input on engine stuff
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Mountain Pass
Joined: Nov 2015
Posts: 153
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input on engine stuff
I started out on ' big truck ' but thought here would be more on target ; 78 F-600 4X4 389 XD engine with IMPCO 425 lp carb , compression check not bad mostly 135 with one 130 & one 150 , burning very little oil . GOAL : approx 25% more torque at 2000 rpm ( currently governor limits to 3700 & have no desire to increase ) prefer not to install different engine.
IMPCO suggests no more than 9 to 1 comp ratio for truck service. will the current heads & intake with the fresh installation of 9 to 1 pistons & a mild cam for my rpm range easily meet my goal for torque increase ? my desired performance increase is conservative to protect the lifespan of certain driveline components . I currently believe this 389 has sodium cooled exhaust valves ? If i overhaul the heads should sodium cooled be used again or just have stellite valves & seats installed ? I am aware of cost / benefit concepts but this truck is my pet bucket list project ! thank you
IMPCO suggests no more than 9 to 1 comp ratio for truck service. will the current heads & intake with the fresh installation of 9 to 1 pistons & a mild cam for my rpm range easily meet my goal for torque increase ? my desired performance increase is conservative to protect the lifespan of certain driveline components . I currently believe this 389 has sodium cooled exhaust valves ? If i overhaul the heads should sodium cooled be used again or just have stellite valves & seats installed ? I am aware of cost / benefit concepts but this truck is my pet bucket list project ! thank you
Cargo Master
Joined: Oct 2020
Posts: 2,703
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Replacing the old stock exhaust valves with new ones is always a good idea on those old truck engines. Your heads will already have a high quality hard seat stock and I think that it will probably do ok on just about any fuel. I have not ever plotted a stock Ford truck engine camshaft and it might be pretty optimized for low speed performance and lower EGT but maybe not. The cam would probably work the best would be a single pattern cam with about 185 @ .050 duration on a tight lobe sep, 105-106 something like that. This will keep the EGT down and help get the low speed cylinder pressure up even with the gaseous fuel which tends to reduce VE.
Cargo Master
Joined: Oct 2020
Posts: 2,703
Likes: 799
A friend of mine used to grind cams for Reed Cam and they did a lot of cams for an outfit down in Texas or Oklahoma that built engines that were used to run on natural gas for either irrigation or for pumping gas. They experimented with several different grinds trying to come up with something that would run really well under high loads at low RPM while running on gaseous fuel. They ended up with a cam about like I told you about.
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