mine were set up @ 320 at the seat.
What are those springs rated @ full open?? And what was the installed height? We run 225 on the seat @ 1.950 which seems to be plenty...Why so much seat pressure?? ..............MP
PS The lifters are over 25 yrs old, (Engle rollers w/ a rev kit) and we've never had a valve train failure......
I can't remember what it was at full lift. It was alot. I just remember the seat pressure because I used to check them all the time. I'd have to dig up the build sheet to find out installed height and pressures at full lift.
Don't ask my why. That's the way Clay Smith set them up. George want's to make sure they close and the roller stays in the cam I guess.
That big spring pressure is why I'm running a flat tappet in the station wagon.
I'd like to hear CStrub's take on spring pressures and these big lift rollers that people seem to be running in lake boats.
He definately used way too much spring for a low RPM boat motor and i believe that is the reason for the quick failure. It was a result of a Pro Stock guy building a pleasure boat motor. I like the Isky 9945 springs which are like 240 @ around 2.050" and 550 ish over the nose. I only have 15 hrs on this motor so the jury is still out. Tell us more about the motor with 25 year old lifters!! Sounds very interesting.
Craig
The big pressures are not needed on the open side. Moderate pressure is needed on the closed side to control bounce. Harvey said this years ago but no one seemed to listen. Open pressure were exceeding 1000#'s in some applications then with rocker arm ratio they could exceed 2100#. Top PS teams started hiring Cup guys and they brought their technology. Spring pressures have come down some on the seat pressure, but have come down dramatically on the open side. I have been told that 40 to 100HP has been found in "fine tunning" of the valvetrain on these engines.
I feel for most of these hot BBC set ups with lighter valvetrain components that seat pressure of 240ish and open loads of 600#'s are suffecient. Now camshaft will play a part. I would also recommend to those running 3/8" diameter pushrods to go to a single taper style. These will greatly reduce pushrod flex at max lift and the "rebound effect that happens as the lift exceeds max lift and starts its journey down. There is easy HP in this fix. I like the 7/16" to 3/8" stuff.
Chris
Yes the cam, lifters, rev kit, pushrods are from 1977. This is a BBC in a Pro Stock 77 Revenge. Over the years Engle has changed their rev kit springs and in the early 90s they gave us the newer version. Periodic maintaince has discovered a couple of "not as good as the others" rollers and Engle replaced them. Also a couple of poppets had tightened up, they replaced them also. In Sept. this year they supplied some newer valve springs, which woke the engine right back up, and Air flow had changed out the retainers during the last head re-work.........All and all, the original Engle set up has lasted without a single valve train failure. This year alone we ran 26 heats of 5 miles each and with the comp cams girdle I only found 2 or 3 valves had changed .001 or .002. This cam/lifters has out lived several engines that broke rods, 4 bolt main caps, and generally tried to fly apart. We run this motor 7250-7700, wringing its neck all the way. You can't beat Engle for customer service, although we haven't spent $200 there in the last 15 years........When I was talking to Mark Engle about the valve springs he seemed to think the long life was due to the rev kit keeping everything in contact...A note, when we had the heads off for springs, I pulled each roller and ran them over my hand looking for rough or un even rollers, not a one!!!! Engle now supplies crowler lifters with their roller kits, and rev kits seem to be a thing of the past, although he said he could probably dig one up for our backup motor, and even bring us into the 90s in cam design. But you know what everyone says about fixing something that isn't broke...........MP
It's not polite to beat those guys with old parts.
Surpised you run a rev kit. But if it works for you I would not change a thing for sure.
The big pressures are not needed on the open side. Moderate pressure is needed on the closed side to control bounce. Harvey said this years ago but no one seemed to listen. Open pressure were exceeding 1000#'s in some applications then with rocker arm ratio they could exceed 2100#. Top PS teams started hiring Cup guys and they brought their technology. Spring pressures have come down some on the seat pressure, but have come down dramatically on the open side. I have been told that 40 to 100HP has been found in "fine tunning" of the valvetrain on these engines.
I feel for most of these hot BBC set ups with lighter valvetrain components that seat pressure of 240ish and open loads of 600#'s are suffecient. Now camshaft will play a part. I would also recommend to those running 3/8" diameter pushrods to go to a single taper style. These will greatly reduce pushrod flex at max lift and the "rebound effect that happens as the lift exceeds max lift and starts its journey down. There is easy HP in this fix. I like the 7/16" to 3/8" stuff.
Chris
Controling valve bounce has become a real big issue. If any of you want to pick up a considerable few more hp and experience a much smoother and more responsive motor, tighten your valve lash up to .016/.018, or even .014/.016. What's been found on spin-tron testing is that the excessive lash settings increase the speed at which the valve hits the seat. In some cases an extra .010 of lash doubles the speed at which the valve hits the seat. Valves can bounce as much as .030" in excessive conditions, and anything over .020 is asking for trouble. Valve bounce = lost power, broken valves, radical power variations. If you've ever looked at the power curve on a dyno sheet, you probably noticed there were dips in the curve as rpm increased. This is not due to manifold design, as a lot of guys might tell you. It may be true around peak torque, but as rpm climbs, it's caused by valve bounce.
An entire book could be written on valve bounce and it's effects. This is why I prefer Comp Cams products. They have a full time cam designer and a full time spin-tron operator.
The Comp Cams 3/8 dia. X .065 wall push rods help control valve bounce as well, as they have a higher frequency.
Controling valve bounce has become a real big issue. If any of you want to pick up a considerable few more hp and experience a much smoother and more responsive motor, tighten your valve lash up to .016/.018, or even .014/.016. What's been found on spin-tron testing is that the excessive lash settings increase the speed at which the valve hits the seat. In some cases an extra .010 of lash doubles the speed at which the valve hits the seat. Valves can bounce as much as .030" in excessive conditions, and anything over .020 is asking for trouble. Valve bounce = lost power, broken valves, radical power variations. If you've ever looked at the power curve on a dyno sheet, you probably noticed there were dips in the curve as rpm increased. This is not due to manifold design, as a lot of guys might tell you. It may be true around peak torque, but as rpm climbs, it's caused by valve bounce.
An entire book could be written on valve bounce and it's effects. This is why I prefer Comp Cams products. They have a full time cam designer and a full time spin-tron operator.
The Comp Cams 3/8 dia. X .065 wall push rods help control valve bounce as well, as they have a higher frequency.
I agree with what has been said above except the last sentence. . . the lighter wall stuff does not prevent pushrod deflection, it increases it. There was a PRI mag issue about pushrods last year and the heavier wall stuff was talked about along with the single and dual taper stuff. Now this is not needed for your average 500HP engine. But for those of you pushing the limits a std 3/8" diameter or 7/16" diameter pushrod will not do what a taper type, heavy wall pushrod will do.
Thanks
Controling valve bounce has become a real big issue. If any of you want to pick up a considerable few more hp and experience a much smoother and more responsive motor, tighten your valve lash up to .016/.018, or even .014/.016. What's been found on spin-tron testing is that the excessive lash settings increase the speed at which the valve hits the seat. In some cases an extra .010 of lash doubles the speed at which the valve hits the seat. Valves can bounce as much as .030" in excessive conditions, and anything over .020 is asking for trouble. Valve bounce = lost power, broken valves, radical power variations. If you've ever looked at the power curve on a dyno sheet, you probably noticed there were dips in the curve as rpm increased. This is not due to manifold design, as a lot of guys might tell you. It may be true around peak torque, but as rpm climbs, it's caused by valve bounce.
An entire book could be written on valve bounce and it's effects. This is why I prefer Comp Cams products. They have a full time cam designer and a full time spin-tron operator.
The Comp Cams 3/8 dia. X .065 wall push rods help control valve bounce as well, as they have a higher frequency.
How much sooner did the exhaust valves fail from not being on the seats as long? By reducing the time the valve is on the seat the exhaust valve temp is going to be higher. I could see this for a drag motor but not for a indurance motor. I would just switch to the the beehive springs comp makes. They cost more but they control bounce better and the valves get to stay seated longer. Just my .02 cents worth
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