4.0 piston rings

[Ronin8002]

4.0 piston rings..replace or not?

I don't have my chilton's manual handy and had a question about piston ring replacement:

I'm taking my 4.0 engine down to the block next month sometime so I can do the following:

-replace my cylinder heads with P&P heads (which include stainless valves and dual valve springs)
-replacing the stock cam with the compcams 422
-replacing stock rockers with hardened cups and custom length chromoly pushrods
-porting the lower intake
-replacing my granatelli MAS with an 80mm pro-m MAS which is calibrated for..
-24 pound injectors that I'm installing
-As well as a bbk supercharger
-190 lph fuel pump
-MSD DIS-4
-and maybe a ZEX nitrous kit with a 75 shot later.

I ran a compression check not too long ago and came up with 150 on each cylinder.

I am wondering if I need to replace the rings, if only to make the gap bigger to deal with the increased heat and pressure. I am not planning on honing the cylinder bores because I'm keeping the stock pistons.

Do I need to replace the rings, and if I do, is this something that I can do myself (I have a lot of tools available) or do I need to get involved with a machine shop? I don't want to do all these mods only to have the rings blow out 20k miles later (or less), so all suggestions/adivce/comments are welcome.

thanks!

-James

 

[Josh]

Man what I would give to have your bank account! there are 2 guys that know this info, Alec and Doug. Doug has a 4.0 performace website. If you do a search you will find a lot of info. Below is the link for 4.0 Performance.

http://www.4.0performance.com/products.html

 

[Ronin8002]

Thanks for the reply....I decided to go with the Vortech supercharger because I can just swap a pulley and get my chip reburned and get more power that way without having to do nitrous.

I may be asking for trouble...but if I blow a ring or break a con rod, I'll just rebuild it with the forged pistons from Doug. A guy with a mid 90's ford ranger on the rangerpowersports forum was running 9lbs of boost without any problems...and his setup didn't include the p&p heads or the blower cam.

in any case....this will be a good test to see what an older 4.0's bottom end can handle.

 

[Josh]

Hey good luck and post back with your results since I have the same motor, maybe one day I'll have some cabbage to burn. Of course my engine has 212K so I will rebuild before I do anything major.

 

[Josh]

Also, with all of those bolt ones, did you notice a big difference?

 

[SteveVB]

If the compression in all the cylinders is within specs you should be OK. I would do so with the knowledge that with a few miles on the engine you may have to rering at a later date when you start increasing the cylinder pressures.
I would say this though- be very careful when you remove the heads- if you dump a bunch of coolant in the cylinders you may end up ruining the ring sealing ability. Make sure you drain the coolant before hand- just dont pop the heads and dump coolant into the cylinders.

 

[andyp_4.0]

If you are not planning to tear into the block then leave the rings alone. I should mention that if you do replace the rings you should hone the cylinder walls. The rings need that in order to seat properly.
Keep in mind that once you have the heads off you might notice that one or more of the cylinders are badly scored. You'll be able to tell alot more about their condition with the heads off and make a better decision.
Andy

 

[Ronin8002]

thanks for the info everybody. With those bolt ons I got about 35 HP and abou 10 ftlbs of torque....pretty good considering I didn't change any internal parts. It helped throttle response and mileage....plus they are good building blocks for even better performance if you're going with the supercharger route, so all in all, i'd say it's money well spent.

-James

 

[CowboyUp89]

when replacing the piston rings can you just remove the oil pan drop the crank shaft and pull the pistons out of the bottom and put them back in that way or do you have to tear the everything of the top half of the motor as well

 

[Josh]

I dont think you can pull the oil pan with out lifting the motor.