Grinding To A Halt - I'm Building This 426 Hemi For A 1970 Dodge Coronet (But I Found A Big Problem)

Added: 2026-05-09

[00:00:00]When did I become a lawn mower mechanic?

[00:00:02]I don't like it. Angry noodle.

[00:00:06]Look at him go. Lol. Should have bought a Mopar. Hey, it could be worse. It could be a Nissan. I have changed my mind again. I've been doing that a lot lately. This is my July 1966 Cast 426 Street Hemi, and it's covered in hair.

[00:00:23]Wait, is that a one? Whatever. Doesn't matter. I think this will be the third video I've done on this particular engine. In the last one, Peter and I cleaned it up to get it ready to reassemble, and I told you I was going to put this thing in the Flying Banana with a blower. It turns out that was a dirty, nasty, disgusting lie. Thanks to a unique combination of dumb luck and assistance from Tom Hurt, I actually own two 426 Hemis, the Street Hemi and this 1964 cast race Hemi. Just like every other factory cast 426 Hemi block in the universe, both of these have seen some stuff. This one had two big giant windows, which my friend Mike and I actually patched. It looks okay. It also has two cylinder repair sleeves. This one only has one crappy repair where a rod went through the side of it, but it actually has eight sleeves. So, yeah, these two blocks are virtually identical and functionally interchangeable. And no one would know unless they knew which one I put where. But putting the factory race Hemi block in my period race car kind of seems like the right thing to do. So, I've decided to go back to that idea. I'm not assembling this one right now because I still don't have pistons.

[00:01:30]And once I do, the bottom end is going to have to be balanced. I am continuing to collect parts for that project, though. Here, for example, my BDS drive hub. For the other engine, I would have had to have the crankshaft machined to drive that thing. It just so happens that the crank I have for the race Hemi is an X-ray part, and it is already slotted for dual keys to lock this thing in place. So, that problem solved itself. I also got a single V-bolt drive pulley. This is to run the alternator and water pump. Note, it has the big hole in the center for the 3/4inch Chrysler bolt. Here's our lower blower drive pulley. Like many of you, I sure would like to see all of these things put together on that other engine in that truck. And I'd like to be doing wheelies right now. But the thing is, race season is here. And I don't think this is going to happen this year. I'm just trying to be realistic. Just so we all understand what's going on here. The engine alone isn't why the Banana could not possibly be done this year. As I've discussed in previous videos, this thing needs an entire chassis rethink.

[00:02:27]Currently, the rear axle is welded to the frame, and we are not going to race it that way. I've got all kinds of plans for this, but it's a big crazy fab project, and I am just not prepared to tackle that yet. You know what could happen this year, though? Well, a street Hemi and a four-speed and a Dana 60 could all go together in this glorious thing. This is my plum crazy purple 1970 Dodge Coronet 440. and it's pretty cool.

[00:02:49]Tom Herbert brought this thing back from one of the Dakotas or something. As soon as I saw it in person, I fell in love and I had to own it. This video is not really about this car. We're going to do a video in the near future going over the car in detail and all of the history we found on it, which is kind of awesome. Suffice to say, it's seen some stuff, but it's mostly solid and mostly kind of sort of complete. Look at all this glorious original plum crazy paint under the hood. I mean, with just a quick cleaning, how great will a 426 look in here? Now, I'm sure I've alluded to this project in the past, and I've been hoarding parts to make it happen for like a year now. Long before I actually got the car, I was buying things like these Bbody or E or C body, V8 to Gen 2 Hemi conversion mounts from Shoeacher, original late street Hemi, 10 and 1/2 in aluminum bell housing, flywheel, pressure plate, another flywheel. Not sure how I ended up with two. somewhere in there. There's a set of 1970 Bbody pedals. There's a correct Bbody shifter with rods. Yeah, I've got a lot of the stuff. I've got a BE transmission case right here. It is just a bare case at this point. I have most of the guts for it in this pile somewhere, I think. But that case needs a bit of repair, and I'd really like to have the proper 18 spline input. So, we're not quite ready in that department. Like the rest of my projects around here, I'm not going to be able to finish this one in one video. I have a couple days right now to take a bite out of this thing, and I think that time will be best spent assembling this short block. In the last episode, I was ordering all of the rebuild parts. Well, I actually have them now. These are the ones I selected for this particular build. These are Cleite 20,000 under main bearings, Sealed Power 30,000 under rod bearings, and Speed Pro rings. Now, there were some concerns about using Molly rings like these for a boosted application. This is what I could find that fit my particular pistons and were available quickly. I'm going to be placing a ridiculously expensive order in the near future for pistons for this thing. And at that time, I'm going to ensure we get rings that are suited for the job. I had to order this Speed Pro number R95905 because it matched the 4 and a/4 bore.

[00:04:54]Yes, this block is factory bore size thanks to those sleeves, but the thickness of the rings match the groove sizes in these old school J pistons.

[00:05:03]Now, even having measured the bore and the groove sizes and ordering rings that match that, we do not automatically know that these rings are going to fit these pistons. There are two other things we need to check. One of those is side clearance. The side clearance is the gap between the ring and the side of the groove. As you can see, I've currently got a feeler gauge of 0015 shoved in here. So, that's a thou and a half. I don't have a 1,000th feeler gauge on this set. The 15 actually fits snugly.

[00:05:32]So, this gap is definitely between one and one and a half thousands. According to the Speed Pro specs here, one to three thousands is acceptable. I feel good about it. The other thing we need to verify is the presence of back clearance. Back clearance is the space behind the ring in the groove when it's installed in there. There has to be some. There isn't actually a measurement specified here. We just need to ensure that this ring does not protrude from the piston when it's bottomed all the way out. If it does, things are going to break. Here's the quick and dirty way to check. Flip your ring around backwards and put it in the groove. Notice right there, it just barely disappears. In fact, I've got to get you at exactly the right angle to verify that. Yeah, there you go. I don't know how much back clearance that is. It can't be much, but it is some. Got to check the second ring, too. Of course, that one must be a little thinner or the groove is a little deeper because, as you can see, there's a good bit more clearance. You don't typically run into fitment issues with oil rings, but it's worth checking. This looks really good. There we have a complete oil control ring assembly.

[00:06:33]Looks good. Moves freely. In the last video, we did clean these piston and rod assemblies pretty thoroughly. We also pre-lubricated the pins. Aside from some grubby fingerprints, these are pretty much ready to lube and assemble. Once we've got our ring gaps verified anyway, to check ring end gap, of course, you want to take a given ring, you want to set it in the cylinder, and you want to square that, typically using a piston.

[00:06:54]Tell you what, that's really hard to do with a domed street hemi piston. But anyway, I got it. There's like no groove here at all.

[00:07:02]>> No gap. Words are hard.

[00:07:05]>> So, I'll be doing some filing today.

[00:07:07]Before we just start grinding, we do need to know what gap we're looking for.

[00:07:10]It's important first to figure out what type of piston you have. This is a forged J piston. This has conventional ring grooves located pretty far down here. If this was a more modern hyperutctic piston with the highmounted top ring, well, we would be grinding a much bigger gap in that. And you can find that information right here in this chart. We're building a street strip engine. Yes, this thing is probably going to see a racetrack, but it's mostly a street car. We've got a forged piston, so our gap factor for the top ring is going to be 0.0045.

[00:07:41]If it were a hyper piston, well, it would be 0.65, which would result in a much larger gap. The second ring gap size is consistent between either design. For a typical street engine, the factor would be 0045. For our purposes, we're going for 005.

[00:07:57]That means in this build, the top gap is actually going to be a little smaller than the bottom gap. To determine what your actual ring gap should be, you multiply your bore size by the gap factor. Here, I've done that for our top ring. We're looking for 19,000. 19 thou is a relatively small gap compared to all the hyper piston equipped engines I've been building lately. Our second ring is going to be 21,000. Time to break out my trusty well-used ProForm ring grinder. Once again, this thing kind of sucks actually.

[00:08:28]Ground it once, it was too tight. Ground it briefly a second time. It's way too big. It's like 22 or three. This is supposed to be 19 guy. Thing is, the gap spec is really more of a suggestion.

[00:08:40]It's a minimum size. You need to get it at least to there to prevent any possibility of the ring expanding and the ends butting into each other and breaking your piston. A little bit big isn't going to hurt anything. I moved that first ring over to number three where the gap was still a little bit big but less. Then I ground another one. And this one after three tries and a little bit more care landed perfectly at 19 thou. I don't like grinding rings. It's easy to mess up, but more than that it's just fiddly busy work. As a matter of fact, the necessity to custom grind a set of rings once delayed me on assembling an engine for like three or four years. There's nothing to it but to do it. So, I did it. And I timed myself.

[00:09:21]24 minutes to grind all eight of these top rings. Is that 3 minutes a ring? I think that's good math. Eight more to go. There's the last second ring done.

[00:09:31]19 more minutes on those. Pretty much everyone was oversized. Something like 22 23. It's fine. It's not going to be the end of the world, but I do have to advise if you're going to grind these yourself, take your time. Be patient.

[00:09:43]You know what they say, a loose engine is a happy engine. I'm starting to get the feeling this one is going to be delirious. Speaking of which, it's time to check our oil clearances for the crank. Now, I've shown checking these oil clearances before, and I don't want to spend all day rehashing that, but basically, I've got an outside mic here.

[00:09:59]I measured our number one bearing journal. Then, I got my dial board gauge set up here to measure around 2.8 8 in, which is pretty close to what we've got.

[00:10:07]I zeroed this guy in this. So, what we're going to be seeing when we measure is the oil clearance difference between the actual diameter of our journal and the inner diameter of our bearing.

[00:10:18]Here's what taking that measurement looks like. What we're going to do is search around for the needle goes the furthest towards zero and then turns around. See that? So, this is going to be our measurement right here. And each little hash mark is half a thou. The big ones are one thou. So, oops. Well, take my word for it. It's just under two. I rechecked that like three times. It's not almost 2,000. It's actually just over 1 and a half. So, that's not great.

[00:10:45]According to people on the internet who know things, something a bit closer to 3000 would be ideal. A good rule of thumb is 1,000th per inch of bearing journal diameter. In this case, it's a 2.75 or actually 2.73 once it's turned down. So multiplying that by O1, we would end up at 2.7,000.

[00:11:06]Now, there are a couple different things I can do here to try and solve this. One would be give up, go for a swim, maybe get a tan. Um, two, I could order a different set of bearings and hope they're better. Three, before trying either number one or number two, I can mix and match these shells and see if I can come up with a combination that gives us a slightly bigger clearance.

[00:11:26]Now, I can't do the mix and match thing with the number three, the thrust bearing, because those bearings have the thrust surfaces on the side, unlike all the rest of them. So, I'm going to check those, and if the clearance is acceptable there, we'll move on. Okay, that one's like bang on. It's just about three or a scoch under. In case you were wondering, I did rezero that off of the number three journal, but I went through and checked all of them, and they're really, really close. I'm going to check number two next with a random pair. If that one's good, we'll move back to number one. Then, we'll take all of them out and check the rear. This one main bolt is not threading in nicely. So, I grabbed one of these thread chasers.

[00:12:00]Yes, I happen to know that these tools are not for starting new holes. I did manage to start some new holes with one the other day, and it worked. Just saying. Anyway, it went right down there. So, this must be a problem with the bolt. Running a tool like this through every single hole in every single block is highly recommended when engine building, but I've pretty much never done that. Somehow, the very last thread on this main bolt got goobered, but I fixed it. Here's what we've got for two.

[00:12:28]Looks like just over 2000 on that one, which isn't great, but is better.

[00:12:34]Completely different set of bearings dropped to number one. Almost exactly the same result. Obviously, before I ever put any of these bearings in to check them, I did clean the cap and the area where the bearing half sits in the block. I had noticed this, but I didn't really think anything of it. See those lines running across this cap? I don't know if you can actually catch those in the light, but that's a really interesting marking. Can't say I've ever seen anything like that before. And I'm wondering if this happened after this was honed last. You can see the nice hone marks there. And that created little raised areas that are shoving our bearing downward. I gave those marks a quick cleaning. I popped in the last bearing I had. I torqued the cap down to 100 lb feet, which is the main bolt torque spec for a 426 Hemi. slightly more than a big block, which is a very similar animal. But anyway, I measured it here and I got 3000.

[00:13:24]I measured it here and I got a thou and a half. So, that opening is not round. I actually turned the thing just about as far as I could sideways without running into this gap. And I measured almost 4,000. Did you know that clamping loads will vary between different types of fasteners? I was checking before with factory main bolts. I had the idea that maybe someone built this thing previously with ARP main studs. And because I happen to have a set, I thought I'd throw some in to check. I did slightly forget that there are longer and shorter fasteners on these mains in the 426 Hemi. I torqued these down to the requisite 110 lb foot spec, and it made almost no difference. I happened to go back and measure number two again for science. It's worse than I thought. If you put the tool straight up and down, just like in number one here, it's a lot tighter than it should be.

[00:14:13]Now, you should know that these bearings crush into place, and I wouldn't necessarily expect this to be perfect, but if I can catch it right with the camera here. Yeah, you could see daylight around this shell, but not at the top. It's touching at the top, but pretty much not anywhere else. Pulled the bearing shells, retorrked the cap for like the fifth time, and now I've zeroed the dial here. Now, I'm going to go measure here, and it's coming up fine. I've actually already done this off camera in case you were wondering.

[00:14:43]Get all the way to here. It's like half a thou, I guess. All the way at this angle. I do see a bit of a variance.

[00:14:51]Barely over a thousand. If you can focus, it doesn't seem like the bore is as far off as the bearing is, but it's also not a circle. So, I'm going to have to make some calls. And of course, it's after business hours now, so I guess that's going to be a tomorrow thing. I don't think whoever built this engine last time was paying the most attention.

[00:15:10]On one of the caps in this area here where it meets the block, I found some like carbon buildup or something. On this one, I found a little chunk of metal like driven into the surface. It has occurred to me that I might not exactly be the greatest at measuring things. So, I'm going to back up those measurements with some cheap insurance.

[00:15:28]A clearance check with plastic gauge. Do you know how many successful engines I've built without checking oil clearances at all? a lot, like most of them. I elected to check all five bearing clearances with plastic gauge.

[00:15:42]So, there are all five caps torqued in place. Note, I did oil the block halves of those bearings. I did not oil the cap halves because you have to do the plastic gauge check dry. Now, I'm pulling the caps back off. Of course, something I've noticed, these middle three caps are not actually that tight.

[00:15:58]I've seen in other 426s where these are like fully wedged in there. These caps actually have the holes there which you can use for bolts or some kind of puller to tap them out, but I'm not going to need to do that, I don't think.

[00:16:11]Unfortunately, it seems I do actually know how to measure. You can see the chart here on the plastic gauge also agrees with the thou and a half reading I was getting. That was number one.

[00:16:20]Pretty much the same on number two here.

[00:16:22]Might have been a little off on number three. This is showing just under 2 thou, but it's not as small as one and a half. Okay, here's number four. It's 1,000th, like maybe just a hair over that. Of course, with plastic gauge, the more it squishes, the smaller the gap is. And number five is also a thou or even less. Wow. So whether these bores are as out as I was thinking or the bearing clearances are just super tight, it's not good. All I wanted to do was build a hemi, but no, that's it. I'm going back to small blocks where everything is normal. I have spoken to an machinist and it sounds like we're going to be able to solve this problem with a simple line hone. Line honing is an operation where you torque the main caps in place and then you run a big hone down the middle and obviously it takes material off and enlarges the circle somewhat. But you shave a little bit of material off the caps so they go down farther into the block and then you hone back to a circle of the proper size. To complete this operation, the machine shop will need my block, the caps, the bolts, and the bearings so they can check the clearance afterward. They'll also need the crank.

[00:17:30]A quick note on main bolts. This engine only came with the main main bolts. It did not come with the cross bolts. Now, for a drag racing type application, or what I'm going to do, you really don't need those. They were added to help lock these middle bearing caps in place during sustained high RPM use for like NASCAR. This engine will never see that and so they really don't matter. You can omit them, but I don't want to. I'd like to have them there. I'd like to plug the holes. So, I need to get some bolts.

[00:17:58]According to the internet, a basic grade 8 3/8 coarse thread bolt about 2 and 3/4 in long. And this set of hardened washers would be perfect for this application. I don't really have time to run and buy those right now, though. ARP main studs are probably overkill for this application. And I did consider using them anyway, but I noticed a bit of a clearance issue with this stud, which is the shorter stud in this rear main hole fully bottomed out. It actually sticks up past the oil pan ceiling surface. Now, maybe that wouldn't be an issue. Maybe it's far enough in that it wouldn't hit, but it makes me a little itchy. And I didn't test fit these other ones with a windage tray, but it kind of looked to me like the taller ones would contact that. I just don't want to mess with it at all.

[00:18:40]again for the power level we're going to make and what this engine's going to be used for. I don't think the studs are necessary. I'd like the main studs to go in that engine, but that engine was already line board with a set of ARP main bolts, so I guess we're stuck with that. The crossbolts really don't do a whole lot, but I feel like they could distort the main caps a little bit and that could throw off the hone. So, I want to have them there. I went ahead and robbed the fancy ARP ones from that block. I don't think this will be a major issue. Yay. might have slightly parked a lift arm on my bed. That's fine. You know, years ago, someone told me once you have a lift, you figure out how to use it for everything. That's true, man. I like Hemis.

[00:19:20]So, the bad news is I no longer have a Hemi to assemble for now. The good news is I do have heads to put on the Hemi that I don't have. In the last video on this build, I noticed that the deck surface on one of these heads was scored really badly next to a combustion chamber. And really, they didn't look that great in general. So, I took them up to the machine shop to have them resurfaced. At the same time, I figured we'd better check valve seats and all of that to make sure these are actually worth running. Remember, these were on a running engine, like not all that long ago, so they couldn't be too bad, right?

[00:19:51]Well, Dan, the headman at Johnson noticed right away that only like two springs had an inner spring and the rest did not. So, that was kind of weird. He also noticed that these had the old style positive valve seals, which were almost certainly cracked to bits.

[00:20:05]Because I'm a cheap bastard, I really didn't want to have to do more than necessary here. Dan figured the best thing we could do is a vacuum test. To do that, you take a vacuum pump with a gauge on it and a little pad that covers up the port with the vacuum hose running to the middle of it. You put it on a port, you pump up vacuum, and you watch the gauge. If a port holds vacuum, that means its valve has a good seal. And each valve on these heads pass that test. If you don't have a vacuum pump on hand, you can always do something similar using gasoline or brake clean or something like that. You put the fluid behind the valve and see if it leaks out. I actually did that on these heads myself, and they pass that test, too. I already knew about this very obvious pre-existing mechanical damage, but these heads have definitely been reconditioned since that happened. We decided to sort out valve springs, redo the surfaces, and just call these good.

[00:20:54]Now, for the valve springs, we actually stuck with the main outer springs and dampers that were already here. Dan checked these for pressure, and they were a little bit on the light side.

[00:21:01]What we ended up doing is adding the inner springs out of this random set of new old stock comp springs that I had on the shelf. Our pressures are still a little bit low, and I can't remember the exact numbers, so I asked. It's 150 lb on the seat and 325 lbs open. Now, we're running a hydraulic flat tap at cam. Not much bigger than the factory street Hemi grind. And this thing is never going to see 7,000 RPM. Dan figured this would work for what I'm doing. So, the inner springs went in and a set of new positive seals did as well. With that sorted and the decks resurfaced, they got a quick cleaning and here they are back. Now, it's a Tuesday and you're supposed to see this video tomorrow. I'm not saying I could have had this engine completely done, but dang it, we would have been close, but I've put some money and quite a bit of time into this project, and I figure we all deserve some kind of payoff. You remember wrong Hemi mocked up in front of Flying Banana. Now get ready for wrong Hemi mocked up in front of coronet. There's your big reveal. It's a Hemi in front of a coronet. Would be a lot cooler if it was done and in the coronet. Now I've shown most of these components that would have been in a video way back. I think I called it the leftover elephant or something like that. This is a set of factory valve covers that were ched and had Dick Landy stickers affixed to them.

[00:22:17]These are some wellbeaten Hooker Bbody headers. Chrome timing cover is a nice touch. So is the direct connection electronic tack drive distributor. If you're keeping score at home, that's the same type of distributor I'm using on the Barracuda. The Barroso cable drive TAC is like my favorite thing of ever.

[00:22:31]And it just so happens I have two of these now. I'm not necessarily committed to dropping that thing right here on the cowl cuz I don't want to put a hole in the hood or whatever. But it sure would be neat. Oh yeah, this thing needs a windshield among many other things.

[00:22:44]Factory dual quad intake. I think this would have been from like 1970 or something. factory casting repair on the late Hemi intake. Notice there's currently no oil pan. I actually have two factory Hemi oil pans, but I'm not going to use one of those things. I'm actually going to get an aftermarket piece for this. I haven't done that yet, though. I did decide to mock up the shoe mocker mounts. I think this is right for the passenger side. The driver side bracket slightly contacts the header, so we're going to have to fix that most likely with a hammer. Speaking of fixing things with a hammer, I don't actually know if those headers clear power steering. We might have to swap this for manual, which would be fine. Better even. Oh, yeah. It's all coming together. Well, it's not. You know what I mean? Well, that was cool. Now, we'll shove all this back in a dusty corner for the next who knows how long and get back to this someday. It's pretty cool, though. Yeah, it's pretty cool. Anyway, tune in next time when we're probably messing with a small block again. Not that one yet.

[00:23:42]We'll get there. Maybe we'll put that one in the truck finally. after removing the intake again. Another long story.

[00:23:49]I'm going to go take a nap. Until next time, as ever, thanks for watching. And remember, the more you know, the worse it gets. Now, we just have to push this thing 100 ft again. Yay.