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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old May 15th, 2017, 06:08 AM
Drewski Drewski is offline
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Default Fuel additives

Hi everyone, I'm just curious how many of you use any lead additives or anything in your fuel. Basically, I use additives in my 1936 Plymouth just because of the age of the engine, however I don't need to use any in my 1976 porsche 914 engine and she does fine. Ive just gotten a lot of mixed answers and now that im about done rebuilding my V6 and how rare parts are becoming, I'd like to keep this engine running well for as long as possible so maybe my daughter can enjoy it for a while too.

Just to let you all know, everything has been left stock on the engine. She's always been great. The only things I had to do throughout this rebuild was the basic cleaning and replacing of bearings and gaskets and whatnot.
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  #2  
Old May 15th, 2017, 12:44 PM
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Default Re: Fuel additives

My brother has several older cars, A '36 Ford Tudor sedan (85hp flathead V-8), A 64 T-bird Ragtop (V-8) and a '74 Ford Ranchero (351 Cleveland). He uses Seafoam in all his engines. https://seafoamsales.com/sea-foam-motor-treatment/
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Old May 15th, 2017, 05:19 PM
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Default Re: Fuel additives

unleaded fuel came out in 1975, most engines built before 1975, have cast iron valve seats. those engines require the lead to lubricate the exhaust valves. i have seen heads that additive was not used, and the valves wore the head down 1/4 inch where the valve seats. i'm not sure if you can install hardened seats after the valve wears that far. hardened seats can be installed in most heads if they are not worn, but check with a machine shop to see if you can get seats for our v-6 engines. if you are taking the heads off, it would be a good idea to replace the valve seats, lead additive would not be needed with hardend valve seats.
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Old May 15th, 2017, 06:09 PM
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Default Re: Fuel additives

Leaded fuel has been on my mind for my 305E. I drive that truck everyday and since I got the truck, have not been running leaded fuel. Not sure about the past owners either. Valves seem ok though. I'm thinking of running this additive here: https://www.napaonline.com/en/p/NCBM5012
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Old May 15th, 2017, 06:32 PM
Drewski Drewski is offline
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Default Re: Fuel additives

I appreciate you all giving me some info on this. Simply put, I'm kind I in the same spot TJ. I have no idea what the previous owner was running as far as fuel in this truck. Before I bought it i was told that the ladies late husband did do a full rebuild on the engine a few years before I bought it. Even that made me nervous as you can never really know how much your average Joe knows about rebuilding an engine. However, I can say that after I broke the engine down, it seems as though he did a really good job and the insides look surprisingly good. That being said, I had been using lead additives since I took ownership, but it was that "unknown" with the previous owner that was a big factor in making me want to rebuild and ease my mind.

I am happy to say that my valve seats still look good, but I might just go for the hardened seats anyway since that could be a good precaution to future wear. If anyone has any suggestions as to the best lead additive that they've used then I'm all ears. Otherwise, I've just been using this stuff since I find it at the oreillys right down the road for cheap. http://m.oreillyauto.com/h5/r/oap/si...0401&ppt=C0126
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Old May 15th, 2017, 07:00 PM
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Default Re: Fuel additives

That's cool, the stuff you posted in your link is the same stuff I'm thinking of getting! Gonna grab some today. It's something I've never used so I didn't want to just go dumping unknown fluids in the gas tank!
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Old May 15th, 2017, 07:14 PM
Drewski Drewski is offline
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Default Re: Fuel additives

Haha well so it is. As with anything, everyone has an opinion when searching information on forums. But, I found a few people who have been using this lead additive on a chevy forum and they had no complaints. And honestly, I didn't find too many negative comments about it either so I just decided that it was good enough to me to use lol. So far I have no complaints, so I'm glad that helped you out TJ.
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Old May 16th, 2017, 04:30 AM
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Default Re: Fuel additives

Just bought two bottles today. Put one in at half tank and will put another in when I go to fill up next time. Nice red stuff. haha Hopefully it'll help!
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Old May 16th, 2017, 09:15 AM
BobBray BobBray is online now
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Default Re: Fuel additives

I run plain old 87 octane Chevron or Mobil, no additives. I do have '73 478 heads on my 351, which have hard valves and seat inserts. No worries!
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Old May 16th, 2017, 04:08 PM
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Default Re: Fuel additives

Does anyone know if the 1968 305E has hardened seats?
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1964 Chevy C20 292/SM420
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