Oil pressure vs lifter pump up
- Thread starter 388dart
- Start date
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340mopar
Sorgermotorsports
Are you saying that your lifters are bleeding down at 60psi? It should only take about 5psi - 10psi to get a lifter to pump up and take up the clearance in a motor as long as the lifter pre-load is right and you have a reasonable valve spring rate.
340mopar
Sorgermotorsports
There are exceptions to every rule but valve springs are the main component in the valve float department. What happens with weak valve springs and hydraulic lifters is when the valves start to float it makes a clearance in the valve train then the hydraulic lifters being their purpose is to take up clearance, will try to make up this clearance. Now the lifter, until it bleeds down a little will hold your valve open. This is why some people blame the lifter when really it was doing it's job and the valve springs are the ones that needs to be replaced.
Chuck
Chuck
moper
Well-Known Member
Yes, oil pressure can help. A mentor of mine ran Stock Eliminator witha Ford 351 Cleveland. It was a hydraulic cam engine factory, so he had to keep it. But he ran 130psi oil pressure. The car set several NHRA national records that way. He'd drop the clutch at 6800, shifting at 7200. The car ran 11.teens witha 4sp. Also, the only oil filters he found that could withstand that pressure were OEM Ford. The others would pop the cans..lol. But, if you have sloppy lifter bores, a higher pressure may not be the fix. Poor geometry and spring choice and setup have a lot to do with valve float too.
longarm
Car sold back to original owners
i'm curious moper,
what was the reason for running so much
oil pressure?
what was the reason for running so much
oil pressure?
D-mailman
Well-Known Member
Good topic. higher oil pressures from hi-volume/pressure oil pumps will/can reduce the effectiveness of the 'bleed-down' (Rhoads type) lifters. Just wanted to throw that out there. Terry.
perfacar
Well-Known Member
hi, the 351 C ford needs that kind of pressure. mopars don't. 60 # of pressure will hold the lifters. one item to consider is, run zero preload, this way, it's like having a solid lifter in motor, this is an old stocker trick from way back. in the old 283/ 327 chevs, was worth bout 500 or more RPM, and no valve floting.
perfacar said:
I tried this last summer running minimal (2-3thou) preload as I am running the snap ring type hydraulic lifters.
When I had the heads off and checked the lifters I found that nearly all (but not all) the ends of the snap ring were curling upwards - and possible ready to squeeze out of its locator. I attributed this to having less than what I had as an initial preload - maybe at high rpm and thus may have ended up with with a "hammering" effect on the snap ring.
Any thoughts?
340mopar
Sorgermotorsports
As I stated before if your valves springs are weak and your valves start to float your lifters are taking up the clearance to the point were the lifter tops out on the snap ring. The speed trick that perfacar is talking about works because since the lifters are already topped out they can't take up anymore clearance that might be added by weak valve springs. Since the lifters can't take up anymore clearance the lifters won't hold help hold the valves open. Bottom line is the springs are supposed to return or keep the valve train in check, you need better springs.
Chuck
Chuck
63dartman
Well-Known Member
Why not just switch to a solid cam? I ask this because I am thinking about swapping to a solid just for the same reason. I find it hard to believe that hydraulic lifters don't bleed off a little at the higher RPM's I may be wrong as usual
I know that the springs, geometry, preload, rocker orientation, and a slew of other calculations add into the big picture. I just like the idea of the solid cam.
No room for mistakes with the solid though, I would imagine that everything better be right the first time or you"ll be buying new parts pretty quick.
I know that the springs, geometry, preload, rocker orientation, and a slew of other calculations add into the big picture. I just like the idea of the solid cam.No room for mistakes with the solid though, I would imagine that everything better be right the first time or you"ll be buying new parts pretty quick.
perfacar
Well-Known Member
hi, few years ago, a fella with a hydraulic cam in a stock eliminator motor, tried a cheater lifter, a hyd lifter with out the guts, in essence a solid lifter.
NHRA decided to start checking for hyd lifters, so they were removed, and a set of speed pro, anti pump lifters were installed, the motor turned same RPM and MPH as the solid lifters did. speed pros. are ran at .004 lash. that indicates, the hyd lifter wasn't bleeding down at RPM. by the way, RPM was 7100 ,both cases. a solid cam is better, true.
NHRA decided to start checking for hyd lifters, so they were removed, and a set of speed pro, anti pump lifters were installed, the motor turned same RPM and MPH as the solid lifters did. speed pros. are ran at .004 lash. that indicates, the hyd lifter wasn't bleeding down at RPM. by the way, RPM was 7100 ,both cases. a solid cam is better, true.
moper
Well-Known Member
longarm said:
As was said. The cam had a wild ramp speed, and he had to run factory design and weight lifter. The std hyd lifters would compress at high rpms. He didnt tell me exactly where the threshold was. But I know he spun that engine 7200 at the lights. It made 485hp as I recall on the dyno. That's a .030 over 351 Cleveland, 9.5:1 compression. Stock crank, stock rods, stock pistons (ok we all know "stock" is a relative term in NHRA), stock heads and valves, stock iron intake and stock 4?? cfm Autolite Holley with a factory lift cam. Teh duration was super secret as were the lobe designs. But the thing looked like a roller cam..lol. I do know the oil system was basically stock save the high pressure he ran. I like to see a max pressure of 65-70 psi. Any more than that and you're just using hp to create heat.
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