Hey i have a 73' with a 350 in it. I bought it from an elderly man and i'm trying to do many modifications to it. I haven't been driving it for a year, but it had all stock stuff on the engine. I switched carburator's to a 750 cfm Holley 4 barrel. I had to change manifolds. I don't feel much of a difference in performance. What could be some factors resulting in a lack of performance?

What's your timing set at?

it's set at whatever the correct setting is for a 350 engine. I forget what that is off hand. -jeremy

The reason I asked was sometimes when you change the intake you can get the timing off.

Would lifting the camshaft to about 3/4 in. do any justice? Or what will get the most performance out of this new carburator? What adjustments should i make to the engine?

Would lifting the camshaft to about 3/4 in. do any justice?
3/4" above what?

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Jeremy, what type of manifold did you install? Let me say this, if your engine is bone stock other than the carb, your probably overcarburated now. Sometimes bigger is not always better. Installing a higher lift longer duration cam can improve performance, but picking the right one is the trick. Your question was should you install a 3/4 in lift cam, and what I think you mean is 3/4 race, which is old terminology. 3/4 in. lift would equate to .750 inches in lift and if you installed a cam that big, you'll stick your valves right through your pistons. Camshafts are designed to give you the best increase in performance in RPM ranges. Without going into it too deeply, do you want your Elky to make it's most horsepower and torque at low end, top end, somewhere in the middle or a combination of two of it's RPM range? This is something you need to decide before you start buying parts and start throwing an engine together. You stated you want to do many modifcations to it...I don't know if that means to the car itself or the engine. However if it's to the engine, you should start by buying the correct first part, and that would be "How to build small block Chevy engines for performance" or something similar, even a subscription to a magazine like Super Chevy will help. Anyway, no, your not going to see a noticeable gain by throwing on a 750CFM carb on an engine thats bone stock, what you will probably see is less gas mileage and less money in your wallet. Although building performance engines is an art (IMO) you don't need to be a Pablo Piccaso either. What you need is direction (how you want the car to perform) and a plan (what correct parts to assemble together to reach your goal), changes can be made in the process due to parts availability and of course money. Don't be outrageous or unrealistic either...you wouldn't run 13 to 1 compression on the street and you wouldn't run a .750" lift cam either. Read tech articles on builiding street performance engines, and when you finish reading them, read them again and again and again. That's the first step...and it's OK if you use someone elses' plan, many guys do, right out of a book...I do!

Good advice. Especially the carb comment. Very few small blocks need bigger than a 650.

ok so i wasn't thinking correct when i said all of that. I got dual exhaust put on it and omitted the catti's. So i was thinking of going out on a limb and doing a few mods. I've been a subscriber to Chevy High Performance for over a year and have been reading on what others have done to their cars and i think i've decided exactly what i want out of my elky. I'm going for low end torque. So.............i looked into having everything match. I'm looking into holley performance sets such as a aluminum dual chamber holley intake manifold matched for a 750 cfm carb, 1 3/4 inch short tube hooker headers, holley electric fuel pump, holley billet distributor, and an Annihilator ignition system ( Pro strip annihilator). The question i have for you is, would i need to upgrade the heads for top performance? - Jeremy

I would go with a set of aftermarket aluminum heads (Edelbrock)...however that can be a bit expensive. Try to find a set of used 2.02/1.60 64cc cast iron heads at a fair price at a swap meet(around $400 or less) have them checked out to see if they need anything, like a valve job, seals, springs, whatever. A nice low to mid range hyd cam with a good set of anti pump up lifters (TRW), remember a 4th gen is a heavy car, you might want to go to a 3.73 gear, but it'll kill your gas mileage, well almost. I believe the compression ratio of a 73 350 is 9 to 1. If you can do it, but we're talking about a rebuild, go with a set of 10 to 1 cast pistons. I don't know if your willing to go that far at this point, but it's something to think about. Anyways it should be fun to drive, and you should be able to whack a few Mustang GTs. 8)

so you mean i would need to get a torque converter? I've been reading about those and i don't know exactly how those fit in, can you explain that part to me? -Jeremy

Hey i also forgot. I have new chrome 8" wheels. Should i get new performance tires on it?

No, you don't necessarily need a torque converter, however it would help if you got one with around a 2000 or 2200 RPM stall speed, this will get you off the line quicker. I was talking about new gears in the rearend. A torque converter bolts to a flexplate (flywheel) which bolts to the crankshaft. It allows slippage so that the engine doesn't stall when your stopped. Going to a higher stall allows slippage up to a higher RPM before the trans starts to turn your drivshaft. Kind of like a clutch, you can bring up the engine RPMs higher before the trans reacts and starts the car rolling. This allows you to launch at 2000 RPMs instead of 1500 RPMs. The higher the stall speed of a torque converter, the less streetable the car becomes, also the higher the stall speed, the more slippage, which is why there's lock-up converters today (better fuel economy). The more the slippage the more fuel you use. You have to remove the trans to install a torque converter. You don't need one. A posi rear with 3.73 gear ratio is about the max you want to go with, unless you own your own gas station!

Hey i have a 73' with a 350 in it. I bought it from an elderly man and i'm trying to do many modifications to it. I haven't been driving it for a year, but it had all stock stuff on the engine. I switched carburator's to a 750 cfm Holley 4 barrel. I had to change manifolds. I don't feel much of a difference in performance. What could be some factors resulting in a lack of performance? Check out http://www.demoncarbs.com/demon/default.aspx?page=8 Thier 625cfm would be perfect in my honest opinion.

Excellent info and advice Mike! I cant think of a thing to add! http://www.corvetteforum.net/c4/alchemist/thumb.gif