carb trouble

[MKHAYNESAZ]

let me start from the begining. i have a 355 (350 bored over .40) with headers and an 2.5" exhaust all the way back with 2 flow masters muffers. i have small chamber heads i belive are stock. soild steel and balenced crankshaft. rv cam and preformer carb and intake i belive. (came with the truck when i bought it) i have hei stock distributor and thats it i think i fill in the blanks if more info is needed. but here goes ....

i am having trouble with my carb i belive. the exhaust smells like gas and am geting like 5 to 6 miles per gallon.(which is killing my pocket book) now i have tried to tune the carb myself using the guides on her and from elebroke. but to no sucess nor can i find a shop that i can trust to tune it for me. i live in tucson. when i adjust the fule mixture screw it doesnt seem to change anything except bump my idle down a lil. i have screwed the screws almost to the shut off point but still smells like gas and runs like crap. i have adjusted the idle on it several times but nothing it runs basicly the same excpet when i play with the idle adjusmtent up or down . still smells like gas and crappy gas milage . i am at a loss i have been talking to guy from cliffs but i am unsure which carb to get or if i am even on the right part ? i dont know much about carbs . to be honest my old man told me they are a pain and to have a pro rebuild them . well where are all the pros at ? i just dont know what to do .



thanks for the help in advance mark !

[04SilveradoMykk]

Hey Mark. With the engine idling, can you see fuel dribbling out of the boosters in the venturi's of the carb? It sounds like you have a float level or fuel PSI problem.

What is your initial ignition timing set at? If initial timing is to retard you would need to have the carb idle screw open so far you would be idling with the transition circuits, and that too would make it idle extremely rich and the carb wouldn't react to the fuel mixture screws.

If you ever find your way up to Prescott I can take a look at it for you.

BTW, your .040" over 350 is a 357 cubic inch

Cheers ~Mykk

[MKHAYNESAZ]

thanks about the info on the 357 . i kinda feel a little dumb now .lol ! the guy i had the machine work done at said it was a 355 . doh !

but i dont kniow what the timing is set at the timing marks are not on this engine ( by the timing chain ) . no marks no way to set the timming i thought so i just found tdc but inserting a pencil in the spark plug hole and turing the engine (when it was out of the truck ) to find tdc. i know i am going to get flamed for that but its what i had at the time. its my daily so i had to get her running as soon as i could and it was fine at that time. i have played with the distributor a couple time trying to find a happy place the starter liked and the carb liked . and when i get home tyoday i check out the carb to see if i can see fuel. i thought it might be a fuel pressure problem too . the reason i say that is i have a clear fuel filter on the side of the carb and when i shut it off sometimes it bubbles dry ? but it still starts fine? idk i am at a loss and yeah i will see if i can get up there one weekend. i want to put more into this truck but it seems i cant get by the basics first . so should i just spring for a timing marks set up ? and start there or ?? and also its an 80 sorry i shoudl have metioned that too with a turbo 350 in the tranny

[04SilveradoMykk]

It's pretty tricky to set timing by ear without timing marks. Personally, without timing marks I would just keep advancing the distributor minimally until audible spark knock was heard and than dial back the dist a couple degrees.

You should have a timing mark on the balancer, it could be just as simple as buying a timing tab from your parts store and bolting it to your existing cover.

[MKHAYNESAZ]

ok thats a great ideal .. will do today thanks no what the hell do i set it at .. and how do i know its knocking ? if i try it your way ? and i am pretty sure i do have the timing mark on the balencer.

[Dunnz28]

As 04SilveradoMykk said, advance the distributor till your idle stops raising or you start hearing it knock then turn it back just a tiny bit and see how that is,then read up on your carb so you know what the factory specs of the screws and turn them both all the way in and then start turning them back out,a good starting point would be 2 full turns out,both screws should always be the same amount out,good luck

[MKHAYNESAZ]

so i had a chance to play with it last night . no joy. i tired turning both screws all the way in and let them out 2 turns each . then turned the distrib clock wise till i ran out of room for the vacum line ( i was plan on buying a longer length today) and it ran a lil better but no knock i also tried counter clockwise as well both ending with about the same results. truck poped smoked and geneal ran like ****. i dont know if i turned it far enough either way. i have orederd a timming tab but wont be here till saturday .. i was just tring to get the truck to run a little better i never heard a knock from the engine. but from the exhast i could hear something maybe a knock idk. i am going today to get more hose and try aadvancing the distributor again. i dont ami going about this the wrong way?

[MKHAYNESAZ]

oredered a rebuild kit for my carb since elbrooke makes 2 kits either electric coke or maunal . i have a manual choke with no cable could that be a problem? picked up the vaccum line i was needing still waiting on the timming tab. ( stupid usps lost my package) and hopefully i will be running alot better. i have a question thou while i was out on the weekedn i found a little parts store and ran across a fuel pressure regualtor for a carb rated engine? as far as i know i dont think i have one on my truck. do i need what does it do i know what one does for fuel injected keeps the pressure even (right?). i cant wait till i get this truck running right again now its backfiring at shutoff and no power cant get it to slip into passing gear . i stand on her and it stays ruffly the same as mid petal

[04SilveradoMykk]

You only need a pressure regulator if your using a fuel pump that makes to much pressure for the needle & seats in the carb (7psi+) You typically see pressure regulators with electric fuel pumps. If your using an original style mechanical fuel pump on the engine block your only making 4-5psi, if it's a performance holley mechanical pump that's capable of 14psi+ than you'd need a regulator.

[MKHAYNESAZ]

well i got it all timmed ran great now another issuie came up .. still think i need to rebuild the carb. but it ran great for the 20 some mins before i was unable to start it again

[04SilveradoMykk]

well i got it all timmed ran great now another issuie came up .. still think i need to rebuild the carb. but it ran great for the 20 some mins before i was unable to start it again

How far off was it?

[MKHAYNESAZ]

man it was at 0 when i got it on and checked it bumped it 3 different times to get it where it was good. started good and ran great idel was a lil high but i adjusted that down and ran smooth. but sadly i got beat by and 92 accord that night on the way home. trucked toped out at 85 just surged like i had no more gear or something .. very confused by that one. but no smoke or back firing it was nice .. still got a lil miss to it i belive i have a fouled plug or a bad wire they are up next for matinence then the carb the kit is cheap but i want to do some more reading on it before i tackle such a job

[04SilveradoMykk]

Still sounds like it needs a considerable amount of tuning. Smog era GM HEI distributors aren't known for performance timing curves. They are usually designed to run little initial timing with a very slow advance rate and a ton of vacuum advance. Too much vacuum advance can cause surging while cruising. Unplug the vacuum advance and cap the vacuum port (either on the ported vacuum switch on the manifold, or the vacuum port on the carb) to see if this gets rid of your surging problem.

Also, the mechanical max ignition timing setting is far more important than the initial. 10-12 degrees is a good initial timing for edelbrock carbs & manifolds, however you probably don't want to exceed 38 degrees of timing max. Ideally you would have loose enough distributor springs to bring the mechanical max timing all in by 3200rpm without advancing timing at idle.

[MKHAYNESAZ]

so update ! yeah ! .....
well i couldnt get the truck to run right and so i bite the bullet and called a buddy of mine. well after getting the truck over to him we discover the tranny was leaking eveywhere front seal real seal everywhere. so i droped the pan to find it full i mean full of sand mud crap.. .i am guessing i had a freind come help my truck by adding this to my tranny. and when i say freind i mean the asshat that slashed my tires. so i knew the tranny was shot which is fine. so i got the goodies for the tranny hughes tc and bm shift kit and other goodies the tranny guy asked for me to get. cleand the tranny 30 years of gunk on it. let the tranny guy do his thing and blam.. new tranny for the chevy. now on to the orginal problem.. the non starting and crappy idle. so we start by checking the plugs and wires the wires are ok not great but ok, so i pull the plugs and first 2 fouled as can be the rest where ok. ok new plugs and got me some nice new plug wires. start it up and still running crappy now i can hear the valves clacking .. so i said screw it lets pull and rebuild carb ..opened it up to find a bunch of crap in it and sooo he did something i never seen before . he tasted the fuel told me it tasted sweet .. then he told me maybe somebody sugered my tank .. so we drop the tank and there is a of clearish crap in the tank he said it was sugar .. so we cleaned that all up draoped the fule pump and cleaned it good and blew all the lines out and changer both fuel filters. so i strted to look for the parts to have a hood and grill again. and i got a locking gas cap. so basicly at this point i got her all tore down figure i should fix the wiring that was messed up the oringinal problem to begin with that i just worked around. and clean engine bay up and spray it all nice and clean, and also clean up the wiring. found a smoking deal on a victor jr intake that i couldnt say no to and picked up a 4 core alum raditor and all the parts for the swaps. so basily the truck has been modifyed again .. had an 6al msd box siting on the slef and decided this is as good of a time to install it as well .. so the run down is new go fast parts and new tranny .. truck should be done by this weekend i cant wait !

[04SilveradoMykk]

Mud in the trans and sugar in the tank? You know some good people.

The Vic Jr intake is a bit much for that engine and drivetrain, but it will look cool sitting up there.

[MKHAYNESAZ]

yeah i know its a bit much .. but the price was too good to walk away from at 140 buck brand new. and as far as the "people " that did that he was my step daughters x boyfreind.. i amnot the only person he has messed with. he will get his but not by me. if i get him i will most asured i will hurt him super bad.. better to let somebody else catch him and do work on him.