'65 GMC 1500 project. From the Netherlands

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Installed the 478 today. Took the engine off the stand with the engine hoist, then installed the bell housing, flywheel, pressure plate, clutch, starter, engine wiring harness. Checked the bell housing runout, .003". Pilot bearing runout is less than .002". Used the same method of removing the rocker assemblies and using a head bolt with a piece of strip as a mount for the chain.
Very satisfied with the install. Then installed the transmission.
Had to take the SM420 top cover off to clear the firewall.
Used new motor mounts (Thanks for the Anchor part numbers, Funky61)

After installation, we pulled the engine as much forward as we could to give the right side exhaust manifold as much clearance as possible. There is about 7/16" clearance between the manifold and firewall now.

Now, onto reinstalling the rest...

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Been busy, but slowly building up the engine and hooking up everything.
Got most of the to-do list taken care of.
Hope to fire her up for the first time next week. I'll be sure to take a video.
We'll hook a manometer to the oil pressure sender, prime the engine beforehand, and then do a few rotations with the starter without the sparkplugs installed. Then add some gas to the carb and fire her up. Probably take her to 1000 RPM or so for 10 minutes and verify the lifters are rotating.

The carb fuel line is a temporary addition. It came with the carb and is easy for testing.

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What was supposed to be an easy start-up didn't turn out to be one. When we went to start the engine we quickly had coolant between the block and heads. Had some problems with poor starter performance as well. After a lot of attempts without any success, we gave up and drained the oil. Full of coolant...

Then made the decision to take off the heads. This went rather easily and soon was discovered that the coolant passages in the block do not line up with the head gasket. See pictures. This NOS head gasket (picture 5) only relies on crush rings to do the sealing. I never noticed this misalignment during assembly. This probably caused the leakage.
Also discovered that the cylinder crush rings seat inside the bore. Which is bad for detonation and gasket life.

Anyway, I have some Fel-pro 305/351 V6 head gaskets. They rely on gasket material instead of crush rings to provide the seal on the coolant passages. Fel-pro also turned these coolant passages into slots, which do line up, which is great. Even if they did not completely cover the bore, the gasket material would take care of the sealing. Now the bores still need to be opened up. I have tested one and it can be done, by moving the crush ring to a larger diameter. Now to make some specialized tooling to facilitate the process...

I was given the original GMC 478 head gaskets (that came off the engine, picture 3) as well. They line up properly. Which got me thinking... Maybe I've been given NOS 401 V6 head gaskets... which would explain the crush rings sticking into the bores...
And for the coolant passages, they probably moved them away from the bores to deal with the larger 478 bores... But this is speculation.

I'm glad we discovered it now instead of later... But it makes you feel like an idiot for not noticing.

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Picture of the 401 gasket (bottom) compared to the original 478 gasket (top). Notice the bore difference and the offset in coolant passages. What do you think?

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As talked about I made some tools to help form the gaskets from the 305/351 size to the 478. First off a plate with the locating dowels is made. In the center of each bore a hole is milled to hold a steel cup, which fits a bearing. This is the center is my bead roller setup.

The process starts by grinding down the old crush ring until they can be separated. This also separates the gasket. One bore is formed at a time, to keep the pieces properly located.

Then with a Dremel, the blue gasket layer is enlarged to 5.125" + some extra. A piece of plastic is stuck between the steel backing and blue gasket material to protect the steel backing from being cut.

Then with the roller and forming dies, the sheet metal backing is brought upwards and a new ring is formed. The length is then ground down to the right height and deburred. Then it is rolled over, forming a new crush ring. The sheet metal works easily and takes the shape well. The crush rings look good and smooth.

See the last picture for the finished modified gasket.

One head has already been installed with a new gasket. I also used some head gasket sealer as an added measure. So far it looks good. Tomorrow planning to reassemble the engine, then hopefully a first start without any troubles. I will be running straight water for the first start (without any calcium).

Of course, this is an experiment, maybe they blow out quickly, maybe not. We'll see. Some redneck engineering at its finest

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Got this far today.

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First start of the 478 V6!

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Here is a video of the second run:

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Runs much better, throttle at idle wasn't opened far enough and we retarded the time some. Two of the valve lifters are spinning slowly, and two aren't spinning at all, these will be replaced with new Melling lifters from Rockauto.
For the experiment, I switched two lifters around, a fast and slow turning lifter, and the lifter is at fault, with no proper crown. These are the OEM lifters.

Lifters are easy to change, back off the valve lash adjustment, remove the pushrod and use a stick magnet to retrieve the lifter.

The 305 starter doesn't have the oomph and drains the battery rather quickly, have to figure out what causes it.

The haze from the manifolds is the paint baking.

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Bought me some new Melling lifters from Rockauto to replace the slow-turning or stationary lifters. After replacing them with the Melling lifters nothing happens at all.

Pretty ticked off. Makes me wonder if the cam is still decent. I measured the lobe lift before assembly and all intake/exhaust lobes had about equal height, but I couldn't detect any noticeable taper then. Might have to pull the cam, and have it reground, along with the lifters... Not the news I was waiting for, to say the least

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I am using oil with proper ZDDP content.

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Going to pull the camshaft out and have it reground according to Bigblock V6 (Pete) specs. Also, new lifters.

Need to wait a bit before I can get the cam ground, but in the meanwhile, I can finish most of the tasks that still need doing:

Remove the camshaft
Exhaust downpipes welding. Bought an air-fuel meter to install.
Propane mixer adapter
New battery cables
Leaking rear axle seal
All sorts of odd jobs that need to be done

Keeps one busy.

Traced the slow starting to the starter itself. Have to look it over. Seems like the new brushes aren't seating properly. When the switched them for the old brushes, it cranked over just fine.