some carb questions from a newbie

[coreyhayman]

hey i dont know much about carbs at all or pretty much how they work.....im just new to the whole carb scence seeing as how i am an ex import guy.....my questions are 1, what carb is this i have, i know its a holley and im pretty sure its a 750 dp, but how do i tell for sure?.....also is this a chokless carb?...and finally my cars runing like **** right now, bogs when i try and floor it, but is ok if i gradually let on the gas...somebody told me i might wanna play with the mixture screws, haha i went to take a look at them today and i think ones missing.....heres the pics, just wondering if these r the mixture screws and if i am in deed missing one.

 

[1985 5.0]

how old is this carburetor??
b4 i got my new steet avenger 670 cfm($450 for everything i needed ), i would floor it and it would bog because of how old and dirty the carbuertor was...went to rebuild it and it ran perfect top end, but it would die every time u let off of the gas b/c their was an air leak somewhere. SO if ur dealing with an old carb, i would recommend to not pay $50 for a rebuild kit and just go ahead and buy a new one

 

[coreyhayman]

the motor was all done 80,000km ago, so i dont think its all that old

 

[NOSNotch]

that carb doesnt look too fresh so i dont know, in your last pic there i cant really make out the #s but the one that starts with 4 should identify the carb 4777 is a 650 4779 is a 750. No choke from what i can tell and im not positive on the mixture screws but with how your cars running if its the same when it gets to temperature you might want to have someone go thru it, buy a new carb or get the Proform center section. good luck

 

[coreyhayman]

it looks to me in the first pic where i made the arrow as if somethings missin from in there

 

[crazypete]

That is indeed a holley. Not all secondaries have idle mixture screws. Only the really top end hollies carry secondary mixture screws. Trust me, you dont want them. 750 cfm is too big. You are bogging because

a. Your carb is way too big and you are losing all vacuum signal when you snap the throttle open. A 650 or so would be better. 750 is for feeding some truly deep breathing motor. I went from 670 holley street avenger-> 600 and wow. Absolutely wow. Throttle response/idle/everything is 10x better
b. You have a mechanical secondary carb. When you snap the throttle open, the air loses all velocity and it bogs.

For laughs, go to the primary-> secondary linkage and undo it. Just unhook it so your secondary side is shut all the time and "gun it" again. Night and day difference. I guarantee your bog will disappear. The mentality of more is better is a great way to shoot yourself in the foot with carbs. Thats the little bar going from the throttle arm to the secondary's throttle arm.

I dont know anything about your engine but I can tell you youd be much much much happier with a vacuum secondary 600 cfm carb.

 

[coreyhayman]

ya the car was fine before, it didnt always bog like it is now, jsut started once i brouhgt it out of storage, heres a little run down of my motor, 306,x-cam,ported 351 heads,crane 1.6 rockers,pulleys, edelbrock torker intake, electric fan, forged crank and pistons,msd 6al, msd blaster coil yada,yada

 

[crazypete]

Ok, depending on what it's for

600 cfm for throttle response and 650 for top end HP

Remove the linkage and take for a drive.

If it is a vacuum leak, simply put a beam of RTV around the base of the carb. Works wonders. Put it around the outside of an already seated carb or it will suck into the carb's passages underneath.

Get some carb cleaner and pull out one of the top fuel bowl screws on either side and fill the fuel bowls with carb cleaner then start the car. Cleans her out from inside to out. Dont leave that stuff in there for any length of time though. This is just good at knocking loose the grunge that forms when fuel evaporates (possible side effect of storage is the gas in the bowls evaporates and leaves some residue). You'd be surprised what they put in gas these days.

 

[coreyhayman]

thanks for the tips man, im gonna go out righyt now and tinker with it, right now a 92hp civic can take me, lol i cant even let her rip....lol

 

[Boss 351]

I would just get a rebuild kit and not play with any "mixture setting screws" if the car worked good last year. I got a 650 double pump carb with mechanical secs and that sucker pulls like a bastard on red-pepper sauce! (that's an expression, I think?) lol But when I first put the carb on the engine, it didn't work too well but after the rebuild - wow! BTW it isn't real hard, I've never done this before and it worked the first time! Just be careful and take it apart slowly. I also lightly sanded the metering block (i think that's what its called) with some smooth sanding paper over a piece of glass - that's not recommended though or so people tell me lol

 

[crazypete]

The idle mixture changes from season to season so that does need to be played with....The 650 DP doesnt kill the velocity of the air as much so you probably get good throttle resonse.