Raven One

I have two 350 motors, used in my 74 Nova;

one has 202 dart heads high rise manifold, long tube headers, mild cam, aftermarket flattop pistons..., it is under carbureted right now though with an Edelbrook 600 cfm.

The other one I recently pulled to put the above engine in because it is supposedly pushing out around 400hp, where as the old one ran real strong, but when I started taking it apart to freshen it up, found it had stock heads, pistons etc... same headers and carb, it did run with a lower vacuum, i have not taken the bottom end apart.

I can smoke the tires with both but they seem relatively close is power, I suspect the bottom end of the old one is fairly built.

Compared to the crate motor that was stock my brother had in his Nova, they both blow his away.

I’m new to building motors, and just want to know why I can have one engine that appears to be fairly built and one that looks old and mostly stock yet they run pretty close.

What could be making the old one so quick? Would a high lift cam make that much of a difference?

I thought with the new one I would give my dad a run for his money in his 72 cougar with his 460 but his feels much quicker.

How can I easily get more power from my new 350? Would a new carb make a huge difference and what would you recommend?

I'm just a bit disappointed/confused that my new expensive engine doesn't really blow away my old motor.

pancherj

If the bottom end is solid and youa re shooting for 375-400HP...just concentrate on the top end. Sell one engine to generate cash for a set of heads (AFR 190's would work nice). It depends on your budjet, but a roller or flat tappet cam can get you there. With older blocks, the flat tappet will be a lot cheaper. A performer RPM or Air Gap with a 650 double pumper and and HEI ignition should do it.

Nice forged, shiney things are not needed for what you want to do. Cylinder heads make power by allowing an agressive camshaft to work.

Isolde

iTrader: (4)

building the bottom end doesn't add power. It just needs to be strong enough for your top end. For 6000 rpm and no more than a 200 shot of nitrous, a stock bottom end should live. Just keep it out of detonation. To use a 200 shot, you'll need to install a Mastermind, and ramp in the nitrous while ramping out timing. A safe setup would be 50% at 3000 rpm, ramping to 100% at 6000. The Mastermind will keep it a nice linear ramp, very safe.
You didn't give specs on any of your parts, but a 350 with any Dart heads that came with 2.02 valves should reach 400 horses no problem, without nitrous. What cc are the intake ports? Which intake manifolds do you have?
You probably don't have the spec card for either cam, so I'd plan on buying another cam. What axle ratio are you running? Rear tire size? Probably a TH350, right?

Raven One

I don't know the exact spec's i'll have to look them up, i'm not interested in using nitrous. It's my daily driver just something fun to cruise around in and tinker with. The Heads are 2.02 Dart i think 180cc intake, the manifold is an edelbrook rpm performer, i think it's a standard block with 4'' bore, would it measure a millimeter or 2 over 4'' on a standard block? The transmission is a th350 built for strip/street. I've got pretty tall tires on the back i'll measure them and i think i figured out i have around a 350 gear in the rear end, i'll watch my speed and rpm and work it out.

I went on Jegs and tried to find what i have

http://www.jegs.com/i/Dart/301/10121...oductId=744650

http://www.jegs.com/p/Sealed-Power/S...44660/10002/-1

It's been a while since i switched them out i probably should of written everything down that i had learned about the engine at the time , i brought it from a mechanic who had some very impressive toys the engine was barley used not long after building it he decided to sell his Chevy and because of the money he had in the engine he sold the car and motor separate to recover more of his money, he didn't have any other chevy's only mopar which is why he sold it and that's how i got this motor.

I appreciate the input. sounds like i need to change the cam shaft and go with a better carb. Would sending off the block and having it bored over be worth while? I have the spare engine in the garage to tinker with. i still don't understand how the old motor thats now sitting in my garage had so much power it wasn't even firing properly on 2 of the cylinders, and how it ran it seemed fairly built but it looks pretty stock, the only think i can think of that certainly wasnt stock is the intake manifold is an edelbrook.
Thanks

Isolde

iTrader: (4)

First thing is 1 mm = 0.040", and you typed 1-2, so that block may be 60 over. If the heads are already off, then clean the carbon off the tops of the pistons and look for a number stamped there. Nearly all oversize pistons, regardless of source, have it done that way.
Your gearing is not very good, your combined first is no better than if you had a 2.73:1 axle with a 700R-4. You have the Dart heads to give good top end power, so you need a torque cam to offset the weak gearing.
The smartest thing you could do is a 200-4R trans, then more rear gear, like a 4.10:1. This would let you make use of the Dart heads. I'd also go with a B&M Holeshot 2400 stall while doing the trans.
when you installed the new 350, I bet you didn't raise the shift points. Those Darts will breathe another 1000 rpm higher than stock heads, which are done by 5000 rpm, so shift those by 5500, unless the cam is so small that it won't pull 5500.
The Dart heads almost require a bigger cam, a looser converter, and more rear gear to realize all the potential they offer.
My experience says you aren't using the power you have, because of the obsolete drivetrain combo behind the engine.
The larger carb will help, but should come after the trans and converter.