To vvt or not to vvt
To vvt or not to vvt I think I'm going to get a different cam soon. Instead of dealing with a hydroboost conversion and getting a bigger stall so my truck actually gets its bottom end grunt/ vacuum back I think I may just change the cam and get something a bit smaller. Current specs are 219/228 .550/.550 114. Been talking to Comp cams and they recommend a VVT cam sized at 210/224 .556/.568 114 for my application. The new cam is listed from 1300-6500 in their catalog and the closest one they have to my current one is 219/235 with 113 LSA which they list RPM range of 1500-6700. I just don't want to go through all the work again and still have similar characteristics. I have also thinking about ditching the VVT since I could almost do it for the same price and get a custom single bolt grind like the 212/216 in a single bolt ? Name of the game on this one is as much useable street friendly torque possible.
My trucks set up is 2010 Silverado 4.8 Ext Cab 4x4
K&N cold air***Magnaflowmuffler***Pacesetter Headers***ls3 hot cam***2800 stall***Nelson Performance tune***Vette servo**3.42 gears
My trucks set up is 2010 Silverado 4.8 Ext Cab 4x4
K&N cold air***Magnaflowmuffler***Pacesetter Headers***ls3 hot cam***2800 stall***Nelson Performance tune***Vette servo**3.42 gears
Keep the VVT! When tuned properly, you get to keep all the low end grunt you are looking for, but can have the peak power of a bigger cam too! Ditch the VVT and you basically have to pick which one of those you want.
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The cam was sold to me as a ls3 "hot cam" and has very similar specs to previous Hot cams. The cam is definitely a VVT cam since it has the oiling journals and set up for the Oil actuator. Its been in the truck for about 3 months now. I had a PCM for less tune on the truck and had tons of lights and when trying to contact them to get a reflash I got a bit of the run around. I ended up getting a Nelson performance tune where I did state I was installing a VVT cam and wanted to keep the system. Truck does run good but I have NO bottom end. I got the cam from a another sites forum member as a single bolt cam, with him not knowing it was VVT, I wonder if I got a cam with the earlier style core and not the newer style my truck has?
VVT rocks, I'd keep it. Trying to maintain bottom end in a 4.8 is hard enough, VVT helps that. They will custom grind you one as well, in our 5.3 here they ground us a 218/222 VVT cam. I just wouldn't talk to the average tech guy there about custom grinding a VVT cam.
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The one I was looking at is based on the 189 core (newer style) its 189-400-13 but still think it may be a bit big for what I am wanting. Do you know the agent you spoke with there ? I was thinking of specs around the 206/218 mark with around 114-116 Lsa and .560/.560 lift. I want it to be well into the power when my converter flashes at 2800
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I would keep VVT. Texas Speed has been doing really cool stuff with it.
If you decide to go that way, I also have that 210/224 VVT Comp Cam never installed sitting in my garage. My truck was totalled so I'm trying to get rid of it.
If you decide to go that way, I also have that 210/224 VVT Comp Cam never installed sitting in my garage. My truck was totalled so I'm trying to get rid of it.
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TECH Senior Member
Joined: Jul 2009
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TECH Fanatic
Joined: Jul 2005
Posts: 1,685
Likes: 7
From: Beebe, Arkansas
The disadvantage of the Gen IV 4.8L is the compression ratio is really low since GM went with the 243/799 heads its 8.8:1 stock. I would look at milling the heads or switching back to the smaller chamber 5.3 heads to bump CR.
The more articles I read I think I got the first VVT core cam installed so it is severely retarded at low RPM. The stock cam pulled way harder with a stock stall then this one does. Stock cam only was slightly less at the top end. Just to explain how bad it is today after a fresh bit of rain I couldnt get the truck to spin if my life depended on it. Stock with a tune and headers No problem... I have really looking at the 189 core version of the xfi 210/224 vvt cam comp offers or getting the LSR 215/223 cam ground on the correct vvt core. Really dont think I need the lift of the LSR version but the intake centerline is 107 vs the xfi's 105 intake centerline. I think that extra 2 degrees would really help with my trucks size and towing and with the VVT being able to retard the cam a at the higher RPMs I shouldnt lose much up top. I'm going to call comp monday and ask them if they can put that 107 centerline on a xfi lobe. Anyone think I should ask about having them move the 114 lsa down to 112 or 113 to give it that sound and increase the midrange also? Truck is shifting at 6000 now and since I am looking for more of a flat curve instead of all out power this would be a good combo for custom grind?
Sitting here thinking I may call Allen at nelson performance Monday also, See if he can look at the VVT tune for my truck and see if he can advance my cam more on the low end and possibly retard it less on the upper RPM.... If there is enough range in the VVT maybe he can "tune out" the core differences....... Just a thought after a couple beers....
Sorry for all the posts but the beer is full effect and it looks like there isnt enough range to make it happen on the advance side to see if my theory is correct.
Article from Hotrod MagThe Gen IV's VVT system is very flexible and allows advancing the cam 7 degrees and retarding it 45 degrees for a total of 52 degrees of latitude.
Tech note from Comp cams VVT tech bulletin. The difference in the pin between 156 and 189 cores equates to 13 degrees cam retard (if a 156 is used
where a 189 is required). {thinking i have a 156 "type" core installed and with only 7 degrees of advance available in the phaser I am not going to be able to make up the 13 degree difference... Looks like I won't need to call Allen..
Article from Hotrod MagThe Gen IV's VVT system is very flexible and allows advancing the cam 7 degrees and retarding it 45 degrees for a total of 52 degrees of latitude.
Tech note from Comp cams VVT tech bulletin. The difference in the pin between 156 and 189 cores equates to 13 degrees cam retard (if a 156 is used
where a 189 is required). {thinking i have a 156 "type" core installed and with only 7 degrees of advance available in the phaser I am not going to be able to make up the 13 degree difference... Looks like I won't need to call Allen..
Top graph was the VVT cam.
This graph the non VVT cam (note this graph also had the advantage of 2 extra PSI from the TVS 1900).
TECH Junkie
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Couple of thoughts.
1. You are comparing a supercharged application to a NA application.
2. Do you think GM and other manufacturos would go to all the trouble of installing a VVT system in their motors if there was not something to it?
1. You are comparing a supercharged application to a NA application.
2. Do you think GM and other manufacturos would go to all the trouble of installing a VVT system in their motors if there was not something to it?
Just thought of something else that may let me run the current cam. Pick up the early style phaser 12585994 if anyone has one of these pleas let me know actually have a damaged late style I can compare it to before I pull the engine apart.
