Bought a 78 F250 300six a few weeks ago, spent all the time between then and today getting it rolling and took it out for its first real trip this morning. The thing smokes like a freight train, runs like a mortally wounded dog, and has no power. Now I've never driven a properly maintained 300six before but I know people that have and I've read the forums on here. Mine won't accelerate uphill, in fact it slows down. And we're not talking about steep hills here either. So I have a smoky six with no power. I've thought about it and I've decided I'm going to rebuild the motor. It needs it. Its got some kind of mortal problem. Hole in a piston, rings stuck, burnt valves, broken head gasket, cam lobes worn away, something serious. I have no idea what it actually is mind you.

Now heres my questions.

Do they make a master rebuild kit for this motor to take it back to stock? Just a regular, pistons, rings, bearings, and gaskets, maybe a timing set or oil pump, a rebuild kit.

If they do make one, who sells it? I've looked on summit and jegs and rock auto. Rock auto sells one but its outrageous for as popular as this motor is and what it is they're offering for it.

If nobody makes a master rebuild kit for it I'm just gonna tear it down, new cam and lifters, new valve springs, P&P the head, new pistons and rings, and new main bearings with all new gaskets and then whatever else looks worn while I'm in there. Anyone want to add to that?


What I'd like to do is get the Offy DP manifold and put a quadrajet on it, run a header going into duals with cherry bombs, comp 260 cam, chevy 292 rockers, the usual stuff without having to take the motor out of the truck.

Any help, as always, is greatly appreciated

 

Same-o as here:

https://www.ford-trucks.com/forums/n...te=1&p=8024994

 

First,I'm confused,Do you intend to rebuild this in your truck? If so,your in for trouble before you start.You can't do a 1st class rebuild with the engine in the vehicle.Now that that's out of the way,depending on what the bores are like,you would want to hot tank the block,bore cylinders if needed,replace cam bearings,check/line bore mains,check/deck the block,clean all oil passages,check all hole threads,replace all freeze plugs and now your ready to start a standard rebuild.Remember to torque and check the rods for round,if not,recon rods.I can't really type out the whole rebuild procedure,but stay in spec and surgically clean and be thorough,find all the info you can before you start and plan it out.This is a lot of work and money,so don't short cut.I would use a new Melling HV oil pump.If you do it right,you will have a great engine,if not,a lot of wasted time and money.

 

If you're doing all that you might as well get forged higher compression pistons and forged rods and make some real nice numbers.

 

PAW sells the kit. They also let you upgrade on the ring and gasket selection. Get the Fellpro gaskets, and chromemolly rings. With the DP manifold the carb sits 90 degrees to the engine. With the C man. it sits parellel. Think linkage.

Piston selection is important. Do your research. With your cam buy the ket, springs, lifters, retainers, locks. You might want to consider going with the over-size valves, 1.94 intakes, 1.60 exhaust for a boost. SBC valves for the 327 v8. With the valve job, p&p, milling, new seats, etc., you're looking at $1,000 for the head alone. Also, with the dp manifold it is very difficult to match the runners to the head. Mill the head .020, and the deck the same. It bumps the compression but allows you to stay on regular gas. Recurved dizzy, DS11, with high power coil, and aftermarket ignition box. Use EFI plugs with 55 gap.

Have your shop check alignment of the cam journals too. Start writing all these tips down so you don't forget/loose them. They are valuable.

For your carb. I would say to go with a new Edlebrock 500 for $300. Been there.

Do all that and you'll be getting about 250 hp, and getting decent mpg too.

 

Alright there seems to be a few misconceptions here. First I'm not looking to build a sweet motor at the moment, just a reliable one. Sweet comes in the spring when the weather is fine and the bank account is in better shape. (I just moved here a month ago and remember I just bought a truck lol) Next everyone is making a big deal out of me thinking about building the motor in the truck. That idea isn't some half baked notion I pulled out of my corn hole, I've done it before, several times in fact, with respectable results. These aren't performance builds mind you, these were "my motor smokes so I'm gonna throw some rings in it and some valve seals" type builds just to keep truckin until I had the time and money. I've built 6 motors on stands, two were L6's, this ain't my first rodeo. The only question I actually asked here initially was about a kit, who had one and where could i get one. My situation is that winter is coming fast and I just plain don't think my 97 escort is going to handle it quite as well as this F250 would if it was running right.

With all that said I just ran a compression check on it and the motor is coming out, all that worrying for nothing. I left the card I was writing on in the garage but from memory, number one has 50psi, number two has 120psi, number three has 110psi, number four has 60psi and the plug was oily, number five had 110psi and was a little oily, number six had 80psi. Shes got real problems.

New plan: Buy a used motor for hopefully around 300 bucks to drop in the truck for the short term. Pull the old motor, strip it, mic it, machine it, build it, swap it back in. Anyone got a six they wanna loan me? I promise I'll be gentle

And just for the record I make my living as a manual machinist.

 

OK, I get it. If it works for you, that's all that counts. Good luck with the swap etc.

 

Save some $ and go with the head off a 240. Port it yourself. Put on the chevy rockers, EFI exhaust, a used intake and a rebuilt 4v carb.

 

Why the head off a 240? Are they just cheaper to build with equal performance? I already have an EFI manifold though. Along with my oil pan with the dipstick in it....to compliment the dipstick in the block... Valve cover is also off an 85 or newer I'm told. Actually I don't know if its even the original motor for the truck, its a 300 with a single bbl though and thats what its supposed to have. The exhaust needs done though anyways, I'd say a 6 year old welded mine together but I wouldn't want to offend the youth. It only goes to the back of the cab. For some reason it has bung in the pipe for an A.I.R. tube despite the carburetor... and that blows DIRECTLY through the gaping hole in the passenger side floor. Both things will be fixed in the next 2 weeks, new floor pans from LMC truck and custom exhaust from whoever wants to bend the pipe cheap, but I think I'm gonna buy a header for it, I've never owned anything I actually worked on that had an exhaust manifold.

 

Hey,Now your talking.Your new plan is the best plan.The used engine is way easier and cheaper than a short term rebuild and it gives you the time to do a good number on your engine rebuild,Plus you can swap that engine out in an afternoon.Now that I know your a machinist,I know you know how important specs,clearance,plastigauge and cleanliness is.When you first read someones post on here,you don't know what their idea of a rebuild is,and I'm always wanting to save someone from a lot of grief just because they missed something.My posts are never meant to offend,only to help where ever I can.I've never been rich and I know what it's like to see hard earned money and work go up in smoke.I hope your project turns out great for you and I'm sure that the guys on here will also be there for any help you may need.

 

300 Buster thanks for the advice all the same, you were only trying to help and help is always appreciated. Rebuilding the motor was never a concern for me, I'm my fathers son all the way and even though he lives in an RV next to a lake in Virginia now he spent his entire professional life under the hoods of other peoples cars and its thanks to that I've got all the fancy tools, years of experience, and in depth knowledge I do. I don't imagine I'll have any trouble with the build but I know if I do you guys will will be there with answers and I greatly appreciate that. Thank you all very much.

 

I mentioned the 240 head because the compression chambers are a bit smaller, thereby bumping your cr a bit. Most guys mill the deck and head to get higher compression.

The main hinderence to performance on these engines is the head. If you want any kind of boost in performance, it will start at porting the head.

 

Yup. A port match, not a gasket match to remove the ledges in the downstream flow. Take care on the short radius side...you don't want to strike water. Polish the combustion chamber and exhaust ports and you are good to go.

 

Seems like the main focus of everyone on every thread I've read about rebuilding these motors is to port and polish the head, I think when I get around to building mine I'll port and polish the head haha.

In other news I drove my truck about 3 hours to a little place called Sciotoville, Ohio and bought my 250 dollar motor to run while I rebuild mine motor. My POS motor burned 9 quarts of oil, take that hippies!