I have a 73 with a stock base 350 engine except for, Edelbrock 2101 performer intake, hooker headers, side pipes. It's also an automatic transmission.

The carb I have on it now is a 750 cfm Edelbrock which came with the car when I bought it. The car starts and runs great however I'm thinking the size is too big for this engine. I have plenty of mid range power but from a stop it's a bit lacking. Timing is dialed in and the carb is tuned. I'm thinking of switching to a smaller cfm carb so I have a little more from a stop. I mainly drive the car around town and will get into it on back roads. Based on this, would it make sense going with a 600 or 650 cfm carb? Or would I be wasting my time/money?

 

The best carb for this car is a Quadrajet. Q-Jets are 750cfm, just properly tuned and have the air valve to feed demand.

99% of carb problems are actually timing problems. You say the timing is dialed in. What does that mean? Most people like 36 degrees mechanical all in by ~2500 rpm and then another 14-16 degrees of vacuum advance. Also have the vacuum advance hooked to manifold vacuum so you get advance at idle to help smooth things out.

 

Well, a '73 base engine isn't going to be a rocket no matter what you do.
I recently had a carb problem--different car, different carb--but the end result may help you.
I had a high speed miss that turned out to be the carb. New filters, fuel pump up to spec. etc., helped, but it still missed at wot high rpm's.
I tried a can of SeaFoam, and within a few miles it started getting better. I was truly amazed.
So, for $8 on sale at Napa, give it a try.
Other than that, buy a book, get internet info, etc. on how to correctly tune what you have.

 

A smaller carburetor won't help. The stock engine is fairly weak and the stock torque converter and probably 3.08 rear are also killing the low end response.

 

Some good timing information at this link

http://www.crankshaftcoalition.com/w...ance_Specs.pdf

 

To boost power, you need to increase the amount of air and fuel passing through your engine. The base camshaft and cylinder heads/valves are the limiters. L82 cam with bigger valves and better cylinder head ports will allow your engine to take advantage of those side pipes.

See signature for the options I went with. Your stock smog heads intake ports are probably 160-165cc. You need 180cc 190cc to boost flow. Then, 2.02/1.60 valves, smaller combustion chambers (65-70cc) with good swirl. Your stock flat-top pistons don't help as they are probably also dished. I'd consider flat-top pistons with valve reliefs for a bump or get no larger than 65cc chambers.

Then, you want a camshaft that can increase lift to flow more air through the larger valves and improved intake ramps. I chose to increase lift but keep the duration close to the L82 cam but with a Comp Cams retro-roller Xtreme Energy cam. Lift is great and duration is where I want it as my power band is in 1600-5400rpm range (street performance).

AFR makes an excellent aluminum cylinder head. DART makes a great cast iron head. I upgraded conservatively to the 72cc chamber DART with 180cc intake runners. Since I am running just .020 over on my 350, I wasn't boosting cubic inches to 383. If you go 383, consider 190cc runner heads. 406cubic inches, consider 200cc intake runner heads. But, keep it at 65cc combustion chambers.

I kept straight plug heads as I run my Hedman (68300) and did not want to deal with angle plug. Good combustion chamber shape is preferred over angle plug unless you are trying to wring every last HP/TQ out of an engine.

Also, if you are inclined, refresh the bottom end with rings, bearings and seals. That will ensure your platform can be reliable with the upgrades. Or, just buy a Blueprint 350 or 383 and rest easy. I

 

Your car looks really cool.

Nothing will make it feel faster than a third pedal. My wife's 79 L48 3.55 auto is a dog compared to my 80 L48 3.08 4-speed. Both have stock Q-jets, and the Lars-style ignition tune.

 

Appreciate everyone's response as I'm fairly new to carbs. Been doing lots of reading. Of course this all came about by someone I was talking to at the gas station telling me my carb was too big for my engine (yea i know gas station advice/comments ) I think I will leave it be for now as I believe it's a fairly healthy engine. Compression test was within 4% between all cylinders, no smoke at start up or while running. I guess I'm just looking for some more power (aren't we all?)

Lots of good threads on here about stroking and original engine vs buying new. Better start researching and saving.

 

Get a higher stall torque converter. Something like 2500 stall. That puts the engine rpm higher when you stomp the pedal from a stop and it fully engages at 2500 instead of the stock 1600.
the higher rpm means more torque and HP from a stop.

I did this on my 77 with the stock motor and th350 trans with the 3.08 rear diff and it made a noticeable difference. All of a sudden I could spin the tires.

another mod might be a shift kit for the trans. That also make a big difference, particularly in the 1 to 2 shift.

 

The smaller carb will help off idle response....but as far as a power increase, not much. If it were mine...I would find a nice Q-Jet.....they are much snappier around town.
I do have an electric choke 600 Edelbrock here if you are interested.....about 50 miles of run time on it.....$250. It was bought new in August of last year.

Jebby

 

See? You came for carb advice and left with the need for a full on engine rebuild! We are masters of spending other people’s money.

The dude at the gas station is quoting carb lore that is more accurate for a Holley than the Edelbrock you are running. The Edelbrock is much more forgiving with the air valve and stepped metering rods. Unfortunately, the advice you are getting above on increasing flow through the engine is the real answer.

 

the 3.08 gears (if you have them) are likely the cause for sluggish takeoff performance... they are on my 10:1 355 with dart heads, cam sidepipes and sidepipes and 680 quick fuel carb ..

I just picked up a 3.55 posi rear end for $500 which has about 5000miles since rebuilt to swap into mine... but then its a snowball effect... I want better top gear rpms as well as better low gear ratios for takeoff so Im also swapping to a 2004r overdrive transmission which should give me an improvement at both ends of the spectrum.

Long story short, theres no single bolt on that I know of that will make a big difference without negative tradeoffs unless more is done.

 

It's hilarious how quickly it snowballs with these cars. Last summer I needed to fix my tach, oil pressure gauge and a couple burned out light bulbs. That turned into a while I'm in here I mine as well put down some heat/sound deadener, to then, well everything's out mine as well add working AC to the car, to then, lets get new foam and recover the seats......

I checked and it doesn't appear the rear was ever messed with so I'm assuming it still has the 3.08 gears. I didn't even think of a higher stall converter.

I think for now I'm just going to drive and enjoy it since I had it off the road a bunch last year. Also think my wallet will thank me.

 

Check to see if the accelerator pump (in the carb) is doing its job. With engine OFF and air cleaner removed, manually open the choke valve and look down into the primary venturi. Now do a manual full-throttle pump of the carb's throttle linkage. You should see a strong squirt of fuel being spewed into each of the primaries. If not...or if it is a weak stream (or a 'dribble'), the seal on the accelerator pump is bad/missing/etc. That will cause a HUGE off-the-line stumble when you WOT the engine. Fixing that is lots simpler than reworking the engine.... [if that turns out to be the problem]