kalli

hi all,
the 302 I have is mighty. but only occasionally.
I have pertronix II running at 12V with edelbrock 650, 10degrees initial idle vac adv disconnected and plugged
I'm at around 34 degrees at 3200 so that seems good.
I once had the car running at 14deg idle and there was gobs more power when I floored it (upper rpm area). but the car jittered when idling in first gear.
i do this as a test just put 1st gear in no accellerator (just idle) sometimes in 2nd. If it jitters I am usually too far advanced for idle. I retarded to 10 which caused that jitter to go, but the power in upper rpm is gone as well.
It likes to rev but it's not quick getting there when flooring in 3rd

the choke seems far too rich (stutters when cold) and a lot of smoke and (YESSS!! i don't loose any liquids. i burn no oil or water whatsoever!)

once the choke is off there is no smoke but I have a feeling it's too rich

i once tried with the holley 570 street avenger I have and with that carb I get the effect that when the secondaries open I get a kick of power, which makes me believe that i was too rich without the secondaries and opening causes 'lean' condition which brings me into proper AF ratio ...

i don't know if I should put that holley back on or try my best with the Edelbrock

anyone any ideas what to try first?

Kalli

67mustang302

Well, first of all with those heads and cam, and depending on intake, it should really be at more like 14 initial, maybe more. 30-34 total is about right probably for best power. You have to get the timing right, then tweak the carb. And sometimes performance engines just run a little rough. And sometimes they require a lot of advanced tuning.

urban_cowboy

Alright! Now you get to the fun stuff. I love tuning.

If you car wants more timing up high, you can always change out the timing advance stop and springs in the dizzy. You are not limited on the total advance by the initial advance. I would wait on that though until you get the AFR right. The AFR can fool you.

You can fix that by adjusting how fast the choke opens. You basically want the choke on just long enough for the engine to heat up enough to run. Who cares about a little black smoke on cold start and that may go away when you get the jetting right.

If you do not have a AFR meter... Put clean plugs in. Drive it under normal cruise so that the secondaries are not opening. Check the plugs. Adjust the primary jets accordingly. Then you can do some WOT runs, check the plugs and set the secondaries. After you finish all of that, then you can play with the accelerator pump and nozzles to limit any stumbles.

Personally, I love Holley carbs, but if you think you will get frustrated, an Edelbrock may be best for you.

kalli

thanks lads. first thing tomorrow i'll put it back to 14 and check again (the fella i bought engine off said he had it 14 as well)
if it jitters I'll either go back to 10 and use lighter springs (to advance earlier) or see if I can tweak that with the carb (maybe i'm just too lean or too rich in that condition).
for the choke I'll just increase the fast idle and turn the housing back (towards lean) and see how that goes.

thing is that the engine behaves like my old 289 but occasionally when everything seems to be right goes like a raped ape. unfortunately don't have an AF meter, so i'll check on the plugs next.

thanks for the tip to try just cruise and when good (spark picture) try WOT. i'll report back/.
tomorrow we're going on a 200 mile cruise (100 each way with night out to get pissed). very excited. see how that goes :-)

67mustang302

You need good timing at idle in a performance engine. Without it you can't get consistent vacuum on the idle circuit in the carb, so it doesn't idle right and you end up having to set your idle improperly and then end up with off idle hesitation/stumbles, or you have to idle it rich to get it to run etc. Just cuz it runs a tiny tad rough doesn't mean anything is wrong though. Mine tends to run a bit rough from around 2,000-2,200rpm, smooths out if the timing is dialed back, but then it loses power everywhere and the throttle response goes to crap.

The problem with both the carbs you have is that neither may have enough adjustability to get it dialed all the way in(maybe). They can get close though, but things like part vs WOT AFR, cruise signal, booster sensitivity at differing rpms etc can't be altered without at least playing with air bleeds. Edelbrocks are nice though since they have metering rods, it gives you a lot more flexibility in terms of AFR's at differing throttle positions when you start changing rods and springs, even if they're not the best for max performance.

What you have to remember about a performance engine though, cammed, heads etc, is they need initial timing to run right. Ignition curves can be a pain in them, they typically want more initial and less total than a more mild setup, and in some cases make best horsepower with less timing than they need to make best torque. More and more performance EFI engines these days are running timing curves with craploads of initial, running up to good timing at around peak torque in the mid rpm range, and then DROP timing as rpm increases towards peak hp.

Sometimes it just takes a lot of work to get a carb setup dialed properly, but once it's done they'll typically outperform EFI on the same combination. Most people never get a carb dialed properly though.

kalli

thanks a million for all your comments. very much appreciated.
I guess it's playing playing playing with it :-)

kalli

retarted the choke and increased fast idle a bit. it's far less smokey cold now.
Warm i know changed to 14initial (vacuum plugged) and see how it goes. max advance (no vac) is at 36 degrees at pretty much 3100
i leaned the idle circuit a bit more. nothig else changed. see how it goes. So currently i'm still driving the edelbrock carb

Starfury

If you want more advance at idle, you may consider hooking the vacuum advance straight to manifold vacuum. It gives you lots of advance at idle and drops back to pure mechanical under WOT, unlike ported vacuum which still gives you some vacuum advance under WOT. Under part-throttle, manifold and ported vacuum are the same, so cruising advance isn't affected. You do need to adjust the accelerator pump to work out some driveability issues, but it does work, and actually gives you better control over WOT advance.

Gary H

The kick of power you felt with the holley was probably because the secondaries were opeining to soon and boggin it some. You shouldnt feel them open at all. With the timing at 14*, adjust the idle mix for the highest vacuum.

67mustang302

Ported vacuum won't give you any advance at WOT unless something is messed up. They typically pull all the advance out by like 8" hg, at WOT regardless of engine rpm, even with a small carb, you'll never see more than about 1.5-2.5". If the vacuum advance is still on at WOT then the advance mechanism is screwed up or you have a retardedly small carburetor, like a 300cfm 2bbl on a 6,000rpm big block.