Valve ?

[Fathead Racing]

I want to put BB chevy valves in my 690 heads. What valve do I order? Do I order Stock BB Chevy length? 3/8" stem? Are the Exhaust and intake the same length? 2.19" intake / 1.72" exhaust right? I want to put BB valves in so I have a better selection of springs. What is the stock length of the 409 intake and exhaust valve? What is the length of the BB Chevy int/exh valve?.

 

[MRHP]

I believe the bbc valves are .100 longer. These valves will give you a lot more choices with your valve combonation. I am running a 2.250 1.80 if I recall correctly. Aubrey helped me with my valves and springs. Give him a holler. I am sure he can shed some light on the subject.

 

[MRHP]

oops

You will also need longer pushrods to compensate for the increased length. If you run roller rockers you will probably need valve cover spacers as well. I did.

 

[Ronnie Russell]

Ray, If you are not stuck on using big block valves, you can use Isky 3105 D springs and use std. lenght valves. You can confirm with Curt Harvey or Jack Gibbs. My machinist called today who is assembling my heads and said " man, these are kick-as* springs!" It is a tough decision because there are many opinions. Good luck

 

[Fathead Racing]

Solid roller.

Thanks guys for the quick answers. The problem is not that I can't find good springs for a flat tappet cam , although it is a hassle with the short 409 valve. I will be running a solid roller in this "phase I" engine and I am afraid I won't be able to find a suitable spring if I use the short 409 stock valve! What's out there for us solid roller , big spring pressure guys? I will be using the stock 409 rods and will limit rpms to 6200 rpm because of this. Without checking I think I will need spring pressures well over 350 lbs open and 180/220 on the seat, maybe more? Wazzup Aubrey? I was going to replace the valves with stock size also. Should I step up to a larger valve size??? Lift will be in the neighborhood of .580"

 

[Ronnie Russell]

Ray, please disreguard my suggestion. Solid roller will definitely require longer valves and springs.

 

[SS425HP]

springs

The Isky 3105-D spring is the one I use. I have a flat tappet cam, but all else is there like yours, Ray. Lift and duration are near the same. This last set of springs I installed at 1.800 height. I use the retainer Curt sells, which gives more installed height availability. It will turn 7000 with no trouble. Seat is 120, open 350 if I remember right. As Ronnie said, they are good springs. One coil with a flat dampener inside. And they don't break the bank. I'm using SS valves I got from Curt. Not sure of the length, but probably 409 length.
A roller cam might need more pressure. I don't know as I have never run a roller cam. Always used flat tappets. As was said, using longer valves will need longer push rods, too.

Fred

 

[CDNpontiac409guy]

Fat, there's no worry with .580" lift. Through a careful selection of retainer, and a slightly "sunk" valve ( by-product of grinding seats ), as Fred said, near 1.80" installed height COULD be possible. I don't think 120 lbs is enough on the seat for that lift and 7000 RPM... The factory was 135" with .518" lift.
The only reason my Stocker needs this ridiculous 250+ pounds on the seat, is because of the OUTRAGEOUS ramp on the cam lobe.

just my thought on it

 

[Fathead Racing]

Aubrey/Roller lifters?

It's my understanding that with the roller lifters stock length pushrods would not be suitable anyway. I will contact Comp Cams for spring pressure recomendations. Aubrey, I read your response as, I can use the stock lengnth valve with my roller cam and still find a quality spring with the correct seat/open pressures?????

 

[JimKwiatkowski]

Off Subject

Ray,are you working in your new garage?

 

[dq409]

Ray, Should be no problem to sure stock length valves with your roller combo.
I`m running a 644 lift with my roller with no problems !!! ,,dq

I`d have to look and see what spring I`m using,,, CRS !!!!

 

[MRHP]

beehive

You could also try a beehive spring with a stock valve. The oval wound wire spring and the tapered design afford more lift with the same installed heigth. Try comp cams, I believe they have quite a selection.

 

[CDNpontiac409guy]

Yes Fat, I think it would be fine.
Again... there are as many opinions as there are members . Mine is only one.