i have a 67 camaro, 355, 2.02 heads, holley 600 carb, with #70 jets. i am burning so much fuel i get 8-10 mpg. my friend has a 76 vette with just a 350 and 1.92 heads and an edelbrock 600 cfm carb, he gets 13-15 mpg. it doesn't make sense to me, and no i dont have the pedal on the floor all the time, when i do that i get 6-8, 8-10 is normal driving.

How do i know forsure if my car is to rich, and how do i lean it out? how lean do i want it? and how do i know forsure?

when i used to help my brother with his 2 stroke race engine i know u want it like as lean as possible without stickin a piston so i dont know.

 

Look at your plugs. If they are black and sooty you are too fat. Ideal colour is a nice tan. I get around 9mpg in mine and I drive it fairly hard all the time. If you have a double pumper and lower compression those work against you. Do a search on reading spark plugs online. THere used to be a few good pages.
CoryM

 

k so, ill check the plugs, but if they are black, how do i lean it out? and what do you mean low compression will give me bad mpg. if i get higher compression raito my mpg will go up?

 

watch for black smoke to come out of the exhaust thats to rich and to adjust the edelbrock therea re 2 screws on the front on the carb they have springs behind them with the car off turn them all the way in the back each one out 3.5 turns then adjust slowly till the car feels the best anyone else have a better way to do this

 

i have a holley carb. where would i adjust it on a 600 cfm.

and do i turn it all the way in then open it 3 1\2 turns as well?

 

if im right the holleys are a pita cause you need a little allen wrench and they are recessed in the base plate one on each side and you screw them all the way in im not real fond of holleys so im not real familar with them

 

i dont like my carb at all, my choke doesn't work so i have it wired wide open, i think thats what my gas mileage sucks.

i can buy a edelbrock 600 cfm, electric choke for about $200. im really thinking about that. what do you think? should i go edelbrock? it will be much easier to tune. but will it give me any performance? my holley is runnin like ****.

maybe ill just throw my buddies edelbrock 600 on my car. see how i like it.

 

edlebrocks are alot easier to tune holleys are harder but i think with the right person tuning them they make more power

 

Start by checking the float levels. With engine idling on a level surface, remove the front sight plug. It will be on the passenger side of the primary bowl, made of brass. Fuel level should be right at the bottom edge of hole and dribble out. If it flows out, either float level is too high or there is a small piece of trash in the inlet needle/seat. If you get a flood of fuel, you have a big piece or trash in there.

One of the things I love about Holleys is that you can just pop the inlet needles out the top of the bowls. Hold the adjust nut (5/8") and remove the lock screw. Remove nut and gaskets. Note how many threads of the needle are showing. Needle unscrews right out, then pull it up. Hit it with some carb cleaner and pop it back in. Try that with an Edelbrock/Carter or a Qjet.

To adjust, rough install to previous position (about 3 threads showing with no gasket on). Pop on gasket, nut, gasket, then lockscrew. Fire engine back up and check level. If too low, loosen lockscrew, give nut a 1/4 turn CCW, relock screw. Do it quickly cause fuel will squirt out when you loosen lockscrew. Wait to see where it ends up. If too high, go CW.

Try to adjust first, pop needles only if necessary; don't want to risk tearing a gasket unless you really have to. I don't think they are sold seperately. I have a bunch left over from bajillions of rebuild kits.

Then check rear float.

To do idle feed screws: with engine off, screw mixture needle all the way in lightly. Then back out 1 1/2 turn. Same on other side. Fire up engine and let it fully warm up. Start turning mixture needles in an 1/8 turn at a time, first one side then the other till you get best idle. You'll end up around a turn to 3/4 of a turn. Engines with bigger cams will need more. If you turn all the way in and engine keeps running, you have an internal fuel leak. Loose bowl screws, or high float level maybe causing main boosters to drip gas. BTW, idle feed screws are on each side of the primary metering block and are small slotted screws.



I think 600's come stock with 66 primaries. If float levels are ok, you might want to lean down primary jets. If it surges, you went too far.