LQ4 Build

RockChucker

English is important. Engineering is importanter.
Location
Highland
Close to 5 years ago, I picked up an LQ4 out of a GMC savannah with 205k on the clock. The van had been rolled, but I did hear the engine run, since I had to turn the van around in order to pull the motor. The effort was worth it and I snagged the motor and 4L80 attached to it for $550. I sold the 4L80 for $200 and voila, $350 LQ4 ready to play with.

And there it sat on a stand for years. I had always intended on building the motor. At the very least tearing it down to inspect bearings, replace the rings, etc. 205k is a lot of miles and I didn’t want to worry about the motor. Plus I felt I had a little room to put some money into the motor since I got it for about 1/4 the price of the going rate for a 6.0 at the time.

The scheming and research began. And I quickly realized how little I knew about engines and the nuances of building an engine to accomplish what I wanted it to be able to.

My list was as follows:
1. Smooth idle. Sure. The chop from a clearly cam swapped engine is cool. But not practical when you are trying to gingerly work through a technical obstacle.
2. Maintain vacuum so my brake booster still works. I didn’t want to deal with hydroboost and manual brakes suck. I like having power brakes. Call me spoiled.
3. 500ish horsepower. Because why not? After having my suspension tuned, I quickly realized I was running out of horsepower to drive as aggressively as the suspension will allow. Plus hill climbs and sand dunes.

Now how to get there...here’s the recipe I came up with.
1. A “moderate” cam. Comp Cams #54-424-11. Nice wide lobe separation angle of 115° to meet the requirements of 1&2 and put it well on the way of getting to number 3. This cam is optimum from about 1800-6700 rpm if I remember correctly. Been a minute since I chose. Ok like 4 years haha.
2. L92/LS3 heads. Casting number 823 or 5364. Scored a set on eBay for $500. I did have to replace all the intake valves. But I couldn’t complain. These are the best factory flowing heads aside from LS7 heads. I did install aftermarket beehive valve springs that are capable of the taller lift from the cam.
3. Gen IV truck intake. Because L92 heads have rectangle ports instead of cathedral ports. Along with an OEM 90mm ACDelco throttle body. Should breathe easy.

Now to the what I’ll call the consequential parts from looking inside the motor. After tearing it down, I found the cross hatching of the cylinder walls was all but gone. And there was a slight lip at the top. Bummer. Couldn’t get away with just a hone. Deeper inspection after taking the block all the way down to bear indicated that everything else was in ok shape. I told myself that if it was ok, I’d draw the line and not stroke it. That would have happened if the crank was done. But amazingly it looked good. No sludge buildup in the motor either. This motor had clearly been maintained pretty well. The cam bearings were toasted though.

I dropped the block and crank off at clegg’s in Orem. They did great head work on my duramax when I did head gaskets. I didn’t see any reason to not use them again.

The cylinder bores were no longer cylindrical. They thought they could clean it up with a .020” overbore, but I chose a .030” overbore for more common (cheaper/more plentiful) piston options. They also had to take .006” off the deck to square up the deck to the crank centerline.

I went with a flat top piston and aftermarket 4130 I beam connecting rods. I have it written down somewhere. But with the machined deck and piston heights available, the pistons come out of the hole a fair amount. The quench height is close to zero and the static compression ratio will come in a shave under 10.5:1. Pretty high. But the dynamic CR is under 9:1 with the cam I have selected.

Clegg also balanced the rotating assembly. Initial read showed the crank 1200# out of balance at 10k rpm. Not terribly surprising since the crank was balanced for the stock rods and pistons. After balancing, it is now only 11# out of balance at 10k rpm and only 3# out at 6000 rpm. Should make for a reliable motor.

I spent a small fortune on gaskets, new hydraulic lifters (a few of the original ones were cracked oddly enough) and the other parts to assemble the motor.

As of right now, it is a bare block with cam bearings installed. I applied a few coats of engine enamel last night while the block is still bare. As soon as my micrometer arrives, it’s time to get down to business and start assembling this bad boy. Should be fun. First time I’ve built a motor.

Plan is to have Matt Snell at Pauls auto and 4x4 tune it when it is all done. In addition to making the stand alone 6L90 shift like magic as well. More to come....
 

Greg

Are you not entertained?!
Admin
Great thread, love engine builds! ;) Really excited to see this come together and get in your TJ!

The cam looks like a great choice, the lift @ .050" tells a lot.... 212 int./218 exh. That's not a crazy cam, but should be plenty for your Jeep. The compression ratio is great, IMO. With that intake & the LS3 heads, I think you're going to have a monster... should sound amazing & have a meaty power range.
 

NYCEGUY01

Active Member
Location
Willard, UT
Needs more chop-chop...lol

Should run great though. Especially in a lightweight rig.

I brought home a 2500 Silverado a while back for the 6.0 and 4l80 for my newest project.
Ill prob just run it as is to get it together and then toss in a too big cam and converter because #RACECAR....
 

Mouse

Active Member
Thanks for the reply. I did some reading on the TCM-2650 and it sounds very promising in terms of running an 6L80E with just about any engine. Do you have first hand experience with it?
 

RockChucker

English is important. Engineering is importanter.
Location
Highland
Thanks for the reply. I did some reading on the TCM-2650 and it sounds very promising in terms of running an 6L80E with just about any engine. Do you have first hand experience with it?
Not yet...give me a few months 😎
 

Greg

Are you not entertained?!
Admin
Just for fun/discussion and comparison, here's the cam I've chosen for my El Camino 5.3 build... this one should have a good lope to it and make power from 1,500 to 6,600 RPM. I have upgraded the stall convertor to one that should stall 500 RPM higher than stock, to help get the car into it's power range quicker.

But.... is my cam is bigger than yours? :eek:


 

RockChucker

English is important. Engineering is importanter.
Location
Highland
Just for fun/discussion and comparison, here's the cam I've chosen for my El Camino 5.3 build... this one should have a good lope to it and make power from 1,500 to 6,600 RPM. I have upgraded the stall convertor to one that should stall 500 RPM higher than stock, to help get the car into it's power range quicker.

But.... my cam is bigger than yours. :p :eek:


Will be interesting to see how different they are. But...how is yours bigger? Yours has slightly longer duration and a smaller lobe separation angle, but my cam has more lift 😬

23361172-CF9E-49E3-A886-D2B5FA1B8680.jpeg
 

RockChucker

English is important. Engineering is importanter.
Location
Highland
After waiting for far too long to get a micrometer in the mail, it finally showed up.

Over the weekend I measured the crank journals (main and connecting rod) and cam journals.
The mains are a couple tenths over GM's mid range spec of 2.5585" ranging between 2.5586" and 2.5588". The connecting rod journals are a few tenths under GM's mid range of 2.0995" ranging between 2.0992" and 2.0994". The cam journals are a few tenths over mid spec of 2.1650" ranging between 2.1653" and 2.1655".

I installed the main and rod bearings, torquing the caps to spec. Using my mic as a reference, I zeroed my bore dial indicator to check bearing clearances. After talking with Earl at Clegg's and Matt Snell, I'm targeting 0.0015-0.0020" bearing clearance on the mains and 0.0020" on the connecting rods. GM spec on the cam should be between 0.0010-0.0030".

The mains clearances are mostly great, with clearances ranging between 0.0018 and 0.0025". Main #1 and #3 are a little wide at 0.0025". I'm going to do a little work double checking that there aren't any hooners on the cap mating surfaces causing the larger reading. I was careful to clean everything, but it is always possible there is a small burr or something. I'll hit the mating surfaces with my really fine stone I have to sharpen knives to knock down any high spots, reassemble and remeasure.

The rod clearances are too wide though. The rods themselves are in spec on the large side (Earl at Clegg's said that is common since you want a little more clearance on a high hp motor). I'm not worried about that. However the clearances range between 0.0028-0.0032". I think I have a little bit of a tolerance stack up worst case scenario on my hands. The crank journals are on the small side, the rods are on the big side and the bearings are on the big side (assumption on the bearings). I ordered 0.001" undersized bearings today that should be here tomorrow. Summit racing for "free" overnight shipping FTW!

The cam bearing clearances are my biggest concern. I measure 0.0038-0.0074" clearance. No good. After talking with Earl on the phone, he wants me to bring my cam and block back down to them so they can verify my measurements. They should take care of it, since I had them install new bearings for me. I'll drop that off to them tomorrow on my lunch break.

Tonight, I'll finish up making sure my ring gaps are good. I've checked all the top rings, and they are perfect. I imagine the 2nd ring will be good too.

I was hoping to get be close to having it assembled by this weekend and ready to degree the cam, but it looks like that might not happen. Hopefully it won't take to long to turn around at Clegg's checking the cam bearings.
 

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bryson

RME Resident Ninja
Supporting Member
Location
West Jordan
After waiting for far too long to get a micrometer in the mail, it finally showed up.

Over the weekend I measured the crank journals (main and connecting rod) and cam journals.
The mains are a couple tenths over GM's mid range spec of 2.5585" ranging between 2.5586" and 2.5588". The connecting rod journals are a few tenths under GM's mid range of 2.0995" ranging between 2.0992" and 2.0994". The cam journals are a few tenths over mid spec of 2.1650" ranging between 2.1653" and 2.1655".

...
"Tenth" must mean something different to an engineer than it does to me...?
 

RockChucker

English is important. Engineering is importanter.
Location
Highland
Clegg's verified my measurements on the cam were accurate. They installed some teflon coated bearings that should have tightened up the clearance. No dice. GM has a service limit of 0.006". They were going to install GM's service bearings and call it a day. I didn't want a brand new motor with service limit clearances. So, they are going to install 0.010" undersize cam bearings and grind the cam journals as needed to get to a 0.002" clearance. A small setback, but worth it in my opinion.
 

RockChucker

English is important. Engineering is importanter.
Location
Highland
Spoke with Clegg's this afternoon. Sounds like they will be grinding close to 0.005" off the cam journals to get 0.002" clearance for the cam. Should be done tomorrow afternoon.

I took advantage of the wait time on the motor this weekend to pull my really lightweight transfer case and crate it up to send in to TWF. This is for two reasons. Originally I was going to swap the 32 spline input shaft out and install the 29 spline input myself. But things came up and it needs to go in for inspection because I can't figure out why the range interlock is malfunctioning.

Last October when I was in Moab, my rear driveshaft started to squeak pretty badly. Sounded like the center ball in the CV was starting to go out. I was running front wheel drive only, unless I needed 4wd (read: lots of rallying up stuff in FWD is fun). Each time I put it in 4wd, the squeak got louder. I was milking it along so I didn't seize the joint up and cause a need for driveshaft replacement. A few of the times I popped the rear output into neutral, low and behold, the stupid thing went right past neutral and into high range. Luckily these all happened at nearly stopped speeds. Because when it happened, the jeep was stopped. Hard.

It was a massive pain to get the bound up drivetrain released and get the rear back into neutral. With some team effort and jeep rocking forward and back, we were able to get the front hubs freed up enough to release. Then 3 seconds later, the rear output was in neutral and we were on our way again. I took the "Hero" block visible in the pic off, and it seems like the range interlock should be working right. But something is up. Spoke with Todd, the owner of TWF and the case is going in for them to diagnose it. I'm not super happy about it, but it is what it is. Hopefully the turn around will be pretty quick and the case will be back before I am waiting for it after swapping in the new motor and trans.

Side note on the 6L90. I was hoping to gain about 1.5” of length in the rear driveshaft. No dice. Even though the actual trans is 1.5” shorter than my 4L80, I have a super short 2.5” t-case adapter. The 6L80 adapter that came with my 6L90 is 4”. I think everything will land less than 1/8” from where it is with the 4L80. Oh well. All good. This trans will be miles ahead of the 4 speed.
 

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