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I have a 1978 f150 4x4 400/c6. I have never been able to get it to run correctly and am going to start driving it in college and need a truck for some internships I have lined up and have been looking at rangers and the market on those right now is crazy so figure I’d just put some money in this dent and finally get to enjoy it (owned it since I was 13).
Pulled the motor and tore it down and bits of cam bearing fell out and all are pretty shredded. Main+rod bearings are worn and crank would need a good polishing or maybe undersize. Cylinder walls have no scoring but good grooves in tops of all holes that catch a finger nail. Heads are crusty and one valve has bits missing.
Needs lots of machining. Is a virgin block.
I guess I’m wondering what people that have been there done that would do. Is this 400 even halfway worth it to machine? Should I just toss new cam bearings, hone and see (just need it to make it 2-3 years or so). Should I go 460 (what I would like and always wanted to do but truthfully I’m in college and money is fairly tight but is doable). My plans were to just freshen this motor up as it ran okay and somehow had oil pressure but needs a lot more work than I was hoping for. I know this is a decently stupid post but never built a motor other than a sbf for my foxbody and there’s a lot more info on those. Any advice would be appreciated. Thank you in advance.
I'd rebuild the 400. That's a burnt valve. Tom Monroe's book is great, I have two. First I bought new in the early '90s, second I found on eBay a couple years ago.
OMG Metal Mites!
I would put a new valve in the hole, (hand lap it in with some valve grind compound) or "tap it in" and see if it holds Brakleen
Chances are all you need is a few valves and the motor will run fine
I generally just tap them in and see the witness mark of the valve seat on the valve
Then double check with Brakleen
The metal mites have been eating well on yours
Check the valve job all ports on both heads with brakleen
Cleveland heads are notorious for worn guides
A bit of a leak is okay, but you don't want the brakleen to just run out
Fun stuff, good luck
It cost me a ton to get bronze guides installed in my Boss 302 heads which are the same design
Not sure where you live, but here in PA, i am still tripping over 351's and 400's.
For a college aged kid with a dent (<- was me at one time) i would highly recommend just buying a good used engine and swapping that in.
I can get one of these for $500 without looking too hard.
You'll have well over $500 just in parts before any machine shop labor...assuming you don't even have to buy new pistons but get by with a hone/ring job.
You can also swap your engine in a weekend and be back on the road unlike the weeks it will be when getting rebuilt.
College, money tight, internships.....Just a personal opinion so take it for what its worth....This is not the vehicle to drive daily if you are on a budget. Aside from the engine issue, if its been off the road sitting, there will be a lot of other maintenance needed and everything is expensive. just put your money in a smaller beater car ready to drive and wait until the time is right to put money into the truck and get it roadworthy.
OMG Metal Mites!
I would put a new valve in the hole, (hand lap it in with some valve grind compound) or "tap it in" and see if it holds Brakleen
Chances are all you need is a few valves and the motor will run fine
I generally just tap them in and see the witness mark of the valve seat on the valve
Then double check with Brakleen
The metal mites have been eating well on yours
Check the valve job all ports on both heads with brakleen
Cleveland heads are notorious for worn guides
A bit of a leak is okay, but you don't want the brakleen to just run out
Fun stuff, good luck
It cost me a ton to get bronze guides installed in my Boss 302 heads which are the same design
The problem with doing crap like this is that it doesn't fix what caused the valve to burn in the first place. This happens many times because the seat gets too wide. Without grinding it with a top angle, usually I use a 30 or 37 degree angle for a 45 degree seat to narrow the seat you don't fix the cause. If you take the heads apart you'll probably find more than one seat that is very wide from wear and tear.
Thank you all for the replies. I guess I could clarify that I have already budgeted money for the truck so it would be near 100% before trying to daily it and the budget for the motor would need to increase and thus be tight if I tried to machine or source/build a 460. Before pulling the motor ran pretty decent aside from carb issues and the hole with the valve was always cold compared to the rest. No smoke idling and no sounds. I am in GA and 400s are pretty few and far between or $1500+ for a complete one in unknown condition which wouldn’t help much.
I think from y’all’s replies I’m getting that I should just do cam bearings and hone.
Head wise I agree that just replacing valves would not sort the why. Realistically it would probably be fine for the time I need it but still not optimal. Cleveland heads are fairly plentiful around me and I could definitely get some replacements/upgrade and be happy money wise. From the research I’ve done 400 heads are fair flowing open chambers. What would be comparable or if I can find some closed chambers should I go for them.
Im going back home from college for the weekend so I can take some more pictures of it all tonight. Thank you all again
Ranger is/was a great idea, but I had not priced them recently, but then they are well represented on our roads. I grew fond of them driving deliveries in my post retirement part time job, with the dual plug "Pinto" 2.3 & auto. Was FI too. I think it was a 2003 model, after Advance retired it, it was bought by a leasing co., and I think is at our NAPA now.
Reading some posts, that valve needs to go away, that hole needs a new one and the seat may be damaged. Hand lapping will show you if not useable. Check all 16 valves while apart. A light hone, rings, some cam, main, & rod bearings, a timing chain, some gaskets .... might see it go for a bunch of years yet.
That book I mentioned above has been a huge help over the years, in assessing and repairing mine, well worth what I bought it for.
Last edited by tbear853; Jan 16, 2026 at 11:19 AM.
Ranger is/was a great idea, but I had not priced them recently, but then they are well represented on our roads. I grew fond of them driving deliveries in my post retirement part time job, with the dual plug "Pinto" 2.3 & auto. Was FI too. I think it was a 2003 model, after Advance retired it, it was bought by a leasing co., and I think is at our NAPA now.
Reading some posts, that valve needs to go away, that hole needs a new one and the seat may be damaged. Hand lapping will show you if not useable. Check all 16 valves while apart. A light hone, rings, some cam, main, & rod bearings, a timing chain, some gaskets .... might see it go for a bunch of years yet.
That book I mentioned above has been a huge help over the years, in assessing and repairing mine, well worth what I bought it for.
yes I love the rangers but it seem with the cost of new trucks everyone is snatching up rangers or holding onto what they have. I have noticed around a 2k increase in price over the past year and the number of halfway decent trucks that don’t need a few grand put in are small. I would still love a ranger and I was prepared to pay more for one in good shape but I can’t justify spending so much now and likely the market correcting in a year or two and being way upside down in one.
From your description it sounds like your engine is just plain worn out from head to toe. The used engine idea seems the most economical choice for a 3 year run. Put the 400 on the back burner until you can do it right, because it needs it all and no short cut is going to work any better than you're doing now.
The 460 swap sounds easy only because the bellhousing bolt pattern is the same. Every other thing is going to need replaced from fan to flywheel. It will get involved and expensive before you're done, and take more time than you'll have to spend on it.
You won't find any closed chamber 400 heads. All 335 series heads are open chamber except early large port (70-71) 351C 4V heads. The only exception would be Australian heads, but that's another story for another time so as to not confuse our issue at hand, not readily available or affordable here in the states.
I'd overhaul or rebuild it depending on your budget.
Spun out cam bearings are not uncommon. You can easily improve the oiling system by plugging one of the redundant oiling lines to #1 main bearing, and then adding the special cam bearings from TMeyer. I'd have the heads professionally rebuilt by a cylinder head shop. New guides, positive valve stem seals, a valve job and stainless valves. Decked just to be sure they're flat.
For the block - honed and new rings at least. New cam, lifters, and "straight-up" timing chain. A hydraulic roller if you can possibly swing it! All new bearings an NO high volume oil pump. I wouldn't even get a new one unless yours has had a bunch of debris from.the cam bearings run through it and scored it up.
