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Lab Rat Gets A Few Hearts.

Lab Rat's original 1973 engine seized due to sludge in 2016. We covered this in the original Lab Rat post here. This post covers the brief history between the original engine, and the current Turbo Engine.

Lab Rat's second engine was donated by "parts truck" D-150 at the beginning of 2017. This engine was a late model hydraulic engine. It notoriously smoked and consumed 1 Qt. Per 30 miles, and had an obvious misfire that was present at all speeds. This misfire eventually led us to pull the cylinder head and swap it for an early 70s head. Once we pulled the head, we could clearly see the damage.

A clearly burnt valve

The exhaust valve was burnt. When we bought the truck, it always had a little smoke, but we figured we would tear it down soon enough anyway. We swapped the freshened head that had been milled for higher compression onto the engine.

Now since this was a non-hydraulic cylinder head that we were bolting onto a hydraulic engine we had to swap a few valve train parts. We cut the ends off of the rocker shaft so we could thoroughly clean out the built-up sludge from the inside, and put pipe plugs in each end. We used all the same rockers and rocker shaft from the hydraulic engine.

Once this was all installed you could tell the rev-ability difference in comparison to Lab Rat's original engine. The cast engine was notably lighter weight, but all was not well. The engine had more power, but still smoked excessively. The rings were the culprits, but we didn't have our reconditioned block finished yet, so Lab Rat had to wait until we could give it a proper heart.

Lab Rat didn't have to wait long before we pulled it back into the shop to swap its engine out for a donor D-150 that was given to us due to a cracked block in early 2018.

Originally this truck came to us to finish HEI ignition upgrade, but while testing we heard a slow drip sound, and quickly found that the engine had a foot long crank right below the freeze plugs. The crack was due to a frozen block, the previous owner had run mostly water in the engine and when it came time for winter there just wasn't enough antifreeze. The water froze and then expanded out of the weakest link, the block.

We set to cleaning the block and attempting a crack repair. We used a bluing dye to show where the cracks were and set to grinding the cracks, so that a deep weld could be made at the source.

We also employed a drill method that helps to stop crack propagation. We pre-heated the block and began welding it. Most of the large cracks sealed up, but there were so many micro cracks under the surface that it continually cracked while welding. A brazed welding method would have served our purpose better, or a "stich and pin kit", but we wanted to give some crack sealers a chance. We installed new core plugs and swapped Lab Rat's refreshed early 70's head onto the engine. We pressure tested the block's cooling system and only saw minor weeping.

Once Lab Rat was running with its "new" cracked block we could tell an immediate difference. This engine compression tested at 100-110 psi (before swapping the refreshed early 70's head). We tried several " big name " engine sealing products, giving each one a couple weeks to try and do its best. We won't mention all of the products, since we feel that the test subject didn't give them a fair chance, but we will say that of all the one's we tested K-Seal did the best.

Between taking all the time to give each product a good test trial, we ended up with close to 10K miles on this engine. None of the products ever worked enough to stop the leak. The engine needed 1 Gal. every 30 miles or so, but it allowed us to see what a proper running slant six with our manifold could do. The smoothness and drivability felt exactly like a modern car. The throttle response was excellent, and the car could easily be driven by those who weren't familiar with a carb. The slant started every morning and performed its routine perfectly. It started flawlessly in subzero temperatures and ran smoothly.

The time finally came for us to build Lab Rats official engine. We started on this project in 2016 but didn't start assembly until late 2018. We received all the parts from a few machine shops we outsourced to and began double checking their numbers. This is where we ran into trouble. We had three machine shops, that different pieces went to, but only one of them was accurate. The one that was accurate was impeccable to work with all the way through. One of the less accurate ones promptly corrected their work. And the last machine shop didn't respond.

Whenever you receive anything from a machine shop you should thoroughly clean every hole and measure every surface.

Our bores were as follows:

Cylinder #1 3.4395"

Cylinder #2 3.4395"

Cylinder #3 3.4396"

Cylinder #4 3.4397"

Cylinder #5 3.4396"

Cylinder #6 3.4396"

All these readings were considered fine for our goal.

When you begin building your engine all we have to say is clean clean clean. You want the engine to be as clean as possible. The crank in the photo above is not the crank we used in the engine. We were going to use this crank, but it was designed for the older 904 torque converter style and would require adapting. We decided to leave it be for a later project. A good small rifle cleaning kit can work perfectly for cleaning the oil passages. Often these passages aren't cleaned by the machine shop and tanking won't always get these areas clean either.

The " accurate machine " shop performed the work on our crankshaft. The work they put out was as follows:

Crankshaft Connecting Rod Journals:

Rod #1 2.167"

Rod #2 2.167"

Rod #3 2.167"

Rod #4 2.167" +/- .0005"

Rod #5 2.167"

Rod #6 2.167"

Crankshaft Main Journals:

Main #1 2.7392"

Main #2 2.7395"

Main #3 2.7396"

Main #4 2.7395"

This is a perfect example of the quality this machine shop produced.

The machining on the block was performed by the machine shop who didn't return our calls. They did some of the work correctly, the bores and general cleaning for example, but their crank saddle align boring, put our bearing clearance over .004" off of what was acceptable in any Chrysler manual. This forced us to have the crank saddles, re-machined by the more accurate machine shop.

Once we received the block back from the final machine shop, we began cleaning it again and inspecting every passage. We used a bristle brush from a gun kit on every oil passage. We ran a tap through every threaded hole, and vacuumed every bit of dust we could find. Once we completed cleaning every surface, we did it again twice over.

We only performed a few modifications on the engine, we drilled a very small hole in the front oil gallery plug to oil the timing chain and a small hole to oil the oil pump/cam gear. We drilled and tapped the oil gallery boss on the passenger side to provide an oil feed line for our turbo.

We checked the pistons for any scuffing or damage when they were pressed on by the machine shop that didn't respond. We ran into issues when checking the piston big ends. Every connecting rod was out of round. We took them to a local machine shop (the less accurate one) that was known for their Mopar work, but when we received the connecting rods, they were still out of round. We called them and they immediately took care of the problem, and this time we asked them to reverse mount the pistons (In retrospect (6 years later) we wouldn't have bothered with this modification). With that all fixed, we began organizing the pistons and checking ring gap.

We used a rebuild kit for this Slant Six. It was just a standard kit from Clegg Engines. The crank did require undersized bearings, and the pistons were .040" oversized, but all the other aspects of the engine kit were stock.

We gapped the Hasting's rings at (bore x .006) for the first ring and (bore x .0057) for the second. Please note that you should follow your ring manufactures recommendations when choosing a ring gap. For this engine the gap was set the old way (with 2nd ring slightly tighter) this is not recommended, the modern setting is for the second ring to be slightly wider than the first ring to relieve pressure and prevent sealing issues of the first ring. This ring gap is set more aggressively to allow growth under our turbo pressures. We dipped all the piston rings and pistons in oil; clocked all the piston rings on the pistons; and installed the pistons using a piston installer and light plastic hammer taps on a wide wooden dowel.

We performed a 3-angle valve job to clean up our refreshed late 70's-cylinder head and changed the valve stem seals. We didn't do any other modifications to the cylinder head.

We installed a new stock style camshaft with new lifters. We would recommend that you degree your camshaft. We used the standard dot line-up on this engine, but the tolerances of this dot-to-dot line-up are very poor often giving you what can be a tooth worth of timing off either way.

We did an engine break in using our old tune " msq ". We knew this method would work well since the engine hadn't changed drastically. We primed the oil gallery with 30 weight oil via our oil filter outlet. We used the starter to prime the engine the rest of the way before giving the engine fuel or spark. Once everything was primed and we read oil pressure, we re-enabled our fuel & spark. We gave the engine a crank and it fired immediately. We broke the camshaft in (this is a perfect time to make sure your push rod and lifters are spinning. If they aren't spinning you will put a flat spot on them or the cam which will lead to a wiped-out cam and lifters.)

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1 Comment

Thanks guys. I have been to your shop and bought an intake manifold plus Dutra Duals from you guys. Unfortunately life has gotten in the way of my project and I do not have it running yet. I plan on getting my car running without a turbo, then buy your turbo kit when it is ready. Thanks for keeping the Slant alive! Kenny Crenshaw, Millington, TN

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