internals

[butthead]

G'day

I've got a GTR R33, the person before me spent around 40 grand on it. Could anyone tell me if there is any way to find out if the internals have been modified, without pulling the motor apart, like a compression test or sumfin

[G0DF4Th3R]

whut have u done so far to the car?

[butthead]

HKS,- turbos T-28s, air pods, intercooler 100mm thick, blow off valves, 4 dash gauges & exhaust, all HKS, Blitz turbo timer & boost control. Full nismo dash, nismo suspension bigger injectors(dont know what size) nismo twin plate clutch & r34 factory GTR rims. DATS all that i know , might be more, just bought it a month ago . DOnt know much about turbo cars

[butthead]

& brembo brakes

[butthead]

any ideas on how to check for modified internals without pulling the engine apart

[Guest RedLineGTR]

not really unless you got xray vision

[Guest RedLineGTR]

but as far as it goes the car sounds pretty serious..

[butthead]

wat about a compression test

[siksII]

A compression test would not help you.

A compression test helps when you want to get an idea of how worn an engine is, in terms of individual cylinders,

ie. the pistons in the cylinders with poor compression would have worn piston rings. This could be the cause of exessive oil usage etc...

So you could do a compression test on your engine(i did before i bought my car for peace of mind), but all it would tell you is how worn parts of the engine are, no matter if they are original or aftermarket.

[butthead]

wouldnt modified pistons give different readings than the stock ones

[Roy]

Grab an endoscope, remove the spark plugs and look into the bore, you may be able to tell by the (domed/machined perhaps) pistons that the pistons arent stock.

Reome rocker covers to see about cams is pretty easy.

Thats about the best i can offer other then bouncing it of 10,000rpm a few times and seeing if she holds together:D

May be able to get the endoscope thru the oil pan hole and see the bottom end???

[JimX]

Don't forgies get piston slap when cold due to different heat expansion characteristics?

[siksII]

Aftermarket pistons could give a different reading to stock, but the ones in your car might just be to the same specs as the stock ones.

JimX :

What is piston slap? My knowledge doesnt extend that far lol

I have Wiseco forged pistons in my car (everything else is stock i feel dumb for not upgrading it to take advantage of this...) and the engine feels just like any other when cold or warm...

[JimX]

Piston slap is when the pistons rattle around in the cylinders due to being a tad too small. There was another thread here somewhere where someone was talking of their forgies being "noisy" when cold because they expand more with heat, or something.

If you have Wiseco forged pistons and it's completely normal when cold then they're the kind that I think I'll be after at rebuild time

[puckish]

Piston slap is the piston moving left and right in a rocking motion as it travels down the bore.

It tends to dent the bore on the way down if bad.

I seriously doubt performance bit would have piston slap on purpose.

[darkstar]

The standad cast pistons have different tollerances than forgies.

An enginebuilder should get the bores matched to the pistons used in that bore only, to get a better, overall balanaced engine.

Some aftermarket forgies expand at different rates due to the different material, and piston could be a few thou smaller than the bore which will cause the slap to occure when the engine is cold. As the piston warms up (5-10 mins to get eveything warm) then the tollerances are better and more to what you would expect.

You will blow your motor if you were to give it a trash when cold running forgies. Maybe not in an instant, but do that every time you drive your car (even comming on 6psi + boost) then its a road to trouble. In warming up your engine, your warming up the fluids which are at different viscosities when warm and your giving everything a chance to expand to the right tollerance. Iron expands differently to ally, the powered steel conrods expand differently to the steel block and metal bearings etc.

Some car manufactures run forgies standard in daily driver cars, but they have invested millions in fabrication and have designed the engines to incorporate with the ups and downs of forgies.

Using an endoscope might yield some results, particularly detonation signs, burn characteristics and other things that might be of interest.

[siksII]

Ah ok so 'piston slap' is pretty self explanatory, i figured that is what is was... thanx for the explanation.

to JimX:

I have never heard any rattles from the engine when cold, it idles perfectly smoothly just as you would expect it to. I have also never heard it while driving when the engine is cold....

But then again, i dont think i have ever driven the car without letting it warm for several mintues, or keeping the revs way below 2 grand till warm

So i guess in my case the engine builder matched the tolerances, while in the person in the other thread who was complaining of slap did not have a mechanic who cared as much..