For those who know engines well

[-ben-]

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Ok, Ive been saving a little money up to do some engine work once winter comes along. The first thing i wanted to do is put a nice pair of heads on. Someone I know told me that i should put new piston rings in before i do this, because the new heads will make more compression, and I could start burning oil from messing up my rings. My car has 120,000 miles on it, but it runs fine, and it burns absolutely no oil right now. I figured I could make sure every cylinder has good compression, and then if they are all good then go ahead and put the heads on. Im just no expert and dont want to fry piston rings once i get the engine back together. Suggestions please. BTW, car is an 88 lx.
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[mackey]

You really don't have to do that. You are'nt going to get much more compression with the heads that you are going to look at I bet. Which pairs have you most recently looked at?

 

[-ben-]

I was looking at the afr 165's, but I dont think ill have the money for them. I might look into a pair of those "turbo swirl" y303 heads that they sell on ebay. Nothing extremely fancy, just a little extra power.

 

[Camman]

do a compression check. 120,000 miles is a walk in the park if the car was well maintained. So follow your initial plan and if the compression check is good...

Also, you wont see much gain without swapping your intake as well. I didnt see a sig so not sure if your still all stock.

 

[9T3SVT]

100K plus miles and a stock bottom end (see sig) No problems at all

 

[thumper460]

Guys.. the rings are only part of a high mileage engine!! Not that 120 K is real high..! The rod and main bearings have been hanging in there also.. IF you were thinking of over haul.. and the time and funds are there.. do IT!! With the money saved on the Y heads vs the AFR's you can over haul the whole engine , buy a cam, and still have a buck or two for a few beers..
And you will be JUST as happy, Performance wise, with the Ys as the AFR's !! Just a thought!!

Just me.............................

Thumper

 

[90mustangGT]

Get the engine to operating temprature, then pull all the plugs. Do a compression test. Don't worry about the actual numbers as long as they are over 80psi because 70psi is minimal for combustion, but just be sure otherwise they are within 10% of each other. Then do a leakdown test. 10% or less leakdown is excelent, under 20% is good, under 30% is acceptable, over 30% and you have issues.

 

[ss93cobra]

Should probably consider switching to mass air vs. speed density too. Heads, cam, and intake on speed density is

 

[I_AM_CANADIAN]

80psi? I wouldnt put on heads if i were anything under 130 let alone 80.....

 

[vristang]

Under 20% is good? Under 30% acceptable?

With all respect, I have to disagree with those numbers. These guidelines might be ok for teh daily driver, but if you are going to rev to 6k, I suggest tightening that tolerance.
I had 20% leakdown on my new motor due to low tension piston rings. The blow by was so intense that it launched the dipstick out of its tube, and sprayed oil out the tube. The PCV was overwhelmed to the point that I had large puddles of oil in the intake. When I pulled the heads the chambers were caked with oil.

If leakdown gets you under 15% you should be ok , but any more than that and I would recommend tearing into the block.