[oldman]

I don't think we know, just that the LS7 had more lift and probably more valve spring pressure, lastly, the LS7 had a fuel cut at 7000 RPM, so one would assume it is a stronger lifter. GM offers other performance and / or low bleed down lifters. Nothing is wrong with the OEM for applications near enough to what they were designed for. Problem with "small" cams, is GM ramp is we assume to be very mild and even the Cam Motion "gentle ramps" are probably a lot more aggressive than anything GM ever made... EVER. This starts a domino effect as the stepper ramp requires a stronger spring or you get valve bounce, which can lead to a whole lot of issues besides valve failue. So the higher spring pressure needs stronger stuff: pushrod, lifter, rocker arm and timing chain. IMO that is why GM stock with weak valve springs due to the AFM cam on the LT4 went with titanium for the intake valve, titanium is light and there is boost holding the weak valve open, so the lighter the intake valve (by far the bigger and heavier valve) is titanium and the valve that should be titanium due to heat is actually hollow and filled with sodium to internaly cool the valve head by wicking the heat to the guide. The LS7 lifter is cheap period, that is why it is under consideration.

For me and my boosted high RPM build, I felt the hollow LT1 valves were unacceptable from a strength and heat tolerance perspective. Also the undercut head Manley valve does off a mild flow boost and still be WAY stronger than OEM steel based vavles. They are also a WHOLE lot heavier, so I'm stuck with kinda stiff springs and even though I have a sub .600 lift custom Cam Motion cam, I selected some pretty stiff Texas Speed dual valve springs. 160 lbs seat and 415 at .660 lift (I don't get there) so say I'm at 380 at .592 lift. Install is 1.81", they are PAC springs which I've come to appreciate as IMO they don't fail as often.

[RUQWIKR]

Originally Posted by oldman

I could NOT get them to work and I personally tried, The AFM lobe has a special ramp profile that prevents the LS7 lifter from leaking down. So there is a issue with the valves closing due to lifter overfill. This is my thinking after trying. I have access to all different lengths of pushrods. Others may know more; I raced a Challenger before this so no beforehand knowledge on AFM.

Once again it is lift, ramp speed, and RPM that cause most failures. My specific failure added in boost and stiff springs leading to what I think was valve bounce. Ramp speed is The number 1 issue that fails the ls7 lifter for most failure IMO, hence I’d spec it only for the GM hot cam. I’d talk to Cam Motion to see if they rec the LS7 on their small sub .600 lift cam.

The cam lobes on OEM GM LT1/4 cams on the AFM cylinders have tall ramps to take up the mechanical lash in the AFM lifters. Unless an aftermarket cam was designed for AFM, which virtually none are, they should not have those tall ramps allowing a regular non-AFM lifter to be used.

That said, regular lifters in the AFM cylinders with the OEM AFM cam would cause early valve opening and late valve closing. You'd suddenly have a lot more overlap just on those cylinders.

[oldman]

Makes sense

[JROC]

Originally Posted by RUQWIKR

The cam lobes on OEM GM LT1/4 cams on the AFM cylinders have tall ramps to take up the mechanical lash in the AFM lifters. Unless an aftermarket cam was designed for AFM, which virtually none are, they should not have those tall ramps allowing a regular non-AFM lifter to be used.

That said, regular lifters in the AFM cylinders with the OEM AFM cam would cause early valve opening and late valve closing. You'd suddenly have a lot more overlap just on those cylinders.

Just when I think DOD can't be any dumber of a system you prove that thinking wrong.

Bravo to you sir.

[oldman]

can't say I like it. But the CAFE standards of the last administration may well have doomed the V8. GM needed to whatever it could for a few MPG. In that light, it was and is an elegant solution. GM did so many polls all the way back 1997 LS1 customers have been asked and MPG has been way down on the list. In 2008 with the rising CAFE standards, many platforms and engines were on the chopping block. The LT1 was designed facing this reality. I'm impressed that on the LT2 that 495 HP is coming from a slightly hotter cammed engine (amoung other mods). So I'm not hatting it, I do see some room for a hotter cam, definitely a fuel lobe as a cheap upgrade.

For me personally, I went with a real cam and lifters... you may say I voted with my wallet.

I'm completely willing to help anybody in the Austin area install a cam only, you do 75% of the work, I'll do 25% and eat the nice lunch that you will provide. Let's see how well it would work. I'd spec a custom AFM cam with fuel if this is a LT4. We would do the install from the front.

But yeah a simple cam in cam could replace this VVT /DOD system and be at 550 HP, at IMO a lower expense.
https://www.mechadyne-int.com/products/duocam/

[NickeyMatt1LE]

Would require a cam change as the stock afm cam has different lobes for the deactivation cylinders. You can certainly run them through with an aftermarket cam. The wrong combination of valve spring pressure and aggressive lobes is what takes out lifters. Hence why Johnson offers a pressure fed pin. I have done dozens and dozens of cam jobs on ls7's and ls3's over the years without changing out the stock lifters and never have seen a failure using beehive singles and comp lxl lobes. Dual springs with 140 to 150 lbs on the seat, over 400 at peak lift, and quick lobes like lsl's is what can take them out especially on the 1.8 rocker stuff like the lt engines.

And just because it's sub .600" lift doesn't mean it can't have an aggressive ramp on the lobe. Duration and ramp profile dictate the acceleration of the valve more than just lift.

[EDFHOBBIES]

I agree to disagree.. I think the LS7 lifters are ok if the RPM is where it needs to be and the valve train geometry is correct.. for instance proper push rod length, correct rockers ratio and correct valve spring tension. change valve springs often and trunion upgrade for protection.. If the johnson lifters are 100k mile lifters running any cam by all means then use them. But there have been so many LS builds with big cams its hard to discredit them and millions of LS motors with 100k miles still running strong.

I think the LS7 lifters got bad rap from over night shops that swap cams not doing extra steps like degreeing cams and checking push rod lengths. And instead of taking the blame, they blame it on cam material or lifter failure.

[JANNETTYRACING]

Originally Posted by JROC

What's the difference between LS7 lifters and the non-AFM GEN5 LT1 lifters?

I still am annoyed GM couldn't name the GEN5's something other than LT. It gets confusing, and you have to often distinguished between the motors.

It gets even more confusing when you have a Gen5 engine in a Gen 6 car, and a Gen 4 engine in a Gen 5 car

[KingLT1]

Originally Posted by EDFHOBBIES

I agree to disagree.. I think the LS7 lifters are ok if the RPM is where it needs to be and the valve train geometry is correct.. for instance proper push rod length, correct rockers ratio and correct valve spring tension. change valve springs often and trunion upgrade for protection.. If the johnson lifters are 100k mile lifters running any cam by all means then use them. But there have been so many LS builds with big cams its hard to discredit them and millions of LS motors with 100k miles still running strong.

I think the LS7 lifters got bad rap from over night shops that swap cams not doing extra steps like degreeing cams and checking push rod lengths. And instead of taking the blame, they blame it on cam material or lifter failure.

LS7 have so much plunger travel that getting a acceptable lifter preload via push length isn't difficult. That is why everyone likes to use them. It's the lazy shops lifter.

Imo LS7 lifters get a bad wrap because they are often used in the wrong applications because again they are easy to setup so everyone wants to use them even on builds they should know better.

like I said before, They are not designed for aggressive cam lobes that have lifts above .600 with valve spring seat pressures pushing 400lb pushing north of 7k rpm. They work fine on mild cam shafts that pair well with lighter beehive springs and light weight valves. It's all combination, but I see a lot of cam kits on the market that are pushing LS7 lifters right to their limits out of the gate. Spend a little extra money and get a Johnson 2110 that is designed for high rpm, high lift, high spring rates...etc.

[EDFHOBBIES]

Thanks for the info.. King, How does one choose the leak down rate?

Also the lifter is was referring to were these... 88958689

[KingLT1]

You really only need slow leak down rate on some of the larger more aggressive lobe cams. I think reduced travel is more in important in most builds. LS7 have so much travel you actually lose some lift at high rpm. Johnson's have less then half the plunger trave of LS7's which require precise push rod length for proper preload. The reward is more lift at the valve at higher rpm, better stability, and less chance for them to pump up.

[oldman]

Originally Posted by NickeyMatt1LE

Would require a cam change as the stock afm cam has different lobes for the deactivation cylinders. You can certainly run them through with an aftermarket cam. The wrong combination of valve spring pressure and aggressive lobes is what takes out lifters. Hence why Johnson offers a pressure fed pin. I have done dozens and dozens of cam jobs on ls7's and ls3's over the years without changing out the stock lifters and never have seen a failure using beehive singles and comp lxl lobes. Dual springs with 140 to 150 lbs on the seat, over 400 at peak lift, and quick lobes like lsl's is what can take them out especially on the 1.8 rocker stuff like the lt engines.

And just because it's sub .600" lift doesn't mean it can't have an aggressive ramp on the lobe. Duration and ramp profile dictate the acceleration of the valve more than just lift.

This seems precisely correct. Here is a list of comp lobs:
fastest LSK, XE-R, XFI, LSL, LXL, HUC, XE-HL slow.

[oldman]

Originally Posted by EDFHOBBIES

I agree to disagree.. I think the LS7 lifters are ok if the RPM is where it needs to be and the valve train geometry is correct.. for instance proper push rod length, correct rockers ratio and correct valve spring tension. change valve springs often and trunion upgrade for protection.

The LS7 lifter life expectancy is dependent primarily on ramp rate, then overall lift. Geometry really is not ajustable ( spec push rod length is really for lifter plunger travel).

IMO, lifts above .600 need a roller tip.
IMO, the fast ramp speed that requires a stronger spring and heavier stronger pushrod just leads to an increased failure rate.

Basically, IMO the LS7 lifter can be used with hotcam or the smallest Cam Motion (know for gentle ramps), oh and a DoD compatible cam on the non-DoD lobs. Thats it, spec either the stock Beehive or something slightly heavier on DoD cam. Spec a PAC spring either the most mild or one step up on the smallest Cam Motion or GM Hot Cam.

Originally Posted by EDFHOBBIES

If the johnson lifters are 100k mile lifters running any cam by all means then use them. But there have been so many LS builds with big cams its hard to discredit them and millions of LS motors with 100k miles still running strong.

I knew I was going with a forged engine and got my cam as part of a designed package. I figure it would be in about 10K miles, so I thought and many people and vendors confirmed that the LS7 lifter would "hold me over". In fact 18 months ago, I may have gone back to an DoD custom cam with fuel lobe, so really my cam and LS7 lifters was going to be a 1 year experiment. I would at that point:
1) keep the .63x Texas Speed cam and change the lifters to Johnson
2) Go to a custom DoD cam with 35% fuel lobe
3) go to a sub .600 lift cam motion cam with a large duration for the sound and RPM I like to drive my toy at, this is a sound and RPM cam, has NOTHING to do with power... which I adjust pulley size for.

My LS7 failed at the needle bearing at the roller, all intake lobes look like there is some lifter impact on the decel side of the intake cam lobe. I equate this to my much heavier pushrod, extended RPM (up to 7200 rpm) and boost level, I have some float on the spec Texas Speed dual spring. The failure literally happened with a few weeks of me taking out the engine. I had already decided to go with option 3 above. Every vendor I talked to, including Cam Motion urged me to use a bigger than .600 lift cam. All vendors even AFTER my lifter failure said there should be no issue with the LS7 lifter, well it did and there are other people that have failed the LS7 lifter and you and I will agree to disagree that this is related to install or proper adjustment which is limited to pushrod only AFAIK. I think I was push the lifter on my temp build and loss the bet. It was not a costly mistake for me because I would not have used the cam or LS7 lifter on my forged, high RPM build. I probably would have sold them as is sub 10K mile cam and lifter for a few hundred bucks in the classified. In hindsight I knew better, I lived through the LS1 valvetrain failue. Do a search in early 2018 I already posted on this forum that I'm shy of cams above .600 for the street and debated many people that these cams / valve / rockers / lifters tend to fail on street cars. So I see it as a risk that I loss that luckily did not cause me any financial damage (outside of the few bucks for selling a second hand cam). But I was "lucky" with my failure, I think most guys would be out $2000 to $4000 bucks minimally. Long story really short, the LS7 lifter should only be used under the limited scenario I've outlined.

I decided that a sub .600 lift Cam Motion setup and Johnson lifters were the only way that I would be comfortable saying the build is good for 100,000 miles. I will probably change valve springs at 40K. They are designed for .660 lift so they are way over-engineered for my application.

IMO the LS7 lifter can only be used with the limited amount of combinations I've already listed.

Originally Posted by EDFHOBBIES

I think the LS7 lifters got bad rap from over night shops that swap cams not doing extra steps like degreeing cams and checking push rod lengths. And instead of taking the blame, they blame it on cam material or lifter failure.

Degreeing a cam in has NOTHING to do with lifter failure.
I see little issue with factory length pushrods, with a factory engineered lifter and factory valve train geometry given the massive amounts of plunger travel on the LS7 lifter. I've spent a lot of time on this engine with LS7 and Johson lifters, and the LS7 lifter has a lot of travel. Also and this is IMO, I see no reasonable failure scenario caused by factory length and installed stuff, they might not work, they may make noise, but I don't see how needle bearing fail due to pushrods being slightly too long or too short. All LS7 lifter failures that I know of are in the needle bearing in the roller tip. Once again and to be clear, pushrods are used to stop pump up, it is hard for me to envision how it causes roller bearing failure.

[JROC]

Originally Posted by JANNETTYRACING

It gets even more confusing when you have a Gen5 engine in a Gen 6 car, and a Gen 4 engine in a Gen 5 car

Lol. I know, right?

Or GEN2 and GEN3 motors in GEN4 cars.

BTW what about Morel lifters? It seemed like just a few years ago they were the most recommended aftermarket lifter company, and now you don't really see them get mentioned much. It seems like Johnson lifters took over being the most popular aftermarket lifter. Are they just better to the point of making Morel not a relevant choice for their price?