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FSJunkie 
AMC Addicted 
Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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 Posted: Feb/27/2017 at 9:38am |
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Keep in mind that the octane rating at the pump is different now than it was back then. Today we use the (RON + MON) / 2 method, back then it was just RON. 91 RON was regular grade back in the day. 87 R+M/2 is regular today. Their actual anti-knock rating going down the road is the same. 91 RON = 87 R+M/2. So that fancy 101 octane fuel people talk about being able to get back in the day but now the highest octane is 93? That old 101 RON is actually equal to modern 96 R+M/2.
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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ccowx
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Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Feb/27/2017 at 10:18am |
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Good morning! Taking a look at the chart I referenced and hearing the intended use of the car, here is my (updated) suggestions. It seems you have everything dead stock, including the distributor, cam etc. Given that, you probably have around 30 degrees mechanical advance, so having it at about 3-5 degrees btdc initial, plus the vac advance hooked to manifold vacuum should be about perfect. If you use an advance curve kit like the 927G you might sharpen up the throttle response a bit, with no trade offs, but other than that it is probably fine.
Nice car, love 343's myself! Chris
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Boris Badanov
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Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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Posted: Feb/27/2017 at 11:12am |
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93 octane fuel today is as high a octane rating
as anything but SUNOCO 260 or similar fuels. What is missing is the lead "TEL". For better or worse I might add. Beside being poisonous and a nasty pollutant lead helped the valve seats from getting pitted and self destructing. Your 343 has the old soft seats if it is stock. The additives (Bromides) added to Gasoline to keep the TEL from settling out are a vapor abrasive after combustion. This is why few Gas engines were lasting past 100,000 miles without smoking and also why there were those nasty ridges in the tops of the cylinders. Unleaded gas is great stuff, far superior to leaded gas if your valve seats and valves are up to it. |
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Gremlin Dreams
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Doug in New Freedom
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Joined: Aug/02/2014 Location: NEW FREEDOM, PA Status: Offline Points: 149 |
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Posted: Feb/27/2017 at 11:53am |
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No smoke yet. About 5 years ago I needed to replace a leaking Real Seal and when I turned it over to the shop I deal with to get the seal replaced I told them to pull the engine and go in from the top, fix anything they think it needed. So everything was checked out and all new main bearings went in along with Gaskets and Seals The 343 is original to the car and has 62K on it,55K when I bought it 12 years ago.
The other saving grace is the rear Axle is an open rear with a 3.14 gear ratio, plus it's an Automatic Tanny and I'm on Bias Bly 14" Red Line Tires. Not a track set up is it. The only things I've done to it other the general things like Tuning and Lube, Belts and Hoses, was to install a rebuild Carter AFB 4V and the Pertronix. My question about the timing that you all gave me really helped a lot. It concerned me that the spec called for Zero Degree's which I don't think I've seen on any of my other engines and the explanation about the way the advance timing curve is what I wasn't clear on till now. I actually sounds like a good thing and for what I should stick with. One other thing I need to clarify is to get the 97 Octane, I'm using an Octane Booster added to the pump gas which is 93 octane at the pump.
Edited by Doug in New Freedom - Feb/27/2017 at 2:09pm |
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Feb/27/2017 at 1:49pm |
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I just finished rebuilding my 360 that ran on leaded gas its whole life (last ran in 1988). I spent several whole days chipping and grinding the lead deposits out of the exhaust ports and manifolds. Definitely don't miss leaded gas.
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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ccowx
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Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Posted: Feb/27/2017 at 1:54pm |
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AMC engines were pretty good when it came to valve seats. Unless you are beating on it or dealing with detonation it should be ok. Ideal is leaded gas, at least for the seats, but you can get by for a long time or forever without it.
Good luck! Chris
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Feb/27/2017 at 3:11pm |
People ask me all the time about whether to run a lead additive. I just tell them to run it on unleaded until the seats pound out, which could be 10,000 miles or it cold be 100,000 miles. Just run it and if or when the seats fail, pull the head off and redo it with hardened seats and replace the timing set while you're at it. The engine was probably due for a top-end overhaul anyway. |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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purple72Gremlin
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Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16611 |
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Posted: Feb/27/2017 at 3:31pm |
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I've seen pounded seats from running leaded gas. I agree with chris. Been there done that. Now if I have original heads that has had no valve jobs done, Most likely I would have hardened seats done. I don't feel like pulling the heads off because the seats got wide and won't seat. I have my own valve grinder. But in my case, if the valve guides are worn, to me there's no point in doing it because the valve job will not last.
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Bruce Clarkson
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Joined: Feb/09/2013 Location: New Bern, NC Status: Offline Points: 538 |
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Posted: Feb/27/2017 at 7:34pm |
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Just one more data point from a 343 driver. When I put pistons in I dropped the compression to about 9.6. I run everything else stock and burn 93 high test. We cruise all over the place. I keep the idle timing a bit less than 10 degrees. This works significantly better for me than the TEAM numbers.
Bruce Clarkson |
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Bruce Clarkson
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ccowx wrote: