The truck was restored with donor doors and the plate was never transferred.
1978 351M Advice
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Freshman User
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1978 351m F350
Hi. I just purchased a 1978 F350 4x4 auto with a 351M. I've only had it a couple of days now, but I am not impressed with the power or performance....or the low single digit gas mileage. This truck was previously restored by a guy who had more money than brains. He rebuilt the engine back to nearly stock condition. The only exceptions are an Edelbrock Performer manifold and Edelbrock 4bbl with vac. secondaries. I checked the timing, carb., sparkplug conditions and nothing seems out of the ordinary. The only odd thing is that the plugs look lean (nearly all white) while the exhaust looks to be rich (black, but not heavy). Not really sure I have seen this before.
I hate to give up on this motor because it seems to be a solid foundation to build on. The main things I am trying to achieve is better throttle response, some more power and maybe an extra mile or two. Seeing that everyone has a lot of collective experience here, what are my best options (besides an engine swap) for:<O
</O
1) Where to set the timing?<O</O
2) Will a set of headers help?
3) Will a different carb improve things?
My last question is gearing. I have not checked what's in the truck yet, but I can say it pulls a fair amount of rpm at 60-65 mph. I'm willing to give up some low end power for gas mileage, what is the best setup for my situation running a set of LT265/75/16 tires?
Thanks.
I hate to give up on this motor because it seems to be a solid foundation to build on. The main things I am trying to achieve is better throttle response, some more power and maybe an extra mile or two. Seeing that everyone has a lot of collective experience here, what are my best options (besides an engine swap) for:<O
</O1) Where to set the timing?<O
</O2) Will a set of headers help?
3) Will a different carb improve things?
My last question is gearing. I have not checked what's in the truck yet, but I can say it pulls a fair amount of rpm at 60-65 mph. I'm willing to give up some low end power for gas mileage, what is the best setup for my situation running a set of LT265/75/16 tires?
Thanks.
Laughing Gas
Joined: Mar 2007
Posts: 754
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From: southwest Wisconsin
IMHO the Edelbrock carb should work fine. Best option by far is to install a 400 crank kit and get 50 more cubes to work with. Won't help your milage but won't hurt it. If you don't want to go that deep into it right now you could try an aftermarket cam(assuming you now have stock), and headders. These you will still use if you decide to stroke it later.
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3.54 gears but that truck is made up not original.
The 4v will give better hwy mileage but less torque at low rpms and higher HP at high rpms.
Putting the intake and carb back to 2v will give you more bottom end torque.
The 351M is shorter stroke engine so it will be weaker in the bottom end of rpm's scale
If he rebuilt it he may have installed a 3 position gear making the timing straight up.
Without pulling the engine apart or oil pan off to ID the crank, it's simply a guess what he did,unless he wrote it down and put it in the truck somewhere.
The 4v will give better hwy mileage but less torque at low rpms and higher HP at high rpms.
Putting the intake and carb back to 2v will give you more bottom end torque.
The 351M is shorter stroke engine so it will be weaker in the bottom end of rpm's scale
If he rebuilt it he may have installed a 3 position gear making the timing straight up.
Without pulling the engine apart or oil pan off to ID the crank, it's simply a guess what he did,unless he wrote it down and put it in the truck somewhere.
Junior User
Joined: Oct 2004
Posts: 92
Likes: 1
From: Rock Island, Illinois
The gang has not told you, as far as I can see that makeing a 351m into a 400m not only takes a differant crank, but also differant PISTONS! The 351m NEVER had a 4V from factory to my knowlege. The heads are restrictive, and with that 4V you lose lower end, and throttle response, but you won't gain any milege either. The original 2V carb flows all those heads can deliver, and putting a 4V on is like cutting open your pcv hose. (Too much vaccuum loss). My 351M is all stock, and I have extreamly crisp throttle responce for a truck, and I haven't found anything yet it wont pull. Top end on the highway is about 85, but I didn't but it to be a race vehicle. It's great for pulling and carrying loads. (It's a truck). If you want more speed, (forget gas milage), get a set of 1970 351 Cleaveland 4V Heads. They will bolt right up. I think you may need adapters, not sure. Also check with the other guys that have done this, there may be an exhaust duct that needs to be blocked off. Good Luck.
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To 85e150six4mtod The timing is set to 8 degrees. The one thing I discovered this morning is the vac. advance going to the distributer is blocked off. When I reconnect it, the truck seems to run on about 5 cylinders, warm or cold. It so bad that my timing light triggers about a 1/4 of the time. The engine pulls a steady 14 in of vac. at idle. What gives?
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To fatherdoug: Is there any distinctive differences between a F250 and a F350 other than spring count? May be its a F250 with F350 badges? What I do know is that it was origionally purchased by the State of New York, owned for 10 years and then sold to the guy I bought it from. The title does not show a standard VIN code, it shows a NYxxxxx. I guess I should have paid more attention when I bought it.