Checking out poorly tuned motor

[E.Murray]

I'm considering buying an engine that a guy gave up on tuning. It has a pretty stout bottom end and some good stuff, but I'm nervous since the guy doesn't seem to understand much about tuning a turbocharged engine. If there's anything I've learned in my time on syty, it's just how fast you can screw up hardware... The motor starts and idles fine with no knock from the bottom end and no lifter or top end noise. Wideband shows good AFR. But give it much throttle and it spits and sputters and coughs.
The guy claims that it just really needs somebody who understands the whole system to go through it. I'm fine with that. My fear, though, is that he's done damage in messing with it. So, here's the question: What can I look at to know if he's detonated so much that damage has been done? I have compression numbers and they seem solid and are within 5% across all cylinders. What else do I need to check before I hand over any cash?

 

[QWERTYphoon]

Re: Checking out poorly tuned motor

Check the oil. You could have it sent out to have it checked professionally. Also, how much are you paying, sometimes its just worth the price. The sputter is probably ignition related, wrong plug wires on the wrong plugs or dist is off a tooth. Compression is the most important thing I think.

 

[Pau Hana]

Re: Checking out poorly tuned motor

Sounds exactly like what my truck was doing with a clogged cat converter. Starts fine, diles fine- any load, it gets angry and doesn't want to perform.

Otherwise, check the usual suspects- fuel pressure rising with demand, ignition system including dist timing, balancer spun, etc.

 

[Don W.]

Re: Checking out poorly tuned motor

Along with Dave, cut the oil filter. To really check it remove the paper, let drain over night then stretch out the folds and look in the crease.

 

[E.Murray]

Re: Checking out poorly tuned motor

Wow, excellent stuff Dave. I've been looking for an excuse to buy an inexpensive bore-scope. Thanks for the justification.:tup: The price is good enough that I won't get hurt even if it has needs, but I like to know what I'm getting into ahead of time. Thanks.

 

[blue83z]

Re: Checking out poorly tuned motor

Cool story about the lt1 air car.