Lets settle the LS7 lifter discussion
Thread Starter
Burning Brakes
Joined: Jan 2008
Posts: 1,005
Likes: 1
From: springfield MO
Lets settle the LS7 lifter discussion
So everyone says that LS7 lifters need shorter pushrods. Typically .050" shorter.
I see people running pretty close to my exact setup using 7.325-7.35
But Im using the stock pushrods with no issues with LS7 lifters.
After talking to my guy that does my tuning and installs he brought up a good point. If LS7 lifters really are .050" more than LS1 lifters than why is it a direct replacement?
Meaning if you have a failed lifter and go into GM for them to replace it, they are going to use the LS7 lifter, but they are not going to change out your pushrods for shorter ones.
So wouldn't this fact basically disprove that LS7 lifters require a shorter pushrod just because of the lifter
I see people running pretty close to my exact setup using 7.325-7.35
But Im using the stock pushrods with no issues with LS7 lifters.
After talking to my guy that does my tuning and installs he brought up a good point. If LS7 lifters really are .050" more than LS1 lifters than why is it a direct replacement?
Meaning if you have a failed lifter and go into GM for them to replace it, they are going to use the LS7 lifter, but they are not going to change out your pushrods for shorter ones.
So wouldn't this fact basically disprove that LS7 lifters require a shorter pushrod just because of the lifter
Safety Car
Joined: Aug 2011
Posts: 4,451
Likes: 410
From: Portland OR
You are correct. Dimensionally identical to the originals. In fact in my case, the lifters I took out look identical to the LS7 lifter. Mine is a 2000.
I think the LS7 name needs to be dropped, and just called an LS lifter.
Ron
I think the LS7 name needs to be dropped, and just called an LS lifter.
Ron
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
go check this out on ls1tech. There are measurements there showing that the ls7 lifter cup sticks up higher than the LS1 lifter but it allows for more travel so the oem pushrod wont hurt anything. Using a pushrod measuring tool and .080 as a standard preload they have shown that oem pushrods come out to be too long.
Tech Contributor
Joined: Jan 2007
Posts: 19,493
Likes: 1,178
From: Dyer, IN
Yep....also a lesson in not listening to what "everyone says". This topic was discussed in detail by forum member EricD.....who is a GM engineer on the corvette program.
http://forums.corvetteforum.com/c5-t...ic-lifter.html
A large part of the guys on these forums could not find their a$$ with both hands tied behind their back.....yet they make recomendations everyday on these forums(with conviction and certainty)....based on what "everyone says".
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
After talking to my guy that does my tuning and installs he brought up a good point. If LS7 lifters really are .050" more than LS1 lifters than why is it a direct replacement?
Meaning if you have a failed lifter and go into GM for them to replace it, they are going to use the LS7 lifter, but they are not going to change out your pushrods for shorter ones.
So wouldn't this fact basically disprove that LS7 lifters require a shorter pushrod just because of the lifter
Meaning if you have a failed lifter and go into GM for them to replace it, they are going to use the LS7 lifter, but they are not going to change out your pushrods for shorter ones.
So wouldn't this fact basically disprove that LS7 lifters require a shorter pushrod just because of the lifter
GM isn't going to design a direct replacement lifter that will cause issues if the stock pushrods are used.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
Lucky posted the link that gives some interesting dimensions.
In the 97 and 98 cars it appears the stock lifter had about a 1mm taller cup height than the 17122490 lifter but about 1mm more preload. So, the 1712240 should drop in at about it's listed 2.09mm preload.
In the other cars, it appears the stock lifter had about a 1mm shorter cup height than the 17122490 lifter and about 0.5mm less preload. So, the 1712240 should drop with about 0.5mm more preload than it's listed 2.09mm preload.
In the second case, the 17122490 lifter has a full travel of 4.22mm so going to around 2.59mm of preload would work. Might not be ideal but it would work.
This data does not really prove or disprove anything. The question should be, is there an advantage to using 2mm or 0.80" preload vs say 2.5mm or 0.1" preload? Could there be an advantage to using 1.5mm or 0.060" preload?
Seems similar to the gen 1 small blocks where different sources would say to turn the rocker nuts either 1/4, 1/2 or 1 turn past 0 lash.
In the 97 and 98 cars it appears the stock lifter had about a 1mm taller cup height than the 17122490 lifter but about 1mm more preload. So, the 1712240 should drop in at about it's listed 2.09mm preload.
In the other cars, it appears the stock lifter had about a 1mm shorter cup height than the 17122490 lifter and about 0.5mm less preload. So, the 1712240 should drop with about 0.5mm more preload than it's listed 2.09mm preload.
In the second case, the 17122490 lifter has a full travel of 4.22mm so going to around 2.59mm of preload would work. Might not be ideal but it would work.
This data does not really prove or disprove anything. The question should be, is there an advantage to using 2mm or 0.80" preload vs say 2.5mm or 0.1" preload? Could there be an advantage to using 1.5mm or 0.060" preload?
Seems similar to the gen 1 small blocks where different sources would say to turn the rocker nuts either 1/4, 1/2 or 1 turn past 0 lash.
Last edited by lionelhutz; May 5, 2012 at 08:46 PM.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
That's a whole separate and large debate where ever lifter per-load is discussed. Per the chart in the link, it looks like GM designed all their lifters to be per-loaded pretty much in the center of the plunger travel. That might work great for stock engines, but when more radical valve trains are used there are lots of opinions on how much lifter per-load should be used.
Last edited by ZeeOSix; May 5, 2012 at 09:16 PM.
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Tech Contributor
Joined: Jan 2007
Posts: 19,493
Likes: 1,178
From: Dyer, IN
That's a whole separate and large debate where ever lifter per-load is discussed. Per the chart in the link, it looks like GM designed all their lifters to be per-loaded pretty much in the center of the plunger travel. That might work great for stock engines, but when more radical valve trains are used there are lots of opinions on how much lifter per-load should be used.
