Need more power

[eugene]

The stock motor just doesn't do it for me:

 

75 280 JTR conversion:

91 stock 350, holley street avenger intake, 600 vac sec., block huggers, 2 1/4s into single 3 inch mandrel bent exhaust

 

700r4(2,000 stall locking converter), 3.54 open r200

 

Don't get me wrong, I'm somewhat pleased with the increase in power, and it is a good daily driver, very quiet with the resonator in the tunnel.

 

However, it kills me to know that there is so much more available power, and I'd like to extract some of that power without spending too much money.

 

My question: I figure it is about 250 hp right now. Can I get 350hp or more with a cam change and maintain good daily driveability? I need more info on the heads (casting # 14102193) and block (casting # 10054727, K0219UKA) Mortec says 350 heads 1.94 / 1.50 valves, but no info on flow or chamber size. The motor is stock, so I am guessing pretty low compression ratio.

 

I would like a good launch and strong power band from 2K to 6K . Since I have a decent flowing intake, exhaust combo, I figure the only remaining variable for a cam choice to complement my intention is the head info. If I can get 350 hp with just a cam change, I'd be really happy. If I have to change heads I'll just have to wait on it. I could probably swing some stamped roller rockers too. Does anybody have more info on these heads or know where I can find it? All I want is 100 hp, that's not too much to ask, is it?

[DavyZ]

Jason, if you have low compression and stock heads, you'll be hating life with a big cam.

 

I am no expert, but I am in your situation with a similar motor, so I started reading books on budget build ups (this includes Car Craft, and real books from Vizard, Tarrant & Hawkinson, etc)and of the books I have read, with the stock heads and 8.5:1 compression, a good cam would have specs about 214/224 deg @ .050" if I remember correctly. This dual pattern cam will help compensate for the heads and offer some decent torque. However, I think you are limited with the stock heads to about a realistic 300 hp (at a low compression). With heads offering a smaller cc, you could bump your compression up a point, and then swap in the cam: BAM, instant 350 to 400 hp.

 

Some may argue over my cam choice, but then again, there are guys running this combo here. Perhaps a little more aggressive cam would not hurt and I would definitely call the cam companies and get a recommendation from them. Keep in mind that it pays to know what compression ratio you have and what the heads really are. You may actually luck out and only need a cam change! Just food for thought.

 

Davy

[labrat]

Get ya a pair of vortec heads. I picked some up off of ebay for 300 bux brand new... The 64cc chambers will bump your compression up, and they flow great out of the box.

 

Just my $.02

 

Bill

[Guest the_dj]

This is EXACTLY the situation I was in. I am installing new small chamber big valve heads and a new cam on Saturday.

 

Now I'm thinking I'll also need new fuel injectors to bring out full potential.

 

Sam

[grumpyvette]

THIS HAS BEEN POSTED BEFORE BUT NEEDS REPEATING HERE,

I constantly get E_MAILS on this so heres some GENERAL TIPS on engine planing

things to keep in mind!

 

(1) your normally limited to makeing about 1.25hp per cubic inch of displacement unless expensive high rpm parts are used or power adders like nitrous are used the larger the engines displacement ,the easier it will be to make any power level, starting with a 283 or a 307 puts your at a distinct DISADVANTAGE compared to a 350 or 383, 400 size engine

 

(2)hp= torque x rpm/5252 so.....

400 ft lbs at 3000rpm=228hp

400 ft lbs at 5000rpm=380hp

 

get the IDEA, the higher in the rpm range you make max torque the higher your hp will average!

 

(3)looking at cylinder head flow numbers

((.257 x cfm at max cam lift x number of cylinders = hp POTENTIAL))

so...you can normally make ABOUT a MAX POTENTIAL HP of

411hp with heads that flow 200cfm

514hp with heads that flow 250cfm

617hp with heads that flow 300 cfm

 

(4)all parts in an engine MUST be matched as to the ONE rpm range that your trying to make max hp in..... if you mis-match the rpm range of the parts the results will be far lower than the lowest rpm level of the least effective parts!

(5) by far the most comon mistake is buying DEALS on parts that don,t match the rest of the parts in yout engines rpm range or not matching all the parts in the engine to a planned rpm range

(6) the cross over point between useing a dual plane intake and a single plane intake is approximately reached at 3500 rpm and 230 deg@.050 cam durration or put another way if your engine spends almost all its time below 3500rpm and your cam has less than 230@.050 durration a dual plane intake will work best, if you spend almost all your time with the engine spinning OVER 3500rpm and your cam has more than 230@.050 durration a single plane intake will be best. this of course assumes your smart enough to know that the cam durration must also MATCH the ENGINES intended RPM RANGE and youve matched all the parts to the cams rpm range(the cam is the brains of the engine and determines what rpm range all the other parts should match, so FIRST PICK the rpm range/hp goal,

pick heads that flow enough air to meet that goal,

pick a cam that matches that goal

and pick all the other parts to match the heads and cam

(7) youll gain about 3.4-4% in torque for each point in compression you gain so within limits a boost from lets say 8:1-11:1 would give you about an 11% boost in torque over the whole rpm range, that could easily mean a 30-50hp gain on a 350-406 chevy engine, and keep in mind that if your going to buy new high compresion pistons and get the assembly reballanced you should probably get a stroker crank and gain displacement and compression while your at it, example

a 350 with flat top pistons with 8:1 cpr might gain 20hp by going to 10:1 cpr but by going to a 383 crank and 10"1 cpr a 40hp gain is more likely with no other changes and ALL other changes made later will also work better with the greater displacement (remember 1.25 PER CUBIC INCH)more displacement normally means more power all other factors remaining the same!

 

here this will give you new guys some basic info

 

 

cams

 

http://www.newcovenant.com/speedcrafter/tech/camshaft/1.htm

(theres 10 lessons ., read them all)

 

http://www.howstuffworks.com/camshaft1.htm

intakes

http://victorylibrary.com/mopar/intake-tech-c.htm

 

compression,

http://victorylibrary.com/mopar/cam-tech.htm

 

oil

http://www.micapeak.com/info/oiled.html

 

pistons/rods

http://www.babcox.com/editorial/us/us20114.htm

 

http://victorylibrary.com/mopar/rod-tech-c.htm

 

http://www.engr.rutgers.edu/~llongo/8K.html

 

headers

http://www.geocities.com/MotorCity/Track/6992/vizard.html

 

http://www.ssheaders.com/header.htm

 

hp/torque

http://www.carcraft.com/editorial/article.jsp?id=868

 

basics

An internal combustion engine burns a mixture of fuel and air in an enclosed space. This space is formed by a cylinder that's sealed at one end and a piston that slides in and out of that cylinder. Two or more valves allow the fuel and air to enter the cylinder and for the gases that form when the fuel and air burn to leave the cylinder. As the piston slides in and out of the cylinder, the enclosed space within the cylinder changes its volume. The engine uses this changing volume to extract energy from the burning mixture.

 

The process begins when the engine pulls the piston out of the cylinder, expanding the enclosed space and allowing fuel and air to flow into that space through a valve. This motion is called the intake stroke. Next, the engine squeezes the fuel and air mixture tightly together by pushing the piston into the cylinder in what is called the compression stroke. At the end of the compression stroke, with the fuel and air mixture squeezed as tightly as possible, the spark plug at the sealed end of the cylinder fires and ignites the mixture. The hot burning fuel has an enormous pressure and it pushes the piston strongly out of the cylinder. This power stroke is what provides power to the car that's attached to the engine. Finally, the engine squeezes the burned gas out of the cylinder through another valve in the exhaust stroke. These four strokes repeat over and over again to power the car. To provide more steady power, and to make sure that there is enough energy to carry the piston through the intake, compression, and exhaust strokes, most internal combustion engines have at least four cylinders (and pistons). That way, there is always at least one cylinder going through the power stroke and it can carry the other cylinders through the non-power strokes.

 

http://www.howstuffworks.com/engine.htm