just got the new 350 in and ready to go... i am running 10.9:1 CR 062 heads and a XE274 with a summit air gap knock off

set timing to 14-15*,checked float level, then went to adjust my idle mixture with a vacuum gauge... then it started

i my vacuum was about 14 before i started and the exhaust would burn your eyes out.

i turned both idle mixture screws in and backed them out 2 turns, then i couldnt get the car to idle at all no matter how much i adjusted the idle speed. i backed both screws out another half turn now it will idle but it is inconsistant with every rev it settles at a different RPM some times 1000+ sometimes around 300-400 all the while holding about 12-14 vacuum... so i try again and i notice that when i turn out the driverside mixture screw it gets better even though they were both perfectly 2 1/2 turns open

i go and check my rpms and i am at about 1100.. i start backing off the idle speed screw and it stalls so i went back in as i had totally closed the blades and a notice the the primary throttle shaft has some side to side movement

could that be causing a vacuum leak? could my vacuum really be more than 14 with that cam? could that cause my problems?

as of now the car will idle but its like a box of chocolates you never know what rpm your gonna get

 

inconsistent idle rpm is due to timing 99% of the time. What springs do you have in the dizzy? Typically if you run the light springs they may not be able to snap back shut and the idle will fluctuate because of this. With that cam it will want more initial timing, somewhere around 20-24 and then 32-38 total depending on what brings the most MPH on the track.

 

well i got it straightend out 2 problems... fuel pump was randomly shuting off... the small advance spring i was using was weak now running medium spring and sorted out the blasted fuel pump...

now the new problem...


when i originally set the float level the car was up on stands and it didnt occur to me that it wasnt level so under heavy breaking or off ramps it would want to stall checked the float level and it is high reset it... now i have a 1/8-1/4 throttle bog...a very smooth bog.

right now i am running stock jets and the stock power valve

i have 35 squirters pri & sec and what would have to be the green cam for my primarys and what ever is stock looks black but cant tell...

arent the black cams for the 50CC pumps?

 

if it's tip in bog then that might be a power valve issue as well, what's your idle vacuum in gear with the motor hot and what's your pv in the carb? You might have the floats a little too low now that this issue popped up after lowering them. How are your idle mixture screws setup?

 

i have the stock 6.5 pv my idle vacuum seems to be around 10 i question the gauge at the moment though

my idle screws are at 1 1/4 turns out

i set the fuel level right at the bottom of the sight plug threads... thats the right spot correct?

would you think a higher PV would help?

 

higher PV might help, although with 10" at idle I wouldn't change it. Did you adjust the mixture screws with a vacuum guage for highest vacuum? Try to richen them 1/8 turn and see if the off idle dead spot goes away or not. It's a 30 second fix, let me know if it helps or not.

 

i richend them up this morning i now i get about 9 for vacuum so i said screw it give it a try the bog is still there but it is a very quick pause in the accel

so did richening the idle cover for some of the PV that i am missing?

 

no i just wanted to make sure that it was due to a lean bog, up your squirter size by a bit, if it's 28 make it a 31 on primary, if it's 31 make it 35 and that should clear up the issue. They're $8 a package at a speed shop. If this doesn't clear it up and you're sure the acc. pump linkage is set up correctly, then changing the front pump cam would be next, but since squirters are cheaper, i'd try that first.

 

How much initial timing are you running now at idle?. Ya have to slow down the engine idle speed to check initial timing to ensure that you are not already started up on the curve. Initial timing should be 24deg BTDC at 650rpm. it should advance to 32 to 36deg at around 3000-3400rpm. Many times vortec motors do not need quite as much total timing as engines with other heads.
(fast burn combustion chamber) could be as little as 29deg for max power.
But will want lots of initial. (24degBTDC). That means you have to limit the mechanical curve to around 10deg of travel (advance pin limit bushing or reduce advance slot length) . At that point a medium tension spring will be fine. Your idle will be much cleaner. You can remove the carb, flip it over and look at the primary and secondary throttle blades opening relative to the idle transfer slot. readjust the throttle blade opening on both the primary and sec barrels so there is just .015 to .030" of transfer slot exposed under the blade. Reinstall the carb, warm it up and readjust the idle mixture screws.
Should idle rock steady but roughly at 800rpm. Make sure the PCV is hooked up to the carb base and functional (vented valve cover) or the carb will idle too rich.
Bet when set up like this you won't need big accelorator shooters to get clean throttle response when the motor is fully warmed up.. .025 to .031 should be fine.
If the motor is hard to crank over hot (starter labours) with the timing set at 24dBTDC at idle. install a ignition power cutoff switch to allow you to disable the spark during hot cranking. Crank it over and throw the switch and it will fire easily.

 

right now i have the timing at about 17-18* as much as i can and still start turn the engine even cold i will try and find a gear reduction starter
i am idleing now at 750RPM that is with the primarys just barely open maybe an 1/8 of a turn on the curb idle screw...
and i am running a fully functional PCV and breather the PCV is hooked up to the rear port on the base

ATM i am running 35 squirters front and rear with the blue cam on the primarys in the #2 hole and i adjusted the pump overide spring so it wouldnt depress the pump arm at idle... is that the right way or is there something else i should have done?

 

well my wandering idle has returned... this time a new culprit air cleaner...

i am running a 14x3 element with a drop base air cleaner and a 1 inch spacer... when i set the curb idle speed then re assemble the aircleaner hop in the car to look at the tach and back down to 500 rpms go back out take off the air cleaner and the engine will come back to 750 .... is a 3 inch open element filter to small?

 

no sounds like there's a restriction somewhere, why the drop base and a spacer? Is the hood resting on the air cleaner or some other obstruction? My 14x3 k&n air cleaner doesn't change idle speed off or on for that matter.

 

well i bought the drop base with the anticipation of not getting my hood to close but then the base wouldnt clear the fuel bowls so it got a spacer for now and the hood just touchs the cover it is getting alittle scratched

 

does the drop base have indentations for the fuel bowl screws? I've never seen a drop base that wouldn't fit on a holley, do you have a pic of the bottom of the air cleaner? It should have 2 indentations which would line up with the fuel bowls on the carb.

 

it does have indentations for the fuel bowls but there isnt enough clearance for the locks on the float adjustments

 

i'd pick up a different drop base then, perhaps the edelbrock cheapie that is $30ish at parts stores.

 

yeah i forgot mines a spectre... i will look at the edelbrock ones...

in a couple of weeks i plan on a set of 2210s and header mufflers...how much of an effect will that have on the mixture? any effect on timing? should i even bother trying to nail this down before the headers?

 

mixture will change, timing will not

 

enough to make any of the adjustments i have made so far different?

 

the idle mixture will need to be reset, the jets may have to be changed as well. Go pay for a wideband tune and it would take 1-3 hours total and you'd be done.

 

get the GM L-88/L-72 427 corvette air cleaner base. Search my posts. You have to remove the choke horn and choke on a holley to use this base with a 3" filter. Any top will do.
More hood clearance than other setups.

 

how hard do you think starting would be in the cold? without the choke i mean it gets cold here probably not as cold as canada but still 10*-20*F isnt out of the question for NE

 

well i followed F-birds advice and opened up both primary and secondary blades so that .015 of the transfer slot was exposed... then i let the car warm up and attempted to re adjust the idle which was now at 2K ended up closeing the primarys completely and both mixture screws and it was still idleing at about 1200 on the secondarys is that normal?

 

Seems that maybe your .015" throttle opening may be a little bigger than my .015". Could be the metric system we used here. Anyways you may have to remove the carb again and try a smaller balanced throttle blade opening as a starting point. You want the primary and secondary blade open to be fairly closly mathched front to back as a starting point as the idle is shared by all 4 barrels on a holley carb. Unless the throttle blades are in the sweet spot the carb will not meter fuel correctly at idle, creating a crappy idle and less than best throttle responce off idle.

 

Is your power brake booster or trans vacuum modulator line leaking vacuum?

 

i used a .015 feeler gauge and opened the secondary blades until i could just see the slot then closed them until i couldnt same thing on the primarys

i had to open both blades about 2 1/2+ turns to get the .015 and the blades looked to be open pretty far after that

i have hose clamps on my brake booster and no modulator

 

but i think i have found a vac leak when i apply vacuum to my vac advance can it will not hold any and gives off quite a nice squeak it is a GM can...can i just replace it?

 

Post a close up picture of the throttle blades at idle showing the idle transfer slot edge exposure under the the edge of the throttle blade. Are your throttle blades bent? (Nitrous backfire, dropped the carb).

Hold your finger over the hole that the carb aircleaner stud goes into. Does the idle speed change?
This hole should be a blind hole unless it was modified by drilling it thru to allow extra airflow at idle (for big cams)
Is the brake booster leaking internally?

 

buy a Crane adjustable vacuum advance canister with adjustable stop limit plate and adjustable diaphram spring rate)

 

i will get pics tomorrow after work the carb is new with no mods to the aircleaner stud

 

well i have finally figured out my mystery vacuum leak... aparently the 50cc accelerator pump is hitting the intake... was fine when i first checked it witout the carb tightend down but now i have a little wear spot on the housing and the intake... will try reseting my idle once i get that clearanced

 

well that didnt help i guess it isnt a vac leak my base timing is 24* with med springs.

when i opened the secondarys to expose about .015 of the idle transfer slot along with my primarys i end up with a 2000 rpm idle... then i can close the primarys completely and the mixture screws and i still have about a 1500 rpm idle... after enough playing i can get 750-800rpms but it isnt steady it will hunt a bit then eventually stall and it seems really rough like that and when revved it is okay but it sorta hangs before returning to idle

here are some pics of the idle transfer slot... i tried to get a pic of the throttle blades but couldnt get a good one to show exactly how far they are open because it seems like alot to me

 

that's not .015 of the slot...it looks like a rectangle. It should look like a square. If it revs ok then hangs before idle that sounds like the dizzy springs are inadequate. It also could be from too lean an idle mixture. Regardless you want both slots to be open the same amount, so keep closing them until you get the idle speed you desire. Mine are slightly more closed than looking like a square and the motor has locked out timing(which will cause the idle slot to be smaller due to more ignition lead) and idles 1100 cold and 1000 hot and 800-900 rpm in gear.

 

yes i guess it doesnt look like .015... seems to with out the camera blowing it up...

 

well i tried it again opened them both so the slot looks like a little tinny line still wont idle at all...

 

well in a effort to get the secondarys open a bit, i closed them so i could get a reasonable idle... they just barely cover the transition slot... with the primarys open about the proper amount... right now the car is idleing at 950-1000rpms and it seems to be much stronger... really affected how the car drives... on a quick shift the tranny used to snap the engine back to the proper RPM now the engine will actually pulls the car forward...

new problem i have noticed... is a slight i guess surge on engine braking or slight throttle openings at speed. any ideas?

 

surge on slight throttle opening is too lean. Open mixture screws on the primaries 1/16th turn and try again.

 

that took away the surge but left me with a 1500 rpm idle...

what do you guys think about opening both barrels to expose say .020 of the transition slot and come out to 1 1/2 turns on the mixture screws then pull timing until i get an idle of about 900 RPMs then re adjust my idle mixture with the new base timing

 

don't touch timing. Lower the idle speed to what you want and then readjust the mixture screws again. You may have to do this several times before you get it right.