jspecteggy

iTrader: (13)

I am purchasing an Evo and am having some doubts about the compression test results. Engine is a 4g64 bottom end with a IX head. It is running GSC R2's, Supertech .5mm oversized valves and Supertech beehives. Inside the block are Manley 9:1's with an 87mm bore on 156mm I beams, and I believe the crank is a 100mm stroke.

My concern is that the picture I was sent for the compression test shows about 95psi. Lowest I've seen from searches on EvoM is 110psi. The leak down came back good and was even across the board, holding 100psi with 0% leak down.

Should this be anything of concern? Also would the large FFTEC V3 manifold have any influence?

barneyb

The seller should allow you to take the vehicle to an independent garage for inspection.

jspecteggy

iTrader: (13)

That's who performed the compression test.

hutch959

iTrader: (18)

ix heads with big cams wont ever have much compression due to the way the cams overlap.

i cant say the motor is good... but, this is not a tell tell sign that the motor is bad.

Dakota Evo

big cams will usually have lower compression plus the ix gasket is thicker...

lowest ive seen on r2 is 125 but the car ran well

if theres a doubt dont buy it and stay away or compression test it while warm to see if it gets better

RightSaid fred

Compression numbers tell you nothing apart from the fact that they're too low.

Broken pistons often have higher numbers, cams out a tooth often have higher numbers, hotter cams have lower numbers. Cams out the other way give you lower numbers, strokers always end up with a CR that's not what you expect.

Waste of time and effort.


BUT



Looking at the plugs tells you far more and if you're doing a compression test then why didn't you take notice of the plugs?


Most modified cars are lemons.

It's got zero to do with the overlap, it's the intake valve closing point.

barneyb

And, what was the opinion of the mechanic who did the inspection?

jspecteggy

iTrader: (13)

He said it was G2G. But this is where he gets all his work done, so I was uncertain. Maybe his gauge is off?

hutch959

iTrader: (18)

rightsaidfred....

yes, wrong choice of words for me... i meant the mivec side keeps the valves open longer.

aurigagt2

I have an IX with a stock block, 2.3 stroker crank and s1 cams. It measures in at 140 to 150 on crappy harbor freight gauge. one thing I've noticed is that the longer you crank it over, the higher the gauge tends to go until it plateaus at some result. So if you only let it crank one or two revolutions, it might read 100 (it takes time to fill the gauge and hose). I think it is also important to note that bigger cams may read lower pressures because of all the overlap. I would say that if the leak down is good and all of the cylinders read the same compression after 10 revolutions then you're good

barneyb

The seller should allow you to take it to an independent garage for inspection does not equal the seller took it to his shop for inspection and you weren't there.

Aby@MIL.SPEC

iTrader: (161)

did you have the throttle open when doing the compression test?

if leakdown #'s are good, thats a positive thing.

how many revolutions did you let the engine turn over to achieve your compression test #'s?

kaj

iTrader: (60)

I would take it to an independent shop. Assuming they would know what to expect from a Frankenstein motor.

lilbro23

jspecteggy

iTrader: (13)

Right, I agree. However I cannot force somebody to do something they do not want to do. I could walk away from it, but I figured I've built one before and worst case scenario I have to build another one.