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So my 5.3 has an issue... New heads or 6.0?

redheadedrod

SM 2017
PM 2015
Full Member
Joined
May 15, 2011
Messages
3,187
Location
Muskegon, MI
So my truck recently rolled over 260k miles and I noticed that I have been loosing coolant slowly but not very obvious. Had a mechanic check it out and he said the water pump was leaking and he thought he could see some indications that coolant had been in the heads by looking through the oil filler line but could not diagnose fully without pulling the covers off. The covers leak a little bit of oil at this stage but at this many miles I would not be surprised by any oil leaks I find. Although I only loose about a quart of oil for 5,000 miles so I haven't been worrying about it.

Since I suspect a coolant leak I also took note of the recent revival of the "mysterious coolant leak" thread. I checked and do have the 706 casting on the passenger head. So it is likely that if I do continue to loose coolant that it is due to the head being cracked. At this point this truck is not daily driven and will be monitored.

So now I have to consider plans for the future. With 270k miles I question if it would be smart to pick up a set of performance heads, new cam, and basically the whole top end or should I be considering a 6.0? At the current time I checked an I can get a junkyard 6.0 with 150k miles on it for $1500.  So if I got the 6.0 I really should be rebuilding it anyhow unless I get a low mileage motor.

My biggest concern is if I put a whole new top end on my truck is that I still am using the old piston rings and rest of the lower end and am almost better off yanking it and having a full rebuild done. If I go through that effort I would likely look at upgrading the motor for potential forced induction down the road. But then again forced induction on a 4x4 is looking to replace the rest of the drive train too.

When I retire in 5 years I will have much more financial flexibility...

But for now I am still in school and working full time and more interested in a reliable vehicle.  (Note I have a 2009 CTS-4 with 170k miles as my "beater" car. Those in the rust belt understand what a beater car is... ;)  )

So I would like to open up discussion on what options are out there. I will be getting some quotes on changing the heads as well. I have the ability to do the heads myself but virtually no experience in doing such work. I just took on a promotion at work that will have me doing maintenance work which will range from rebuilding machinery that we use to rebuilding electric motors (bearing installation) as well as rebuilding industrial pumps. So I am mechanically inclined but not sure that I want to be working on the heads of my truck. There certainly is value in getting something done by someone else that does it day in and day out. But then again if I can save myself $1500 and do the work myself it might be worth the shot...

And I assume changing a CAM when the heads are off is not a big issue. Basically pulling off front over,  pulling off the timing chain and change the cam.

Rodney
 
One thing that has always bothered me about coolant mixing into the oil is what happens in the bottom end. Happened to me years ago on a Ranger. Fixed the top end and 10k miles later a crank bearing seized up and made a mess of things all over again. If you're going to take the top off, pull the whole thing, take your time and build it right.
 
X2 once you have coolant in the oil, it will get in the bearing,
 
I had a cracked head about 3 years ago on my avy and leaked a good amount of coolant into the oil. When I pulled drain plug good half gallon or more came out before oil. Couldt afford a new engine so I put 2 new heads and all new gaskets for anything removed. Been running fine ever since.
 
At this point there is no sign of coolant in the oil but from reading the thread about this particular head issue it sounds like the coolant is not real obvious since it is only a small amount and since I just changed the water pump I am not 100% certain that there is an issue yet but I will be closely watching it.

I am more or less trying to decide on the smart options and plan for it now in case I find that it is indeed an issue. Having replaced the water pump it should show up if it is actually an issue.

 
My .2 putting a new top end with that many miles and not knowing what contaminates are in the lower end or condition pushing the compression back up is questionable. Then doing all that work and have it fail. Rebuilding with high miles you could be looking at having the block machined new piston and rings ads up quick if you do not have the connections for the 5.3.
You would be way a head of the game with a low mileage 6lt of like year they?re still out there or like the one you have found with a compression check and checked over with some kind of warranty. Should get you by until you retire.

.2 number two. By the 6lt now hope the 5.3 lasts until you are ready. You could collect the parts for the build you want (FI) for the 6lt. If the 5.3 fails before you?re ready you have a back up to get you by.

I have the mysteries coolant disappearing act. Change the thermostat and water pump when I put the fans on. I still have a low coolant come and go. The AVY now has 180k on it. Never have seen any sings of oil contamination. Hope it last until I get the transmission and rear end beefed up before it goes.    

 
MyBigToy said:
With that many miles and a suspected head issue I would cut my losses and buy a crate motor.

Kind of where I am headed at this point.

I just don't see a good reason not to replace or rebuild the motor?
With 260k-270k the engine has had a good life..

Hmm I should try getting flint 4x4's old truck... But guessing they might ask too much for it.

 
Engine probly already pulled from flints. Ls based engine with that amount of miles don't last long at a scrap yard.
 
I'm pretty happy with the route I went when I was getting a misfire from Cylinder 7 and bought this:

https://www.summitracing.com/parts/hpe-hp93

They had to replace the first one after it dropped a valve, but have about 10K miles on the second one which is running fine.
 
enoniam said:
I'm pretty happy with the route I went when I was getting a misfire from Cylinder 7 and bought this:

https://www.summitracing.com/parts/hpe-hp93

They had to replace the first one after it dropped a valve, but have about 10K miles on the second one which is running fine.

Any idea what the camshaft specs are on that one?
 
Bigtrucklover said:
Any idea what the camshaft specs are on that one?

I can only comment on my impressions since I don't know what camshaft they used.

Engine is rated at 460 hp - 470 ft-lbs.  Has a good bottom end and I'm doing my WOT shifting at 6000 and it's still pulling well there.  That said unlike the 5.3 which seems to be leaving something on the table after WOT upshifting, this engine has enough torque that you keep smiling after the upshift.  I would guess it's something in the 205-212 degrees open at 0.050" range.  Has a slight bit of lope in the idle so I'd say probably 214 LSA or so.  I'm running 42 pound injectors and comparing the duty cycles I'm seeing with them compared to what internet sources say I should be seeing for a 460 hp motor the rating seems to be pretty close.
 
So I may have jumped the gun on this one. After changing the water pump and some hoses and topping off after a couple hundred miles to account for any air removed in the system I have gone almost 1,000 miles since the water pump has been changed and have not lost any fluid.  I have the heads with known issues so I SHOULD consider what I want to do down the road.

(Looking to wait about 5 years then will likely start building my truck into an off roadable "beast")

So since I have no clue what I am doing with the whole lifting and prepping for off road I will need some guidance. For now if I look at upgrading to a 6.0 and build a strong one how much can the stock drive train really handle?

I MAY go with a super/turbo charger as well.

enoniam, that engine you mention looks like it will need a lot of stuff added to make it work. What did you have to change in your system to add this new engine and what changes did you need to make to your drivetrain to keep it durable?

When considering an LT1 engine for my caprice a shop I saw had an LT1 that was built up and was rated at 600/600 hp/torque. Needed just the intake and accessories added to it. Already had the oil pump, pan and everything else on it. They also had a forced induction ready version for same price. Forced induction version was closer to 1000 ft/lbs but had different cam and some other changes to support the forced induction. Of course those engines were both about $6000 in the early 2000's so not even sure if the company is still around.

Not sure that I need THAT much power but I would certainly want to install something that can support forced induction.

Rodney
 
There's lots of info on the site already. The transmission needs to be beefed up at least slightly. You should plan for the G80 possibly giving up the ghost; this is by no means a surety as I put over 70k miles on mine after supercharging it. If you go forced induction you will have to fully build the transmission, especially if you go the positive displacement route (Magnacharger, Edelbrock, etc.) becuase they stress the drivetrain a lot more due to the massive amount of torque they make immediately off idle. Huge torque, 6200 lbs, and a marginal tranny do not play well together. I tweaked mine (shift kit, billet servos, hardened separator plate) when I installed the Magnacharger and it lasted about 60k miles before the clutches gave up the ghost.
 
For me, there wasn't anything added to the 6.0 that wasn't already on my 5.3 but I did tweak the computer tune some of course.

That said, I already had 42# fuel injectors on the 5.3 to support the extra fueling for the supercharger's added airflow.  That is something you will need to add, besides the tuning.

External to the engine, unless you have a flex-fuel vehicle you will probably need to add more fuel pump capacity.  (Flex-fuel vehicles come from GM with higher-capacity pump.)  I've got a Vortech booster pump on my truck that I got with the supercharger.  You can also change to a higher capacity in tank pump, or add a voltage booster to provide more juice to the stock pump.

The G80 rear end isn't the strongest - a True Trac is a better performance choice anyway.

Stock tranny is really marginal at near stock power levels.  I've rebuilt mine myself.  I've used the 5-pinion planetaries from the 4L65, hardened output shaft, Super Shell, Alto Red clutches, wide high-friction band and super hold billet servos to up the power-handling capability, and various other goodies to improve shifting performance, high rpm capability, etc.  I should have kept better track of the mileage when I installed it so I know how many miles are on it now - I'm guessing 60-70 thousand miles.

This 6.0 has more low-end torque than the supercharged 5.3, but the 5.3 with the centrifugal supercharger had significantly more top-end horsepower.  I was about to install a voltage booster for my fuel pumps as the supercharged 5.3 was showing a drop in fuel pressure even with the booster pump.  With the water/methanol injection I was running my wideband O2 sensors didn't show I was running lean, but I may not have been running rich enough to keep the #7 cylinder from developing an issue causing slight misfires.  I'm not having any fuel pressure issues with the 6.0 with the same fueling capability.
 
From the looks of that 6.0 it needed at a minimum an oil pump/pan. The 5.3 fit on? I would have assumed they would include the oil pump and cam etc.. But the picture I saw didn't show the timing cover on and wasn't apparent if the oil pump was in place.

Can your 6.0 handle a centrifugal SC or Turbo? May go with a Turbo for more top end power since it sounds like the low end torque is decent.

Not a BUNCH of boost but maybe enough to get close to 600hp.

I would expect to have to replace components when I start making it an off roader but we can start at the engine at least.

Rodney
 
I had ordered an oil pump from Summit because it doesn't show that an oil pump comes with the long block but there indeed was one with the 6.0 when it was delivered so I returned the one I bought back to Summit.

Oil pan fits nicely.

I've read in other forums that ATK doesn't recommend boosting this engine but they will build one for you that will take the boost.  I believe the limiting factor to be the hypereutectic pistons.  GM claims they are only good up to about 550 hp - their highest rated hp crate engine with them they rate at 556 hp.  Assuming most if going to boost will boost at least 8 psi that will add about 50% to the power output, making about 700 hp at the crank, well over what GM likes to do with those pistons.  That said various car mags have run much higher boost levels through various stock LS engines, some to failure at over 1000 hp.  I'm probably going to end up bolting on the Vortech SC that's collecting dust in my garage eventually to this engine.  I, and KY_Bob who I bought the SC from, both saw up to about 11 psi with it on our 5.3 cammed engines, but I'm thinking it will be a bit more undersized on this engine which will likely keep the boost down to the 8 psi level or so.

In the end it will largely come down to how much do either of us want to risk damaging the engine versus paying for hopefully better reliability.  Keep in mind Bob saw within a **** hair of 500 rwhp on his AV (SC plus nitrous - I was there when he dyno'ed it) so assuming a 20% drivetrain loss, which is probably on the low side considering going through a transfer case and the offroad wheels and tires on his truck, so it was probably at least 625 hp, probably quite a bit more, at the crank.  Other than cam and valvetrain upgrades his engine was stock.  He put maybe 10K miles on it before pulling the SC and selling it to me, and then of course selling me a bit later the rest of the truck.  We put maybe another 20K miles on that engine before selling the truck with the engine having as its only power adder a cam, plus the valvetrain upgrades that were installed with the cam, while we had the truck.  Engine had about 90K miles on it when we sold it and the truck ran fine (02 AV).
 
Ok thanks for the feedback. So your saying the drivetrain held together just fine with it. I guess if I keep from slamming the gears or WOT take offs maybe that makes a difference too?

Like I said, I do have time to study up.

Oh and if you still have that SC and havent installed it in 5 years we should talk... ;)

Rodney
 
redheadedrod said:
Ok thanks for the feedback. So your saying the drivetrain held together just fine with it. I guess if I keep from slamming the gears or WOT take offs maybe that makes a difference too?

Like I said, I do have time to study up.

Oh and if you still have that SC and havent installed it in 5 years we should talk... ;)

Rodney

I'm not saying the drivetrain held together just fine, just the engine itself.

Bob had the tranny rebuilt and had to replace the rear end.  The tranny later went out while we had it.  I rebuilt it once but a year and less then 10K miles later it was going out again so this time I had someone else rebuild it.  When I got into it I could see some things that were done by the previous rebuilder that weren't the way to go rebuilding 4L60s - I believe the shop that Bob had rebuild it was experienced with other types of transmissions but not these.  The problem after I rebuilt it was the 3-4 clutches went out - we drove it 10s of miles in 2nd gear.  The shop that I took it to said there was some fix that wasn't too well known that they did to keep those clutches alive longer - maybe they just said that to make me feel better about my rebuild not lasting?  I've got around 60K I think on Ol' Yellar's tranny that I rebuilt, may be more like 80K.

I don't think WOT takeoffs are a problem but slamming gears hard can be.  Bob had that thing chirping the tires on the 2-3 WOT shift.  However I had to re-rebuild my tranny less than a week after I initially rebuilt it when on a hard 1-2 shift, at less than WOT, I shattered the tranny output shaft.  This was before installing the supercharger.  You can read differing thoughts online but from Bob's and my combined experience I believe the longer output shaft on the 4wd 4L60s has a bit more torsional give to it which allowed Bob's to live while Ol' Yellar's (2wd) shattered with the biggest engine power adder installed at the time being a cam.

Bob pushed that truck pretty hard.  Chirping big off-road tires and wheels on most 1-2 shifts and WOT 2-3 shifts, running down the dragstrip in 4wd to get better traction off the line, etc.  Bob felt he had the fastest lifted AV, period.  It was an 8-second 1/8 mile truck which he was pretty proud of.  Drivetrain parts behind the engine were found to be the weak links but there was never a problem with that truck's engine.
 
So I am bumming again... Noticed today that when I start the truck the first 1-3 seconds there is a tick that goes away. My guess is the top end isn't getting lubricated right away. Checked the coolant level and the coolant level was at the bottom of the bottle so it looks like I do in fact have an issue still. Since I know my valve covers leak a little bit I will likely pick up some gaskets and pull off the covers and inspect for cracks.

I will be contacting that engine place and see if they have any suggestions for a blown motor. If I am going to install a 6.0 I might as well plan for the future.

Due to having another vehicle I won't be using my truck as a daily driver but more of a backup to my car and eventually just a toy. But first step I see is to get the motor solid.. Guessing I should also upgrade/replace the motor mounts when I have it out but will the stock radiator work with this engine? I have a mechanical fan on the water pump so should I consider switching to an electric fan setup?

Rodney
 
I didn't change motor mounts (unless mechanic did so without my knowing).

I'm running a "stock" replacement radiator and e-fans.  Seems to work ok for now although definitely running the fans more now in the summer.

I've thought about rewiring the fan harness so when it is triggered by coolant temp without the AC compressor on both fans run at high speed vice low.  (Fans wired in parallel across 12v vice serial.)  Currently only getting both on high when coolant temp trigger is reached and compressor is running.
 
I will pull the valve covers this weekend to verify the crack in the heads but I am considering what I need to do to make this work since I will need to do the upgrades regardless if I expect to do it due to potential engine failure or as an upgrade.

When I do the engine I will also pick up an HP Tuner license.

For you guys that have added power to your truck what maximum do you suggest to keep the same drivetrain parts as opposed to having to upgrade to a bigger rear end or 4l80e etc?

And would changing to a 6 speed auto from a more recent truck be worth while? Ie do they handle more power?

Should I get a wide band O2 sensor to tune with even if the OEM PCM will use the standard O2 sensors for normal conditions?

Other than fuel pump, fuel injectors, programming and I would assume bigger exhaust and probably headers would I want to plan to need?

Note I will likely have an engine built that can handle boost but not do the boost until I upgrade parts to take the power.

Sounds like a Roots style blower would produce more power than a centrifical blower but maybe a centrifugal blower would be nicer on the drive train durability. Nitrous won't be used...

 
If your shifts aren't programmed to shift hard, or if you don't have a shift kit installed, I believe you can get a lot of miles out of the drivetrain at 500 crank hp.  Conversely with hard shifts you can break things in the drivetrain with close to stock power.

A wideband O2 is very useful for tuning at WOT, especially for when you go boosted.  I tuned mine without one after installing the supercharger but was flying a bit blind...

I'm running shorty headers and a stock-sized exhaust behind them with a flowmaster muffler.  It was probably costing me power when the 5.3 was running with the SC - maybe now as well.

The "stock" ATK high performance 6.0 is 460 hp / 470 ft-lbs.  If yours is biased towards torque, which I think makes sense if you are planning to eventually go with boost, the centrifugal with add to the top end whereas the roots will add to the bottom which is already more robust than the top.  Adding an SC that makes the power plant more well-rounded makes for a nice setup in my book.
 
Will have to see how finances hold up for next semester. I was promoted almost 2 months ago into a job where I will be rebuilding pumps and motors in an industrial setting. Most of my work will be general maintenance and installing/removing broken equipment but I will gain experience doing the types of things that will do me well with automotive stuff. I still do operational work as well. I used to get paid to break stuff or atleast find the broken stuff. Now I get paid to fix what I break... Interesting concept.

So I could potentially rebuild most of my own stuff. And maybe learning how to rebuild my own engine with the right parts will let me not only save money long term but make me able to fix what I break down the road. But then again, it is hard to beat spending a little more money and having a warranty...

Only issue really becomes the specialty tools needed to do a true rebuild.. And the experience needed.

Thank you again for your input. I am sure when I get closer I will have more questions... Half tempted to see if I can get a set of heads and see how well upgrading the heads and cam go... If it goes well and the engine works well then I might consider grabbing a 6.0 and rebuilding it from scratch...

Rodney
 
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