Thoughts on rebuild options

[jmack91z28]

Well i'm going on past 300,000 miles and I know there can't be much more life left in it. My 6.5 still runs great and is averaging 18ish mpg, but i'd still like to have a good plan. I'm trying to figure out the best and most economical option for it.

I've got the 93 model 6.2 with 130,000 on it sitting in my shop. I could swap the 6.5 top end over onto the 6.2 bottom end and have the DB2 sent off to Accurate Diesel. Tim said he can rebuild it and put a .31 pump head on it for around $500 which isn't bad I reckon. I wouldn't mind locating an HX35 or similar and running it with about 8-10 psi boost. I don't tow much with this truck, that's what my 2500 is for. I'm just looking for a solid fairly reliable build that will get best fuel economy possible.

I've also thought of the infamous 4bt swap too. That'll end up running my $5000 by the time i'm done with that, plus i'd have to fab up motor mounts and what not. People claim 30 mpg, but I think thats a heavy exaggeration.

I've always heard better things about the 6.2 than the 6.5, but that's because it's NA. Whats the best all around route here, in yalls opinion.

 

[WarWagon]

Runs great - don't fix it. You may have one of the few high mile capable 6.5's.

Heads are likely cracked on the 6.5. tear down what you have, check for cracks and decide from there. Nothing wrong with 6.2 heads on a 6.2 bottom end with a turbo. The passenger side injectors have zero clearance but it does work.

Head studs, re-ring it, and new injectors and your 6.2 is a viable replacement.

Mean time it will run great till the cracks kill it sudden like. Even if the entire engine is scrap metal you can drop in a used 6.2 and new turbo for less than $3000.00 in parts.

 

[jmack91z28]

Yea that's what I figured a 6.2 rebuild would cost and a little extra for boost and pyro gauges.

Reason I wanted to use the 6.5 heads was I just bought injectors for it, not a big deal really, new delphis aren't that expensive anyways.

Like I said, i'm planning ahead. I'm going to run this engine until it lets loose. I just don't want to be dead in the water for a month or two with no plan at all.

Thank you sir.

 

[tanman_2006]

a 93 6.2 SHOULD have the same heads as a 6.5 with the smaller/econ precups.

 

[dually man]

if you use the 6.2 dont forget to coat the pistons if you are using a turbo. that makes for a good setup

 

[jmack91z28]

if you use the 6.2 dont forget to coat the pistons if you are using a turbo. that makes for a good setup

Are you talking about ceramic coating?

That would be very convenient if the 93 had 6.5 heads and I could just swap injectors when the time comes. Would the lines off the DB2 match up correctly? Would there be enough clearance on the passengers side?

 

[NVW]

Are you talking about ceramic coating?

That would be very convenient if the 93 had 6.5 heads and I could just swap injectors when the time comes. Would the lines off the DB2 match up correctly? Would there be enough clearance on the passengers side?

You should be good.

 

[chevytrucksonly]

Some good Ideas already. Northern auto sells the best re -ring and master kits with top of line components. If you have a 6.2 that has a one seal bottom end then use it and have your 6.5 heads built, ported and coated along with the pistons. Invest into a dual thermo/hi flow water pump.

MDS

 

[jmack91z28]

Some good Ideas already. Northern auto sells the best re -ring and master kits with top of line components. If you have a 6.2 that has a one seal bottom end then use it and have your 6.5 heads built, ported and coated along with the pistons. Invest into a dual thermo/hi flow water pump.

MDS

They actually are about $100 cheaper on the master kit as opposed to enginekits. Looks like better quality parts as well.

 

[WarWagon]

1982 6.2 heads are out. The rest of the 6.2 heads have a different injector angle and bigger exhaust valves. The 6.5 injectors will work in them. The 90's heads may not be like that, but, any 6.2 head can do the job cept the 1982 fine thread.

6.2 turbo passenger side injector lines can use a couple manifold gaskets for clearance. Header wrap helps in all cases. I got away without manifold gaskets, but, will have to pull the manifold to change injectors. Some slight inj line bending is required.

I would not bother with a dual stat housing - just not required. Do the other cooling upgrades.

 

[chevytrucksonly]

Seem to be the best I seen so far including price as you said..
MDS

They actually are about $100 cheaper on the master kit as opposed to enginekits. Looks like better quality parts as well.

 

[jmack91z28]

War Wagon, so you're saying stack 2 exhaust manifold gaskets on the passenger side to allow more room for the injectors and lines to clear?

I see you've used ARP studs for your heads. Have you had any leaking issues at all? If not what did you do to prevent leaking, i've been reading about some people having sealing issues with ARP's. How much boost are you running? Also what CR are you running?

Thank you.

 

[chevytrucksonly]

A dual thermo/ hi flo pump is not required but it provides one of the best cooling upgrades that you can invest in -do the research. Here's one piece of data-there's many more.

The new 130-GPM water pump increased coolant flow through the block and heads by 74%, and through the radiator by 9%. The motivation for increasing the coolant flow-rate was to help eliminate hot spots within the engine and to reduce cylinder head cracking. Dual thermostats were required to both increase the flow rate capacity and to prevent pressure surges within the cooling system. I was told that these surges could result in water pump cavitation, cause gasket leaks and in some cases loosen soft plugs when running a single thermostat.

• The single thermostat would only flow about 90 or so GPM, so when the larger water pump was added, the decision to go to 2 smaller thermostats was less expensive than designing a new larger thermostat and associated housings. They also added a surfactant to the coolant that was available from the medium duty truck program. That product has since been dropped from the GM service parts list, but it is available through NAPA auto parts stores."

The 1992 to late 1996 model-year 6.5 was equipped with an 87-GPM water pump and a single by-pass blocking thermostat. The photo at the top of the page shows what components are necessary to upgrade a 6.5 to use the new 130-GPM water pump.

Why should you not use a single thermostat when installing a 130-GPM waterpump? The photo on the left shows an early 1996 6.5TD single thermostat, which is a "by-pass blocking" design. This means that once the thermostat is fully open and the by-pass port is blocked, all coolant flow must pass through the open thermostat. The by-pass port blocked by a fully open thermostat is shown on the right.
You've got a single thermostat capable of flowing 90-GPM, but you also have a water pump pushing 130-GPM with the engine spinning at 3000-RPM. In this situation, the water pump will either cavitate and/or create excessive cooling system pressure beyond the normal 15-PSI. This pressure will build between the output of the water pump and the thermostat. Will this excess pressure cause coolant leaks, loosen soft plugs, or cause water pump cavitation? GM said it will. To prevent this, you can either install a non by-pass blocking thermostat or install the twin thermostat components. However, you'll need all of the hi-capacity components (including dual thermostats) to fully benefit from the increased flow rate.

• 
  If you use the GMT800 water pump on your 1994, just make sure that you use the entire cooling system, crossover included. If not, the higher flow pump will create excess pressure in the system due to the restriction of the crossover. This also creates some tricky fabrication as the AC compressor and alternator were swapped to allow rear entry of the upper radiator hose.
  
  

This 9-blade 21" fan was a GM prototype that was developed for the (at the time) upcoming 1999 Silverado body style trucks. As time revealed, GM dropped the 6.5 from the new truck engine option list, so the fan never went into production, and the 215 hp rating was shelved. I used this prototype fan and one of the new 130-GPM water pumps with a screw-on style fan-clutch in our 6.5TD Power Project.

I was disappointed that the fan I received wouldn't become an over-the-counter item. I knew other 6.5 owners could benefit from a larger and more efficient fan, but it didn't look like a cost-effective alternative would ever become available. However, soon after acquiring a Duramax equipped 2001 GMC in December 2000, I carefully examined the fan used on the Duramax, and thought it looked very similar to the 6.5 prototype fan I received earlier. I began to think, "what if". So, I ordered a new Duramax fan from the local GM dealer and a new 6.5 fan-clutch would fit the 1997-2000 6.5 fan-clutch.
Today, several vendors, who specialize in 6.5 products, offer the Duramax 9-blade 21" diameter composite fan as part of their "heavy-duty" 6.5L cooling system upgrade. With a wholesale price of about $40 (GM pn-15010202), this is a cheap and effective cooling solution - though you will need a 1997 or newer 6.5 fan-clutch. The fan bolt pattern used on all earlier 6.5 fan-clutches won't fit the new fan.
The dual thermostat components, 130-GPM water pump and 21" fan comprise a great package that was designed to improve both 6.5 reliability and cooling. Some argue that a single thermostat is perfectly OK or is actually preferred, when using a 130-GPM water pump. The complete package, as designed by GM, makes the most sense for those who want the best possible cooling system performance.