The last mechanic that "touched" my car 2 years ago changed the original dished pistons for news flat-top (the block, crank, cam, and connecting rods were machined o.k. - the compression was 242 psi per cylinder until the failure). Now I pulled off the aluminum heads (cause is he used no Felpro gasket and bad used bolts and the failure started this year). Question is: I need return to dished pistons before the re-assembly or the flat-top pistons can remains the same?.

Engine: 2.8 V6

Thanks for your comments.

 

the pistons are fine, if the are bolts made for head bolts used is fine, if they're hardwear bolts they should be replaced. fel pro among others makes good high quality gaskets

 

A cranking compression of 242psi on a compression guage
is too much for pump gas of 93/94 octane.
Probabily whay you had problems.
What problems did you have? detonation?
blown headgaskets, broken ring lands?

You want about 180psi tops on a pump gas motor.
Your compression ratio is prpbabily too high with flat top pistons.

 

EXACTLY!.

Detonation, at first.

Then I tried with 97 octane gas, then I moved to 101 octane (97 + additive for 4 additional octanes) and no solved the problem.

Then, I retarded the spark timing in 14 degrees reprogramming the EPROM and the detonation finished.

Now, the valves requires new adjustment and the head gasket will be replaced.

(And more $$$$ ).

 

Have you considered water injection?

 

Sorry,

What is water injection?


Thanks

 

Injecting a fine spray of water/methanol while the motor is under load is a very effective
way to eliminate detonation and preignition
on high compression, supercharged or turbocharged motors.
Allows you to use more compression ratio, boost and or ignition timing while saveing fuel while running a lower octane fuel than normally required.

When the water vapourizes it absorbs a lot of heat which cools
the chamber and fuel/air mix and controls or buffers
the combustion from uncontroled pressure spikes (detonation)
and does a great job of steam cleaning the chambers and tops of the pistons of carbon.
Also saves on fuel that would normally be needed to cool. (fuel dumping)

 

O.K., thanks,

but how can I inject the fine spray?, with engine running and the car stopped? or at fuel tank?. Only one time or too much times?.

 

http://www.aquamist.co.uk/

http://www.cnw.com/~redline/waterinjectionkit.htm

http://www.frii.com/~maphill/wi.html

Do a search on the net. There is lot of info on the subject..

www.carrollsupercharging.com