Ok I have a 79 Z28....anyway when I take off slow like a normal person my car feels as if it is kinda lugging a little.But if I get on it sometimes, it does ok. But I got home tonight from the beach tonight and got in it and now when I get down on it...she tries to like backfire throught the carb or exhaust not sure exactly where she did so at.

So this all I can think it could be I have a valve cover leak that is leaking oil down on my #7 xylinder spark plug wire. And my carb looks as if it could nee dto be rebuilt, cause you can see where its leaking around all the seals. The car has 221,000+ miles on it and is all original.

 

yea...i think u new carb, i heard alot about how bad rebuilt carbs act up if u do then urself and its cheaper to buy an edelbrock than a rebuilt 1 from JC Whitney..but u'll also need an adapter to ur intake which isn't a big deal easy to put on an costs around $20, my car did the same thing but i took car of it before i got stranded...i ended up putting an edelbrock 600 cfm on mine...it runs great,also if ur looking for better gas mileage they make 1 for that too i have 1 on my truck and it gets 7mpg more although u can notice a loss in power, but I went with the performance one on my car and it ran alot better(not to mention stronger) than before and i'm getting alittle better gas mileage which is always a plus with 3.73's in the rear end.
Out of jegs the carbs cost as follows:

600cfm performance manual choke- $216
600cfm fuel economy electric choke- $245
750cfm performance man choke- $226
750cfm fuel economy elec choke- $270

if ur motor is stock without any mods then the 600 cfm should be sufficient but if u have high performance mods than u need the 750 cfm... it'll get u more overall power if thats what u need but n e hope for gas mileage is gone...sorry for such a long post guys...but i think this is the prob an 1 of the best solutions

 

also if that 221,000 miles is on the original engine...i think it's past due for a rebuild but the carb sounds like the prob at this point...if its still going strong then keep it

 

I apperciate your input man, I fiqured it was the carb. I think I'll end up buying a new 650 or 750 carb. I probably go with the bigger one, since I have a set of full-lenght headers I'm about to put on. And yes the engine still runs strong.

 

I ordered an edelbrock performer 600 cfm carb, the electric choke, they said it was calibrated for fuel economy, but what has been done to it to acheive this? Will my car suffer a significant power loss because I got this carb? I needed the electric choke, I didn't want to deal with a manual one.....

My engine is a Pontiac 400, being rebuilt, and will have over 300 Hp when done, 9:1 compression, XE268H cam, edelbrock intake + the carb I mentioned, headers, dual exhaust, roller rockers, bored .030".........etc etc......this is a mild street performance type of rebuild I have here......Will the 600 cfm calibrated for fuel economy hurt me a lot here?

 

if your looking for extra performance than the electric choke isn't the 1...the differences can be changed to get tha same as the manual choke..in the owners manual it talks about jets, rods, and step-up springs... the manual choke has a main jetting of .100 and a secondary of .095;
the elec choke has .098 main jet and .095 sec jet...this means that when ur cruisin down the road with just two barrels flowing you use less gas with the elec because of the smaller jet size...the secondaries r the same on both which mean that when ur 4 barrel kicks in u get almost the same acceleration... the main difference is that if u like to punch it alot then the elec choke won't help ur gas mileage alot but if u r driving down the road and like to increase ur spped without letting the 4 barrel kick in then the man. choke will allow more acceleration... let me try to decribe this better....u know the feel of the car on ur initial take off before the 4 barrel kicks it thats where the difference is.. also right after u shift gears the difference is felt but as soon as ur speed increases and ut engine will take four barrels then the difference won't be felt thus it will hurt ur acceleration ALOT if u have high gearing and if you have lower gearing the engine will lose power but the rpm will get up to the point to take th 4 barrel faster andit won't b as much of a difference. like i described before i have an electric choke on my truck, i know its alot heavier than our cars but its just an example...it had an old quadrajet on it before. it has a manual tranny an 4.11 rear gears i wanted better gas mileage so i got the electric choke which was a big mistake because my truck now always has the 4 barrel kicked in and since i have less airflow my truck is alot slower and gets alittle better gas mileage but it still only gets 12.. when i take it easy--real easy.. in my opinion if u was you i would order a calibration kit from jegs for ue carb #1406 and it cost $35 dollars. it'll let u set the carb up the same as the manual choke with an assortment of jets, rods and step-up springs but before u change anything u might want to read up in ur owners manual about how u want to set it up

 

Thanks for the info! I'll have to at least get this thing running first, and see what I want to do with it. At least the secondary jets are the same; I will get terrible mileage I bet as it is, so maybe I will leave it.........I have stock gears in it now; I don't even know the ratio......But since my car gets about 12 mpg BEFORE all these mods, I bet I'll get like 10 when I'm done. I don't even know what kind of gears to get, no higher than 3.23 definitely, the 3.42 or + will suck the gas even more, and with only 3 speeds, my car won't even go over 100 with 3.42's that easily, or it might cruise at high rpm. I'm looking for a street setup (this is practically my daily driver, if my car is broken then I might borrow my bro's car) here, so maybe I'll stick with these settings. As long as I don't see a major problem, I'll at least try to stick with what I have for the carb now.....