Joined: Jun 27, 2011 Posts: 262 Location: "Thumb" of Michigan
Posted: Fri Jun 10, 2016 6:35 pm Post subject: Hardened Valve seats?
I'm a "learn as I go mechanic." Working with my mechanic to change the timing gears on my M38A1 recently was quite the education.
My mechanic asked in passing whether I added a lead additive to my fuel, stating: "this engine probably doesn't have hardened valve seats."
Can someone explain what he was talking about and whether I should be treating the fuel in some manner - thanks! _________________ Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft
I have to do a rebuild on my engine, my main bearings went. Been debating with going with harded valves or not. One benifiet no one realy points out, is that its alot cheaper in the long run to install them. I say this becouse of the lead subtitiute, that stuff adds up, since you have to use basicaly one whole can if you fill your 17g tank up. Also for the pure convenice factor of not having to add lead additive. Been also debating, becouse i will be driving at higher speedes more consistantly. Wesk post gave you all the basic hard facts. Varies on what your doing, and where your at on engine. Deff should be adding lead supstitiuce, it also keeps engine from knocking, read wesk scientific for support.
I do not agree. It can only be construed as cheaper to run hardened valve seats (Not Valves!) if you actually increase the performance level of your 60 or 72 HP L-134/F-134 to a level where the additive is needed.
In stock form these engines will run and perform adequately on 40 octane mo-gas from the 50's and 80 octane 10% ethanol unleaded gas today. I ran my M38A1 on a straight diet of unleaded gas in the 80's / 90's at interstate speeds across South Dakota's west side and never suffered any knocking issues or rapid seat wear. Yes my A1 could cruise on level ground at 65 MPH for the 30 mile trips to and from work. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
OOOOHHH SHINY. Yep, wes your correct, valve seats is what i meant. That's awesome you were able to run interstate speeds in stock configuration. I'm actually shocked you did 65. I know 70 is guarantee rod through block. Highest i've personally heard are people cruising at 60, and one guy who hit 70 to pass truck and blew engine. On side note, How you know you did 65 ? speedometer only goes to 60...?
How you know you did 65 ? speedometer only goes to 60...?
Today I use a GPS. From my first jeep in 1970 through the advent of modern GPS' I used the wife and had her drive along side me as I called the speeds I wanted next to her.
Don't underestimate the balls of the M38A1 with a WELL maintained F134 and drive train.
Most original pre 60's cars came with the seats cut directly into the head or block. Then the seat was induction hardened. You could regrind these seats once or twice but that was usually the limit. At that point if you were lucky there were replaceable seats available either OEM or aftermarket for that series engine. If you weren't lucky you started looking for a fresh block or head.
With the advent of unleaded gas and much higher operating temps in the 70's the makers switched to replaceable seats about all around. Initially the market went scared when unleaded showed up and all the hype generated back then for hardened seats and Steelite valves and sodium filled valve stems became folk lore at it's best. Still today there are folks that still believe the hype. Geeze there are even some that believe the valves hammer through the seats. This we all know is malarkey. The seat erosion or recession is actually caused by the excessive heat transfer not any physical hammering. 6,000 RPM 429 Fords with 11 to 1 compressions and high load / high lift valve systems need hardened seats not f134's turning 3500 and developing all of 72 HP! _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 27, 2011 Posts: 262 Location: "Thumb" of Michigan
Posted: Sun Jun 12, 2016 9:34 am Post subject: Valve seats
I really value the great info that surfaces on this site. I guess I need not worry that my occasional 20 mile run at 40-45 is going to cause undue wear. Fastest I've ever tried to take my Jeep was a little under 60 so I'm impressed with the performance Wes got. Me, I do most of my Jeeping on back roads at speeds of 20-30 with the windshield folded down.
Thanks all!
Tim _________________ Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft
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