failed overhaul

[speedibot]

*niky...salamat.isang masakit na experience ito sakin.after buying the car,i have already spent almost 35K in repairs total (including the recent overhaul) kaya it is a lesson na din sa akin.mahirap din maniwala sa, pwede pa...remedyo type na trabaho.as of now neighbors are refering other mechanics to me para sa 2nd opinion.this time I'd be more careful. Salamat din sa forum na ito I was enlightened so much the next time i'll have decisions....i'd be wiser.

[KIANTOT]

Kasama talaga yan sir sa pagbili mo ng second hand car, di mo din maashan yung pwedeng maging sira, even for me na experience ko na din yan, marami din ganyan ang ngyayari, kahit na magnda ang makina bago mo bilhin meron pa din di inaashan,halos ilang months pa lng na nabili namin bigla agad inoverhaul, charge to our experience.......

[speedibot]

Kasama talaga yan sir sa pagbili mo ng second hand car, di mo din maashan yung pwedeng maging sira, even for me na experience ko na din yan, marami din ganyan ang ngyayari, kahit na magnda ang makina bago mo bilhin meron pa din di inaashan,halos ilang months pa lng na nabili namin bigla agad inoverhaul, charge to our experience.......

OO nga sir...charge it to experience na nga lang...pero masakit sa bulsa talaga grabe.BTW po gurus, OT...I just read over the net about glazing cylinder walls ng block.Kasi I just remembered when the overhaul was being done on my engine, when the mekanik was about to replace the piston rings,napansin ko yun cylinder walls nya GLAZED nga,as in super shiny ba.this link *** Engine Break-In *** covers it.just want to know more from you gurus.kasi yun good for nothing mekanik ko didn't even tell me to submit the engine for machining.na dapat pala kahit papano na-rebore yun cylinder walls ko.kahit papano they should be rough para pag break-in mo ng piston rings,it would seat properly.My conclusion is,maybe the reason bakit my plugs get wet from oil is because of the glazed wall of my cylinders,oil is passing through it as well as combustion is getting through it and down the crankcase.There is smoke coming out of the dipstick.Makaya pa kaya yun gurus sa machining...or probably change engine na nga lang? thanks.

[ppcsurfr]

You don't actually get higher compression by revving it higher. The problem may be that the compression is so low that you don't get enough airflow at low revs to ensure a proper mix of fuel and air before the sparks go off. Higher revs means faster air, means a cleaner burn.

Of course... if you're getting oil along with that low compression, your engine is shot... it's probably time to say goodbye to it. Personally, I'd go with the swap to EFI. Pouring more money into the old engine has already passed the point of economic practicality.

You are right if you are saying that you don't get higher compression when you rev it higher, but in the case of a piston and cylinder which is worn out hence losing comression, a drop to a compression ration of 7 to 1 means it will no longer have the right compressed air/fuel mixture to ignite.

At higher engine speeds the rate of loss of this compression may be compensated by the increase in acceleration of the upward movement of the piston thereby achieving a compression ratio closer to that which is required for creating that fireball that then pushes the piston back down for the power stroke.

Try this on a worn out engine. Secure the compression tester on one of the sparkplug holes. Hand crank the engine and see if it compresses air to your specified compression ratio. Now try it again using the starter motor. See if the compression ratio you get is the same.

There are several factors you will have to consider when checking compression ratios. The other factor which is often set aside is the closing of the intake valve prior to the compression stroke. If the valve closes at say 70 degrees after bottom dead center, then you are looking at a reduced compression at lower speeds. Just like the effect of racing cams sounding "palyado" at idling.

Here is a basic test. Get a huge syringe and pull the plunger. Cover the hole where the needle goes and compress the plunger. Obviously a good seal will mean that you will not be able to compress the plunger easily. Take your finger off the hole and compress the plunger against a table slowly. You will see that you will be able to compress the plunger and lose air pressure. Now try this again by hitting the plunger violently against the table and see if that immediate action can compress the piston just as you did when putting slow pressure on it.

A 4AGE at 8000rpm will have a piston speed of 4000 ft/min. and at 4000rpm have a piston speed of 2000 ft/min. At 2000 rpm it will have a piston speed of 1000 ft./min. Let me know which of these speeds can compensate for a slight loss of compression.

As for the compression ratio of NA engines, yes the compression ratio does not increase with speed. But for a worn out engine, the slight loss of compression may be compensated by the higher piston speed. Of course this will be short lived as the increased wear will eventually increase the damage which eventually will lead to an engine which will not compress your air/fuel mixture in a combustible form. (Remember, Octane prevents pre-ignition and controls the burn of the fuel so that it does not explode (knock). And using high octane fuel will also add to the difficulty of igniting the low compression air/fuel mixture)

[KIANTOT]

OO nga sir...charge it to experience na nga lang...pero masakit sa bulsa talaga grabe.BTW po gurus, OT...I just read over the net about glazing cylinder walls ng block.Kasi I just remembered when the overhaul was being done on my engine, when the mekanik was about to replace the piston rings,napansin ko yun cylinder walls nya GLAZED nga,as in super shiny ba.this link *** Engine Break-In *** covers it.just want to know more from you gurus.kasi yun good for nothing mekanik ko didn't even tell me to submit the engine for machining.na dapat pala kahit papano na-rebore yun cylinder walls ko.kahit papano they should be rough para pag break-in mo ng piston rings,it would seat properly.My conclusion is,maybe the reason bakit my plugs get wet from oil is because of the glazed wall of my cylinders,oil is passing through it as well as combustion is getting through it and down the crankcase.There is smoke coming out of the dipstick.Makaya pa kaya yun gurus sa machining...or probably change engine na nga lang? thanks.

Try mo din sir ipa 2nd or kahit hangang 4th opinion sa ibang well experience na mga mekaniko dyan malapit sa inyo, kung kaya pa solusyunan na ipa overhaul ulit yan, kase mas maganda macheck din yan engine mo ng personal, kahit ako, mas ok din sana na ipa overhaul kaysa mag palit ka surplus, kse pag overhaul, alam mo mismo ang mga pyesa, kampante ka na bago, basta yung good quality ang ipalit mo, pag surplus, di mo din masabi kung paano ginamit yung engine ng previous owner, at hanggang kailan itatagal,kaso nga lang nagkamali ng theory ngaun yung mekaniko mo, expected mo na maging ok kaso failed, kung opinion nila magpalit kana, saka ka magdecide..

[ppcsurfr]

When overhauling an engine there are numerous items which have to be checked to make sure they are within tolerances.

From your description that the pistons have "alog" already, it clearly means that the pistons are worn out, the piston rings are worn out, and most probably the cylinder bores are worn out as well.

Just on the subject of cylinders, pistons, and rings. It is almost useless to replace just the piston rings if the pistons are worn out. How do they wear out? well the pistons are no longer round. the bottom parts of the pistons will show wear and taper slightly. Likewise, the cylinder bores will also be out of round which means that the lower portion of the cylinder bores become slightly oval in shape. Replacing your piston rings with perfectly round piston rings will definitely not create a good seal towards the bottom of the stroke.

Usually pistons are made of softer metals which means they may wear out faster than the cylinder bores.

At this stage, a complete engine rebuild is needed.

The engine block is rebored to the next oversize. Or it uses sleeves, a replacement sleeve is used. New pistons and piston rings are installed and the crankshaft is measured for wear. If the crankshaft shows some wear, it will be ground to the next size and corresponding main bearings and big end bearings will have to be used.

When getting new pistons, they come with piston rings, and usually piston pins.

normally if you do open up your engine and replace the bearings, it is wiser to replace all other bearings as well (and oil seals) so that you don't have to open it again until the next major overhaul is needed.

For the top (cylinder head) the things to immediately watch out for are worn valves and valve seats. You can also check the valve guides and if needed, new inserts for the valve guides can be used. When replacing valves, make sure that the valves are seated well by grinding them in. Failure to do so may burn the valves and valve seats which may cost you a lot.

Also, it is a good idea to replace all valve springs at this point. Old weakened springs may be unnoticed until it creates more damage. Weak springs can cause valve bounce or a bad seal that may lead to burnt valves and valve seats. Again camshafts are also checked for the profile of the cams if they are to spec and if the camshaft journals are within spec. Again all seals changed...

Doing so may be expensive, but doing it the right way may bring you another 100,000 Km of reliable workmanship.

[speedibot]

*ppsurfur/*kiantot salamat sa replies.Just got home from work...really couldn't explain the feeling bakit nagkaganun ang overhaul ng kotse ko.Pero I have made my mind sirs I'll go for an engine change nalang.Unang reason,given na model 91 stock pa sya....sobrang haba na ng service life nya,at 200k+++ odo reading when I bought the car...definitley sa akin na maghihingalo yun makina...given pa na halos nasa bad state sya....hindi marunong mag alaga yun huling may ari.feeling ko binenta nalang nya yun pati sakit ng ulo.Pero despite na problema dinulot nun car sakin...naawa pako kasi pinabayaan sya.marupok ako sa ganun.kaya't I've decided to keep her nalang and nurse her back to life.Give her a new engine nalang and hope tumagal pa for the next 10 years or so.Salamat sa inyo guru's...mahaba haba na din itong thread and it was a big help sakin.Alam ko gastos na naman ito pero I pray to God makayanan ko ito...and sa inyo po mga guru's salamat sa mga advices.More Power to the Forum!

[zincks]

sir kung ako sayo magsurflus kana lang ng engine makakakuha ka naman ng maayos nyan,marami kasi mechanic ngayon nagshoshorcut na unang una kasi iniisip nila yung budget ng owner kya hindi mo din sila masisisi,kung magpapaoverhaul ka ng engine make sure gagastusan talaga lalo na yung laman loob nya,yung sayo kasi tinipid masyado,tama si sir ppcsurfr kapag nag-overhaul ka need lahat ng replacement,tulad sa amin nagchecheck pa kami ng mga sukat, kung pasok pa sa maximun requirements nya lalo na crankshaft,camshaft,connecting rod,piston rings,after nun dye check pa,yung mechanic mo bossing basta nagkabit lang yata ng rings ni hindi man lang nagcheck ng clearnce,hindi man lang yata marunong yan magcompression bossing, i preferd na bili kana lang ng second hand na engine kasi masmahal pa nga magpa-overhaul kesa bili surplus....

[speedibot]

sir kung ako sayo magsurflus kana lang ng engine makakakuha ka naman ng maayos nyan,marami kasi mechanic ngayon nagshoshorcut na unang una kasi iniisip nila yung budget ng owner kya hindi mo din sila masisisi,kung magpapaoverhaul ka ng engine make sure gagastusan talaga lalo na yung laman loob nya,yung sayo kasi tinipid masyado,tama si sir ppcsurfr kapag nag-overhaul ka need lahat ng replacement,tulad sa amin nagchecheck pa kami ng mga sukat, kung pasok pa sa maximun requirements nya lalo na crankshaft,camshaft,connecting rod,piston rings,after nun dye check pa,yung mechanic mo bossing basta nagkabit lang yata ng rings ni hindi man lang nagcheck ng clearnce,hindi man lang yata marunong yan magcompression bossing, i preferd na bili kana lang ng second hand na engine kasi masmahal pa nga magpa-overhaul kesa bili surplus....

*zinks...salamat. oo nga po. yung ex machanic ko basta tirada nalang ng tirada. yes oo, i asked him kung may ipapamachine he didnt even answer me so i thought okei yun block at head ko pa. i know things about cars pero lay man lang ako...how do i know kung kelangan ipa machine every overhaul. mga opismeyts ko hindi din ako masisi kasi nga po...i just want my car to be fixed. if in the first place raw the mechanic turned me down already, it would be eye opening na sa akin at talagang kakailanganin ko ng mag isip ng ibang paraan tulad ng engine change. kaso sabi nga nila...tinuloy pa nun mekanik....gusto lang nya kumita pa....was very dissappointed. may balik naman yan..karma tawag. my cousin is already helping me find another mekanik and shop. in the mean time sleep muna car ko sa garage. habang recharge din ako ng wallet.

[zincks]

may mga tropa din ako boss nakakakuha sila ng engine 10k pataas at maayos pa naman,madami kasi toyota dito sa atin as in madaling maghanap kahit saan merun basta toyota,lalo na dito sa subic andami talaga...