john73bb

For street use, is there much advantage to going to the bigger (2.19,1.88) valves on my big block?

I am putting in a Crane 133941 cam with 272/284 duration and .515/.510 lift, and am doing a simple pocket port to the heads, but am not planning to change out my exhaust for some time, or perhaps ever. I am using fuel injection.

Desktop Dyno shows a moderate increase of about 25HP and 3-5 lb-ft of torque, which doesn't seem worth the $400-450 cost to make the conversion, but perhaps there is more to the story . . . . . :confused:

Any recommendations?

ddn

I think going to bigger valves is probably one of the single biggest things you can do. I've heard quotes of 50-80HP. Obviously it depends on cam and how much everything else flows.

norvalwilhelm

Going to the bigger 2.19 and 1.88 valves allows you to have totally new seats. If the stock valves have had a few valve jobs and are getting sunk in the head then this is a easy way to start out fresh . I would go for it. Also look at the quides while it is out and replace them if at all in doubt.
You do not need the hardened exhaust seats installed in the old heads. As long as you are not continually pulling with the motor it will survive fine with normal soft seats.

mountainmotor

Your stock exhaust port flows .580 lift.With the cam you have chosen,the stock exhaust manifolds you will use it is a waste of time,money and effort in your application.Do some intake bowl work if you want and polish the exhaust port.Your rear tires will be none the wiser :)


[Modified by mountainmotor, 2:22 PM 2/5/2002]

john73bb

Thanks for the inputs. My engine has had only one valve job done on it, so I don't need new seats. I had hardened valve seats put in when I had the valves done before (5K miles ago), so if I went with larger valves, I would have to go with hardened seats again (the hole to hold the current seats is too big not to). I guess I will stick with my current valves, and if I ever decide I just gotta have more power, and coincidentally also have a bunch of spare cash sitting around, I will pull the heads, do a real porting job, put in bigger valves, put on headers . . . . . . . . .

norvalwilhelm

We have a flow bench here at work and with the large 1.88 exhaust valves and a ported and polished exhaust port the best we could get from a rectangular port head is 205 at .500 lift. It did not improve at .600 or .700 lift so any cam lifting higher then .500 is just of no use. Stock intakes 2.19 can be made to flow 326cfm at .600 with alot of work. This is rectangular port heads. These heads will not work below 5000rpm on the street but will go to 7500rpm.

bence13_33

Norval:
I remember reading in my "How To Hot Rod Big Block Chevys" book about the bigger 2.19/1.88 valves. They highly recommended changing from the 2.06/1.72s to the larger 2.19/1.88s. The book said that by changing the valves it increases your top end capability and did so without compromising ANY low end power. So it seems to me that you have nothing to lose and everything to gain by changing to the larger 2.19/1.88 valves (which is what I have in my heads). They did mention that some low end was lost when changing to the bigger 2.25 intake valves though. Just something I thought I should point out. After all your engine is only going to be as good as your cam and heads....if you are going to put big bucks into an engine here is where you should start.

Injected

Depending on chamber design(closed, semi, or open chamber) moving up to a bigger valve can actually hurt your performance due to valve shrouding. I would stay with the smaller valves, I get 600hp/tq out of 454's with small valve closed chamber heads. As mentioned earlier I would get some bowl work done, IMHO it's a better return for your money. If you do, make sure they know what you will be using it for, hog out those heads like Warren Johnson and all you'll have is table fodder.
As I'm sure you're aware of, unless you throw a set of headers on it your
killing the other engine work.

Greg