r0nin89

Alright so I have a pretty hot 350 sitting on my stand waiting for my drop. Its about 300hp and I'm hoping to bring it up to 350 without buying new heads. They are stock heads ported a polished and completly rebuilt at my machine shop. The car already has a hot roller cam and edelbrock intake with 9:1 compression. Will upgrading to roller rockers yeild any HP without increasing my cam or is it only to allow a larger lift?

Also does anyone have some general info on valve springs and rocker arm upgrades? I really dont know what I am looking at as far as diameters and pressure of springs, just that the right combo will yield more HP.

zz4monte

1.5 roller rockers make 2-7hp more than non-rollers.Not much power is gained from a roller swap.Most of the increased power comes from a higher ratio rocker 1.52,1.6 etc.I am not sure about the valvesprings or what type you have.1.6 are usually worth around 8-15hp from my experience. What size cam and heads are you running right now?350hp is not hard to get from a 350 with stock or ported heads and a bigger cam.Your valvesprings will have to be checked for clearence if you go to 1.6 rollers.This is a common upgrade when people don't want to change the cam but what a little more power.

r0nin89

I dont know the exact numbers on my cam but I know its hot. I beleive my machinist said it was something like .460 lift and that was the only number he gave me. So whats the difference between changing rockers and rocker ratio?

Klortho

I really hate to say this, but .460 isn't that big of a cam. It's just a shade bigger than the stock cam in my LT1.

The stock lift cam in my 5.0 Mustang was .444

You might want to find out the complete specs on the cam with duration and lsa (lobe seperation) that way people can chime in to tell you which way would be good to go.

Also you may want to find out if it's domed pistons, dished pistons, flattop pistons and if they are flycut as well which will also help determine how much rocker you can put in whether 1.52, 1.6, 1.7.

Changing the rocker ratio increases valve lift, say the .460 your machinist gave you is on a 1.52 rocker, will be more with a 1.6 rocker.

r0nin89

Ok that brings things into perspective for me then! I guess I am gonna pick up a new cam then. What do you suggest to get 350hp out of an already 300hp motor?

Klortho

Do you know that the motor is a 300hp motor? If it hasn't been attached to an engine dyno and run, I wouldn't belive that the motor put out 300hp until I saw some numbers.

r0nin89

Now but he said based on everything in it and the port and polish he did on the heads its 300hp

F-BIRD'88

What is the casting number on your heads? (look under valve cover)

r0nin89

I'll get em tomorrow been busy.

booboosean

If you're running a roller cam, might as well run a set of roller rockers......especially for the cost these days. If you increased the rocker ratio to 1.6, you would increase your gross lift from .460 to .491 (assuming a .307 cam lift). That's a pretty big increase. Be sure to check piston to valve clearance at lifts above .500. Not to mention, the roller rockers will do away with a ton of heat and friction.

Just my 2 cents,
Boo.

nelapse

iTrader: (17)

Yeah, I am not thinking you are going to get that thing to 350 hp with that set up. Not even 300 . What kind edelbrock intake is that? What carb? Headers? Exhaust? Look at my setup... thats maybe 300-350 hp and my comp ratio is higher etc... time for a reality check..

r0nin89

I dont have a carb for it right now. I know that the intake is edelbrock but i do not know which model. It seems to just be the performer style one but I could be wrong. I got everything when i bought the motor. My plans for the future are to purchase a cam so I KNOW the specs for sure and do 1.6 roller rockers.

No offense but I have a machinist in the range of 30 years experience telling my its a 300hp motor and to be quite frank I beleive him...

zz4monte

Stock heads and a aftermarket cam will put you in the 300hp range as long as you have good induction and exhaust on a motor.There is nothing not to beleive in what your saying its just that you need to give us better info on heads,cam and intake.Here is a combo that many have built and makes 370+HP.

350
vortec heads 9:1 comp.
Comp cams extreme energy 268H 224 230 dur 477 480 lift
Performer RPM intake
Full exhaust with headers
and a good short block

Thats all you need nothing special.No race heads or Huge cams.350HP is easy to make!!!!!!!!!!!

r0nin89

Thank you thats exactly what I needed... I am going to get some vortec heads for my engine. Are there any differences between heads or are all vortecs the same? Should I buy new or look for used?

nelapse

iTrader: (17)

This thread is silly, now we have people thinking they have 370hp due to a cam and vortec heads....

QwkTrip

iTrader: (22)

You mentioned the engine was already equipped with a HOT cam. You can easily make over 350Hp if you have the right cylinder heads. If the engine is truly in the 300Hp range right now, then the cylinder heads are holding you back. No amount of modifications will bring you to 350Hp without changing out the clyinder heads. A good set of heads is the foundation for any high performance engine.

Fortunately, you can easily make a combo that has been documented countless times in magazines to be worth 350Hp. Just add a set of GM Vortec heads and an Edelbrock RPM intake. Make sure the heads are equipped for your HOT cam. The stock heads can't handle that much valve lift. You can order the heads ready to bolt on from Salee Chevrolet or Scoggin Dicky.

QwkTrip

iTrader: (22)

Reality check: A ZZ4 crate engine makes around 370Hp with a HOT cam and Edlebrock RPM intake.

Reality check: You have an LT1 cam and make the power of a stock Corvette LT1 engine. You could benefit from better cylinder heads and dumping the Edlebrock carb.

nelapse

iTrader: (17)

He doesn't have a ZZ4 now does he?
I may have an LT1 cam, but my comp ratio is much higher.

Klortho

Reality Check He also stated that the lift on the cam was .460.....that is not the Hotcam

QwkTrip

iTrader: (22)

You're right. He has multiple threads going on this same topic. I was under the impression he had a HOT cam from the other thread.

QwkTrip

iTrader: (22)

No, but the Vortec heads are just as good or even better. It's an illustration to make the point that a basic engine with Vortec heads and a moderate cam can indeed make 350Hp.

chevyhahha

a chevy 350 with how much hp hahaha i never seen one i been building them for years 255hp peak hp
if you had twin turbos and a super then sure. but your smoking crack and dreaming. chevy them self with 1000s invested in there zo6 with every hi tech and best parts they could make it peak out at 400hp peak. 325hp on brake thats off the wheels to you dummies.

chevyhahha

a chevy 350 with how much hp hahaha i never seen one i been building them for years 255hp peak hp
if you had twin turbos and a super then sure. but your smoking crack and dreaming. chevy them self with 1000s invested in there zo6 with every hi tech and best parts they could make it peak out at 400hp peak. 325hp on brake thats off the wheels to you dummies.

QwkTrip

iTrader: (22)

Maybe some day you'll make 260 Hp and shock the world.

ULTM8Z

With a Chevy 350, you have to actually try to not make 300 hp. Just a basic Edelbrock Perfromer style manifold, a cam with at least 215@.050 intake duration, some inexpensive Vortec heads and a decent exhaust.

Not sure what all the hubbub is here...lol