Engine Breakin
Thread Starter
Instructor
Joined: May 2013
Posts: 184
Likes: 2
Engine Breakin
I just recently rebuilt my LS3 engine. After cranking it up and letting it run for about 5 mins. I turned the car off because it was smoking. I thought it was the piston rings at first but when I conducted a crank compression test they all read 150 psi. I know this seems low but I have a new cam with a .624 lift so I'm assuming that's the reason for the 150 compression. My question is the break in procedures. Does anyone know the rpms an time I need to keep the car running to help the engine seal properly? I though I just crank the car but there are articles out there that say, rev the car to 2500 rpms for 20 mins. Some say constantly rev the car up to 3500 rpm for 10 mins. For vettes what is the base line break in procedures before you drive the car. I'm thinking the car is smoking because I used synthetic mobile 1 when I filled up the fluids vs break in oil. Today I will drain my oil system and put the break in oil in the engine and hopefully sometime this weekend I can restart it with the correct break in procedures and hopefully the engine will start to seal.
please provide some advise
please provide some advise
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
Hello Smokey Engine,
A properly rebuilt engine will not have visible smoke.
Did you adjust the valves correctly, that might be the reason for lower than expected compression and smokey exhaust. The next problem may be your valve seals, were they installed properly?
Keep us updated,
Douglas in Green Bay
A properly rebuilt engine will not have visible smoke.
Did you adjust the valves correctly, that might be the reason for lower than expected compression and smokey exhaust. The next problem may be your valve seals, were they installed properly?
Keep us updated,
Douglas in Green Bay
Race Director
Joined: Mar 2011
Posts: 13,262
Likes: 3,151
From: SW Florida
2021 C6 of the Year Finalist - Modified
That initial 2,500 RPM for 20 minutes was used for cars without roller cams ... Your engine has a roller cam, so it don't pertain to you.
BTW, the valves on the LS engines are non-adjustable.
BTW, the valves on the LS engines are non-adjustable.
Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
Supporting Vendor
Joined: Feb 2011
Posts: 3,523
Likes: 885
2024 C6 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (track prepared)
2019 C6 of Year Winner (track prepared)
I just recently rebuilt my LS3 engine. After cranking it up and letting it run for about 5 mins. I turned the car off because it was smoking. I thought it was the piston rings at first but when I conducted a crank compression test they all read 150 psi. I know this seems low but I have a new cam with a .624 lift so I'm assuming that's the reason for the 150 compression. My question is the break in procedures. Does anyone know the rpms an time I need to keep the car running to help the engine seal properly? I though I just crank the car but there are articles out there that say, rev the car to 2500 rpms for 20 mins. Some say constantly rev the car up to 3500 rpm for 10 mins. For vettes what is the base line break in procedures before you drive the car. I'm thinking the car is smoking because I used synthetic mobile 1 when I filled up the fluids vs break in oil. Today I will drain my oil system and put the break in oil in the engine and hopefully sometime this weekend I can restart it with the correct break in procedures and hopefully the engine will start to seal.
please provide some advise
please provide some advise
1) Using synthetic oil will not cause an engine to smoke.
2) A compression test will not give you any indication as to the health of the oil rings.
3) A high lift cam should not cause low compression test values as I have a .684/.666 lift cam and usually see numbers in the low 190s.
4) Did you rebuild this yourself and are you absolutely sure the rings weren't installed upside down?
Item #4 is from experience as the first time I rebuilt an LS7 by myself it started smoking fairly bad. I talked to a machine shop to get some advice and his first question was "did you install all the rings in the right direction?" to which I replied "there's a right direction???".
Basically what I ended up doing was inadvertently install 6 of the 8 rings upside down (can't remember if it was the top or second ring) which caused them to scrape the oil upwards instead of down and subsequently smoke while it was running.
The good news is that all is not lost if this is what happened to you. Although it's a MAJOR pain, it is possible to fix the engine from the bottom and not have to pull the whole thing again.
