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Lq4 compression for towing

General engine tech -- Drag Racing to Circle Track

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White Stripe
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Re: Lq4 compression for towing

Post by White Stripe »

Thanks. I did read that thread and copied it in cleaning up the intake ports. Just seemed strange to leave a 1/8" step in the middle of the port after taking time smoothing out the bowl area and other spots that thread mentions.
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Re: Lq4 compression for towing

Post by mt-engines »

White Stripe wrote: Wed Jan 06, 2021 9:59 pm Thanks. I did read that thread and copied it in cleaning up the intake ports. Just seemed strange to leave a 1/8" step in the middle of the port after taking time smoothing out the bowl area and other spots that thread mentions.
its just not that critical for what you are doing, if it helps you sleep better at night, go for it. otherwise you wont gain any performance from matching it.
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Re: Lq4 compression for towing

Post by White Stripe »

Ok thanks.
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Re: Lq4 compression for towing

Post by rustbucket79 »

I’m puzzled by your choice of a stage 2 cam for an application requiring torque. Have you looked at the dyno charts on their website? Your chosen cam (on a 5.3) makes minimal improvement below 4500, do you plan on sustained towing above 4500?

A stage 1 seems like a more suitable choice, IMHO.
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Re: Lq4 compression for towing

Post by White Stripe »

rustbucket79 wrote: Wed Jan 06, 2021 10:25 pm I’m puzzled by your choice of a stage 2 cam for an application requiring torque. Have you looked at the dyno charts on their website? Your chosen cam (on a 5.3) makes minimal improvement below 4500, do you plan on sustained towing above 4500?

A stage 1 seems like a more suitable choice, IMHO.
I watched the Richard holdner btr truck cam dyno test video on youtube for the 5.3 and 6.0. Seemed like on the 6.0 torque down low wasnt lost until he went to stage 3. I couldn't find any cams that improved torque below 3k rpm compared to the stock lq4 cam. I think I'll have the same low end torque with the stage 2 but with more torque after 3k rpm compared to the stock lq4 truck cam. I think going from stage 1btr to stage 2 btr picked up about 5 to 10lbft and 20hp. Apparently the version 2 truck cams arent much different. I got the stage 2 version 2.
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Re: Lq4 compression for towing

Post by mt-engines »

rustbucket79 wrote: Wed Jan 06, 2021 10:25 pm I’m puzzled by your choice of a stage 2 cam for an application requiring torque. Have you looked at the dyno charts on their website? Your chosen cam (on a 5.3) makes minimal improvement below 4500, do you plan on sustained towing above 4500?

A stage 1 seems like a more suitable choice, IMHO.
Because of runner length and csa, no matter what cam you stick in it under say 230@.050. 46-4800 is still where peak torque happens.

stage 2 will have more passing power.

You'd be puzzled at my cam choices...
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Re: Lq4 compression for towing

Post by mt-engines »

White Stripe wrote: Wed Jan 06, 2021 10:51 pm
rustbucket79 wrote: Wed Jan 06, 2021 10:25 pm I’m puzzled by your choice of a stage 2 cam for an application requiring torque. Have you looked at the dyno charts on their website? Your chosen cam (on a 5.3) makes minimal improvement below 4500, do you plan on sustained towing above 4500?

A stage 1 seems like a more suitable choice, IMHO.
I watched the Richard holdner btr truck cam dyno test video on youtube for the 5.3 and 6.0. Seemed like on the 6.0 torque down low wasnt lost until he went to stage 3. I couldn't find any cams that improved torque below 3k rpm compared to the stock lq4 cam. I think I'll have the same low end torque with the stage 2 but with more torque after 3k rpm compared to the stock lq4 truck cam. I think going from stage 1btr to stage 2 btr picked up about 5 to 10lbft and 20hp. Apparently the version 2 truck cams arent much different. I got the stage 2 version 2.
Your choice in cams is fine. i cant tell you how many LS engine combinations i have dyno and tuned.
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Re: Lq4 compression for towing

Post by White Stripe »

I just watched the Richard Holdner video again. The stage 1 did not lose any torque down low over the stock lq4 cam. The stage 2 lost 6 or 7 ftlbs below 3500 but sustained the torque curve significantly further before dropping compared to the stage 1. Its been a while since I bought the cam, but it must have been the sustained torque curve was the reason I chose the stage 2.
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Re: Lq4 compression for towing

Post by White Stripe »

mt-engines wrote: Wed Jan 06, 2021 10:58 pm
White Stripe wrote: Wed Jan 06, 2021 10:51 pm
rustbucket79 wrote: Wed Jan 06, 2021 10:25 pm I’m puzzled by your choice of a stage 2 cam for an application requiring torque. Have you looked at the dyno charts on their website? Your chosen cam (on a 5.3) makes minimal improvement below 4500, do you plan on sustained towing above 4500?

A stage 1 seems like a more suitable choice, IMHO.
I watched the Richard holdner btr truck cam dyno test video on youtube for the 5.3 and 6.0. Seemed like on the 6.0 torque down low wasnt lost until he went to stage 3. I couldn't find any cams that improved torque below 3k rpm compared to the stock lq4 cam. I think I'll have the same low end torque with the stage 2 but with more torque after 3k rpm compared to the stock lq4 truck cam. I think going from stage 1btr to stage 2 btr picked up about 5 to 10lbft and 20hp. Apparently the version 2 truck cams arent much different. I got the stage 2 version 2.
Your choice in cams is fine. i cant tell you how many LS engine combinations i have dyno and tuned.
Cool. I really appreciate all the input I get here. Lots of experience here. This is the vehicle I'm upgrading to a 6.0. Its my daily driver multi purpose truck. Probably very unusual for this forum I'm guessing.
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White Stripe
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Re: Lq4 compression for towing

Post by White Stripe »

Quick question about my cylinder heads. The machine shop did a light deck on the heads for a nice gasket surface. I noticed the edge of the combustion chamber is pretty sharp. Should I knock down the sharp edge with a file or sandpaper roll or something?
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Re: Lq4 compression for towing

Post by motormonkey »

Yes, knock down the sharp edges.
My opinion for your build is keep compression ratio to stock paramiters ,add a good cam, clean up heads and a good cooling system.
Nothing worse than having to high compression and all the timing pulled out for reduced knock, egt will get high, long pedal down towing situations. Your cooling system is going to be a high a priority over anything else in your truck, barring the rest of drive train.
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Re: Lq4 compression for towing

Post by 69427 »

White Strip

Thanks for posting the build.

I have a 01 Yukon XL 2500 I should do this on.
Spring time rust will dictate which way to go.
1.28 5.96 @ 115 @ #3250 Better in 2019
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Re: Lq4 compression for towing

Post by miniv8 »

I crack the door open into the Lq4 Towing Thread..

Stick my head just far enough so those in the back can hear, but those in front can't see...
I fill my lungs with air as they can hold.....

THAT SOUNDS LIKE A PERFECT CANDIDATE FOR A LOW BOOST REAR MOUNT TURBO!!!

I slam the door and run down the hall as fast as I can
Magnús Aðalvíkingur Finnbjörnsson
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Re: Lq4 compression for towing

Post by White Stripe »

So what kind of radius should I go for when removing the sharp edge from the combustion chamber? Something very slight or something bigger like a 1/8" radius?
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Re: Lq4 compression for towing

Post by mt-engines »

just bump it with a tootsie. no need to chamfer, just break the edge. a small file would work if you dont have any tootsie rolls
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