GM 3.4 DOHC power tweaks/maintenance tips

to those of you who own and drive one of these great GM V-6 engines, here's a few free power/tuning/maintenance tips:
1. unplug the EGR valve connectcor, located just behind the throttle
body near the firewall- your 3.4 DOHC will WAKE UP and make about 20-30 more HP at part throttle driving conditions- it will literally glide along on level roads at 70 mph with the EGR disconnected- and will not require as much throttle input to pull from a dead stop or uphills- most "low power" complaints on the DOHC can be totally eliminated by simply unplugging the EGR valve- it will throw a code and turn on your "check engine light"- but will not harm the car in any way- after removing the EGR plug, run premium fuel for best performance and to eliminate any ping/spark knock. The DOHC is a relatively high compression engine 9.6:1, and really should have premium fuel.
2. the DOHC uses both a timing belt on the overhead cams, and a standard timing chain behind the front cover- with age, the timing chain will stretch about 4 to 6 crank degrees- even though the belt is NEW and replaced. Don't simply mark the cams and put a new belt on, where the old one was. That will put the cams BEHIND (retarded) in timing, due to the timing chain stretch. (you only changed the belt, not the chain). Make sure you lock the cams, unbolt the timing sprockets (use a stout 6-point impact socket and breaker bar, to get the cam cog bolts loose)- and retime the cams to the crank. When you do this, make up for the timing chain stretch, by rotating the crank forward to take the play out, aligning the balancer mark with arrow on timing cover, THEN locking the cams in place. My timing chain had about 4 degrees of slop, when I retimed it.
3. It's a lot easier to time these engines, with the inner fenderwell plastic cover and right wheel removed, and a hole cut in the inner fender so you can see the timing marks. This way, you won't have to remove all the front engine accessories and belt, to see the marks- and you can look at the marks "straight on", instead of at an oblique angle from the top. You can cut the sight hole in the inner fender with a hole saw, or sawzall.
4. Use BOSCH 4-tip platinum plugs- I have put 55,000 miles on a set of these plugs, and I could have left them in and run it another 50,000- but changed them for good measure. They really work- require no gapping- and they don't foul. They are pricey, $5-7 per plug, but well worth it in maintenance time saved.
5. Use synthetic oil- I use Amsoil 10-30 or 10-40, this will extend your oil change intervals to 25,000 miles, with oil filter change at 12,500 miles, and add oil in between for what you may use/burn off.
6. Use a K&N lifetime air filter, so far I have 55,000 miles on one of those filters as well.
7. Oil leaks- if you DOHC 3.4 gets up in mileage, over 150,000 miles, it would pay to have the top end of the engine removed and gaskets replaced. Replace cam carrier gaskets, cam seals, head gaskets, intake upper/lower gaskets, oil distribution block gasket (between heads in valley, like a valley cover), and also replace the oil pump drive plug O-ring. Under the oil pump drive plug itself, place a GM Chevy distributor gasket, for good measure. Some of these DOHC engines have oil cooler lines near the oil filter adapter (my 1995 did not)- replace the lines and oil filter adapter gaskets, and your DOHC engine will be leak-free.
8. Use synthetic oil in the automatic transmission.
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