Smokey Motor - Compression reads perfect

[MR 1JZ]

how many klms and what motor are we talkin?

its done 5000km's
motor is a 1.6EFI bottom end with an 8V carby head
head has been decked to bump up the comp...its definitiely pretty high comp...very hard to push start it and burnt through my old starter motor pretty quick

[o_man_ra23]

Another thing could be the ring gaps. If they aren't right, then you can get blowby... especially if the ring gaps line up.

What do the spark plugs look like?? Are they all the same, or is one/two worse than the rest??

The dynamic compression read by a compression guage will be very dependant upon the camshaft. A cam designed for low end torque (ie 22R) will give a much higher reading than a cam designed for high RPM (ie 18R-G), even if the latter engine has a much higher static compression ratio. So that 185psi could actually be a low reading for your engine.

[MR 1JZ]

motor wasnt this smokey when I first installed it...it only came about after it was properly tuned and I was able to rev it to the top

185 could be low but its an even 185 across all four

spark plugs all looked pretty similar to me

[o_man_ra23]

Photo of spark plugs??

[MR 1JZ]

ill rip them out this weekend and take some

[Shakotan_Aaron]

if they are even compression figure then it doesnt mean that everything is a-okay though. that just means that there isnt anything majorly broken, not necessarily that clearances arnt a bit high.

[andrew_mx83]

wet test.

this will tell you in 5 minutes if the rings are leaking or not.

as someone said above dry test will only tell u if something is majorly broken (ie BHG, burnt valve or one very dead cylinder). do a wet test and if the numbers come up by more than 10-20% the rings arent sealing.

[mick08]

My bet is its in the cylinder head region, have you definetly checked that the crankcase breather is clear and working properly, any pics of the enginebay layout, the bottom end sounds fine if your getting 185 static on all cylinders, my mates ford V8 had closed chamber heads with a stockish cam giving it close to 10.5:1 plus compression, it would static test at 180psi.

[MR 1JZ]

how do you do a wet test?

im going to check the breathers tomorrow night

[mick08]

how do you do a wet test?

im going to check the breathers tomorrow night

wet test is just a few squirts of oil down the sparkplug hole to make a better seal against the bore, if it improves the test then there is probs with the rings, if it stays the same its most probly valve related or cylinder head if you like

[oldeskewltoy]

you can still have a decent compression test which would mean that the compression rings are still in good nick, but the oil rings could still be shot.

they could easily have been misinstalled as well. The main part of the oil ring can VERY easily get overlapped when being installed. If this occurs, nothing short of complete disassembly will remedy the problem

[o_man_ra23]

Don't put much oil in... you only need just enough to seal against the ring, so a few drops should suffice. Too much and you reduce the combustion space and will not get an accurate reading.

[andrew_mx83]

yeah dont use too much... i use the cap off the bottle and a quick pour down each pot... prob only gets 1/3 - 1/2 of the cap in

[lexsmaz]

Does it smoke worse when it warms up under the same conditions ...

I would personally say it sounds like the oil rings as has been mentoned before ..

I'm curious that when you mentioned that you ran heavier oil the engine was a fair bit slower, what oil weight did you use ? i personally have never noticed oil viscosity changing how a engine ran ( obviously within reason ) ..

[mick08]

they could easily have been misinstalled as well. The main part of the oil ring can VERY easily get overlapped when being installed. If this occurs, nothing short of complete disassembly will remedy the problem

If the oil ring was installed incorrectly it would have done this from day one, just my opinion, its an experience thing you know when the piston slips in nice or gets hooked up somewhere.