Cam and valvetrain longevity....??? low duration high lift...
10-04-2016, 06:18 PM
#1151
Registered
Reminds me of the shop that replaced the seats and rebuilt my old heads. Install heights all over the place. However, those were 15 year old castings, that been thru a few hands. If the install heights varied that much on a new set of heads that never been cut, I would think that is , well, not so great. At the very least, even if the seat height varies that much, or like sutphen said, the casting itself having different heights of the spring perch, you would think that someone would go thru them, record all install heights with the retainer and locator installed, and shim accordingly, so at least, all the springs have equal pressures. .040 variance, is alot!
Any good shop worth its weight, would blueprint a set of heads so to speak, and check each valve. Not check one valve, throw 16 springs in there, and call it good.
Any good shop worth its weight, would blueprint a set of heads so to speak, and check each valve. Not check one valve, throw 16 springs in there, and call it good.
10-04-2016, 06:47 PM
#1153
Registered
I have a question.
What do you guys think , is ideal spring pressures, for a hydraulic roller, pleasure application, that sees lots of idling time, and won't be turning more than 6000 RPM, with 11/32 valves. Naturally aspirated?
What do you guys think , is ideal spring pressures, for a hydraulic roller, pleasure application, that sees lots of idling time, and won't be turning more than 6000 RPM, with 11/32 valves. Naturally aspirated?
10-04-2016, 06:54 PM
#1155
Registered
I ran my MK cams for one season then pulled them due to abnormal lobe wear and the engines didn't make the power I was expecting. They kinda went flat after 5000 rpms.
Motors
605 inch blower motors with brodix bb3 xtraO heads.
Cam
254/262 at 50 duration 705/680 lift
The cam doctors numbers were farther off than what I would have expected. Cam doctor showed the cam to be larger by a few degrees at 50.
Motors
605 inch blower motors with brodix bb3 xtraO heads.
Cam
254/262 at 50 duration 705/680 lift
The cam doctors numbers were farther off than what I would have expected. Cam doctor showed the cam to be larger by a few degrees at 50.
10-04-2016, 06:56 PM
#1156
Registered
From crane cams. Thoughts on this ? I looked up the cam card on the "651" crane cam. Their recommended seat pressure is 132lbs, open pressure, 413 lbs.
3) HYDRAULIC ROLLER CAMS require higher spring seat pressures to control the heavier roller tappets and the more aggressive opening and closing rates available to roller cam profiles.
a. Small Block applications: 120-145# seat pressure
b. Big Block applications: 130-165# seat pressure
4) HYDRAULIC ROLLER CAMS use higher open pressures to control the high vertical opening inertia of the heavier roller followers.
a. Small Block applications need at least 260# for general driving applications up to 4000 RPM.
b. Moderate performance small block applications like 300-360# open.
c. Serious small block applications can tolerate 400-425#* open pressures and still expect
"reasonable" valve train life when top quality springs, pushrods, and lubricants are used.
d. Big Block applications need at least 280# for general driving applications up to 4000 RPM.
e. Moderate performance big block applications like 325-375# open pressure.
f. Serious big block performance applications can tolerate 450#* open pressure and still expect "reasonable" valve train life when top quality springs, pushrods, and lubricants are used.
*Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Crane hydraulic roller and solid roller tappets are made from 8620 bearing grade steel to withstand the stresses of high-performance use. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads.
Open Pressures need to be high enough to control the valve train as the lifter goes over the nose of the cam. Ideally, the minimum amount of open pressure to eliminate or minimize valve train separation is desired. Any excess open pressure only contributes to pushrod flex,
which can aggravate valve train separation.
3) HYDRAULIC ROLLER CAMS require higher spring seat pressures to control the heavier roller tappets and the more aggressive opening and closing rates available to roller cam profiles.
a. Small Block applications: 120-145# seat pressure
b. Big Block applications: 130-165# seat pressure
4) HYDRAULIC ROLLER CAMS use higher open pressures to control the high vertical opening inertia of the heavier roller followers.
a. Small Block applications need at least 260# for general driving applications up to 4000 RPM.
b. Moderate performance small block applications like 300-360# open.
c. Serious small block applications can tolerate 400-425#* open pressures and still expect
"reasonable" valve train life when top quality springs, pushrods, and lubricants are used.
d. Big Block applications need at least 280# for general driving applications up to 4000 RPM.
e. Moderate performance big block applications like 325-375# open pressure.
f. Serious big block performance applications can tolerate 450#* open pressure and still expect "reasonable" valve train life when top quality springs, pushrods, and lubricants are used.
*Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Crane hydraulic roller and solid roller tappets are made from 8620 bearing grade steel to withstand the stresses of high-performance use. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads.
Open Pressures need to be high enough to control the valve train as the lifter goes over the nose of the cam. Ideally, the minimum amount of open pressure to eliminate or minimize valve train separation is desired. Any excess open pressure only contributes to pushrod flex,
which can aggravate valve train separation.
10-04-2016, 06:58 PM
#1157
Platinum Member
Platinum Member
I ran my MK cams for one season then pulled them due to abnormal lobe wear and the engines didn't make the power I was expecting. They kinda went flat after 5000 rpms.
Motors
605 inch blower motors with brodix bb3 xtraO heads.
Cam
254/262 at 50 duration 705/680 lift
The cam doctors numbers were farther off than what I would have expected. Cam doctor showed the cam to be larger by a few degrees at 50.
Motors
605 inch blower motors with brodix bb3 xtraO heads.
Cam
254/262 at 50 duration 705/680 lift
The cam doctors numbers were farther off than what I would have expected. Cam doctor showed the cam to be larger by a few degrees at 50.
10-04-2016, 07:00 PM
#1159
Registered
Are bobs cams designed for a .700 lifter wheel, a .750 lifter wheel, or what? Does anyone know the answer to that? Or has that ever been a question? While a minute change, the lifter wheel diameter, does play a role in the actual cam timing. Not a ton, but, I mean we are talking about super secret squirrel custom cams, I would think that would be a consideration. The johnson lifter has a .700 wheel, morels, PBM, lunati, howards, upper end hyd rollers use a .750 wheel.
