Engine inspection for purchase

greg75vette

greg75vette

The Traffic Baron
Joined
Jun 9, 2009
Messages
703
Location
Lindenhurst, LI, NY
Hey guys, I found a few LS1/T56's I want to check out, but they are pulled out of the car already and are being sold by local sellers. I'm all very new to this and have never just bought an engine without the rest of the car :noob: So I ask you, what do I look for and what do I ask?

I already know I should pull the plugs, rotate the engine, shift the transmission, check the oil, but what else needs to be done?

When I pull the plugs what do I look for/at? What size are the plugs (I only have a 5/8 plug socket)?

Can I do a compression test?

What size fitting do I use to turn the engine over with? How hard should it be to turn over?

Any and all advice is welcomed. Thanks in advance!
 
It would need the starter and electrical stuff hooked you for a compression test (unfortunatly). After it's already out, you're kind of at the mercy of the seller- ask questions about why it's out, did it run, make noise, use oil, and maybe pull the spark plugs and look at them for unusual deposits.
I'd try to get some kind of guarantee that if you start it and it knocks, you get money back. Good luck!
 
They used to mark the milage on them when they pulled them with yellow paint. I wonder if they still do?
 
The last time the car was registered there should have been a mileage statement. Isn't the engine stamp still a derivitive of the VIN number? Maybe run a Carfax just to see if the mileage they are telling you and the reported miles match.

Is the tranny off the engine? If so, take the clutch out and look at the disk. Is it OEM, is it worn? These might be an indicator of miles.
 
Private sellers or a junkyard?
Either one might lie trough their teeth to get the engine sold.
Apart from looking for the obvious:
  • external signs of oil leak
  • pulling the plugs
  • pulling the dipstick and smelling the oil (coolant in the oil smells like rancid butter)
  • bring a magnet and drain a little oil
there is really not much that you can do.
My friendly car shop's got a borescope that I can borrow at any time.
If you have the funds, buy two and assume a total rebuild of one.
 
You can do 2 things that are effective and reliable in determining the condition and mileage of the engine:

1. Cylinder leak-down test. Unlike a compression test, the leakdown does not require use of the starter, and the leakdown test produces an actual number indicating the absolute condition of the cylinders (unlike the compression test which only produces comparative data). You will need access to compressed air at the location of the engine, but this can come from a portable air tank that you can bring yourself. If cylinder sealing is in-spec, the engine is tight. Leakdown on all cylinders should be less than 10%. A fresh, well-built engine will often be in the 5-7% range.

2. You can pull the distributor cap and observe rotor rotation as you "rock" the crankshaft back and forth: Turn the crank in one direction until the timing mark lines up with "0". Then slowly rotate the other direction to take up the timing chain slack. If the crank can be turned 4 degrees or more before the distributor starts to rotate, the engine is a high-mileage unit in need of rebuild (or, at least, the timing chain has seen so much mileage that it's worn out).

Lars
 
lars said:
You can do 2 things that are effective and reliable in determining the condition and mileage of the engine:

1. Cylinder leak-down test. Unlike a compression test, the leakdown does not require use of the starter, and the leakdown test produces an actual number indicating the absolute condition of the cylinders (unlike the compression test which only produces comparative data). You will need access to compressed air at the location of the engine, but this can come from a portable air tank that you can bring yourself. If cylinder sealing is in-spec, the engine is tight. Leakdown on all cylinders should be less than 10%. A fresh, well-built engine will often be in the 5-7% range.

2. You can pull the distributor cap and observe rotor rotation as you "rock" the crankshaft back and forth: Turn the crank in one direction until the timing mark lines up with "0". Then slowly rotate the other direction to take up the timing chain slack. If the crank can be turned 4 degrees or more before the distributor starts to rotate, the engine is a high-mileage unit in need of rebuild (or, at least, the timing chain has seen so much mileage that it's worn out).

Lars
Click to expand...

SCRATCH the above as being kind of a tuff to do on a LS1....for or that matter on a LT1-4......:fishing::rofl:
 
Well thank you for the info guys. All good info. I had two engines in mind, but won't be going after either. One was an undesirable year and couldn't verify any condition and they other guys just seems shady. I googled his phone number and wasn't thrilled with what I came up with.

So as a recap, the following should be brought or is a solid suggestion:
-magnet for oil fillin test
-smell oil for coolant in oil
-pull the plugs, look for burnt (orange tint right?) or heavily deposited plugs
-check for obvious leaks
-rotate engine for resistance
-run VIN of donor car (if everything else pans out)

Lars, How do you perform the leakdown test? I assume there is a time limit to the test, right?

Keep it coming guys, this is helping a lot.
 
A leakdown is easy- you turn the engine until the cylinder you want to test is TDC with both valves closed. Apply air to that cylinder and see where the air s going. If you hear it at the crankcase vent it's rings, or which valve it's escaping from.

The usual air pressure is 80 PSI (for aircraft engines) but no reason you need that. If you have a correct leakdown gauge you read the 2 gauges as 80/78 or like that. 60/55 or whatever. from that you can figure the percentage of the leak.
 
TimAT said:
A leakdown is easy- you turn the engine until the cylinder you want to test is TDC with both valves closed. Apply air to that cylinder and see where the air s going. If you hear it at the crankcase vent it's rings, or which valve it's escaping from.

The usual air pressure is 80 PSI (for aircraft engines) but no reason you need that. If you have a correct leakdown gauge you read the 2 gauges as 80/78 or like that. 60/55 or whatever. from that you can figure the percentage of the leak.
Click to expand...

Well that seems easy enough, but (please forgive me) what is the best way to determine I'm at TDC with both valves closed? All I can think of is pulling the valve cover which may or may not be easily done on the spot. However, if this is the way it must be done, so be it.

Imo Apita said:
I googled his phone number and wasn't thrilled with what I came up with.
Click to expand...
Whadiya come up with? Sheriff's office....?.:smash:
Click to expand...

Nothing too bad. He just seems to move alot of different parts and he's a mechanic. Both aren't bad, but the way he would dodge a question or not really detail anything out, just bugged. I got a bad vibe and seeing he knows what he is talking about means he could take advantage of it. As you can see by this thread, I'm rather new to all of this. He also can't talk that english good.
 
TDC is the best spot, air will turn the engine if the piston/rod are not exactly TDC for that cylinder. It takes a little doing- if you start with low air pressure you can feel for it as you turn the engine. Low pressure, turn the engine, as that cylinder comes up to TDC it'll be pushing against you and then all of a sudden it'll try to run. Back up a little and you're on. Pretty easy on a little airplane, just hold the prop to turn it. More difficult on a car (no prop) but a long breaker bar will get you there.
 
Tomorrows the big day. I'm going to see an engine/transmission combo. It should still be in the car (at a salvage yard) so seeing it run should be in the realm of possibility. I'm even hoping ot take it around the yard (it was totaled because it was drug confiscated vehicle, not an accident) So far things are looking ok. I'll let you guys know when I can of how it goes. Bad news is I'm flying to Vegas on sunday, haha. Gotta keep busy :hunter:

Wish me luck.
 
I have a 454 I will try to sell someday. It hasn't been ran since 1994. I don't think the engine pressure check is going to work with an engine that hasn't been ran for so long. I once had a 427 that I didn't run for 4 years. When I started it, it blew a lot of white smoke which I would think was caused by piston rings not sealing. After several minutes of running the white smoke went away. I assume the rings reseated. Drove the car for several years with no unusual oil usage or power loss. I assume my 454 rings will also not hold pressure, even though I think the engine is basically OK.
 
Well, I saw the engine/transmission and bought it. I didn't see it run because someone took the MAF sensor already, but the oil smelled ok, had good color (wasn't freshly changed) and the plugs looked ok. They claimed it ran fine and they almost used the car for their own projects (they had a nice Cobra in the shop and a Viper to be dealt with next), but decided not to use it. I got pretty much every wire under the hood, including the headlight harness with the engine harness, the full engine/transmission drop out complete with hurst shifter, clutch master cylinder and reservoir, stock Fbody radiator fans, pcm, all sensors (minus MAF), etc. I think I got a good deal on it too.

Now I just need to get the rest of the parts in order to swap.
Thanks for the advice guys.
 
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