I'm currently in search of a healthy VQ35DE with less than 50K on it to put into my Z and I ran across a potential candidate but need some opinions/advice. The below paragraph is what I know about the engine so far and I've attached the pics I was sent.

Details on engine:

• engine was father/son project to put in a rolling chassis to race (father works for Snap On and son is recent HS graduate)
• purchased from auction engine only, 05 VQ35DE with 3X,XXX that apparently ran before being pulled
• disassembled down to bare block, every part cleaned in parts washer
• 1 piston was dropped during tear down so it replaced with brand new OEM piston
• used Nissan engine rebuild kit including gaskets
• carbon cleaned off heads, cams were taken out to get to head bolts but valves/springs left alone
• engine's been sitting for 2.5 years on a stand or pallet out of elements after re-assembly
• cold leak down test result: around 20% across all 6 cylinders with 1-3% variance (apparently with a make-shift tester)

Everything sounded all right until I asked for leak down numbers, which concerns me. I'm not looking to tear anything down and the new-to-me engine will be thrown in upon delivery. My 350Z isn't daily driven and will only see autox/track time once up and running.

Given that the motor had been sitting there for 2.5 years after being "refreshed" and the leak test was performed cold, do you think the results are invalid?

I'm intentionally leaving price out as I'm not asking about value here. What are your thoughts? What are some questions you'd ask the seller to find out more about the engine?

 

With a makeshift tester for leakdown, the variance is probably all that you can rely on. If it really is 20% that would be high. I presume it is by design based on ring clearances. You will have increased blow by until the engine warmed up (depending on how much silicone content in pistons). It might make power just fine. I'd ask for all the clearances and run it by your engine builder.

 

The seller stated that everything was done to OEM specs -- whatever that means. I think they re-used all the parts except that one piston so I doubt it was intended. I do agree that 20% is high at 100psi, though. They claim 1-3% variance so I'm really hoping it was a faulty tester or that nothing's really been set yet since it's never been run. I've since asked the seller to get a hold of a proper kit to do another cold leak down test but it'll probably be a low psi one from Harbor Freight.

Ran across this thread while searching:
http://www.supraforums.com/forum/sho...n-engine-stand


What do you think about the fact that the coating on the piston skirts are no longer there? Considering there's no trace of it in the pictures, they probably scrubbed it off.

Assuming only the single piston was replaced, and there was no honing done to the cylinders, how detrimental is that? How does the cross hatching look to you?

How big of a deal is it if the torque-to-yield bolts were not replaced during assembly? I'm not sure if TTY bolts are included in rebuild kits, which I thought only included gaskets.

 

All right, I have some more info on the engine.

• purchased and disassembled strictly for educational purposes
• all internal parts were already clean and nothing was damaged
• no work was done to heads other than cleaning
• rings gapped to spec and ball hone on all cylinders
• pistons were cleaned in parts washer but no wire brushes
• did not recoat pistons before assembly
• piston rings, rods, and main bearings all reused
• no parts were replaced (minus 1 piston) and everything was reused, except gaskets
• ran another cold leak down (w/ spark plugs in on other 5 cyl this time) and all cylinders showed <3% @ 100psi

Thoughts?

 

It is a risk even if all that was said is true. I am not an engine builder but I have spent enough money to know that it requires diligence and experience to be done right. If this engine is in a state where you can verify all clearances, you should be good to go. Keeping some money held back until you verify might be prudent.

Fwiw, I had an engine run fine for 25k miles with a piston ring apparently installed upside down at 500 whp, so just by running it you will not know for certain if something is prone to give out earlier than expected. It did score the cylinder wall leading to gradually decreasing compression in that cylinder over time.

 

Are they giving you that much of a break in price to warrant the risk?

 

Do you know these people? Such an incredible amount of variables that you cannot see or verify.