Compression results. Rebuild time?

[MadManMeasures]

So I've just carried out a compression test on my stock Sr. Which has done 178k Miles, and has been running at just over 300bhp for the past 5 years. Its used mostly for track days, shows and country laneing in the summer time. The results with the engine warm and the throttle fully open are:

Note. All pressures are in psi

1=120
2=115
3 =115
4=120

I then carried out a leak down test using 1 cap full of 10w 50 in each cylinder with the engine warm and throttle fully open. The results are:

1=166
2=166
3=166
4=165

I had planed to upgrade to a GT2871r APW manifold and a few other bits before the summer (already purchased 90% of the upgraded parts) I hadn't really budgeted for a rebuild this year. My question is will I get away with running the engine for another season (usually about 4-5 track days and 3000 odd road miles) or am I better off to bite the bullet and go forged bottom end MHG and a general freshen up before it comes back out again?

[green_rs13]

looks like you need new rings, its cheaper to rebuild a 'good' engine than a knackered one. I would carry on using it as it is then rebuild and stick all your high power bits on next year.

cost you about £500 to get it mapped so no point doing it twice as you would need it redoing when you rebuilt it.

if you just want 2871r power then you could just go for a refresh and not bash new pistons/rods in it. saves you about a grand.

[ex-ctr]

Hard to do a proper leak down test on a sr engine as the pistons have a 11cc dish where oil will remain after a leak down test increasing compression test results


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[Slamz]

My engine was at around 120psi across all 4 for many years, never had issues, used no oil and pulled hard so I'd say just keep using it.

[Mark]

That looks fine, I really wouldnt bother.

[MadManMeasures]

So do you guys think it will be fine to run it at 20-22 psi of boost on a GT2871r with out a rebuild for another year?

I had noticed a bit of a drop in power before it came off the road for winter, it was also putting out quite a bit of smoke when I lift off after going flat out. But it has always put out a bit of smoke when lifting off ever since I had it mapped 5 years ago, but lately the amount of smoke seems to have increased.

[Mark]

Thats probably your turbo

[MadManMeasures]

I was hopeing so. I've just calibrated my compression tester (using a dead weight tester) and it was pretty accurate, only 2 psi out at 120. The engine has developed a noisy lifter as well so I think I will end up at least doing a top end rebuild this year. And if I've got the head off I may as well rebuild the bottom end as well. Just for peace of mind if nothing else. If I leave it as is and fit the new turbo, injectors, ECU, etc. I will constantly be worried something is going to break every time I push it.

[immy21]

Just curious, what does your vacuum gauge read at warm idle?

[MadManMeasures]

Usually around 22 in. Hg. I think