Just picked up an 84 Z28, which has a 350ci out of a 72 K10 Pickup. It has a fair amount of hop-up parts, including Dart S/R Heads, custom grind cam, shorty headers, edelbrock rpm air-gap intake, edelbrock 750 carb (1407), etc, but doesn't feel nearly as powerful as it should be. It's also freshly rebuilt, with a .030 bore. It sounds real mean idling, and at low rpms, but it just feels like a dog when you step on it.

It has only been together for a little while now, and the guy before me didn't mess around with the carb that much, in fact all he did was turn the air/fuel screws out 1/2 a turn to be "conservative". Obviously that was far too rich, so I had a buddy play around with it a little today, which made it a little bit better, but it still doesn't seem to have the guts I expected. I just went out to the car, to see what the screws are currently set at, and he has them only 1/2 a turn out from being all the way in.. And on the way home the exhaust would pop and crackle under deceleration, could those be lean pops?

Obviously a good place to start would be to check the spark plugs, but I don't have the time right now, I'll do it asap tomorrow, I'm just wondering what a good "starting point" for the air/fuel screws would be. And actually, a good starting point for the timing would be appreciated as well. Other ideas on what may be keeping it "weaker" would be cool as well, it's been a while since I've been under the hood of a Camaro

Another thing I should add is when under full throttle it just doesn't sound right. It has this weird sort of "chopping" noise, like (I'm guessing) the timing is way off, and its just not sparking when it should be, and therefore not making near the power it should. If the timing was off a good amount, could it severely reduce the WOT performance, yet run seemingly fine at low rpms?

Also, apparently the accelerator pump on the carb could use a new plunger/gasket, would this be something hurting my performance significantly?

 

Until the ignition timing is where it should be, there isn't any sense messing with the carb.

I don't have any love lost for Edelbrock carbs, but when you say "custom grind cam", that tells us nothing. It could be the entire reason for the problem.

 

Yeah, I know.. Thats the problem, I don't know the specs on it. The current owner had a cam card, but he apparently lost it. He has all the paperwork and receipts from the motor rebuild, I'd assume it'd be in there...

 

Make 100% sure that you have no vacuum leaks and that your fuel pressure is in the range it needs to be for that carb.

Then purchase and install an air fuel ratio gauge to start tuning the carb using hangars and jets.

 

wouldn't a vacuum gauge suffice? i doubt he has an O2 sensor to install the air fuel gauge to. there is a good edelbrock sticky and the search button does wonders.

first off though, fix that timing

your car with a 305 timed at 6ºBTDC at sea level, advance 1 degree for every 1000ft above

with it being a 350 i'm not sure what it would time at with your cam but its a start

 

You can't tune the secondaries with a vacuum gage.

 

Ok, I had someone that has a good amount of knowledge with SBC's take a look at it, and he re-did the timing (its now around 8ish degrees initial timing), messed with the air screws and replaced the plunger in the accelerator pump. It definitely seemed to help, the car pulls stronger now, but with the mechanical secondaries, it still falls on its face unless you roll into the throttle. And even then, it doesn't pull nearly as hard as it should. I'd guess it's roughly an upper 14 second car, give or take.

Now, I've heard from numerous people that this carb is too much for this motor.. But would having a little to much carb really hurt performance this much? Would a 650cfm be a better choice?

It also seems like there may be a little misfire.. I've noticed the plug wires don't "snap" onto the plugs very well, sometimes its hard to tell if they're on all the way or not. Could this cause a little misfire?

Another thing is there is a tad bit of ticking from the rockers.. We're thinking they might not be adjusted properly. I'll have to take a look at those soon.