GM Diesel Trucks & SUVs 

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Pictures of our 6.5TD truck

Performance Data

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NOTICE:
About
Discussion
Forums

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Recommended
  Products for 
  the GM 6.5TD 

6.5 PDC: Pump Driver Cooler

6.5 PMD / FSD Remote Harness

Gauges 

6.5 Dash Mounted Adjustable FUEL Control

Transmission Control 4L80E

All Hi-Flow Air Filters

6.5 TD Performance Cool Air Intake

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FOAM Air Filter WARNING

6.5 TD Turbo Downpipe

Performance EXHAUST Systems

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COOLING:
WATER
Mist Injection

Aftermarket
Fan Clutch
WARNING

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6.5 TD Intercooler
ADVICE

Dual Auxiliary Electric Cooling Fans

6.5 Hi-Flow Dual Thermostat Cooling Upgrade

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6.5 Oil Cooler Hoses/Lines
NOTICE and Upgrade parts

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Serious POWER:

PROPANE Injection

NITROUS OXIDE (N2O) Injection

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6.5 Gear-Drive
Timing Set
WARNING

IMPORTANT MUST READ NOTICES are Highlighted

6.5 Pistons, Low Compression, ADVICE

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Headlight Light Switch Saver and Light Intensifier 

Oil Pressure Switch Saver

 Ignition Switch Saver 

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6.5 Stock Airbox

6.5 Stock Exhaust 

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Recommended
  Products for  
  the Duramax  

Duramax 6600 Performance 

Cool Air intake

Power Box

Performance Exhaust

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The Magnus-Moss Warranty Act ______________

GM 2001 HD Silverado / Sierra Power Launch Tour

SEMA 2000 Show LV NV

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SCARAB Offshore Powerboat

1979 Pontiac Limited Special Edition Trans-Am

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Disclaimer

LINKS


ABOUT: Lower Compression Pistons

 Lower compression pistons were tried in later model GM 6.5 in an attempt to lower piston temps and reduce pistons from 'grabbing' the cylinder walls when hot. For a manufacturer or engine builder it is easy to change pistons you just change the ones you are using in the parts bin, for those of us with them already in an engine it's a lot more involved and to be done correctly an engine rebuild is required. The cost of such is prohibitive and even if you are doing a rebuild the prices are way over those of stock ratio pistons.

 I have found the best thing to do is to use water-mist-injection, this keeps piston temps down acts as an air-charge cooler and also helps to keep the combustion chambers and engine oil cleaner.

 Because I hate to see people fall victim to marketing 'scams' and buy over priced parts when they don't need to, I will tell you other ways IF you still feel you must lower compression, and this can be done other less expensive ways than the guys trying hard to sell you on their (or their friend's) pistons will tell you, you can either use thicker head gaskets or if you are getting new pistons, get stock ones that have some material milled off the top, the small amount milled off will make little if any difference in the strength of the piston, however lowering compression should reduce power output and efficiency of the combustion process. 
 The higher compression that can be run safely without overheating and detonation then the better the efficiency and power output, the key is to keep things cool. 

  We do offer quality pistons and rings and have lower compression available, sometimes they take longer as they are not a popular item. 

Then BEWARE, another tactic of those pushing the low compression 6.5 pistons is to then push "splayed main caps"...
Splayed main caps are not usually a "gimmick" but IMHO when used on the one for the 6.2/6.5 they are... Just because product or concept that is valid on one engine does not make it a cure all or fix for others, and this is the case here. Like changing rocker arm ratio on one engine type can show power gains, do that on another type and you can loose power, float valves or even break something. Simply put, copying a concept that is successful on another engine type does not make it a good idea, it appears the success of splayed main caps on another engine type is used as a means to try to market the "gimmick".
Now to explain why the splayed caps are a NOT such a good idea on the GM 6.5 Diesel. I've been building Hi-Perf engines since 1978, before I was old enough to get a learner's permit, the shop where I learned was a real turbo specialist call "Turbo People" and you could say I have a lot of experience when it come to splayed main caps, as I've personally used them on countless Chevy Gas V8's, on those we start out with a 2-bolt main block which actually has more meat to them than the 4-bolt blocks, then the block is machined to accept the splayed caps. The splayed caps can help to reduce some crank flex crank and usually do NOT strengthen the block, in fact material removal may weaken a block in those areas but on the Chevy Gas V8s it is not typically a concern as the blocks are not a prone to weakness unlike the 6.2/6.5.
Splayed Main Caps are a basically a waste of money unless you are pushing 600hp/800tq+ even then its hard to justify the expense, many do it for the "peace of mind" effect or bragging right to say "it's got 4-bolt mains". I've run and seen many Chevy V8s with twin-turbos and N2O, etc., run well in to 1000+TQ on stock 2-bolt mains. Hot Rod, Car Craft and many other magazines have written numerous articles and build ups on hi-po motors with huge power output running stock 2-bolt mains and they have lasted. Back to the 6.2/6.5, it is a block that is already weak and has been known to crack so machining it and removing material from an already weak link is not wise. Then the 6.5 block is already a 4-bolt main design, so to do the splayed caps you are drilling 2 MORE HOLES in to the block in places not intended for holes and near other holes, NOT good!. Remember on the Chevy V8s it is mainly recommend to add splayed caps to 2-bolt blocks.

Why do cranks break and blocks crack on the 6.2/6.5? Glad you asked :) Typically because of crankshaft flex usually due to an imbalance or excess vibrations, the harmonic balancer/torsional dampener on these engines is a weak link and should be checked at each oil change, inspect the rubber ring it should be intact and not have and pieces missing, large cracks and should be uniform in fit, if you notice any areas are migrating or bulging out or you see any problems etc. then REPLACE the harmonic balancer/torsional dampener. Another reason for problems is improper installation of the harmonic balancer/torsional dampener, be sure to use the proper removal and replacement tools, even if you have to rent them,- gear pullers and hammering it back on is not wise on a part that is already a weak link. I have noticed that the number of guys running the gear-drive timing set being sold for the 6.5 seemed to have a much higher incidence of crankshaft breakage and block cracking, this is most likely due to the removal of the cushioning effect the stock timing chain has, the harmonics and vibrations of the valvetrain are more directly transferred to the crankshaft. Now add to that the already weak link harmonic balancer/torsional dampener, or one with a deteriorating rubber ring, or one that is improperly installed and you can most certainly expect problems. Keep an eye on the balancer/dampener and do NOT install gear drive timing set, and it is not likely you will need to worry about crank or block breakage problems.

Our recommendations for cooling the GM 6.5 Turbo-Diesel What one website recommends as modifications for cooling the GM 6.5 Turbo-Diesel
Water-Mist-injection (WMI) $449.95, (plus tank avg. $75.00) 
Only basic hand tools and basic skills are usually required to install.
18:1 Low Compression Pistons $1000.00+ to supposedly reduce cylinder temperatures.
NOTE: Requires additional and very expensive engine disassembly, cleaning, machine work and reassembly. 
Read Note about this product.

nothing else needed with WMI

Intercooler $1400.00+ to reduce intake are temperature (IAT) 
NOTE: requires a fair bit of mechanical skill and more than basic tools to install.
nothing else needed with WMI '97 cooling upgrades $325.00+ adds more flow to current system
NOTE: they recommend a gear-drive timing set at the same time. 
NOTE: requires a fair bit of mechanical skill and more than basic tools to install.
nothing else needed with WMI Gear drive timing set $310.00+ 
NOTE: requires a fair bit of mechanical skill and more than basic tools to install. 
NOTE: READ WARNING ABOUT THIS PRODUCT
nothing else needed with WMI Earlier engaging fan clutch $250.00+ 
NOTE: READ WARNING ABOUT THIS PRODUCT

WMI kit is only $449.95 and tanks average about $75.00 in most areas.

TOTAL $3,285.00+ PLUS the added cost for expensive engine work to install the pistons.

 So as you can see from the above chart the site pushing products for GM diesels recommends a large bill of goods to reduce the cylinder temperatures and keep the 6.5TD running cooler, and then when your being sold on that stuff and need the engine work for the pistons you'll be advised to get splayed main caps and other nonsense you don't need and that can even be detrimental to the engine.  All that nonsense is recommended by them when one simply needs to use a water-mist-injection system to keep the 6.5 running cooler. 

Please Beware what you read at some so-called "information" or "resource" sites on GM diesels, often they sell the parts they're pushing. <

Pictures of the truck     Performance Data   
  Boost Control    Fuel Control  Transmission Control
  PMD / FSD Remote Harness   PDC: Pump Driver Cooler  
Performance Cool Air Intake  High-Performance EXHAUST System
 
Water Injection    PROPANE Injection    NITROUS OXIDE Injection
  Dual Auxiliary Electric Cooling Fans   Hi-Flow Dual Thermostat Cooling Upgrade
Oil Cooler Lines, Hose Upgrades    
Transmission Power Relay System   Headlight Relay and Light Intensifier  
  Fuel Lift Pump Relay System 

Downpipe   Converter Test-Pipe 
Stock Exhaust  Stock Airbox

GM 2001 HD Silverado / Sierra Power Launch   SEMA 2000 Show, Las Vegas, NV 
SCARAB Offshore Powerboat    1979 Pontiac Limited Special Edition Trans-Am LINKS     Hummers at a local dealer

 

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Disclaimer: Some products can adjust and/or increase power levels beyond factory parameters, so their use could possibly void your warranty, and may not be legal for use on emission controlled vehicles in some areas, due to these facts buyer accepts all responsibility for use, and his/her actions, there is no warranty either expressed or implied as to use of products, improper installation, settings and/or use of such could possibly cause property damage and or personal injury.  The Magnus-Moss Warranty Act prohibits a dealer or manufacturer from voiding your warranty unless a product is directly responsible for a failure.  Although effort has been made to try to present accurate information this website, it can contain some opinion, conjecture, errors, mistakes and typos so use any information with that in mind and if in doubt research anything you do not understand or question.  There is no guarantee or warranty on information on this website or any others it links to and visitors agree to hold authors, page owners internet service providers and web hosts free from any liability arising from use of information provided. Prices subject to change without notice.

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Last modified: June 01, 2002