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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old October 4th, 2015, 03:35 PM
campy campy is offline
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Question Original 1964 305E V6 Piston Size

Good morning all,
I am in the process of rebuilding my 305 V6 and to say the least I am pleasantly surprised at the condition of the motor. The question I have is that I noticed that the piston say .040 on the top of them. Now its been awhile since I have rebuilt an engine, but I am pretty sure that it means the pistons are forty thousandths over. Am I correct? Does that mean that this motor has been gone through before, or was this standard? Thank you in advance for your help.
Jon
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  #2  
Old October 4th, 2015, 03:54 PM
bigblockv6 bigblockv6 is offline
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Default Re: Original 1964 305E V6 Piston Size

At .040 it's definitely been bored out from the standard bore, so it has been rebuilt and hopefully if there are not too many miles on the rebuild so you won't need another overbore, if not then it would be a wise choice to find another engine because .060 overbore is the max and piston availability would be scarce for that size.
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Old October 4th, 2015, 04:25 PM
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Default Re: Original 1964 305E V6 Piston Size

The number on the side of the piston is 946P. When I googled it, some folks say its for a 350 motor. Should I be concerned that this is not a good part? Another site http://www.summitracing.com/parts/slp-946p says that it is for the 1964 305 V6. What are your thoughts?
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Old October 4th, 2015, 04:28 PM
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Default Re: Original 1964 305E V6 Piston Size

Those pistons look to be .125 over....unless I'm forgetting the stock bore size. I think those would be a little much for an overbore. Heck...those .040 over pistons you Have are rare!
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Old October 4th, 2015, 04:38 PM
bigblockv6 bigblockv6 is offline
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Default Re: Original 1964 305E V6 Piston Size

The standard bore size of the 305 V6 is 4.25 inches while the 350 is an even 4 inches. Also mentions the piston pin diameter is 1.24 inches. The ring sizes sound about right too. Sounds like 305 V6 pistons not 350 pistons.
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Old October 5th, 2015, 06:57 PM
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Default Re: Original 1964 305E V6 Piston Size

My bad...For some reason I thought the 305 bore was 4.125. lol
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Old October 6th, 2015, 01:28 PM
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Default Re: Original 1964 305E V6 Piston Size

Thank you all very much. I appreciate the feedback. Looking forward to getting the motor put back together!
Jon
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Old October 6th, 2015, 03:18 PM
George Bongert George Bongert is offline
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Default Re: Original 1964 305E V6 Piston Size

Greetings Campy!

I'll throw in my two cents worth here as well. Indeed, the stamp ".040" on the top of the piston means that the engine has been rebuilt once before. Now for a little further information, if you wish to "refresh" your engine, and if the bores DO NOT exceed a .010 taper (from top to bottom of ring travel in the cylinders, anything over .010 taper is unacceptable for re-ringing an engine) you can get by with running a glaze breaker or other cylinder honing tool, and installing new .040 overbore rings, and new rod bearings. Be sure to note the stamp on the backside of the bearing shell i.e., STD (standard), .010, .020, etc, since this will indicate whether or not the crankshaft has been reground. Also note the condition of the rod bearing shells. They should be dull grey in color with no exposed copper backing, not pitted or "galled," scored, or otherwise show any signs of damage that would indicate that a crank regrind is in order. By the same token, the crankpins should be relatively smooth in appearance and not scratched or showing other signs of foreign material causing scratches or gouges in the crankshaft. Use a good micrometer to check the crankpins for out of round and taper. Please note that re-ringing ("refreshing") an engine should only be done if the engine block is not severely worn and in need of another re-bore and new oversized pistons and rings, and/or a crankshaft regrind.
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Old August 9th, 2023, 02:55 AM
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Default Re: Original 1964 305E V6 Piston Size

Hi
I’m trying to rebuild my 305e (64) but the lack of pistons is killing me
Can I mate a 305c short to the rest of my 305e?
Any advice would be appreciated

Thank
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Old August 9th, 2023, 11:30 AM
James James is offline
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Default Re: Original 1964 305E V6 Piston Size

Quote:
Originally Posted by Dukes View Post
Hi
I’m trying to rebuild my 305e (64) but the lack of pistons is killing me
Can I mate a 305c short to the rest of my 305e?
Any advice would be appreciated

Thank
Yes.
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