Hey everyone I hope all is well. I was searching the internet for a better truck than the last 73 I showed everyone and think I found what I’m looking for. A 77 f250 400 engine with 4x4 and 4 speed granny low. Not much rust good paint etc. supposedly has over 300K miles but freshly rebuilt engine. Only problem is these engines seem to have a real reputation for knocking and pinging under load or elevation. This is a problem to me because I can’t afford premium gas (not at 8MPG) and I don’t want this thing pinging all day long. Are these motors really that bad?

 

A stock 335 series engine is a low compression gutless wonder. they don't require higher octane fuel so if you're having problems you need to check your timing curve. you're almost certainly advanced too much.

If it was rebuilt with higher compression you may be forced to run higher octane if you can't manage the detonation with decreased timing advance.

are they really that bad? yes. but not because of detonation that is the least of their problems and you should be able to cure that.

 

You should put it under a load before buying it and see if it pings. One solution for pinging is Snow Performance water/methenol injection. A bit pricey but could save a lot in the long run.

 

In stock form they are prone to detonation due to the huge deck clearance (top of piston to top of deck), huge dish in pistons, and open chamber heads. You can buy expensive pistons that are designed for optimal deck clearance then have them put on rods, have block cylinders machined for said pistons, install a straight up timing set, work with ignition curve and if cammed right end up with a strong engine but It's expensive when considering machine work etc.

 

Or, you can set your timing properly.

I have two low mile original 400's on the ranch that still run and they're not pinging whatsoever on pump ethanol blend regular.

 

My original '78 400 does not ping. The low factory compression ratio helps deal with the open chamber design common with emissions engines in the 70's.

Agree a good test drive is in order. Enough to warm it up. "Rebuilt Engine" can mean lots of things.

 

Thanks everyone for the replies. If detonation is not the worse what are some typical problems these motors experience? I’m not new to old cars and old v8s but I’ve never worked on a 335 series v8

 

Only time mine pinged, I was trying leaner jets and more timing. Fattened up jets, relaxed timing a hair, it's not done again.

 

Not to be a Richard, but I believed all of the lies, myths and BS surrounding 335 series engines based on rumors and "reputation", I'd have never bought one with a 335 in it. Over 30+ years, Ive owned 3 dents with 351M/400, and they've all been good running, strong workhorses, albeit sluggish and very thirsty in stock form. EVERYTHING out of Detroit in the mid-late 70s was a smogged down, low compression gutless wonder. A few basic hot rodding tricks brings them to life.

Think about it. The M motor in your truck lasted over 40 years and 300 thousand miles before it was rebuilt, just like mine. It cant be too bad. Yes, there are some better options out there, but not many that will last 40 years/300K.

Check the timing, and hope that the rebuild included flat tops/zero deck, and a straight up timing set. Get ready to enjoy rock solid dependability at a cost of single digit fuel economy. Keep your eyes out for a 429 or 460 if the M motor doesn't make you happy.

 

I hear from the motor heads it was the tall deck combined with the open chamber heads(which all smogs had, lowering compression) that led to **** poor air velocity through the valves and restricted the motor from really eating what it needs under load... id be extra intrigued by the rebuild in this case. If they where able to raise the compression, any detonation issues under heavy load are long gone... although not exactly cheap to build, 400s are far from the boat anchors they once where. Good luck

 

The 335 had lots of problems but the biggest is a horribly weak bottom end. these engines were famous for the bottom end going out at around 50,000 miles . and they did , it was common knowledge . so if in stock gutless form they failed at 50,000 how long can you expect them to last if they're built to produce actual power? it's illogical to dump money down a rat hole in my opinion. the 385 engine is and has been the fix since they started doing the conversion in 1979.

No they didn't all fail at 50,000 , some made it to 60 or 70. if only used as grocery getters I've seen them make it to 100,000. woo hoo it lasted a normal life. but we used our pickups as they were built to be used and the simple truth is the 351-400 earned it's awful reputation honestly.

That said you can tune a stock 335 to run on pump gas just fine for as long as they're going to run anyway. back the advance down until the ping stops then check your curve and see where you're at. . if it's too far off you may have to work it over to get what little performance you can but it will cure the problem. I've never had to go there though they were fine.

 

Thanks everyone. My bottom line is for $1,200 is it a decent buy. Not much rust on it 4x4 with granny low 1st gear 4 speed. Owner claims about 600,000 miles but rebuilt gearbox and engine recently. I’m not looking for something crazy I want something I can pull a car with or go off roading with the friends in. If these engines are crap I’ll pass

 

If your asking if the truck is worth 1,200. All day every day. I’d hound someone for a running 4x4 without much rust at 1,200... unless thats a typo and you meant 12,000.

 

No it’s typed right. $1,200 recently rebuilt after like 500,000 miles. Fresh gearbox as well guys moving and has medical emergency can’t bring it with him so he’s letting it go cheap




interior is mint

 

I’ll start a new thread for this one so we don’t go off topic