Why Delete VVT?
Thread Starter
Instructor
Joined: Oct 2022
Posts: 213
Likes: 58
Why Delete VVT?
Hi All,
I've been looking at some upgrade paths for my LT1 and I'm wondering why in 2014-2016 most people used aftermarket cams with VVT intact, but the general consensus now seems to be to used a non-vvt cam and to delete VVT? It looks like VVT affords this motor a lot of low end torque. Why would you want to remove that? I'm sure there is a good reason, it just not readily apparent to me.
I've been looking at some upgrade paths for my LT1 and I'm wondering why in 2014-2016 most people used aftermarket cams with VVT intact, but the general consensus now seems to be to used a non-vvt cam and to delete VVT? It looks like VVT affords this motor a lot of low end torque. Why would you want to remove that? I'm sure there is a good reason, it just not readily apparent to me.
Drifting
Joined: Jun 2019
Posts: 1,860
Likes: 840
From: near philly
only thing I can think of is people building full out race vehicles and wanting to eliminate the complexity and potential mechanical issues with a VVT system.
just one more thing to go wrong where as nothing goes wrong with a straight up fixed cam profile and no vvt
From an ideal operation standpoint only there's really no legitimate reason to not want ideal valve timing across the rpm range
That'd be like wanting to go back to a carburetor or something
just one more thing to go wrong where as nothing goes wrong with a straight up fixed cam profile and no vvt
From an ideal operation standpoint only there's really no legitimate reason to not want ideal valve timing across the rpm range
That'd be like wanting to go back to a carburetor or something
Le Mans Master
Joined: May 1999
Posts: 6,504
Likes: 1,290
From: Windermere FL
Variable valve timing might be deleted from an engine primarily to achieve more power, especially when installing aftermarket camshafts designed for higher lift and longer duration, as the VVT system might not be able to properly accommodate these aggressive cam profiles, potentially leading to valve damage if left active.
I watch entirely too many engine building shows!
I watch entirely too many engine building shows!
Safety Car
Joined: Jul 2019
Posts: 3,758
Likes: 1,267
From: nashville TN
the first reason is that with a vvt setup you cant degree the cam. remove all that spring stuff go a single bolt cam and now you can use a degree wheel.
second reason is the vvt allows 4* advance and retard. with a higher lift can your degreeing the cam specs according to the cam card so you now dont want movement of the cam sprocket. so by using a vvt phaser lockout (which can still allow up to 1-2* of movement) or a full vvt delete by using a c5r timing chain,lme cam sprocket and cover you have the ability to set timing at the lsa specs on the cam card and it stays there
second reason is the vvt allows 4* advance and retard. with a higher lift can your degreeing the cam specs according to the cam card so you now dont want movement of the cam sprocket. so by using a vvt phaser lockout (which can still allow up to 1-2* of movement) or a full vvt delete by using a c5r timing chain,lme cam sprocket and cover you have the ability to set timing at the lsa specs on the cam card and it stays there
Racer
Joined: Jul 2015
Posts: 487
Likes: 121
From: Maryland
I’ve asked this question to builders and the issue begins with a piston to valve clearance issue. A phaser limited can be used but the issue can become the limiters not holding. I believe that’s why many just use lockouts to protect the valves but not incurring the costs of a new front cover setup.
Supporting Vendor
Joined: Feb 2009
Posts: 4,408
Likes: 1,413
From: Mesa Az
On most N/A setups you would retain VVT due to the low/midrange gains it can have over locking the cam. However on a forced induction car with a cam you would want to lock it out because the added pressure on the valves, springs pressure, etc will typically cause the cam to roll back above 6200'ish RPM's if not locked out.
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Cordes Performance Racing aka "CPR"
Owner of AZ's premier LSX/LTX motorsports shop
http://cordesperformanceracing.com/
www.facebook.com/cordesperformanceracing.com
joe@cordesperformanceracing.com
480-359-5914
Burning Brakes
Joined: Nov 2022
Posts: 910
Likes: 430
From: MN
Hi All,
I've been looking at some upgrade paths for my LT1 and I'm wondering why in 2014-2016 most people used aftermarket cams with VVT intact, but the general consensus now seems to be to used a non-vvt cam and to delete VVT? It looks like VVT affords this motor a lot of low end torque. Why would you want to remove that? I'm sure there is a good reason, it just not readily apparent to me.
I've been looking at some upgrade paths for my LT1 and I'm wondering why in 2014-2016 most people used aftermarket cams with VVT intact, but the general consensus now seems to be to used a non-vvt cam and to delete VVT? It looks like VVT affords this motor a lot of low end torque. Why would you want to remove that? I'm sure there is a good reason, it just not readily apparent to me.
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Racer
Joined: Jul 2015
Posts: 487
Likes: 121
From: Maryland
Is there any difference, other than just increased rotational mass, between using a VVT cam with a phaser lockout, and going with a non-VVT cam? I’m assuming all non-VVT cams would require a new front cover setup while the VVT cams would retain the current front cover setup. But is there any difference between the two setups from a cam performance?
Drifting
Joined: Apr 2000
Posts: 1,390
Likes: 35
From: INDIANA
We reused the VVT with an aftermarket cam on the Escalade build we did with LS9 supercharger. Used a Texas speed VVT limiter which reduced the total amount of change permitted. That allows much better low end torque without a reduction of overall power, a great choice for the street. Note that with VVT operational, it may allow a bigger aftermarket cam without having to change the torque converter due to improved low end response.
Safety Car
Joined: Mar 2006
Posts: 4,410
Likes: 4,886
From: Chester VA
This is news to me; am I reading this right? It sounds like early model C7s had VVT, but at some point that was changed? At first I thought like AnotherNorskie in post #7 that perhaps the OP meant AFM.
If so, I'm curious - what year did VVT go away? And what engine components made the LT1 a VVT engine?
If so, I'm curious - what year did VVT go away? And what engine components made the LT1 a VVT engine?