It high time for assembly to begin on the Jeep straight-six living in the Redline Garage. The steps on a short block go fast, but that doesn’t mean we overlook any essential details. Davin, after all, is never one to take shortcuts. However, sometimes that means taking literal cuts. Stay with us.

The engine block recently returned from a second machine shop trip to re-cut the deck height, and it was  also re-cleaned so it can be ready for final assembly to begin. That process starts with the freeze plugs—and also a few threaded plugs—in the case of this particular engine. Those threaded plugs are a taper pipe thread, which means they don’t technically need any sealant of coating. Davin points out that assembling dry is perfectly acceptable but more than likely will lead to the plugs becoming all but unremovable in the future. A quick dap of teflon sealant will keep them serviceable.

Then it is on to the pilot bushing in the crankshaft, the cam bearings set into the proper places, and then the final torque of the crankshaft main bearings. Toss on the pistons rings and send those into the bores and things were going swimmingly. Almost too smoothly.

The combination of parts Davin uses is all Jeep in origin, but that doesn’t mean they were designed to function together.  The first time these incongruences appear is just as the harmonic balancer is installed on the snout of the crankshaft. The new balancer sits a little further in, and thus Davin has to do some fabrication with the plasma cutter and lathe to make an appropriate “washer” to ensure everything is held properly by the crankshaft bolt. In the end, it’s a fairly easygoing and quick process.

Will Davin keep this pace as the assembly continues next week? We all hope so, but even if it doesn’t you’ll get all the grimy details in the next episode of Redline Update. Be sure to subscribe to the Hagerty YouTube channel to never miss a new episode.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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The light has appeared at the end of the tunnel for Davin and the Jeep engine. It’s still quite far away, but he can see it. Before taking steps toward that light, another trip to the Thirlby machine shop is required to lower the deck height in an effort to raise the compression. And another issue pops up that needs to be discussed with the machinists.

Before loading up and heading off to re-deck the block, Davin takes the time to check the oil clearance on the main bearings. This is an important step, because while most of the time the numbers come out fine, engine building is always a game of “trust, but verify.” With the main caps torqued to spec, Davin measures the diameter of the bearing location on three axis. What he finds is a little uncomfortable. To him, the holes seem a little egg-shaped and also about half a thousandth too wide.

The machine shop doesn’t agree, however. Before bolting the block into the machine to trim the deck down, they use thier measuring tools to “sanity check” Davin, and they certifiy him insane. Davin is a known perfectionist, and on this job the machine shop guys think he might be going just a bit too far. The return on investment of getting this absolutely perfect is pretty slim, and that’s why they advise it would be best to leave this one alone. Those clearances might be a fraction off, but they’re still well within a usable tolerance.

Back at the shop, Davin is the first to admit things are way out of order at this point. A freshly painted block shouldn’t be going to a machine shop, and a block back from the machine shop shouldn’t be getting casting cleaned up again. It makes for even more cleaning work before assembly can begin, but we all know Davin is not one to take the easy route just to get things done. With any luck, things will come together next week, but then again, another roadblock might also appear. To find out for yourself, be sure to subscribe to the Hagerty YouTube channel to never miss an update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Building an engine is vastly different than assembling one. One involves proper fitting of parts—the other, merely bolting things together. Today Davin takes you on a deep dive into one of the key parts of engine building, whether you’re aiming for performance or basic conveyance: compression ratio.

The concept is simple: The amount of space inside the cylinder when the piston is at bottom dead center compared to the amount of space inside the cylinder when the piston is at top dead center. As anyone who’s built an engine will know, however, that which is easily summed up is not always the easiest to execute. Accurately calculating compression ratio takes a bit of math, a bit of knowhow, and some antifreeze (seriously).

Davin starts by obtaining the size of the combustion chamber in the cylinder head, using a plate of glass and burette to measure its exact capacity in cubic centimeters. With some basic math, he calculates the cylinder volume, and all that is left is the volume added or subtracted by the piston dish or dome. In the case of our Jeep’s 4.6-liter engine, the piston is dished. While Davin could measure that additional area exactly the same way he did the combustion chamber, he decides instead to set the piston a small distance into the cylinder and grab a pencil to do the math and get the final number.

Compression ratio determines a few very important characteristics of an engine. The one Davin is most concerned with is this straight-six’s ability to run on “pump gas.” To Davin, that means 87-octane fuels. For an engine to run on fuel that volatile without any knocking, it is best to target between 9 and 9.5:1 compression ratio. He calculates that this particular Jeep’s engine compression would be around 8.5:1 as it sits now. Not ideal.

He devises a simple fix: Use a thinner head gasket and take a quick trip back to the machine shop to shave the deck height just a smidge more. With those changes made, this engine will be ready for final assembly, a process which Davin can begin with confidence, knowing that all the parts will play nicely together and that the mill will run as he expects it do when it’s time for first start-up.

To see the rest of the assembly and other tips and tricks our resident engine builder, be sure to subscribe to the Hagerty Youtube channel.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Now that our 1993 Jeep Cherokee’s 4.0-liter inline-six engine has been disassembled, Davin has some prepping to do before it heads to paint—specifically, removing the casting shrapnel from what he calls “a poorly designed mold.” Using a die grinder to clean up the mess, Davin’s time-consuming task was becoming a bit tedious. Then he had an idea: Why not try a tool that’s designed to remove rust? Moments later, a descaler is making quick work of the shrapnel.

With that job finished, Davin cleans up the block in the wash cabinet, blows it out, and begins taping it for paint. That’s when he offers another time-saving tip, showing that he made plastic coverings on a 3D printer that slide nicely into the core plug holes. And off we go to Traverse Body & Paint to “let Darryl do his magic.”

With the parts laid out on stands, Davin offers his RockAuto.com Tip of the Day: “If you want paint to stick to anything, the surface cannot be smooth, and it needs to be oil-free.” That means, for example, the coating on the oil pan needs to be scuffed up, and then it needs to be wiped clean to remove any finger prints/oil residue.

Check out the results for yourself and also be sure to subscribe to the Hagerty YouTube channel so you never miss an update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Each and every Redline Rebuild starts with a plan … and most go off the rails at some point. The original scheme for the Jeep 4.0-liter straight-six gets a revision this week, but, happily, for a good reason.

The whole idea behind the selecting the Jeep was a quick in-and-out rebuild using stock parts. Davin has done plenty of stock rebuilds, and there is nothing wrong with restoring a solid design to factory spec. Well, we all say it’s fine to leave well enough alone, but, given the chance, most of us will take the more fun path. For the Jeep, this approach makes a lot of sense, because Davin can bump up displacement without even opening the aftermarket catalog or ordering custom pieces.

It sounds too good to be true, doesn’t it? Davin thinks so—until he reads that pieces of a Jeep 4.2-liter straight-six’s rotating assembly can be combined with a 30-thousandths of an inch overbore in the 4.0-liter block. Suddenly, Davin has a 4.6-liter engine on his hands.

Of course, it’s not exactly that easy. Davin talks through the exact specifics of why plans like this one must be thought through.

Beyond that shift in plans, there are also a whole bunch of RockAuto boxes to open in this episode. With fresh parts gleaming on the shop table, it is not long before the paint is dry on the block and assembly begins.

If you are curious how the final product will behave, be sure to subscribe to the Hagerty YouTube channel to never miss an update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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It’s a new week, but it’s the same ol’ story in the Redline Garage. The Jeep 4.0-liter is torn down to a bare block, which means it’s time for a field trip to Thirlby machine shop. This block might represent the best starting point Davin has ever carried through the machine shop door. Of course, that doesn’t mean there’s any less work ahead for the team

“Everything was in really great shape,” said Davin after returning with the freshly machined parts. “We could have just honed it and thrown it back together. Just not worth it though. I mean, you’re already there.” What he’s getting at here is that the engine is already torn down, so there is no point putting off a job now that will only be harder later. The 150,000-mile block didn’t suffer oval-shaped cylinders or any other signs of terrible shape, but it still made sense to spend the few hundred dollars and give it the full machine shop treatment. From the deep clean to the decking and boring, this block is better than new.

There are other parts of the Jeep that need that same better-than-new treatment, and the flywheel is one of them. The starter engages a geared ring on the flywheel to start the engine, and the ring often wears out in just one spot. The reason has to do with the physics of how an engine stops when the ignition is turned off, and which cylinder ends up on the compression stroke to stop the rotation of the crankshaft. The ring gear here could just be flipped, but pressing on a new one that will last a long time is easy enough once we are already in there.

Next stop is the paint booth, but before the engine gets there Davin puts some color on the block along with some other parts on which he plans to do some clean-up work. Casting burrs and sharp edges can make even the nicest paint job look grungy—and when has Davin ever been one to cut corners?

It’s fast progress on this straight-six, so be sure to subscribe to the Hagerty YouTube channel to never miss an update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Last week you saw us pull in our most recent project, a 1993 Jeep XJ with a 4.0-liter straight-six. In no time, Davin began tearing into the mill. Things go fairly quickly as the pieces fly off this engine, but this is as much an investigation as it is a quick disassembly. After all, you never know what you might find. Could this Jeep have nothing but good news to share?

This is not the newest engine Davin has torn into (you didn’t forget about the Dodge Demon, did you?), but it certainly is a little nicer than a few others he’s dissected. The Jeep’s driveline comes apart so easily—almost too easily. Suddenly, one exhaust stud lets loose. Of course, it breaks nearly a quarter-inch below the surface of the head. No worry this time, though, since Davin is sourcing as much as he can from RockAuto and it stocks refurbished cylinder heads. One is already in the mail.

The next discovery is a noisy timing chain. It isn’t so damaged that Davin can hear something amiss over the sound of the running engine, but turning the six over by hand prompts further investigation. Removing the timing cover reveals the timing chain is indeed tired—and when it is all said and done, that’s the worst of the story. How refreshing.

The main bearings look darn-near new, while the rod bearings show a decent amount of wear on the thrust surface. Overall, the wear might be so minimal the crankshaft may not even need to be turned down. It’s been quite some time since Davin found this much good news inside an engine, but he’s not kicking back and taking a break. No, it’s time for cleaning and parts ordering, which might mean Davin has some fun upgrades in mind. You’ll have to wait for a future episode to find out what his schemes entail. Be sure to subscribe to the Hagerty YouTube channel to never miss a grease-soaked update.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Our Mini rebuilt got wrapped up just two weeks ago, but if you thought Davin would wait longer than required to clean the shop before pulling in the next project, you must be new here. For the latest Redline Rebuild, it’s something bright red, two-door, manual transmission–equipped, and absolutely rust-free—just like Davin likes them. This one is a little different than average though, for a few reasons.

Say hello to this 1993 Jeep Cherokee with a 4.0-liter inline-six. It’s the newest car to be on the receiving end of the Redline Rebuild treatment, which means there are a few pieces and processes that will be new. Those surface right away as Davin yanks the engine and transmission onto the floor to be cleaned and prepped for disassembly.

Two of the new elements of this rebuild are the catalytic converters on the exhaust, but they are rusted in place just like most exhaust systems Davin encounters. One cat is also blown out from years of use. Just because it looks good from the outside doesn’t mean it’s functioning properly inside. The transmission tells the same story, as it just doesn’t shift quite right. Another odd hurdle was all the wiring that had to be removed before the engine could be pulled. From the fiddly fuel injector clips to the air conditioning system, it all comes apart, though. Now, it’s time to get cleaning.

This might appear to be a relatively boring build, but we’ve seen Davin’s search history and suspect there will be a few fun parts going into this one. To see just what he has up his sleeve, be sure to subscribe to the Hagerty YouTube channel to never miss a video.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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We just wrapped up rebuilding our 1965 Mini Cooper S 11275cc engine. It was a journey of trial and error throughout the process, so, join Davin and Ben as they break down what it took to get this little monster running again.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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Davin may not be Michael Caine zipping through Turin, but rebuilding this classic Austin Mini Cooper S brought him a few thrills. This little 1275cc engine from 1965 gave him a few headaches but that’s just par for the course when you’re constantly working on cars you aren’t completely familiar with. It just goes to prove that even the simple rebuilds can be frustrating and rewarding all at once.

This Mini rolled into the Redline garage running but still in need of serious attention. The exhaust pipe was more like a smoke machine, and in general everything under the hood could use a good cleaning. With the literal millions of 1275cc A-series engines on the road Davin had hopes that this rebuild would be a quick in and out job, but of course, the engine had other plans. During teardown, all the dirty secrets came out.

First was the gutted thermostat, which implied there were likely some overheating issues in this Mini’s recent history that someone tried to band-aid rather than fix. Then there was the two large gouges in the engine block that Davin found when the cylinder head was removed. There was no other real bad news, but when the issue at hand could require a new engine block it was obvious Davin and the team were holding their breath as they headed over to Thirlby machine shop to get the machine work done.

“The rest of the block and cylinder head were pretty good, but those gouges were pretty deep,” said Davin about the hand-wringing on if the block would be salvageable.”We got a little lucky in that while decking the block didn’t completely remove the damage it got it plenty flat enough for a gasket to take up the rest.”

Direct from the machine shop to the paint booth, a fresh coat of dark green was sprayed on the freshly machined parts and also a few of the sheet metal cover pieces. With the infamous self-peeling tape out of the way it was time to click off the torque wrench and get things put together. While noting the fact the oil pan was also the transmission case, Davin said, “Taking a lot of this apart was strange, but putting it back together was even weirder.”

Even with a few hiccups on finding just the right part, this Mini still didn’t turn into the maxi problem that it could have. The engine got its break-in and final setup in the wee-hours of Saturday morning and it won’t be long before the car rolls out of the Redline garage and over to the Hagerty Learning Garage for a complete restoration. Of course, Davin is not going to sit and twiddle his thumbs now, as he has other projects running and a new one currently in transit to the Shop. To see what that is and never miss an update, be sure to subscribe to the Hagerty YouTube channel.

Thanks to our sponsor RockAuto.com, an auto parts retailer founded in 1999 by automotive engineers with two goals: Liberate information hidden behind the auto parts store counter (by listing all available parts, not just what one store stocks or one counter-person knows), and make auto parts affordable so vehicles of all ages can be kept reliable and fun to drive. Visit RockAuto.com to order auto parts online 24 hours a day, 7 days a week, and have them conveniently delivered to your door. Need help finding parts or placing an order? Visit RockAuto’s Help pages for further assistance.

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