I know we've had this conversation before, but...

clutchdust

Millionaire Playboy
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I have almost made up my mind. On my new-to-me AFR190 heads, I am planning on running 1.6 rockers which will put the lift right at the advertised limit for the valves in these heads. I've been going back and forth on upgrading the springs or just adding a "rev kit". Some of you have said to do the springs, but that will involve cutting new pockets in addition to new springs and retainers, quickly pushing this budget build close to new head territory.
So I'm thinking of verifying I do not have coil bind at the maximum lift, and if that's true, just using the rev kit to provide that ever so slight additional pressure to prevent valve float. My reasoning is simple, the valve spring has to dampen and reverse the momentum of the valve, rocker arm, push rod and lifter. If the original springs are close to that limit, eliminating or at least reducing the lifter mass the valve spring sees by the installation of a rev kit should noticeably reduce the overall mass/inertia that valve spring has to counteract.
I do plan on dynoing the engine once it is assembled to see where I make peak power so I know the RPM range of the engine. Plus that will tell me if I'm getting valve float also. But with my cam, I would expect peak power somewhere between 5500-5800 and it to drop like a rock at anything greater than 6200.
So what say you (again)?
 
What about just using springs that match your cam? Save the expense of a rev kit that's going to add mass to the valve train by design. And unless you know the total history of the springs that are on the heads now, you're going to need to pull them and check pressure anyway- and even that's no guarantee one or more isn't going to pop the first or ?? time you wind it up. New springs that match the cam you get the correct seat pressure, height, and bind specs by default. Not saying a new spring won't fail too, but at least you have some knowledge of their history.
 
Tim, in a way, that's kind of what I'm doing. The factory springs are rated to handle my cam, just barely, but since these are used heads and I don't have a certified history on them, I'm playing it safe. The other thing I haven't had satisfactory clarification, and the part that worries me, is that I believe that roller lifters have to have more mass, by design, than their flat tappet counterparts. Aside from the potential for coil bind of the spring at peak lift, that additional mass must be accounted for either by the valve spring or the spring in the rev kit. My thinking is that having a spring dedicated to the lifter reduces the amount of mass the valve spring must counteract. Besides, how does a rev kit add mass to the valve train? I actually think it makes far more sense to have a spring counteract the force of each individual component but it's not realistic to have a spring for the lifter, then a separate one for the pushrod, then one for the rocker arm and finally a valve spring. A rev kit in concert seems to be the best compromise, but all this is just my theoretical myopic view of the situation.
 
IF the springs match the cam, then the added mass of the lifter is (or should be) accounted for.
Old school, the rev kits allowed higher RPM by adding the spring compression to the lifter so it didn't bounce on the cam- added feature was the lifter couldn't pop out of the bore if something broke above it. But we're also talking about spinning an early SBC in the 10k ranges in those days too.
I've got a 350 in the basement right now with GM's 3927140 cam and the 3927142 springs. Old time stuff now. I've spun it to 8k an unknown number of times and never had any valve train problems at all. Even Ol' Red- matched up stuff and it's been to 8k a couple of times. (that's why it's got a scattershield- clutch sticks to the floor up there).

Figure out where the spring you have stack, and then adjust accordingly.
 
IF the springs match the cam, then the added mass of the lifter is (or should be) accounted for.
Old school, the rev kits allowed higher RPM by adding the spring compression to the lifter so it didn't bounce on the cam- added feature was the lifter couldn't pop out of the bore if something broke above it. But we're also talking about spinning an early SBC in the 10k ranges in those days too.
I've got a 350 in the basement right now with GM's 3927140 cam and the 3927142 springs. Old time stuff now. I've spun it to 8k an unknown number of times and never had any valve train problems at all. Even Ol' Red- matched up stuff and it's been to 8k a couple of times. (that's why it's got a scattershield- clutch sticks to the floor up there).

Figure out where the spring you have stack, and then adjust accordingly.

And each time you had to buy a new gas tank, because you sucked the fuel out SO fast they collapsed from air pressures.....;):bounce:
 
And each time you had to buy a new gas tank, because you sucked the fuel out SO fast they collapsed from air pressures.....;):bounce:

Not quite, but I have discovered that most gas station pump's won't quite keep up at idle.
:hissyfit:
 
Tim, in a way, that's kind of what I'm doing. The factory springs are rated to handle my cam, just barely, but since these are used heads and I don't have a certified history on them, I'm playing it safe. The other thing I haven't had satisfactory clarification, and the part that worries me, is that I believe that roller lifters have to have more mass, by design, than their flat tappet counterparts. Aside from the potential for coil bind of the spring at peak lift, that additional mass must be accounted for either by the valve spring or the spring in the rev kit. My thinking is that having a spring dedicated to the lifter reduces the amount of mass the valve spring must counteract. Besides, how does a rev kit add mass to the valve train? I actually think it makes far more sense to have a spring counteract the force of each individual component but it's not realistic to have a spring for the lifter, then a separate one for the pushrod, then one for the rocker arm and finally a valve spring. A rev kit in concert seems to be the best compromise, but all this is just my theoretical myopic view of the situation.

You're overthinking things. You have relatively low flowing heads 190cfm. You're not going to be able to get much rpm out of that engine. Just put new quality springs in that fit and be done with it. How much is the dyno going to cost 500-1000?
 
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I imagine I might be making things more complicated than necessary (also thinking of using stud girdles for no other reason than just because) but I would like this engine to pretty much survive a nuclear blast. If it doesn't create additional risk, I'm considering it.
 
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