timing problem...

transamdrifter · 03-08-2008, 10:42 PM

i just installed new pistons and a rebilt head. i use to get 180 lbs of compression but I cant seem to get the timing right. I am getting at most 150 lbs of compression. I think I got it in time. What could I be doing wrong?

LSG2007 · 03-09-2008, 03:31 PM

did you install low compression pistons during the rebuild?

transamdrifter · 03-09-2008, 07:26 PM

ok we got it to turn on. It was an ignition timing problem but we have not checked the compression again. It is an oem replacment piston. It should be at 180 lbs but last we checked it was at 145. Hmmm. I'l see what it might be.

feral4mr2 · 03-09-2008, 07:42 PM

ok you've rebuilt the engine right, so you would of honed the bores so your new rings will bed in etc.
so what you gotta realise is the rings are not bed in yet and you will not get a full compression reading until that is done.

make sure the static compression is 100%, if any of the valves are partly open due to the static timing not being correct you can get a lower reading too.

good luck.

transamdrifter · 03-10-2008, 09:19 AM

Quote:

Originally Posted by feral4mr2

ok you've rebuilt the engine right, so you would of honed the bores so your new rings will bed in etc.
so what you gotta realise is the rings are not bed in yet and you will not get a full compression reading until that is done.

make sure the static compression is 100%, if any of the valves are partly open due to the static timing not being correct you can get a lower reading too.

good luck.

So what your saying is untill the engine brakes in it will not give me 100% compression?

Thanks

feral4mr2 · 03-11-2008, 05:38 AM

that's the way i see it. i dont test mine until i've run the engine in.

have you ever turned over a freshly rebuilt engine by hand before you put the sump back on? spun me out the 1st time i did it the amount of air pushing back past the rings.

transamdrifter · 03-11-2008, 09:19 AM

Quote:

Originally Posted by feral4mr2

that's the way i see it. i dont test mine until i've run the engine in.

have you ever turned over a freshly rebuilt engine by hand before you put the sump back on? spun me out the 1st time i did it the amount of air pushing back past the rings.

Well When we where turning it over before turning it on it felt a little weaker. I was turning the crack last night and it felt like it had more compression. Though I think it might be a tooth of time.

te51levin · 03-24-2008, 07:58 PM

Make sure your cam timing is correct and double-check that all the valve clearance is correct as well. Tight valves will cause artificially low compression test figures. Remember that compression tests need to be made when the engine is HOT, and the throttle must be held wide open during cranking.

03-08-2008, 10:42 PM	#1 (permalink)
transamdrifter Some Skills Join Date: Dec 2007 Posts: 59 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	timing problem... i just installed new pistons and a rebilt head. i use to get 180 lbs of compression but I cant seem to get the timing right. I am getting at most 150 lbs of compression. I think I got it in time. What could I be doing wrong?

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03-09-2008, 03:31 PM	#2 (permalink)
LSG2007 My Muffler Fell Off Join Date: Feb 2008 Location: Olathe,KS Posts: 196 Thanks: 22 Thanked 8 Times in 4 Posts iTrader Rating: (0/0% )	did you install low compression pistons during the rebuild?

03-09-2008, 07:26 PM	#3 (permalink)
transamdrifter Some Skills Join Date: Dec 2007 Posts: 59 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	ok we got it to turn on. It was an ignition timing problem but we have not checked the compression again. It is an oem replacment piston. It should be at 180 lbs but last we checked it was at 145. Hmmm. I'l see what it might be.

03-09-2008, 07:42 PM	#4 (permalink)
feral4mr2 ghetto modder Join Date: Sep 2006 Location: Western Australia Posts: 128 Thanks: 0 Thanked 10 Times in 10 Posts iTrader Rating: (1/100% )	ok you've rebuilt the engine right, so you would of honed the bores so your new rings will bed in etc. so what you gotta realise is the rings are not bed in yet and you will not get a full compression reading until that is done. make sure the static compression is 100%, if any of the valves are partly open due to the static timing not being correct you can get a lower reading too. good luck.

03-11-2008, 05:38 AM	#6 (permalink)
feral4mr2 ghetto modder Join Date: Sep 2006 Location: Western Australia Posts: 128 Thanks: 0 Thanked 10 Times in 10 Posts iTrader Rating: (1/100% )	that's the way i see it. i dont test mine until i've run the engine in. have you ever turned over a freshly rebuilt engine by hand before you put the sump back on? spun me out the 1st time i did it the amount of air pushing back past the rings.

03-24-2008, 07:58 PM	#8 (permalink)
te51levin Lithia Toyota Parts Join Date: Oct 2005 Location: Oregon Posts: 1,924 Thanks: 33 Thanked 146 Times in 125 Posts My Google Map iTrader Rating: (126/100% )	Make sure your cam timing is correct and double-check that all the valve clearance is correct as well. Tight valves will cause artificially low compression test figures. Remember that compression tests need to be made when the engine is HOT, and the throttle must be held wide open during cranking.