Marine 351

[scotts90ranger]

Not on a swap, more just questions about my boat engine since it stuck a valve or two...

It's an '83 351 windsor that's been rebuilt at some point, it used to be the hipo 290hp version but if I've heard right there would be 3 lines on the cylinder heads if it was, which there aren't anymore. I've also heard those needed premium which I'm glad to not need... Anywho I just pulled the one head with issues so far and saw a D8 casting number somewhere. The pistons have a dish in the middle so I'm assuming lowish compression.

Main question I have is what stuck the valve? There was minimal rust on just the cylinder head around that valve, the only thing I can think of is that valve happened to be closed and there was some water sitting over it over the winter and rusted that particular valve guide? Odd part is the cylinder in question is #2, odd... It has modern Felpro valve stem seals with springs on the lips.

Since I can't leave well enough alone I was planning on pulling both heads and all the valves making sure they are all in good shape and do some die grinder work in the ports... can't hurt to be a better air pump... The tack doesn't work and it meets all my needs except fuel consumption (need to do some jetting once it's back together anyway) but more power never hurts .

I'll dig back into it Thursday night and update when I get the valves out, maybe even have pics...

 

[AHenry014]

In my experience, boat engines can be finicky. I believe most of the issues are because most boats tend to sit, wether it be between uses, or in the offseason. Proper maintenance and storage methods usually ensure a smooth transition into the next season, but its always been a gamble for me. How are your manifolds/risers? If they are aged, they may be allowing some amount of water inversion or allowing some water to trickle back in once the engine is shut down. Water can cause a sticky valve, and so can non-use of the engine.

 

[19Walt93]

Three lines on the head would indicate GT40 heads which didn't appear until the 90's. D8 heads would have been introduced in 78 so they might be original to the engine. My friend(our old body shop manager) used to race a Granada and he always ran 351 marine heads because his class required a Ford ID number and they were superior to passenger car heads. I suspect the marine heads didn't have cast in thermactor passages so they flowed better.

 

[85_Ranger4x4]

I always kinda looked at boat engines like combine engines.

They are lower hour... but they sit a lot. And when they run they are ran hard.

That said things stick easier in a tight engine than a wore out engine.

 

[Shran]

Did you run old fuel through it? My buddy ran some really old gas in his 302 and it started missing and eventually just wouldn't stay running. After throwing a bunch of parts at it they pulled the heads off and found several bent valves. I'm not sure how the physics of that work but the machine shop that fixed the heads said they see it a lot and it's usually caused by really stale fuel.

 

[85_Ranger4x4]

Did you run old fuel through it? My buddy ran some really old gas in his 302 and it started missing and eventually just wouldn't stay running. After throwing a bunch of parts at it they pulled the heads off and found several bent valves. I'm not sure how the physics of that work but the machine shop that fixed the heads said they see it a lot and it's usually caused by really stale fuel.

Junkyard Digs on youtube had a similar issue with bad fuel in a early Bronco with a 302 a couple years ago. He was bending pushrods though.

 

[Shran]

Junkyard Digs on youtube had a similar issue with bad fuel in a early Bronco with a 302 a couple years ago. He was bending pushrods though.

Funny, this guy also has an early Bronco.

Bending pushrods makes sense, if the fuel is hydrolocking a particular cylinder, the pushrod should be the weak link but I guess if the valve itself is weaker than the pushrod then it'll bend first.

 

[scotts90ranger]

Oh, it bent two pushrods but the valves were stuck up not down so didn't bend a valve that I can tell... (I'll replace both for good measure likely) the intake valve worked it's way free but the pushrod is still bent, ordered a new set... probably be ordering at least one valve, we have guide reamers at work, Thursday I'll get the valves out to dig deeper...

The fuel was from newyears but that was just from being topped off from summer gas... I don't think I'd call it that old...

I'd planned to use the boat more than I do but life keeps getting in the way of fun this year...

Interesting on the GT40 heads, only learned half the story then...

 

[scotts90ranger]

Ok, got the valve out, it didn't wanna... turns out the valve stem was rusted, I'll try to post pics later... so I need a new valve for sure, I'm pretty sure most issues I've been blaming on carburetors have been this since I got the boat...

 

[scotts90ranger]

Ok, I noticed something tonight... I think there are thermactor ports in the head, looks like oddly in this cylinder and for whatever reason exhaust runs under the intake manifold plenum... I noticed that the wire harness plastic loom was melted on the center two intake manifold bolt heads on the side with the issue and staring at it and the intake gaskets it looks like it has been leaking around the dang port! So with that said and the fact the boat sat uncovered during rain for a while outside with a wood engine box what do you think the chance that water could have made it through the intake gasket and under that valve?

I have a feeling that I've been fighting it for a while but still think this might be plausible, it sat outside with the mooring cover for the previous owner too...

 

[scotts90ranger]

Ok, here's the dumbness...

The cylinders look decent, #4 is a bit clean not sure why yet...

Now that I look at that picture there's an F3 stamping but on the underside of the head is a D8 I swear...

 

[19Walt93]

It looks like cylinder 4 has been ingesting some coolant and that caused the carbon to burn away. The rusty valve stem means the valve guides will need to be gently cleaned out with a reamer- by someone with experience so proper clearance is maintained. If the guides are really pitted, it's possible to get valves with slightly oversized stems and ream the guides to match. I'd do the other head, too, otherwise your apt to be back in there soon.
With the exception of a flathead or a race engine, I've never seen a V8 that didn't have exhaust running through the bottom of the intake manifold.

 

[85_Ranger4x4]

With the exception of a flathead or a race engine, I've never seen a V8 that didn't have exhaust running through the bottom of the intake manifold.

You have to be careful with intake gaskets, the Ford Racing intake gasket set left those ports open to the world. I found a set that just blocked them off and I didn't notice a difference in anything.

 

[19Walt93]

You have to be careful with intake gaskets, the Ford Racing intake gasket set left those ports open to the world. I found a set that just blocked them off and I didn't notice a difference in anything.

If you drove it in cold weather you'd notice a difference.

 

[85_Ranger4x4]

If you drove it in cold weather you'd notice a difference.

Well it was -20 last January when I was pulling my wife's bronco out of a snowbank with it... it seemed to run fine.