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W-Body Performance - Pushrod / DOHC

"No question is ever a dumb question when it comes to cars..."

Ok, after being up on the Internet for quite some time, I've been getting recurring e-mails about the same types of things (which is good, it's made me do my research). So, here's an assorted list of questions floating out there. If you don't see one posted here you're asking, or need more info... please, PLEASE feel free to e-mail me with any comments or questions!!!

Q:  Where can I get a full W-Body service manual for my vehicle?
A:  Easy, Helm Inc. sells full manuals for very reasonable prices.  These are totally better than a basic Chilton's or anything like that sort.  Helm provides full wiring diagrams, assembly pictures, and even dignostic tables to find the exact problem on your W-body.  Check out Helm Inc. for their toll free number to order it to your home or garage.

Q:  What is under steer, and can that be adjusted on my car?
A:  Ah, good question.  Under steer is very common aomng most GM cars; especailly W-bodies.  It's a condition condition when the front wheels are turned and the car continues in a straight line. Understeer is built into almost every factory car; it is the easiest for the average driver to correct, because when it happens the driver car release off the gas and the wheels will return to their proper tracking course.  This condition can be changed with some simple adjustments.  First, try raising the air pressure in the front tires, and lower the rear tire pressure.  This allows them to grip a little more and it has the back swing around instead of "leading" the turn.  Other ideas to use can include: 
- use wider front tires
- softer front springs / stiffer rear springs
- softer front anti - sway bar / stiffer rear anti-sway bar
- reduce front toe - in
- adjust front camber more negative or adjust rear camber more positive.
These are some common corrections, and unfortunatly not all these can be done to a W-body suspensions.  But with minor parts and adjustments the stronger / stiffer rear end, the tail end will want to "fishtail" more often since less tire grip is accomplished.  This should improve a serious understeer problem.

Q:  How often should the engine collant be changed in my Pushrod / DOHC?
A:  A good rule of thumb is around 12K - 15K miles or every two (2) years at most.  Since these engines have a cast iron block and aluminum heads, the coolant tends to break down quicker than normal.  When the coolant turns old, it becomes corrosive, eating away at hoses and head gaskets.  Spending a few dollars on anti-freeze is a whole lot cheaper than replacing rotted head gaskets on your vehicle.

Q:  What about changing my cooling system to Dex-Cool?
A:  Well, it's a toss up... if you do switch over to Dex-Cool you must completely powerflush the coolant system to get all the "green" coolant out.  If Dex-Cool and the "green" mix, it turn into a brown sludge that a pain to clean out.  Both coolants have there set-backs, but lets all get one thing straight: Dex-Cool (if negleted and not changed on a regular basis) is not as bad for aluminum corrosion versus the "green".  However, it should be recommended that the coolant system frequently regardless of the "green" or Dex-Cool to prevent engine problems.
The valve heads, intake, and water pump are aluminum and the green silicate Ethylene Glycol antifreeze will corrode aluminum parts faster if given enough time exposed do to it's phosphate content (not chaged over a long period of time).  The orange antifreeze, know as Dex-Cool, has a different type of phosphate in it that won't corrode the aluminum if exposed over longer periods of time.  Thats why GM has been able to claim (and only claim) high - mileage intervals without changing Dex - Cool in a perfect system.  However, General Motors has been having some problems having Dex - Cool last the 100,000 or even the 150,000 miles they garanteed due to normal and abnormal driving conditions.  Again, as coolant ages from thermal breakdown, it's chemical compound deteriates creating deposits in your radiator, engine block, plus it chemically eats away at your gaskets.  For you onlookers who have Dex-Cool installed, just watch it and take care of the vehicle way before manufactor's recommendations. 
On the other hand, the "green" has one major benefit, it cools about 5% better then Dex-Cool; plus, it's cheaper gallon per gallon.  Bottom line: I personally state this: I'm still running the green and been very happy with it; I say stick to your own... green for green, Dex for Dex... I don't have the Dex - Cool sticker and always change the "green"  every year.  Better be safe than sorry.

Q:  Can I install a 180 - degree thermostat in my vehicle?
A:  A 180 - degree stat will work perfectly fine, as will a 160 degree stat.  The idea behind the cooler stat is to lower the operating temperature of the engine, and for cars with stock intake setups, to lower intake air temp.  However the intake air is not going to matter by the thermostat nearly as much as underhood temps from the exhaust system, or the amount of air flowing into the engine bay (while driving, sitting idle doesnt do much).

So what does lowering the thermostat rating really do?  The cylinder walls are cooler and that means they dont expand as much.  Its probably not even noticable for a 180 thermostat, but a 160 thermostat may have an effect on cylinder wall wear.  It may still be negligable but something to take precautionary measures.  Yet, the lower engine temp will also mean cooler heads and intake manifolds (though the intake charge itself will cool the intakes off while driving).  Lower head temps can help against pre-detonation.

The negative effects of a lower stat include higher emissions, possibility for increased cylinder wear, and more frequent oil changes.  Oil needs to reach a certain temp to burn off unwanted contaminants in the oil system.  It is unproven thus far as to what effect the coolant temp will actually have on the oil temp, but again, want to mention all aspects of the modification.

The computer / electrical side of running a low tempreture thermostat is mostly fine. There are very few parts of the programming that deal with the tempreture range around the stock thermostat settings. You would be hard pressed to notice anything at all with a scan tool, let alone driving.  Your car will go into 'closed loop' with a 160, 180, or 195 degree thermostat.  As long as the coolant reaches about 4 degrees F, you will not have an issue with the closed loop operation.  The rumors about excessive MPG losses are again, rumors.  It may get worse milage because of the other factors from the cooler stat, but the computer is not dumping in fuel trying to reach 195 degrees.

However, to see the full effects of a lower tempreture thermostat, you may want to install a manual fan switch or have your computer programmed to turn the fans on close to your themostat trempreture.  Also, an alternative, based on application, you can match the turn - on period of the radiator fans to start up near or at stock thermostat, then getting a cooler thermostat; this too will help when you are driving.

Q:  How often should the fluid be changed in my transmission?
A:  General Motors does recommend changing it out around every 15K - 30K miles, depending on driving conditions.  Personally, the idea of 15K miles is the most I would go with any type of transmission fluid, regardless of being a manual or automatic.  Manuals are pretty straight forward to service; drain out the old, and fill in the new with correct weight.  For us who have an auto, it's a little more involved, check the Tech Tips page for full details.  Automatic transmission fluid (ATF) is a hydrolic detergent; which means that metal shavings from the daily wear and tear of internal parts are suspended in the fluid.  Once the fluid begins to "burn up", it loses that property, letting the shavings settle in the transmission pan.  Also, burnt fluid promotes clutch slipping and delayed engaging of the tranny.  As well as changing the fluid, change out the transmission filter about every 30K - 45K.  The tranny filter does the exact same purpose as an oil filter, but changed out not as often.  However, that's not always necessary if the fluid is flushed periodically.  If unsure what condition your tranny is in, ask you fellow dealership or quick lube mechanic for some friendly advice on service intervals and procedures.

Q:  I've got an decent oil leak coming from the backside of the engine.  What's the scoop?
A:  Ah, so after hot rotting it one to many times, you've sprun a leak.  Don't worry, it's not that serious but it's something you want to take care of as soon as possible; it only gets worse.  The most common leak on the LQ1 is the oil - pump drive assembly o - ring.  It's located underneath the intake manifold and plenum on the driver side, right next to the rear valve head.  After some deconstruction and tear down of the motor, its accessable to do a quick repair.  Many have used high - tempreture RTV silicone to patch it, and other have replaced it entirely.  Check the Tech Tips for full details on the procedure.

Q:  If my Secondary Timing Belt breaks or snaps while the engine is running, won't it bend or possibly break a valve?
A:  It's possible, but very rare.  The GM engineers have pulled through on this one.  The 1991 - 1995 DOHC motor is called a "Non-Interferring" engine; the valves are always under tension by springs.  Which means if the timing belt breaks the camshafts will return to a normal position and all valves (intake & exhaust) will closed.  The car will stop running and no internal damage will be exterted on the engine.  * However, in recent finidings with high engine speeds, there have been some recorded cases of Non-Interferring motors having valvetrain (bent or broken valves) damage. *  To prevent this from happening on your vehicle, check you timing belt about every 5K - 7K miles for any cracks or kevlar powder (signs of rubbing / old).  Timing belts are usually due around every 60K miles so think ahead, check Tech Tips on how to check the Secondary Timing Belt for yourself.

Q:  Is it possible for such an old / high mileage car to run a Nitrous Oxide System?
A:  Well, this is a more complicated question.  First off, think of what you are asking the engine to do.  It must work harder, run at a higher tempreture, but on the other hand it's only at a couple times a week for about 20 seconds or less.  My best thing to say is that if you know how the condition of your own engine, so read through the FAQ's of the company your thinking about purchacing the system from.  They do have a great staff for answering questions of that sort via e-mail.  But remember, I do know without a doubt, your un-rebuilt DOHC will not hold a high ridiculous shot of NOS.  If you really want to kill the motor, try handling a 120hp, 150hp, or 200hp shot... e-mail me and tell me what you think after you melt your piston rings.

Q:  Are there any companies that produce a supercharger / turbocharger system?
A:  Yes, RSM Racing has produced a supercharger system for the OBDI versions of the 2.8 / 3.1 liter MPFI V6 and 3.4 liter DOHC V6 and the OBDII version of the 3100 SFI V6.  However, no turbocharged systems are available yet.  Some of the owners in the W-Body community have custom fabricated boosted powerplants after long night in the garage / shop and too many hours on the shop to tune.

Q:  What about installing a supercharged 3.8 liter V6 in my W-Body, they fit in right...?
A:  Yes you could, but you must not see the power you already have!  The LQ1 DOHC is one of GM most powerful six-cylinders throughout it's history.  In fact, before selling the engine package to the public, the motor first dynoed at 281 horsepower.  The reason they downsized the power was because Hydromatic didn't think their FWD tranny would hold that much of torque.  So, in keeping your top-of-the-line DOHC, invest in other performance parts beyond the basic bolt-ons; they're out there.  Maybe then you'll appriciate the power of the DOHC not much sooner after that.  Oh yeah, and before I forget, the re-wiring on the supercharged 3.8 liter V6 is a pain since a new ECM and PCM are required to have the motor run.

Have a question that's just burning a hole in your mind?  No problem, check out any W-Body or GM based forums to chat / post questions and ideas.  Best of luck!!!