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When should I replace engine bearings, rings and head gasket in the 2.4l twin cam ? Everything seems fine starts right up every time ( 1 or 2 revs ) no smoke, no extreme crank case pressure, no blow by or very little, burns a quart of oil every 1500 to 2500 miles 

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There is no set time or mileage for rebuilding...

Realistically as long as it is running OK....With good oil pressure and no overheating issues you are probably better off to just leave it alone...For example they use torque to yield bolts..95% of the time they cannot be reused...New bolts for it can be a bit pricey..Chances are that during the disassembly the threads in the block will come out with the bolts and will require most if not all the bolt holes to be helicoiled which in turn causes other problems with the thin castings which are very prone to cracking anyway...If you do get lucky and the threads stay in the block if you try to Chase the threads with a tap to attempt to clean them up... it will loosen them to the point that they won't tighten up or will strip out

The cylinder head is very prone to cracking in the combustion chamber's between the valves they also have weak valve guides that is one of the main reasons they tend to burn alot of oil....The head castings are so thin that even cutting it just enough to get a flat surface for the head gasket to seal can render it useless...GM has three or four different head bolt tightening sequences depending on the year and casting numbers if it is not followed exactly the head gasket is almost guaranteed to fail in a fairly short order...

There are too many idiosyncrasies with rebuilding the Quad four engine to even try to list them all...That is why I have only mentioned some of the most obvious ones.....Again I am not trying to be negative just realistic...

Also noticed that you are in Greensboro... I'm in Winston-Salem

Edited by TWO LANE BLACK TOP

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+1 - There's no need to open it up unless you've got good reason to suspect a problem.

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Thank you both. The whole if its not broke don't fix it thing. I just worry about motors when they get 230k on the clock. Cuz the just driven miles noway to tell how long it been idleing or started you know. Thanks two lane black top for that. Had no idea how weak the block is. That is just craziness

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15 hours ago, Lynn5907 said:

Thank you both. The whole if its not broke don't fix it thing. I just worry about motors when they get 230k on the clock. Cuz the just driven miles noway to tell how long it been idleing or started you know. Thanks two lane black top for that. Had no idea how weak the block is. That is just craziness

The quad four engine is pretty much a throw away engine..... NOT designed to be rebuilt...GM 3.4 V6 engines and V8 Northstar Cadillac engines among others are the same way....Although they can be rebuilt and make good power if they are done correctly...The cost and man hours...Aggravation.... Associated  with doing so...Not mention finding a competent machine shop....Makes them completely emotionally and economically unviable  for the average person to do so.......

Edited by TWO LANE BLACK TOP

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The machine shop is always my worry. My pops has a three bay shop with all the necessary tools so I'm lucky there. Not trying to make a super car or anything. Like you said if it is running that good just leave it alone.

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Let's just imagine here for a minute two lane.. say I got the supercharger kit and changed pull sizes to squeeze just a few more psi. Can the regular internals handle the pressure? I'd like to say the the engine (ld9) has 230,214 miles. I've run the car for about 6000 miles on the current oil and it has only burnt 2/3rds a quart also still has color. Normally I change the oil every 3 to 4k always just checking the health so to speak

20181013_153142.jpg

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18 hours ago, Lynn5907 said:

Let's just imagine here for a minute two lane.. say I got the supercharger kit and changed pull sizes to squeeze just a few more psi. Can the regular internals handle the pressure? I'd like to say the the engine (ld9) has 230,214 miles. I've run the car for about 6000 miles on the current oil and it has only burnt 2/3rds a quart also still has color. Normally I change the oil every 3 to 4k always just checking the health so to speak

20181013_153142.jpg

Just noticed you said Winston Salem cool beans man

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On 10/14/2018 at 8:44 PM, Lynn5907 said:

Let's just imagine here for a minute two lane.. say I got the supercharger kit and changed pull sizes to squeeze just a few more psi. Can the regular internals handle the pressure? I'd like to say the the engine (ld9) has 230,214 miles. I've run the car for about 6000 miles on the current oil and it has only burnt 2/3rds a quart also still has color. Normally I change the oil every 3 to 4k always just checking the health so to speak

20181013_153142.jpg

I think you can run the supercharger kit with no problem. I wouldn't go crazy with pulley sizes to try to add too much boast since GM didn't do that - probably for a reason. My guess is they didn't strengthen the bottom end to handle the additional horsepower. So without rebuilding the whole motor (which is what we recommended above), you could run the supercharger, but don't stress the engine out much more with additional boast. I think that would lead to its demise. 

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