The idea is to get the idle you want with the least amount of throttle opening. So you are not using the transition slots at idle.
C6 is what it came with.. I may switch it out one day.. but for now, I'll keep it... My 65 f100 with a 302 had a c6 as well.. but it had no problem then either. It now has a 93 mustang AOD... much better drive-ability.. but not as strong feeling.. This engine and trans will run fine and even will go 70 with ease and doesn't feel like a complete dog. I mean.. it aint a performance motor by any means.. or close to the one I have in the f100.. but for it to run so good.. I know it has to be something simple somewhere.
Sounds like a timing issue. Look for a good shop that has a distributor machine. Have them spin that distributor and re-curve the timing to better fit your setup. I've seen that cause what you describe, good luck.
I wanted to do that.. I have sent distributors to RHP reincarnation to be curved and he has built me a custom one for my f100.. but, I figured with this motor being all stock a stock dizzy would do. I have tried different advance settings.. even as high as 20 degrees.. it likes it.. but It has to be too much... I don't want to detonate my pistons lol. I initially set up the dizzy on ported vacuum.. but have since moved it to manifold. IT LIKES IT. Feels much better down low in the rpms. feels the same up high.. that is also the way the previous 2150 was setup and I put it on ported thinking I'd fix that.. and it ran terrible.. almost the same to be honest... but this carb manages better.
" I have tried different advance settings.. even as high as 20 degrees.. it likes it.. but It has to be too much... I don't want to detonate my pistons lol." How do you know it has to be "too much"? It's a package deal. Disconnect and plug the vacuum advance and spool up the RPM till the mechanical internal distributor weights stops advancing the ignition timing. What does it top out at? That's the number you're interested in. Forget about vacuum advance until you've sussed out the mechanical timing curve. The initial base timing number doesn't really matter that much, so long as it starts easy. Starter kickback can loom as base timing approaches 20° say. Tune it and drive it till you're satisfied with vacuum advance disconnected and plugged. Then re-connect the vacuum advance and tune that part of the curve. Don't fuck with the mechanical advance again at this point, you're done with that. A common error is to confuse the additional timing brought in by the vacuum advance as part of the base timing. When the distributor is connected to a source of manifold vacuum you're going to see maybe 30° to 35° of timing at idle. It won't hurt anything, it's not "too much", there is no load on the engine. It will go away whenever under load. It will run a lot cooler in stop and go driving. But it can be tricky to achieve a steady idle as well as make manifold vacuum connection work with an automatic transmission, as you've discovered.
Vacuum Advance issues, would be my first guess. I have bought a new Duraspark before and the vacuum can was bad. Also do you have the vacuum advance hooked up to manifold vacuum or the "vacuum advance" port on the front metering block? Just got my car running and hooked it to metering block advance was not working. Hooked it to the full manifold vacuum port worked perfect.
"69thumper, post: 12214171, member: 217764"]Actually a C6 uses up about 65 HP. A C-4 is not Zero, I'm comparing the two. Now if your trying to say a C-6 uses 65 more HP than a C-4 I call BS.......
Have you checked for vacuum leaks ? Do you have a good timing light that will tell you total timing ? Have you made sure the timing mark is in the right spot and the outer ring on the balancer hasn't slipped ? Have you checked the slack in the timing chain ? Have you put a hand held vacuum gauge on it and moved the distributor back and forth to get your highest vacuum reading ? That is a good place to start. I have had nothing but good luck with the Summit brand carbs on street cars. It was made by Holley , but didn't sell because it looked like an old motorcraft carb. Should idle on your stock engine at around 650 rpms not 1100 . That just causes other problems like run on when you shut it off, hard on u joints when it jerks when you put it in gear. Should be able to use ported vacuum for the advance unless you have a bum distributor.
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