Lifters for higher spring pressure and moderate RPM
08-30-2010, 09:26 AM
#1
Lifters for higher spring pressure and moderate RPM I don't plan on revving much more than 6500 RPM with my new build, but I do intend to run a lot more spring pressure than a typical 6500 RPM NA build. Would the LS7 lifters be a better choice than the Cadillac racing lifters?...Morel's are another consideration...but I don't actually know if they're any stronger than GM's offerings...a lifter thats a lot lighter to see 8000+ RPM doesn't matter to me, like I said, 6500, MAYBE 6700 RPM is the highest I expect this engine to ever see.
My logic behind this search is boost...boost is pressure...if the engine is running 15 PSI, the back side of a 2" valve has ~6.28" of surface area (figure a little less because the stem takes away a little)...so 15 PSI X 6.2" is 93 pounds of pressure...working directly against the valve spring...granted there's sure to be a wave/surge of pressure on the spring as the valve lands on the seat that an NA setup also won't see...I'd expect them to see more of just a reflection wave up the port from the valve closing...but rather than float the valves under boost at "high" RPM (again, high not really being all that high compared to big power NA setups), I'd prefer more spring pressure...off of boost I guess it will be hard on the lifters, at peak boost, the lifter will see the valve lighter, and probably closer to what an NA setup would see...the engine will spend a LOT more time off of boost than it will in boost (turbo street car)...I'm interested in feedback opinions...more research is better, it's a build I've been working out for a long time, and it's close to coming to fruition, I don't want an oversight on something now to cause me more frustration when it's running.
My logic behind this search is boost...boost is pressure...if the engine is running 15 PSI, the back side of a 2" valve has ~6.28" of surface area (figure a little less because the stem takes away a little)...so 15 PSI X 6.2" is 93 pounds of pressure...working directly against the valve spring...granted there's sure to be a wave/surge of pressure on the spring as the valve lands on the seat that an NA setup also won't see...I'd expect them to see more of just a reflection wave up the port from the valve closing...but rather than float the valves under boost at "high" RPM (again, high not really being all that high compared to big power NA setups), I'd prefer more spring pressure...off of boost I guess it will be hard on the lifters, at peak boost, the lifter will see the valve lighter, and probably closer to what an NA setup would see...the engine will spend a LOT more time off of boost than it will in boost (turbo street car)...I'm interested in feedback opinions...more research is better, it's a build I've been working out for a long time, and it's close to coming to fruition, I don't want an oversight on something now to cause me more frustration when it's running.
08-31-2010, 05:05 PM
#3
STAY away from the Caddys, A few had good luck with them and some had trouble. Morels are awesome!! My uncle runs them on his racing boats that see sustained high rpm. Never seen one fail... The body is way stronger than a LS7. When you set them up make sure lash is dead nuts on because the acceptable range is much narrower than an LS7. .030 is what Morels recomends.
08-31-2010, 06:39 PM
#5
Good to know about the preload on the Morel lifters...I've considered them as well, but I figured most guys are generally looking for high RPM stability and this is different than that...I think I might give them a call and see what they have to say about it too. Thank you.
Last edited by Mike454SS; 08-31-2010 at 06:57 PM.
08-31-2010, 06:47 PM
#7
Mike454SS,
I say go w/ the LS7 lifters & just don't over pre-load them; maybe to .045". The shorter up to recommended pre-load the better. Also, in regards to valve float or valvetrain harmonics, the valve side of the rocker is approx. 150% more sensitive to weight than the lifter side.
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08-31-2010, 06:56 PM
#9
That's all you have to offer is a smart *** comment? We all know what he's looking for, regardless of the mathematical error (pi x r^2 = 3.1415 sq in, not 6.28 sq in). Good news for Mike, cuz' his pressure is already half of what he was considering.
Mike454SS,
I say go w/ the LS7 lifters & just don't over pre-load them; maybe to .045". The shorter up to recommended pre-load the better. Also, in regards to valve float or valvetrain harmonics, the valve side of the rocker is approx. 150% more sensitive to weight than the lifter side.
Mike454SS,
I say go w/ the LS7 lifters & just don't over pre-load them; maybe to .045". The shorter up to recommended pre-load the better. Also, in regards to valve float or valvetrain harmonics, the valve side of the rocker is approx. 150% more sensitive to weight than the lifter side.
When you say the valve side is 150% more sensitive to weight, is that due to the rocker arm ratio or something else? That concerns me more because the boost pressure IS essentially making the valve appear heavier...so with that, 15 PSI...~3" valve surface area, 45 pounds of pressure that I guess should be made up in the spring...or 45 * 150% so 67.5 more pounds to make up with the spring?
I've always liked beehives for their natural dampening characteristics...but a dual spring can do something similar, and offer the added insurance of holding the valve up should one of the 2 springs fail...I'm glad I'm asking questions, but I'm also confusing myself even more.
Last edited by Mike454SS; 08-31-2010 at 07:02 PM.
08-31-2010, 08:01 PM
#11
Yeah man you're right...over stressed at work, got my simple math wrong...thanks for being polite about it though.
When you say the valve side is 150% more sensitive to weight, is that due to the rocker arm ratio or something else? That concerns me more because the boost pressure IS essentially making the valve appear heavier...so with that, 15 PSI...~3" valve surface area, 45 pounds of pressure that I guess should be made up in the spring...or 45 * 150% so 67.5 more pounds to make up with the spring?
I've always liked beehives for their natural dampening characteristics...but a dual spring can do something similar, and offer the added insurance of holding the valve up should one of the 2 springs fail...I'm glad I'm asking questions, but I'm also confusing myself even more.
When you say the valve side is 150% more sensitive to weight, is that due to the rocker arm ratio or something else? That concerns me more because the boost pressure IS essentially making the valve appear heavier...so with that, 15 PSI...~3" valve surface area, 45 pounds of pressure that I guess should be made up in the spring...or 45 * 150% so 67.5 more pounds to make up with the spring?
I've always liked beehives for their natural dampening characteristics...but a dual spring can do something similar, and offer the added insurance of holding the valve up should one of the 2 springs fail...I'm glad I'm asking questions, but I'm also confusing myself even more.
08-31-2010, 08:14 PM
#12
I think for springs I'm going to go with the Patriot 8501's, which should give me 155-160 on the seat (I'll probably see what the lowest installed height is for all 8 intake valves, and shim the rest to match, then do the same for all 8 exhaust valves).
It's boost from twin turbo's not a blower, so the cam will be different than a blower grind, actually hoping that it will be fairly mellow as a result of a bit more LSA.
It's boost from twin turbo's not a blower, so the cam will be different than a blower grind, actually hoping that it will be fairly mellow as a result of a bit more LSA.
09-01-2010, 06:45 AM
#14
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The pressure on the back side of the valve is worth considering, but the resistance on the ex valve that does not want to let the valve open seems harder on the lifter/pushrod combo when in boost. The Morel has the best track record for durability, but still won't last forever. The limited travel type lifter might be worth some performance on the boosted engine, but may shorten the life slightly.
Kurt
Kurt
09-01-2010, 10:39 AM
#15
I intend to use stock rockers with upgraded trunnions, so if I go with the Morels, I guess I'll then be playing a balancing game of shims under the trunnions and pushrod length to get the correct pre-load on the lifter as well as wipe pattern on the valve optimized...no big deal, I think Katech even sells individual pushrods, though hopefully I'd at worst need 8 of one length and 8 more a second length.
Kurt, by limited travel, do you mean the travel of the plunger inside of the lifter? Or is there something to the geometry of the oil holes on the lifter bodies that limits how far they should be traveling up and down in the lifter bores?...by the way, thank you for the feedback...you've got a track record that speaks for itself, I've always learned a lot from your posts.
Kurt, by limited travel, do you mean the travel of the plunger inside of the lifter? Or is there something to the geometry of the oil holes on the lifter bodies that limits how far they should be traveling up and down in the lifter bores?...by the way, thank you for the feedback...you've got a track record that speaks for itself, I've always learned a lot from your posts.
09-01-2010, 10:44 AM
#16
That's all you have to offer is a smart *** comment? We all know what he's looking for, regardless of the mathematical error (pi x r^2 = 3.1415 sq in, not 6.28 sq in). Good news for Mike, cuz' his pressure is already half of what he was considering.
Mike454SS,
I say go w/ the LS7 lifters & just don't over pre-load them; maybe to .045". The shorter up to recommended pre-load the better. Also, in regards to valve float or valvetrain harmonics, the valve side of the rocker is approx. 150% more sensitive to weight than the lifter side.
Mike454SS,
I say go w/ the LS7 lifters & just don't over pre-load them; maybe to .045". The shorter up to recommended pre-load the better. Also, in regards to valve float or valvetrain harmonics, the valve side of the rocker is approx. 150% more sensitive to weight than the lifter side.
I'm asking how he is figuring this. I don't see how a 2 inch valve could be more than about 3 square inchs. I figure a little under 4?????
09-01-2010, 11:10 AM
#18
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On the limited travel lifters the plunger in the lifter body has reduced travel, seems like it's down about .030 in the Morel brand. This would shorten up the cushion in the lifter and should produce gains in the boosted engine as the plunger should not compress as much under severe loads. That being said I have never tried using this type of lifter without an adjustable valvetrain. It could be done, but would be problematic getting the pre load right.
Kurt
Kurt
I intend to use stock rockers with upgraded trunnions, so if I go with the Morels, I guess I'll then be playing a balancing game of shims under the trunnions and pushrod length to get the correct pre-load on the lifter as well as wipe pattern on the valve optimized...no big deal, I think Katech even sells individual pushrods, though hopefully I'd at worst need 8 of one length and 8 more a second length.
Kurt, by limited travel, do you mean the travel of the plunger inside of the lifter? Or is there something to the geometry of the oil holes on the lifter bodies that limits how far they should be traveling up and down in the lifter bores?...by the way, thank you for the feedback...you've got a track record that speaks for itself, I've always learned a lot from your posts.
Kurt, by limited travel, do you mean the travel of the plunger inside of the lifter? Or is there something to the geometry of the oil holes on the lifter bodies that limits how far they should be traveling up and down in the lifter bores?...by the way, thank you for the feedback...you've got a track record that speaks for itself, I've always learned a lot from your posts.
09-01-2010, 11:37 AM
#20
Plus like LS1-450 mentioned, take away the area of the valvestem too...so the area is a little less...but I don't know what diameter the stem is, plus the stem doesn't meet the valve at 90 degrees, it has a smooth transition...so granted there IS a 3rd dimension to the surface area there on the backside of the valve, where the pressure against the spring would be a component of the PSI at a normal vector to the surface at any given spot...but he's right, it's still going to be pretty close to 3", and the further up the stem, the steeper the angle, and the less significant the pressure at that location as far as working against the spring.