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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old June 27th, 2022, 09:58 PM
Prowbar Prowbar is offline
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Default Got a 478...

Always wanted to get a bigger V6 than the 305 that I now have... Yes sir I found one. To find one of these in the Netherlands, especially a 478, is a one-in-a-million chance...

A standard, non magnum 478. Complete engine with new gasket set, although in parts at the moment. With all the large truck accessories, such as bell housing, flywheel, clutch, air compressor, generator, brackets, etc. If you're looking for large truck accessories I'd be happy to help.

The engine is in very good condition and looks to be a fairly low mileage engine. One of the exhaust valves is burned though, will need a new one for that, or have this one repaired.

My plan is to build this engine to replace the 305 that is now in my 1500.
It will be a stock rebuild, with a couple of minor modifications.

I've been studying Bigblock V6's posts on his 478 swap, but still have a couple of questions. If we could come into contact that'd be great!

The plan is to convert the engine to use all the light truck accessories, such as the bell housing, water pump, and timing chain.
Will have to fab up a flywheel and have it balanced.

My guess is that the engine is a 62, one of the first 478's. No PCV valves in the head, but does have the fresh air canister on the back left side. My guess for a 62 is the fact that it came with a generator instead of the alternator.

Your thoughts?
Attached Images
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File Type: jpg 20220627_182844.jpg (4.38 MB, Multiple views, 8 clicks)
File Type: jpg 20220627_165301.jpg (4.09 MB, Multiple views, 8 clicks)
File Type: jpg 20220627_164404.jpg (5.41 MB, Multiple views, 9 clicks)

Last edited by Prowbar; June 27th, 2022 at 10:23 PM.
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  #2  
Old June 29th, 2022, 02:30 AM
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LEWISMATKIN LEWISMATKIN is offline
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Default Re: Got a 478...

i just sent a message to bigblockv6 over on his facebook profile for you. good luck with the '62 478!!!!!!
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  #3  
Old June 29th, 2022, 08:27 AM
Prowbar Prowbar is offline
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Default Re: Got a 478...

Quote:
Originally Posted by LEWISMATKIN View Post
i just sent a message to bigblockv6 over on his facebook profile for you. good luck with the '62 478!!!!!!
Thank you very much Lewis! Checked out BB V6's profile, seems like he hasn't been active on the forum for a while.
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Old June 29th, 2022, 09:38 PM
Prowbar Prowbar is offline
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Default Re: Got a 478...

Correction: there are PCV valves in the heads, and I just found a replacement exhaust valve in one of the boxes! Couldn't be happier. Here are some pictures:
Attached Images
File Type: jpg 20220629_222527.jpg (4.17 MB, Multiple views, 8 clicks)
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  #5  
Old June 30th, 2022, 05:02 AM
BillT BillT is offline
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Default Re: Got a 478...

You will sure like the 478. I drove one for years in a '62 6500.

Sure is a powerhouse.
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Drove and owned many, but some of the more interesting ones were:

-'60 GMC 2500 Dump, 305 V-6
-'62 GMC 4000 Flatbed, 305 V-6
-'62 GMC 6500 Flatbed Dump, 478 V-6
-'67 GMC 7500 Box, 6V-53 Detroit
-'71 GMC 9500 Flatbed Dump, 637 V-8
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Old July 1st, 2022, 12:57 AM
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LEWISMATKIN LEWISMATKIN is offline
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Default Re: Got a 478...

Quote:
Originally Posted by Prowbar View Post
Thank you very much Lewis! Checked out BB V6's profile, seems like he hasn't been active on the forum for a while.
just got a message from you from BB V6. he said his e-mail is down, but you can catch him on Facebook Messenger. you will find him under Peter Chronis.
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Old July 1st, 2022, 06:25 AM
Prowbar Prowbar is offline
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Default Re: Got a 478...

Quote:
Originally Posted by LEWISMATKIN View Post
just got a message from you from BB V6. he said his e-mail is down, but you can catch him on Facebook Messenger. you will find him under Peter Chronis.
Will do. Thanks.
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Old July 1st, 2022, 06:14 PM
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FetchMeAPepsi FetchMeAPepsi is offline
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Default Re: Got a 478...

Quote:
Originally Posted by LEWISMATKIN View Post
just got a message from you from BB V6. he said his e-mail is down, but you can catch him on Facebook Messenger. you will find him under Peter Chronis.
Is Pete banned or something? Haven't seen him around in a while.
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Old July 2nd, 2022, 12:40 PM
Prowbar Prowbar is offline
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Default Re: Got a 478...

Quote:
Originally Posted by FetchMeAPepsi View Post
Is Pete banned or something? Haven't seen him around in a while.
Been chatting with Pete on messenger, will ask him what's going on.
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  #10  
Old July 2nd, 2022, 12:53 PM
Prowbar Prowbar is offline
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Default Re: Got a 478...

Cleaned up the major grime off the heads. Removed the valves, no surprises. The valve springs are pretty stiff though. The guide from the burned exhaust valve needs to be sleeved, as it has more play than the others.

I will also have the heads professionally cleaned, decked and have hardened seats installed in the intakes.

The castings, as from the factory, are pretty bad regarding port design. The exhaust passages faily are restrictive compared to the intakes. But the worst thing is the short turn into the into the head has a very sharp ledge above the valve seat. I am working to radius these to create better airflow. Both intake and exhaust have these sharp ledges. Also the exhaust ports really need to be cleaned up, they have ledges in them. I removed these also.

I also lightly broke the sharp edges in the machined combustion chambers.

That's as far as I'm gonna go with the heads.
Attached Images
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File Type: jpg 20220702_104638.jpg (3.93 MB, Multiple views, 1 clicks)
File Type: jpg 20220702_104756.jpg (4.55 MB, Multiple views, 3 clicks)
File Type: jpg 20220702_134501.jpg (6.04 MB, Multiple views, 4 clicks)

Last edited by Prowbar; July 2nd, 2022 at 12:58 PM.
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