Blueprint 106 - Cylinder Bore Inspection

We're close to the end of the 100-level series. In this video I show you how to measure the cylinder bores using 2 different tools. I compare the results and illustrate what to look for to determine whether or not your engine is in-spec.

The block I'm using is a 6-bolt turbo 4g63 from early '92. It has 150,000 miles and this video also serves as a testimony for the durability of Mitsubishi's cast-iron solid-decked Sirius I engines. This engine will be cut for a new set of pistons, so these measurements are needed to determine what size pistons I need to get.

.030" is as far overbored as you should ever take a 4g63. Boring larger than that will take too much off the side clearances between the cylinder walls and result in compromised strength from hot spots. The only time you'll ever need to cut a bigger hole is when an imperfection prevents you from using the pistons you have, or if you're changing to a larger piston. If you cut the block to its service limit, you have no room to fix an imperfection should one develop... so it's best to cut as little as you can get away with. Boring a cylinder .020" over does not significantly increase its displacement.

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[rsxking04]

jeff evans is better than you at explaining and he builds 1000hp+ engines

[Jafromobile]

@rsxking04 Go watch jeff evans' videos.

[urgeone]

Thank you, I'm subscribed by the way. I got a cheap $50 dial bore gauge that's got .0005" reference lines, and I keep getting out of whack up to 0.001" on some cylinders! I know this exceeds the .0004" limit but could a light honing be all that is needed?

[Jafromobile]

@urgeone Yes. So long as it's not deep enough to exceed the piston to cylinder wall clearance spec. Measure the hole, measure the piston. Don't let the difference exceed that spec and it will be like a brand new engine.

If it does exceed that spec, you'd need to replace pistons to fix it, but I don't see a thousandth requiring that. If the pistons are in spec, you should be fine with a light hone and a new set of rings.

[sivucit]

hi, i see lot of ur videos, lucking when i was browsing i get to ur videos accidently, iam big fan of watching this kind of videos, from there after i become ur subscriber. I like the way u explain in correct speed, great. I have a question for you if compression of engine is good, will the cylinder bore inspection reveal or not. Do u get to have a chance that compression is good for that cylinder but the cylinder bore inspection result begin failure.

[Jafromobile]

@sivucit No that's not very common. This test is what you do if 1) you can't start the engine and know nothing about its history (like in a junkyard). 2) you have performed a compression test and are trying to determine WHY compression numbers are low on a particular bore.

Often times when a car fails a compression test, you can visibly see the cause. I'm testing a block that never had a cylinder head (when I got it), and really I'm inspecting for machining tolerances as it's getting worked.

[HondaGRST]

Hello from Greece! Very good video. I d like to ask. I ve seen in my service manual (Honda B18C engine) that the service limit is 81.07mm from std new 81.00-81.02. That means 0.05mm (0.002in) difference from brand new. the limit for your engine is sure so much low as 0.0004? Honda has 5 times bigger limit for wear? Thank you!

[thejfactors]

the plural of "axis" is "axes", just emphasize the the E lol. you'll thank me later when it comes up in another video ;)

I used to say axis's all the time until I was forced to do a lot of three space multivariate calculus and got tired of stuttering every time I went to describe anything graphical.

Some good work you're doing there :)

[Serostern]

@HersheyWC A micrometer is accurate down to 0.01mm.

Calipers are accurate down to 0.1mm

A ruler is accurate down to 1mm

A tape measure is accurate down to 1cm.

Of total lenght thatis.

[urgeone]

so did you just do a light honing job to correct #3, #2 and #1? Or did it need to be heavily honed and/or even bore out?