Resizing A Set Of Pontiac Connecting Rods - '68 Firebird 350 Engine Rebuild - Pt 2

all right everybody we're back here today working on the 350 pontiac i've got the connecting rods out of the steel braider they they've been shot blasted and cleaned so that we can get a better look at them and start working on them on this connecting rod that spun the bearing before we go ahead and press in our arp bolts and do any actual machining on it i want to actually measure it up and see see how bad it really is so i'm going to put the original stock bolts back in and we're going to measure it and see how it comes out being a nearly stock rebuild we don't need performance rod bolts but none of our suppliers had a stock set available and we don't want to reuse the original bolts so i've got an old bearing catalog here and i've looked up um for the connecting rod bearing in a 350 pontiac the correct od of the rod bore is 2.3745 to 2.3750 so what i'm gonna do here is i have our mic set up to that you know smaller dimension and we'll basically get this set on 0 there it's kind of tough to do with one hand our housing bore of our connecting rod can be up to five marks past the zero point on this gauge um but my preference is to keep it a little bit on the tighter side so i'll try to shoot for two to three tenths past the minimum spec now this is what we expect to see with the connecting rod that has had the rod bearing out you'll notice that i mean you probably can't see this just with your eye you might be able to the connecting rod has become a little bit egg shaped meaning that this dimension from here to here is larger than the dimension from here to here obviously that's not what we want and you can tell that because when i put that on there it's not raising the gauge any but it's not excessively loose either and when we get around to the side you can see it is tighter because it is making our our gauge wiggle there now i've got a little piece of feeler gauge in there it's a 3 000th feeler gauge and putting that in and measuring again it's bringing us right up to our zero point so what we'll do is we're gonna grind this mating surface of the connecting rod and the cap and what's that that's gonna do is make the bore smaller than it originally was i'm going to do the same thing on the connecting rod and there we have the same thing on the rod itself normally um and you'll see us do it on the other rods we would put just a slight slight angle on both of them as well that way when you torque it down together that pulls the sides of the connecting rod in to make the sides smaller as well being that this one's spun a bearing i'm not going to do that because it's already somewhat egg-shaped i actually ended up taking more than i wanted to so knowing that i actually did cut more than enough off of these um for the rest of our connecting rods i'm gonna turn this down a little bit more i was actually taking more material than i anticipated taking that's not a bad thing in this case it's not excessive and it actually worked out being that this is a a spun bearing it'll just mean a little bit extra to hone out that being said on the rest of them i'd like to keep it a little closer to that size so i'm going to turn down this wheel a little bit so that we're not grinding quite as much off [Music] at this point you can see me using the feeler gauge under one side of the connecting rod in an effort to cut the rod at a slight inward angle so that when the cap is torqued on the sides of the connecting rod will be pulled in tighter as well one of the last things that i always do on these is deburr this edge because you will leave a sharp edge there after grinding the cap it just takes a little touch just like that something that can happen in connecting rods is they can actually become a little bit magnetized over you know thousands of miles of use in the engine um and i kind of noticed that on these connecting rods and this will probably not be very easy to see but they're attracting little pieces of metal filings obviously we don't want that inside our engine because that just pulls all of those little pieces of bits of you know metal in the engine um and attracts them to the bearings so the way we fix that i've got our magnetic yoke here and this is what we normally use for magnafluxing but we can also use it to demagnetize these so i'll just turn it on and then we can pass this rod directly through the magnetic field and that should demagnetize the rod i always use the arp ultra torque fastener lubricant when pressing the bolts in but i especially always use it on the threads of the bolt it's specifically designed by arp to provide consistent and precise fastener torque specifications so it's really a great product to have on hand and to use when you're not only rebuilding the connecting rods but when you're building the engine itself [Music] obviously it's always super important to get the correct cap with the correct connecting rod and that's why we numbered them when we took the engine apart but sometimes you can't trust the numbers as you might have seen in some of my previous videos but um in this case the numbers that i stamped on the connecting rods didn't end up being the correct rod with the cracked cap [Music] now arp calls for these to be torqued to 50 foot pounds so that's what we're going to be doing here typically in a high performance application arp recommends using a bolt stretch gauge to measure clamping loads as it is more reliable and consistent than using a torque wrench as such i did go ahead and check that our torque reading of 50 foot-pounds was putting us in the correct range of bolt stretch and it was with our connecting rods back torqued together when we measure them we've got a little over five thousands to take out there and closer to two there so i'm still a little bit egg-shaped um but that's okay as long as there's enough material there to take out and get us to our correct clearance you know to hit our tolerance then we'll be good to go so i've just started our our honing with our rough stone we're getting the connecting rods roughed out this is that rod that spun a bearing so you can see all those dark areas are the locations where basically the connecting rod is worn excessively from the bearing spinning um but it's looking like we're gonna have enough room to get that all cleaned up so i'll show you the finished product here in a minute [Music] you see we've just got barely any shadow there at the parting line so this is cleaning up nicely what we've been doing is roughing out the bores on our connecting rods so i've got a coarse grained stone in here and basically that's for bulk material removal so that it removes the material quickly that being said you can think of it like sandpaper it doesn't leave as nice of a finish i mean still plenty nice but not as nice but i've gone through all eight of our connecting rods and remember zero is our um the tightest our connecting rods can be and i've got them all within um you know four to five tenths of being within our tolerance range there so at that point i'm gonna let these cool down then we'll check the gauge make sure everything is as it's supposed to be i'm gonna grab some lunch and then we'll put the fine stone in and we'll begin honing these back to our finished size within that zero to five tenths tolerance that we have set here on our gauge i've gone ahead i've put in a finer stone this is the rough stone that we were using we're going to put in a fine stone so that we can really sneak up on that final size that we want and hit the tolerance that we want i'm going to turn down the pressure a little bit that's going to make it machine a little bit nicer so right there you can see this leaves a nicer finish with the finished stone and measuring i'm right at the two to three tenths past the minimum clearance that i want um and that puts me right where i want to be i'm going to shoot to make all of them match exactly the same now with the rod's finished tone i checked the gauge one more time made sure that it was set correctly and just double checking here we're right at that two tenths past our minimum clearance there kind of in that two-tenths to three-tenths range that's what we're shooting for i find any that are tight for instance this one maybe seems a little bit tight after cooling down i'll go through and i'll just touch them just barely a little bit now this isn't the final wash on these parts but for now i'm just going to rinse them off here in the solvent i believe we are going to be balancing this assembly so i'm going to leave the rods together for now so that's basically the process for resizing these connecting rods again we have the arp bolts in them this isn't a performance application it's just those are literally the only bolts that we could find from any of our suppliers for a 350 pontiac right now that being said you know we were able to go through um one of these rods did have a spun rod bearing like we said but it really wasn't too bad um it it was able to come out clean up just the same i took a little bit more material off of that one and looking at them you really would have no idea which one it was other than i know it was this connecting rod and based on the weight if i can get changed over to grams i'll go ahead and zero off of that connecting rod and then we'll go through and check all the rest seven grams heavier four grams four or five grams heavier overall eight grams heavier overall four grams heavier overall eight grams heavier overall eight grams heavier and eight grams heavier seven grams heavier so that's really the only way that you would even know which one had a spun rod bearing because we had to grind a little bit of more material out to make that bore smaller and then hone a little more material out to make it clean up the way that it has but like i said if you did not know um you know you would never really be able to tell that this had ever had a spun rod bearing and obviously we're confident in it we wouldn't use it in our customers engine if we weren't confident we have all kinds of cores connecting rods so if we weren't confident in it there would be no reason to but from here we are going to be doing a bounce on bounce job on this rotating assembly in a later video um but that's how we do the connecting rods from here i'm going to get going on this block i need to get it cleaned up well it's actually it's already cleaned up i need to get it mounted here on the machine so that we can go through deck the block square up the decks and bore the cylinders so that'll probably be the next video in the series so stay tuned

Channel: Jim's Automotive Machine Shop, Inc.

Views: 121,920

Keywords: Engines, Engine Machine Shop, Machine Shop, Engine Shop, Machining, Automotive Machine Shop, Automotive, Cars, Trucks, Tractors, Gas, Diesel, Performance, rebuild, high performance, internal combustion engine, pistons, cylinder heads, jim’s, jim's automotive, jamsi, jamsi online, Blueprinting, rebuilding, engine building, connecting rods, engine block, boring, valve job, engine rebuilding, jim's automotive machine shop, 350 Pontiac, Pontiac, firebird, pontiac firebird, restoration, classic car

Id: 9AeG_XFRe9A

Length: 14min 16sec (856 seconds)

Published: Sun Jul 18 2021