Houston….. We’ve had a problem…..

[ScottinAZ]

New to me 1995 Four Winns 170, 4.3 motor… Looks like I will be tearing into the engine sooner rather than later…. #4 plug shows malice in the combustion palace……zero compression. Its neighbor shows 150 in #2. #6 also shows 150…. So it’s NOT a head gasket…. Maybe I get lucky and it just mushroomed a valve….

 

[alldodge]

Looks to be running real rich
With zero compression might be a bent valve

 

[racerone]

Adjust lifters / rockers ?

 

[ScottinAZ]

well, in the interests of science, I pulled the valve cover this morning, figuring if it was a tuliped valve, that it would be sitting proud of the others, and the rocker tight while on base circle on the cam.... no such luck... so I pulled the head... and yeah, there is a problem... #4 exhaust valve is done... could be mechanical damage from part of the plug going through it, its not "melty" enough looking to have "burned".... so I need a valve job.... or a pair of reconned heads. Short block appears to be OK, but will fill the cylinder with some Marvel Mystery Oil and see how long it takes to leak past the rings....

 

[ScottinAZ]

Looks to be running real rich
With zero compression might be a bent valve

yes, it does to me as well. but with a known bad fuel pump, who knows how they got it "home".... I figure I was gonna go through the carb anyway, so I can tune it to my liking once I get the motor back together.

 

[ScottinAZ]

Offending valve is out. Seat looks OK, so a quickie valve job, and a set of valves should have me reassembling this monstrosity..... Even if the 4.3 is 3/4 of a small block, the head sure didnt weigh any less...... ahhh good old cast iron...

 

[racerone]

Might consider doing the other head , now that your tool box is open.

 

[ScottinAZ]

Might consider doing the other head , now that your tool box is open.

at this point, its only another head gasket away..... but I dont expect any surprises on that side.

 

[Scott06]

well, in the interests of science, I pulled the valve cover this morning, figuring if it was a tuliped valve, that it would be sitting proud of the others, and the rocker tight while on base circle on the cam.... no such luck... so I pulled the head... and yeah, there is a problem... #4 exhaust valve is done... could be mechanical damage from part of the plug going through it, its not "melty" enough looking to have "burned".... so I need a valve job.... or a pair of reconned heads. Short block appears to be OK, but will fill the cylinder with some Marvel Mystery Oil and see how long it takes to leak past the rings....

if you had 150 lbs compression on adjoining cylinders your short block is probably in excellent shape. Doesnt look like any detonation has been occurring nor water ingress. Have a valve job done and go boating.

 

[ScottinAZ]

if you had 150 lbs compression on adjoining cylinders your short block is probably in excellent shape. Doesnt look like any detonation has been occurring nor water ingress. Have a valve job done and go boating.

that is the current plan...

get the heads done, service everything, and get it wet.....

 

[Lou C]

You know that is odd, while there is some carbon build up on top of the pistons, the cyl heads/combustion chambers are pretty clean, cleaner than my old engine was when I took the cyl heads off. I am wondering if the electrode from that plug broke off and got caught between the valve and the seat? It is just an unusual failure. Here's mine from 2017.

I think mine had more carbon build up and also corrosion from water in the cyls due to the blown head gasket.
Anyway I think you can easily get that thing back together and have it running well. Engine looks to be original, no #s stamped on the pistons indicating an over bore.

 

[ScottinAZ]

You know that is odd, while there is some carbon build up on top of the pistons, the cyl heads/combustion chambers are pretty clean, cleaner than my old engine was when I took the cyl heads off. I am wondering if the electrode from that plug broke off and got caught between the valve and the seat? It is just an unusual failure. Here's mine from 2017.View attachment 394845
View attachment 394844
I think mine had more carbon build up and also corrosion from water in the cyls due to the blown head gasket.
Anyway I think you can easily get that thing back together and have it running well. Engine looks to be original, no #s stamped on the pistons indicating an over bore.

That’s what the general thought is. Brought the valve and plug into work and showed our bus mechanic, and he thinks the same. Wrong plug, torched electrode stuck in valve, and that’s all she wrote…. It’s a standard bore and judging by many clues, it’s never been opened before. This one will live again. Parts should be here later this week, and then the rebuild starts.

 

[ScottinAZ]

ok, so the healing starts today..... new valves, intake and exhaust came, along with some other parts.... Machine shops are backlogged for months, so these are just getting lapped in. Not the "best" way, but has worked for decades in many engines in the past. Will work "good enough" for this one for now. I may continue on looking for a set of actual "vortec" heads and a 4bbl manifold, and upgrade this engine later. Intake valve seals should be here tomorrow, so then I can reassemble this head and get it on the engine. Ill pull the second head in the morning, and lap those valves as well (or replace if needed).

seats cleaned up nicely, and valves show a good contact pattern, so this should be good to go for at least a little while.....

 

[ScottinAZ]

and a quickie of what I believe to be the root cause of the problem.... the wrong spark plugs..... no chance the plug on the left wasnt overheating...... with that many threads in the cylinder, I am lucky to have gotten all six out

 

[alldodge]

Now that you mention it the plugs do look long.
Should have AC MR43T, NGK BR6FS, Champion RV15YC4

 

[Lou C]

Looks like they were way too long. The pre Vortec heads took the short plugs while the Vortec heads took the longer ones.
Nice work there gotta love the simple Chevrolet small block!

 

[ScottinAZ]

yeah, I am going with Delco plugs in it, MR43T.... having the correct reach should be better all around. The old plugs were a Champion RS12YC, which indeed is a Vortec plug..... somebody done OOPSed that one....

On another note, the second head is off, and I am lapping in the valves for it now. Hope to have the engine put back together today or tomorrow. I dont like leaving it "open" and under a tarp.... too much crap can get into them.

 

[ScottinAZ]

well, both heads are off and cleaned... just waiting for the damn FedEx dude to show up with the valve seals and head gaskets.... then I can get that all installed..... I hate sitting on my hands waiting for shipments.... Life was so much easier when the parts houses actually stocked parts.....

 

[ScottinAZ]

and its starting to look like an engine again.... heads are on and torqued, rockers reinstalled, and the intake is just sitting in the valley (keeps crap outta the engine....) Ill install the intake tomorrow and run a compression test on #4 to make sure we have a good cylinder.

The carb kit should be here tomorrow, so Ill redo that before I reinstall it. Since its been a while since its been run, I figure a good once over is in order... transom kit also showed up today, so I can work on that as well until the carb kit arrives

 

[ScottinAZ]

well the engine is mostly back together... Still waiting for the exhaust gaskets to show up, along with the carb kit. A new starter should be here on Monday, as long as UPS doesnt keep it in Purgatory for any longer than they usually do....

Old starter is TRASHED.... brushes completely worn out, enough brush dust between the magnets to build a new set or three of brushes.... gear reduction is sloppy, main motor bearings are sloppy (armature hitting the magnets sloppy...) dust shield between the motor and gear reduction is RUSTED THROUGH..... yeah, no wonder this turkey wouldnt crank worth a damn.....
Im just glad its a PMGR type, and not the old direct drive Delco's like my other boat.. those SUCK to hang onto when starting the bolts.... and this one is less accessable than the 2.5 in the other boat.....