So i picked up my '55 out of a field(after 5 or so years of sitting i'd expect the carb to be alittle filthy so it got a deep cleaning before any of this- just to verify that i ran it for a bit after the clean, and then took it back off and recleaned it to make sure nothing was in the gas or anything no gunk etc) Timing is more or less spot on(for what the motor seems happiest with, about 12* initial and the vac. advance on the ported side totaling about 32-33* total give or take. gonna get a pad and paper out and get all my specs down today so im 100% on whats what) Motor doesnt smoke or anything, no valve noise and just did valves so im pretty sure nothings flat as it all actuated how it should and they all adjusted nice and clean. nothing sticking or ticking or anything Now to the problem, So it starts PERFECT no choke or anything(which to me is weird) and runs great on primaries, but the INSTANT the secondaries go to open the throttle blades i get a lean pop out of the carb. you can hit the secondary linkage against the stop cam of the primaries while its idling and it picks up so its getting some fuel atleast it just seems to be sucking in a SHIT ton of air before it has the chance to fuel it properly and lean pops.. flooded the shit out of it once(forgot kill switch off) and it revved fine once then cleared out and back to lean pops again thinking of changing the stepup springs- but want to get a vacuum gauge on there first and see whats what.. that or get a damn holley on there but i'd rather just fix my issue and go from there since i dont like losing to stuff hahaha whats "specs" i have on the motor stock calibration 1411 750cfm edelbrock eddy tm1 single plan intake .60over early 70's 4bolt main 350 stock heads, slight port and polish new guides,seals,valves lapped, stock size etc this is the shitty part- cam is not stock and i was told its a "cunt hair" above 300* duration and the lift was "about .460 or so"......... so in reality until i have proof of what it is im kinda just shooting in the dark there(but the guy was legit and it seems like it was an old drag car like he said so maybe it is close? god i hate guessing) ANY help is much appreciated- its show season and i want the moredoor out there!!!! thanks fellas
What do you mean by "it got a deep cleaning"? Did you disassemble and soak the carb and then rebuilt it with a carb kit? Or what? What do you have for a transmission? if it's automatic, what stall speed torque converter do you have? What have you checked as far as ignition timing? what is the initial? what is the total advance at higher rpm?
completely disassembled and cleaned out- new gaskets upon reassembly(thats how i know its stock calibration, checked the jets and rods and they come out to the stock 1411 calib.) stock t5, which probably makes the feel while driving worse since i have to do more then i would with an auto to drive it- but besides the stupid secondary issue it seems perfect on primaries. doesnt smell, sounds great feels good ect initial is about 12*(old school timing light so im hoping the balancer hasent slipped) made sure its a tdc, dizzy is dropped fine and by about 3k rpm its advanced to about 32*... i cant give it more without denting the firewall more because of my setback, could it need more?? i have a BFH so i could dent for more initial and stuff i need to get a tach, vacuum gauge and some jets,needles/rods and step up springs and just dive in... im just worried im going to be band-aiding a problem because of the airflow its getting vs gas flow
Yea the little flapper thingy- it doesn't move no matter how high I "attempt" to rev it It will move freely by finger/screw driver but no matter of "air" gets it to swing or actuate... Can my motor just not make enough vacuum to move it or draw fuel out of the secondaries!? Comp test was good, valves are adjusted etc how could it make so little vacuum if that's the issue?
You have 2 major issues here, and I won't even begin to address the carb because that's last in the chain. First off is a red flag regarding your cam. 300 degrees duration, and by that you would probably mean, advertised duration as opposed to duration at .050", you would have well over .500-.525" lift maybe more. It doesn't matter the manufacturer, those fiqures you gave do not jive with one another. Secondly, if new guides were installed, you are not getting away with lapping in the valves, sorry it aint happening. The valve seats would have to be cut or ground to be now concentric with the new guides. This is all a segway into the theory of the good-old-boy cammed engine bullshit. They never even have a cam at all, but the such a poorly sealed up engine due to needed a real valve job that it almost sounds and runs like it has a big old race cam. Popping, farting snorting like a top fueler, and all because of a desperate need of a complete and thorough valve job. Do yourself a favor and you or someone do a leak down test on that engine of yours, and verify 100% the condition of the engine internally from a combustion standpoint. Then and only then you can proceed to the tune up and finally correct any possible carb issues. Chances are you don't even have a carb issue at all. Not trying to rain on your parade, but it's the hard facts, best of luck, TR
My second thought was to richen up the transition into secs. With different step up springs(I don't care if it hasd a bog in between or anything just want to be able to accel how a decent sbc with 4.11's and a 5spd should hahaha) Less mpg or a slight rich hesitation would be way cooler to me
I'm actually glad you brought up that point, because that was what was on todays agenda- leak down, re-comp. Testing it(previous gauge was wacky and would fidget then show psi which made me iffy) and I know 100 percent the heads have been gone through- because I'm the person who had that done but I'm posting off a blackberry so I tried to type out the essentials in a hurry. Got motor, had this same issue- also bad valve seals, so in went new HG and the heads I had on a previous motor which are minty perfect and of stock valve size, baby port and polish done though but BABY more or less a casting clean up if anything Like I've said, motor runs AMAZING on primaries- hell it spins 255's on them that's why I cleaned the crap out of it(besides the sitting, figured since it did this when I got it- that maybe I had a clog/debris somewhere in the secondary range) Plus- could have said ".560" as that was what he was trying to tell me as I eased off the clutch and drove away, he sounded kinda like hank hill so most of the conversation between us over 3ft apart wasent understood well. If it was a 2brl- I wouldn't think there was an issue hahaha literally feels perfect on primes. O should mention leak down was 5% give or take per cyl(I think 8 was like 7percent or something but still that should be ok) I guess I could yank the cam and search for number or measure it
I know Ill probably get hammered for this but with a manual setup a holley style carb with a mechanical secondary will help you out transitioning between gears. Ive had a lot of hard luck with elderblock stuff so I have just stayed away... This information wont help you in your current situation but if you go into the market for a new carb thats the route id take.
How about moving the distributor one tooth so it's pointing the right way? 34-36 degrees with old GM iron heads might be where it wants to be. But that's really not enough of a difference to be causing the problem, all by itself. If you're trying to get it to open when the car is sitting still, you probably won't be able to. The engine will only need that much air when it's at WOT turning a lot of rpm. Like, when you're driving.
thats why i figured i'd be close to what i was supposed to be at, i mean i could rotate it a tooth i just didnt think that extra what- 2 or so degrees of advance would be doing that? and i figured that- i'v tried to "run it out" once, but i dont like doing that so i wont try again(as soon as it comes off primaries it loses all power and backfires out of the intake until you let off enough to resume primaries fueling it) and if its running lean like i think it is.. i dont want to keep doing that i wish someone was close enough to experience this- runs like a champ on primaries but once you want that extra umph it says no no on secondaries and just pops out the carb... if i had another carb laying around i'd toss it on but i dont so i have to figure this out another way
The primary jets and metering rods are in the primary circuit, not the secondary circuit. How's the fuel supply? good pressure? flow? float levels?
I was under the assumption the setup springs affected transition into secondaries(that's my issue, can't transition) Stock mech. Pump- I guess I could check there... And float level is set per the calib. Book- I've basically gone by what eddy said to do so far
With the engine off have you actually opened the air valve and looked down through the secondary's with the throttle wide open and seen that the bottom flappers are full open. Some carbs are spring loaded where you can have your foot in it, and a gasket or something can hang the flappers and they never open and if you don't look closely you will never know it. Been so many yrs. since I have had my hands on one like yours I don't remember the specifics on it.
With the car off, it all opens fine- with it on as soon as the secondaries open it lean pops Thinking of richening the cruise and leaning out power mode(on calibration chart) but not sure So far I've checked Leak down Comp test Cam is not flat(as I can tell, all rockers move and non of them seem to go less then the others) Getting new plugs and wires- then going from there with a pack of jets rods and the step up springs I grabbed today Someone told me because of the tm1 being a single plane intake it doesn't give it a good vacuum signal oso with a cam I'm just making it worse and not drawing fuel out of the secondaries
Im with you. Many an Edelbrocks have been tossed. I have built carbs my whole life, calibrated dual quads, tri powers and many Holleys. Edelbrocks dont have the adjustments like others. I love my Holleys!!
Rawr- so it is the carb.... Tossed in silver step up springs, no lean pop anymore just holy shit rich... So I have to go leaner with the jets(probably rods to) and then use the step to compenstate for the lean transition Or get a holley.... Hard choice hahahaaha
I don't think that you have near enough motor for 750 cfm. Try a 600 Holley or Edelbrock, you'll be very happy with the throttle response and driveability!!
Neither do I, and haven't thought for once second I do- I just need a carb with better tuning abilities though so I can rich the transition up but be able to lean out the primaries and secondaries if need be Probably getting a 600-650 holley with mech. Secondaries
How about doing away with the vacuum advance, it kinda sounds like the vacuum drops when the secondaies open and that retards the timing so that it pops thru the carb. How about blocking off the vacuum sorces etc and throw some advance into the distr and see how that works. Kinda simply some stuff. Like others have said, the stepup springs and metering rods affect the primaries, they sholdn't be used as tuning devices for transition circuits. You sure you did the leakdown right?
Are you useing a points dizzy? I was haveing trouble with my sbc fireing out the carb when i opened up the throttle and the only way it would work is by advancing it like you did. Only the first time i drove it it didnt want to rev past 4 grand. It ended up being the dwell, or points gap. You should double check that as it will change your timing.
I have hei, new rotor and cap and weights all seem in good shape nothing sticks(and it advances when I rev up with a timing light on it) Only way I've ever been doing leakdowns, motors pretty fresh so the 7 or so percent seems about right(on one, others were 5ish) My old 396 was like 16 or so percent so I know a bad one when I see it and test it.. I need new plug wires because mine are burnt to shit and older then dirt so maybe somethings up there Firing on all 8 though so I don't see how wires would do it
Ok so I don't want to leave this thread open ended as I solved the problem, but I also have a new one First, the problem was my cam had indeed flattened a few lobes ever so slightly BUT NOW the problem Installed new lunati cam, lifters, made sure pushrods are all correct length everythings lashed right. Timing is pretty spot on and its back to running the 750 because the 650 I swapped on had it running lean but now with the bigger carb the plugs are decent choco brown Now I have very very little power. I mean it cruises fine and sounds great an will rev out of gear nice an high but in gear you secondary and it just makes noise. Sounds like its going like hell an I mean you're going but not lke stink So its leakdown an comp tested .60 350ci 4 bolt main Old iron 2.02 heads Edelbrock tm1 single plane intake 1411 750 eddy carb 4.11's T5 5spd Mr gasket e-fuel pump New lunati cam and lifters(rv2) New hei module,cap rotor, all wiring good etc I mean it should move along nicely right? Atleast spin somewhat off the line lol... Literally has enough power to move itself out of its way an that's it. No missing or surgin no popping etc just doesn't GO
Yet GM put a 750 on a 302 and Pontiac ran a 750 Q jet on a 6 cylinder. A 359 depending on how its built will not like a 600 CFM carb. I run a Holley 800 DP on a factory 400 Pontiac and I head a bunch of people say its way too big. The dyno doesn't lie and nor do my time slips or my 0-60 ft. Throw away the carb calculators. Theres the old CID X RPMs divided by 3456 . This one may be good for an emissions build but its way under carbed in so many cases.
Well see that's what I've been going off, is how the motor likes it and what my plugs read.. Right now I have it tuned to where it feels and sounds AMAZING it just is as if someone had found my motors "power scale" and turned it down to like 40 percent I mean it brakestands- that's a good sign lol barely any clutch and the tires spin a but but 20yr old 255/70/15's with like 45psi in them should just spin foreverrrrrrrrr I'd think.. Even as mild as my motor is
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