LQ4 refresh...looking for guidance

[project_x]

I need some guidance....

My Suburban has an LM7 5.3L with 706 heads.. with 178k miles.

I bought a running 2003 Denali Yukon with LQ4 with 200k miles and a recently rebuilt 4L65e...

I'm planning to swap the transmission in..and would like to refresh the LQ4.

I'm going to do an engine oil analysis and check compression on the LQ4 before I do anything.

I was planning to put a new water pump, oil pump, rear main seal, head gaskets, exhaust manifold bolts,etc...

I was thinking of using the 706 heads to get a little higher compression (read in a few places this was advantageous)....

I'd like better performance than my LM7 mostly for a towing... And to refresh the engine for longevity...

Looking to do this economically. What can I do for $1000?

What parts should I replace? Should I just change all the gaskets, pumps, o-ring and seals on the LQ4 and install it....or just keep driving my LM7 until it dies...

 

[Mudsport96]

For a 1000 bucks? If the oil analysis and compression check come back alright.... put an oil pump oring in it, rear main seal, exhaust bolts( can be done with heads on the engine) if needed and that is it. Well...what year is your Suburban? You may need to swap the intakes to keep the cable throttle if it is pre03. But other than that, the 6.0 is already up 40hp and at least 50 tq over the 5.3. You will not recognize your own rig. However, you will need to have your computer flashed to a 6.0 tune to get the full effects of the swap. For a grand, I personally, wouldn't open a running LS style engine that did not show active signs of a problem. Daughter just got home from college yesterday and I looked over the Silverado. And at 417160 miles it still purrs. All that I've done internally is the oil pump Oring. Don't mess with it if it isn't broke man.

 

[project_x]

For a 1000 bucks? If the oil analysis and compression check come back alright.... put an oil pump oring in it, rear main seal, exhaust bolts( can be done with heads on the engine) if needed and that is it. Well...what year is your Suburban? You may need to swap the intakes to keep the cable throttle if it is pre03. But other than that, the 6.0 is already up 40hp and at least 50 tq over the 5.3. You will not recognize your own rig. However, you will need to have your computer flashed to a 6.0 tune to get the full effects of the swap. For a grand, I personally, wouldn't open a running LS style engine that did not show active signs of a problem. Daughter just got home from college yesterday and I looked over the Silverado. And at 417160 miles it still purrs. All that I've done internally is the oil pump Oring. Don't mess with it if it isn't broke man.

Thanks,
Would you change the head gaskets? Or just leave them (pending oil analysis....)?

I have a 2005 Suburban... The LQ4 is out of a 2003.

 

[Mudsport96]

If the oil analysis looks good, I wouldn't do anything to the engine. Doing this economically, under $1000, you are going to be a few hundred into getting the LQ4 tune swapped over to your ecm most likely. And any performance parts are going to eat up the rest really fast.
Don't quote me on it, but I think the Denali will have better flowing exhaust. And if you have both vehicles side by side you could look for yourself. The Suburban may have the exhaust come together into one pipe before the muffler. And the Denali may have the exhaust have two pipes going into the muffler. If so, use the Denali dual setup and have custom exhaust run behind that with the rest of your 1000 bucks.

 

[Marky Dissod]

I was thinking of using the 706 heads to get a little higher compression (read in a few places this was advantageous) ...

If the static compression ratio with 706 / 862 heads turns out over 10.9-to-1,
1. you'll need to convince a tuner to take up the challenge, as they may hesitate to mess with it
2. VERY SERIOUSLY CONSIDER 91 octane, especially if working or playing HARD
3. 243 / 799 pope hat heads should keep the scr under 10.9-to-1, but they cost more than 706 / 862.

 

[strutaeng]

I just finished refreshing the LQ4 on my 06 Suburban 2500. I had an intermittent lifter tick. I started thinking I was only going to do a top end job, but wound up pulling the engine. I'm currently driving it around doing the break-in. A lot of work honestly, but I'm very happy so far. The last page has some costs.

https://www.tahoeyukonforum.com/threads/tty-head-bolts-with-engine-in-vehicle.147231/

I hope this helps.

 

[project_x]

I just finished refreshing the LQ4 on my 06 Suburban 2500. I had an intermittent lifter tick. I started thinking I was only going to do a top end job, but wound up pulling the engine. I'm currently driving it around doing the break-in. A lot of work honestly, but I'm very happy so far. The last page has some costs.

https://www.tahoeyukonforum.com/threads/tty-head-bolts-with-engine-in-vehicle.147231/

I hope this helps.

That's a great thread, thanks.

 

[project_x]

If the static compression ratio with 706 / 862 heads turns out over 10.9-to-1,
1. you'll need to convince a tuner to take up the challenge, as they may hesitate to mess with it
2. VERY SERIOUSLY CONSIDER 91 octane, especially if working or playing HARD
3. 243 / 799 pope hat heads should keep the scr under 10.9-to-1, but they cost more than 706 / 862.

Most calculations or other people's measurements see 10.5-10.68:1 for 706 heads on a LQ4

 

[Mudsport96]

Most calculations or other people's measurements see 10.5-10.68:1 for 706 heads on a LQ4

On a toy/race application it is fine. On a heavy truck/suv I wouldn't do it. You would see some tq advantages but unless you plan on running E85 for the 106 octane it had, ALL THE TIME the extra compression is not worth it. The 706s are worth about 12 lb ft of torque. If you need that much, a good custom tune can probably get you that with the stock heads. Or throw on some long tube headers and get a good custom exhaust and a tune and you will definitely be over the power the 706s will get you.
I'm not telling you that you can't use them. But, as someone who had done many different engine builds... high compression daily driver trucks are no fun.

 

[project_x]

Most calculations or other people's measurements see 10.5-10.68:1 for 706 heads on a LQ4.

On a toy/race application it is fine. On a heavy truck/suv I wouldn't do it. You would see some tq advantages but unless you plan on running E85 for the 106 octane it had, ALL THE TIME the extra compression is not worth it. The 706s are worth about 12 lb ft of torque. If you need that much, a good custom tune can probably get you that with the stock heads. Or throw on some long tube headers and get a good custom exhaust and a tune and you will definitely be over the power the 706s will get you.
I'm not telling you that you can't use them. But, as someone who had done many different engine builds... high compression daily driver trucks are no fun.

Thank you. That is exactly what I was looking for, there is so much information out there. I appreciate your perspective.... the last thing I want to do is throw some money at this and not be at all happy with what I end up with.

I haven't looked at the exhausts yet...

 

[Marky Dissod]

On a toy/race application it is fine. On a heavy truck/suv I wouldn't do 10.7-to-1. You would see some tq advantages -
but unless you plan on running E85 for the 106 octane it had, ALL THE TIME, the extra compression is not worth it.
The 862-706s are worth about 12 lb ft of torque ...
I'm not telling you that you can't use them. But, as someone who had done many different engine builds ...
high compression daily driver trucks are no fun.

@Mudsport96, would you mind expanding on what makes high compression daily driver trucks no fun?
How'd the SSR / TrailBlazer SS / 9-7X Aero get away with the LS2's 10.9-to-1?

 

[Mudsport96]

SSR was "light at 4600ish lbs", therefore the engine loads were not what you would see in a "heavy" suv. You would be more likely to spin the tires than to load the engine to a point it would knock. The TBSS and Saab had the e38 computer that has far more processing capabilities than the P01 could dream of and still more than the P59 so the fueling and timing strategies could handle the higher compression. They had better gear ratios than even the 5.3 extended trailblazers to help with mechanical advantage. One of my good friends just sold his SS because he was tired of "feeding" it 93.

The biggest deal is the fact that he will be required to run at a minimum of Premium fuel at that compression, and in a Burb with the fuel mileage that will be expensive. Could he run 87? Sure, but he will constantly be on the knock sensors and performance will suffer. Could he get a custom 87 tune and get some back? Probably, but at that point you are negating the power you bolted on in the first place. Rule of thumb when engine building. If you can get close to the same power from a bolt on that a jump in compression will gain you... save the compression for last. He if wanting more should do long tubes and exhaust.
Plus he specifically said for towing .. which in itself adds load stresses to the engine. Why did the 2500 and 3500 HD trucks get the LQ4 and not the higher compression LQ9 if power was needed and compression didnt matter? Because one they knew the customer was not going to use premium fuel when towing. I know after looking at the ignition tables of my father's 2002 2500 GMC that there is a large gap between the low octane and high octane spark adjustment tables. So he ran a couple tanks of 93 to see what would happen. Empty bed and no trailer saw minimal effect. Towing however, saw almost a 2mpg gain on average over 300 miles. Tandem axle trailer loaded with a Dodge Dakota. Why the gain? Could be many things, but data logs showed about a third of the knock counts on 93 vs 87. So the truck could stay on the more aggressive timing table and get more power and mpg.

And two, the ecm processing capabilities were not there yet and they would have to crutch the engine with less timing to stave off detonation. After already ( in my controversial opinion) ham-stringing the LQ4 with the LS1 cam. Yeah it makes more power up top, ( and FAR more than the LM7 at EVERY RPM) but I think the L33 cam would have been better. Buy they used that cam anyway. Why? Maybe they needed to bleed off cylinder pressure at lower rpm to avoid knock so they used the Camaro cam to do that.

At this point I forgot what we were talking about and look like an old man yelling at clouds....

 

[tooleyondeck]

Besides replacing gaskets/components that show wear, the only change you should have to do mechanically is remove the clutch fan from the 03 LQ4. Your 05 Burb should have efans, so keep your ECU and harness from your 05 and have it reflashed with a 6.0 tune that retains the efans and you should be good to go.

 

[project_x]

Besides replacing gaskets/components that show wear, the only change you should have to do mechanically is remove the clutch fan from the 03 LQ4. Your 05 Burb should have efans, so keep your ECU and harness from your 05 and have it reflashed with a 6.0 tune that retains the efans and you should be good to go.

That's exactly what I'm thinking about now.
I will get the oil analysis done and take a look inside the valve covers to see what it looks like