DIY CYLINDER BORE CHECK: How to measure OUT OF ROUND, TAPER, and REBORE size - STEP BY STEP GUIDE

so this here is a cylinder bore and now we're going to do an easy step-by-step diy guide that's going to show you how to inspect and measure your cylinder bores to see if they are out of round or maybe tapered and to know for certain if they need re-boring or not in order to measure bores we're going to need two different measuring devices a dioboar gauge and an outside micrometer now when it comes to diy car enthusiasts our two arsenal typically doesn't contain either of these tools this is because when we rebuild engines most of us just take everything to a machine shop tell them what we want and let the machine shop call the shots but i think we should all in fact own these two simple tools and that we shouldn't just blindly leave everything to a machine shop wouldn't it be better to know for certain yourself whether you actually need boring or not and have actual insight into the condition of your engine by checking and verifying measurements yourself you're providing an additional set of eyes and an additional level of verification to your engine and that's never a bad thing on top of all this you'll be learning a new skill and you'll have better understanding of your engine which will empower you to make educated decisions on its rebuild but dial board gauges and micrometers are expensive how can a diy car enthusiasts justify their cost when they won't be using them often well this is where sites like bang good come in i got my dial board gauge and set of micrometers for an extremely affordable price from banggood.com of course these aren't professional great tools but you really don't need professional grade tools anyway you won't be using them on a daily basis and we're not really trying to start a machine shop business here these are perfectly adequate and accurate tools for our purpose so if you want to learn a new skill and have actual insight into the condition of your engine you can check these tools out by clicking on the links in the description and the pinned comment now the first thing we'll be doing before measuring stuff is to clean and visually inspect our pores during our visual inspection we're looking for two things an absence of damage in the form of deep scratches and scoring and a presence of a cross-hatch home pattern on our bores if there's an absence of damage and a presence of honing marks your engine has passed visual inspection if there's an obvious presence of damage your bores have failed visual inspection and they will need reboring this is just a junk block i'm using for demonstration purposes and as you can see it immediately fails visual inspection this blocked water and or coolant ingress into the cylinder and was sitting for a very long time which resulted in cylinder number 3 being completely rusted if i were to rebuild this engine i would definitely have this block re-board on the other hand cylinder 1 doesn't really have serious rust and there's even some holding marks present however there is increased wear on the trust axis of the bore now increased wear on the trust axis is normal and expected during engine operation combustion forces act on the piston ground and because of the piston's position in relation to the conrod and the crankshaft this part of the bore receives most of the load and therefore most of the wear this is also why pistons have more skirt material along their trust axis more skirt along the thrust axis helps better support the piston and the boar and helps distribute loads so cylinder 1 has an absence of serious damage and even some presence of honing marks which means that it passes visual inspection but it does raise some concerns over increased wear to accurately measure bores we need to zero our tools the first thing will zero is our micrometer and to zero it we need to set it in a vise it's a good idea to use a soft jaw vise and or some wood and definitely do not tighten the micrometer too hard because if you do tighten it too hard you can distort its shape and if you distort its shape then it's going to be useless and it won't be able to accurately measure anything we're using a 75 to 100 millimeter micrometer because the bore of our engine is 81 millimeters to zero it will need our gauge block check that the measuring surfaces of the micrometer are clean and tighten them down to the gauge block use the small knob to tighten as it ensures that you always tighten everything the same amount and that you do not over tighten anything once the gauge block is in place lock your micrometer and look at the measurements because our gauge block is exactly 75 millimeters that's what we should be seeing on the micrometer we're close but as you can see the zero doesn't align with our 75 mark so we'll use the little branch provided with the micrometer and insert it into the pinhole on the back and turn until our marks are perfectly aligned once they are our micrometer has been zeroed now we're going to consult our factory service manual or any other suitable source to see what kind of bore dimensions we should be seeing this is a toyota 4a ge engine block and the factory service manual tells us that our std board dimensions are between 81 and 81.3 millimeters so we'll set our micrometer to 81 millimeters exactly and lock it again now we're going to zero our dial board gauge to 81 millimeters this is probably the trickiest part of this whole process and it requires a bit of patience sometimes we're going to assemble our dial board gauge by using an attachment of suitable length and then we're going to insert the measuring end of the bore gauge into the micrometer we will gently and slowly move the board gauge inside the micrometer as we watch the needle we're looking for the smallest measurement the needle is taking or in other words the point at which the needle stops going further on the gauge once we find that we're going to turn the zero mark on the gauge face to match this location of the needle this requires some fine hand-eye coordination and usually two to three tries to get it right once you've zeroed the bore gauge we can proceed to the measuring and we'll be measuring at six different spots to get an accurate assessment of the condition of the bore so here's our bore and we'll be measuring at the top middle and bottom of both the thrust and non-thrust axis of the bore we're looking for two things here an out of round condition and or a tapered condition of the bores an out of round condition will reveal itself as a difference between dimensions of the trust and the non-trust axis and a tapered condition will be present if there's a difference between dimensions at different board depths our factory service manual tells us that the maximum allowable board diameter is 81.23 millimeters anything beyond that calls for the cylinders to be reborn when measuring at the top you want to measure below the ridge that's usually present at the top of the cylinder which means that you'll be measuring around 10 to 15 millimeters below the top same thing goes for the bottom you're measuring some 10 to 50 millimeters above the actual bottom of the cylinder bore so here's the top of the non-trust side the middle of the non-trust side and the bottom of the non-trust side now we're switching to the trust side and again here we have the top middle and bottom and here we have our measurements as expected we do have increased wear on our trust side and a slight out of round condition because of this but by using the dial board gauge we can see that although there is increased wear it is within tolerances we also have a very slight taper on the non-trust side but again nothing major and definitely within our tolerances so in a rebuild scenario this board would likely be good with a re-hone and some new rings kind of sad that cylinder number three is such a mess but now let's imagine that we don't want to reuse this board we can't tolerate the site out of round condition and we simply want brand spanking new bores how do we determine the size of our new bores well to do that we need to measure our oversized business when you reborn engine you need to get oversized pistons to maintain a proper piston to occurrence and increase bore diameter also calls for an increased piston diameter now the important thing here is the different vehicle brands as well as different aftermarket piston manufacturers measure pistons at different spots it's very important to note where the piston is measured because the piston itself is tapered it's tapered to allow for different rates of expansion due to its ground receiving more heat than its bottom if we check our factory service manual we'll see that the piston is measured on the trust side 42 millimeters from the skirt bottom which turns out to be just a few millimeters away from the oil ring group this is a slightly unusual measurement spot as most others measure close to the bottom of the skirt this is why many machine shops would be surprised by this piston to wall occurrence if you didn't tell them where the piston needs to be measured when measuring always use the small knob on the micrometer to prevent over tightening and a false measurement our piston comes in at just above 81.38 millimeters i will call this somewhere around 81.383 but we can round it down to 81.38 our factory service manual gives us a formula for determining our new bore size it's the piston diameter plus piston clearance minus the allowance for honing in our case that's 81.38 plus 0.13 since these are supercharged for a gce pistons we're using and then we deduct 0.02 millimeters from that the result is 81.42 millimeters and this is the new bore size you would need to achieve for this particular piston in cylinder number one of course this is the new bore size only if you're doing a mostly stock or mild rebuild if you're doing something different such as a lot of boost or a much higher redline or forged pistons or different types of racing then your piston-to-wall currents would likely need to be increased to suit both the engine modifications and the application how much it should be increased is decided on a case-by-case basis while taking into account all the different factors and there you have it i hope you enjoy this simple step-by-step guide and i hope it helps you better understand your engine and maybe even inspires you to take up some measuring tools yourself and broaden your skill set as always thanks a lot for watching and i'll be seeing you soon with more fun and useful stuff on the d4a channel

Channel: driving 4 answers

Views: 149,928

Keywords: cylinder bore, bore gauge, cylinder, bore, dial bore gauge, outside micrometer, how to, engine rebore, cylinder rebore, how to zero dial bore gauge, cylinder dial bore gauge, cylinder taper, cylinder out of round, cylinder out of round limit, cylinder taper measurement, when should you rebore a cylinder, oversized pistons, piston to wall clearance, piston to bore clearance, piston to bore clearance measuring, cylinder honing, cylinder bore inspection

Id: 1vejKSxzGC8

Length: 10min 52sec (652 seconds)

Published: Sun Feb 14 2021