4y compression question (and gaskets)

[Sven]

So i decided to purchase a compression gauge out of pure interest as to what my oil leaking motor is really doing, so i hooked the compression gauge onto each cylinder to get a reading, all 4 cylinders returned extremely close values of between 900-920 kpa, my workshop manual says standard is 1225kpa, minimum 875kpa and variance being 100kpa. so I'm a little low on compression on all cylinders.

So what should i do about it? can i just get the head skimmed and this would increase compression? or would this be a silly move as i might get too much compression when the day comes that i replace pistons and rings? is there a possibility that once upon a time in the cars life somebody could have put in low compression pistons for a turbo and never bothered to remove them? when i bought the car 10 years ago it did have old TRD stickers and performance this and that, and every possible performance mod regarding the brospeed conversion(vehicle belonged to a quad bike salesman) and the lower compression is maybe due to this?

and then one one last note, if i buy a good set of gaskets for the engine, does one still need gasket maker everywhere, why i ask is that the engine has over time sprung leaks through different areas on the engine(every part has red gasket maker), this is why i bought the compression tester as i wanted to eliminate the possibility of piston ring failure and possible replace all engine gaskets(sump/timing chain etc. )

[Mud Dog]

Compression is a bit low, but really not too bad considering it's a 25 year old motor (how many kilos?). I am not a fan of head skimming unless it's really necessary. Yes it will up the compression slightly but that's not the way to go - rather address the main cause, which is of course rings. When it becomes time to do that, then you replace pistons as well (the landings are probably worn by this time). More often than not, I believe you can get away without a re-bore on these motors, depending on mileage, oil quality used and how good your air filtration has been over the years. Have the bores mic'ed up to check how good / bad they are - if you don't need a re-bore then just have them honed.

My old 4Y got an overhaul at 210,000 km but only because it had overheated badly and the piston skirts had deformed - there was very little wear in the bore, we didn't even have to remove the ridge at the top because it was hardly noticeable.

Of course if you pull it apart then you replace the crank bearings as well (big ends and mains) - you will get new gudgeon pins with the pistons. You would also replace front and rear crank seals and check the oil pump (I had no need to replace mine). With all that you would be replacing all the old gaskets anyway, so no need for RTV silicon.

If I had the time / able to spare the vehicle a bit longer, I would also give the valves a grind and replace the lifters if they're already noisy - same applies to the timing chain and tensioner.

Do those things and you will have a motor that's almost good as new and just as reliable, with a noticeable improvement in power.

[dd6]

Above mentioned is the way to go!! The gasket maker could be an indication that the engine was open at some time. Time for some tlc.