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1997 6.5 turbo 2500 suburban power/temp & tuning

Martin White

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Hi I have a 1997 Holden/GMC 2500 Suburban with the 6.5 turbo motor. We have had the vehicle for 12 years and it has done a great job. We have been up & down Australia with it and towed our Ford Falcon race car too. It used to be okay power wise but now it has become gutless & wants to get hot. I have little experience with deisel motors but plenty with petrol engines. We have purchased a new set of heads from Summit as ours are cracked. I have bored and decked the block and balanced the rotating assembly. I would like to look at changing the cam profile to increase the torque. Also we don't have anyone down here who can help check/replace the Stanadyne pump. I am sure this could be part of the heating & lack of power problem! Any help would be appreciated. I AM SURE with the right advice this thing can perform as it should. I know another guy with one and he is ready to give up on his 6.5 and fit a Toyota V8!!
thanks for any help.
 

Will L.

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Welcome. Ya wont find many options for big improvements in the cam unfortunately.

The best reliable power is usually found dropping compression and using much larger turbo.
What injection pump do you have— The electronic ds4 or mechanical db2/db4?
If db2, you might do better to do what I and some others here are doing for the pump- member Rockabillyrat building up ours.

New QUALITY injectors (many junk ones available) makes a big difference and so does having the pop pressures balanced so they are all equal. If the pump is built, getting the injectors to match that output helps a lot.

A set of gapless rings on the second set doesn’t really help the power but sure keeps the compression up longer and keeps oil life much better. Eliminate the cdr and get a provent200 is a good idea too for that oil and keeping the turbo clean of oil.

There is plenty of other little things to do to help. Definitely do some reading in the 6.5 performance section.

If you can return those heads, a set of p400 heads would be better. More price obviously but helpful.

Give a lot more details of what you have, want, and budget and then we can direct you better. Pics are helpful, as well as fun.
 

MrMarty51

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If the crankshaft was turned or polished in the balance process, then, You will want to get it coated. I am not sure what the factory used for coating on the cranks but I have read plenty of cautions to not grind or polish these crankshafts. Possibly a nitride coating would work.
Also install a fluid dampener harmonic balancer and a billet front crankshaft pulley.
ak diesel driver has a thread about installing the duramax electro/viscous fan system on these trucks and that fixes the biggest share of the cooling system problems.
Welcome to the forum. From another Martin. 😹😹😹
 

MrMarty51

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Here is the thread on the electro/viscous fan system conversion.
Be sure to install new poly tech motor mounts before installing this system. If the mounts is sagged then this Duramax fan will drag on the lower fan shroud.
 

Twisted Steel Performance

Anything worth doing is worth overdoing.
Vendor
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Well as stated, I am a firm believer in 18:1 compression over the stock 21:1, more boost and fuel need somewhere to go and with lower cylinder pressures it doesn't present as much trouble long term on hard parts...

I custom machine stock pistons to lower compression AND provide valve reliefs, and I can apply a ceramic thermal barrier to help keep pistons cooler as well with new valve springs better designed for more boost than the stock springs.

I also offer a custom ground camshaft, my towing/rv grind.

I offer the only "main cap Halo girdle" on the market that fits all blocks if you are interested...

With the right intrenal parts and mods, these motors can provide the power and fuel economy needed in today's world..

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This forum can help you go in the right direction much better than FB groups ever can....
 

Martin White

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Welcome. Ya wont find many options for big improvements in the cam unfortunately.

The best reliable power is usually found dropping compression and using much larger turbo.
What injection pump do you have— The electronic ds4 or mechanical db2/db4?
If db2, you might do better to do what I and some others here are doing for the pump- member Rockabillyrat building up ours.

New QUALITY injectors (many junk ones available) makes a big difference and so does having the pop pressures balanced so they are all equal. If the pump is built, getting the injectors to match that output helps a lot.

A set of gapless rings on the second set doesn’t really help the power but sure keeps the compression up longer and keeps oil life much better. Eliminate the cdr and get a provent200 is a good idea too for that oil and keeping the turbo clean of oil.

There is plenty of other little things to do to help. Definitely do some reading in the 6.5 performance section.

If you can return those heads, a set of p400 heads would be better. More price obviously but helpful.

Give a lot more details of what you have, want, and budget and then we can direct you better. Pics are helpful, as well as fun.
I am removing the pistons from the rods so I cam machine the top of the pistons. The pump has DS483 on the tag. I want to do this once so if i need a better setup let me know and i will. It's not the easiest thing to work on in the truck.
 

dbrannon79

I'm getting there!
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Welcome @Martin White . is your rig a manual transmission? if so you might do good by converting the DS4 injection pump to a DB2 mechanical. only mods that are needed is the accelerator cable bracket and foot pedal in the cab as yours is all electric "drive by wire". of course you'll need the timing marks on the timing cover to get it in time manually. for your DS4 IP, there are no "NEW" left available. anything you see advertised as new will be a rebuilt. Stanadyne no longer makes any parts for the electronic pumps. only the mechanical are still being manufactured new.

converting to mechanical with a 4L80E automatic is doable but a little more costly since you need a stand alone trans control unit to replace your existing engine computer.

but before doing this type of modification, check with your local EPA regulators. here in some states it will never pass inspection.
 
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