Marine 440 heads

[Glenwood]

Might be the wrong forum for this but maybe some of you guys have some experience with marine motors.
I sold a set of 906 heads to a guy last night that was desperate for a quick fix for one of his charter vessels. His 38' boat has twin early 70's 440's and he started having trouble with one engine. On one occasion, he blew out a spark plug and then on another he cracked a head at a spark plug. He knows nothing about mopars or engines in general but this 440 had 906 heads with odd looking exhaust valve retainers. I was thinking he should search for RV heads for extra plug cooling like a 213, but he insisted on swapping with 906 heads on the advice of his mechanic.
What sort of event would blow out a spark plug? Over revving?
I assume the engine over heated leading to the cracking, but I was wondering if there's other causes.

 

[badlite]

Never had that problem with a 440, that is something ford engine do but not a common problem on Mopars.

 

[Daves69]

Worn out, corroded, and/or stripped plug hole taps would be my guess.

 

[Glenwood]

Worn out, corroded, and/or stripped plug hole taps would be my guess.

actually, the center of the plug blew out. The guy brought the heads over to compare and they're like new, definitely no corrosion.

 

[Daves69]

Maybe cracked the insulator on install or faulty assembly from manufacture. Any water found in the cylinder?

 

[cryplydog]

I had a flat bottom drag boat with a well developed 440 that I had trouble moving and keeping enough water in the heads and as a result the head gaskets and cracked heads would result after a few runs. So I came to the conclusion after several years of this that as I was up and on top of the water at about 70 to 100+ mph this would occur and suck in river water and instead of having hydraulic lock at rpm it just blows the plug out as a primary result. So, with many years of inboard, V-drive and jet boat experience in high speed/horsepower use tells me this guy has a coolant problem strait forward and needs to check it from beginning to end. the old cam driven water pumps we had back then were just inadaquat even after (working) them from intake to exhaust on the entire system. A lot of crud also finds its way into the block and settles creating confusing probs. too. Basic maint. on older boats in this area is very important and needs frequent checking.

 

[Glenwood]

I was thinking the guy should be using RV heads which are probably the same as marine. My 413 rv block has the extra passages in the casting which I'm guessing his 440 does. He brought the heads and intake over to compare and they were spotless, like they were just rebuilt. So unless the block passages are blocked, he may have had some other water circulation issue.
Anyway, I haven't heard back from him so I guess he's back in business, at least until those 906 heads fail...

 

[dieseldazzle]

He would have had exhaust valve rotators (funny looking retainers) versus not having them on the 906 heads tho I have seen several sets of rv head that have been rebuilt and for whatever reason the exhaust valve rotators were tossed

 

[Meep-Meep]

I had a flat bottom drag boat with a well developed 440 that I had trouble moving and keeping enough water in the heads and as a result the head gaskets and cracked heads would result after a few runs. So I came to the conclusion after several years of this that as I was up and on top of the water at about 70 to 100+ mph this would occur and suck in river water and instead of having hydraulic lock at rpm it just blows the plug out as a primary result. So, with many years of inboard, V-drive and jet boat experience in high speed/horsepower use tells me this guy has a coolant problem strait forward and needs to check it from beginning to end. the old cam driven water pumps we had back then were just inadaquat even after (working) them from intake to exhaust on the entire system. A lot of crud also finds its way into the block and settles creating confusing probs. too. Basic maint. on older boats in this area is very important and needs frequent checking.

Very interesting. Lucky for you there was a safety pop off valve (spark plug!). One thought to the OP or anyone in general dealing with boats regarding this cooling issue is to install a pressure gauge with a range of about 20 PSI in the cooling system. I did this on my jet boat and was happy to see a reading at full speed of 15 PSI. With an efficient pump this can be well over that, or in the case of your flatty, not enough?

- - - Updated - - -

I had a flat bottom drag boat with a well developed 440 that I had trouble moving and keeping enough water in the heads and as a result the head gaskets and cracked heads would result after a few runs. So I came to the conclusion after several years of this that as I was up and on top of the water at about 70 to 100+ mph this would occur and suck in river water and instead of having hydraulic lock at rpm it just blows the plug out as a primary result. So, with many years of inboard, V-drive and jet boat experience in high speed/horsepower use tells me this guy has a coolant problem strait forward and needs to check it from beginning to end. the old cam driven water pumps we had back then were just inadaquat even after (working) them from intake to exhaust on the entire system. A lot of crud also finds its way into the block and settles creating confusing probs. too. Basic maint. on older boats in this area is very important and needs frequent checking.

Very interesting. Lucky for you there was a safety pop off valve (spark plug!). One thought to the OP or anyone in general dealing with boats regarding this cooling issue is to install a pressure gauge with a range of about 20 PSI in the cooling system. I did this on my jet boat and was happy to see a reading at full speed of 15 PSI. With an efficient pump this can be well over that, or in the case of your flatty, not enough?

Oh, and those funny exhaust valve retainers are probably valve rotators. I'd leave them on there.