318/392 Stroker Motors

Trowerpower
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Re: 318/392 Stroker Motors

Postby Trowerpower » Mon Aug 12, 2019 7:12 pm

Well, i have bad news, the port motor has blown another head gasket between cylinder one and three. This is the third one. She will run up to 4,000rpm and then backs off to 3200rpm. No water in the oil thank you Lord. Will probably pull the motor, check for worpped heads and block and try it one more time. Starboard engine still running like a watch.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set

jralbert
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Re: 318/392 Stroker Motors

Postby jralbert » Mon Aug 12, 2019 10:44 pm

Do you have overheating, freq cause of blown gaskets, going on?
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

Fastjeff
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Re: 318/392 Stroker Motors

Postby Fastjeff » Tue Aug 13, 2019 7:24 am

Groan!

In my case, when Mr. Port blew its head gasket, the block was"'fire slotted" (to quote the machine shop) and needed the block milled to eliminate it.

Hope that's not the case here.

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington

Trowerpower
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Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Tue Aug 13, 2019 8:02 pm

I do not believe the overheating caused the blown head gasket. I believe its the result of a blown head gasket. It started at 160 then fluctuated between 160 and 200. Yea it went to 220 but only momentarily. It runs/starts well, only under wot does it start stumbling. Only further disassembly will tell the story after Labor Day.. Bummer. I think a head is warped or block deck is the culprit. The stroker kit has nothing to do with it as cylinder pressures are not above 160. No hot spots on the block or exhaust manifolds.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set

Trowerpower
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Posts: 158
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Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Wed Aug 14, 2019 8:25 pm

Engine builder will disassemble, diagnose and repair after boating season is over. Taking the entire motor to him.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set

Fastjeff
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Re: 318/392 Stroker Motors

Postby Fastjeff » Fri Aug 16, 2019 7:10 am

With those ARP bolts, you can safely add another 10 ft-lbs. to the torque requirements. Be sure the threads in the block and nice and clean, and use lots of oil.

Jeff

PS: Good luck on this, my favorite Marinette power source!
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington

Trowerpower
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Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Thu Aug 29, 2019 9:39 pm

We hope to pull the boat out of the water mid September to pull the port motor.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set

EWRice
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Re: 318/392 Stroker Motors

Postby EWRice » Fri Aug 30, 2019 12:33 pm

This has been an interesting thread. I have always been one to modify and "upgrade" things to see what can improve, or grenade. Reading through all of the posts I have a few questions for you.
1 do you have any pictures of the blown head gaskets? How a gasket fails tells a huge story.
2 what is your compression ratio? The 160psi reading makes me think you bumped the ratio during the build.
3 what base timing are you running and what is your full advance timing and at what rpm? This plays a huge factor in performance and longevity and is affected by question 3.
4 what year are your engine blocks? Chrysler had different series of blocks cast over the years and like most auto companies started lightening blocks in the mid to late '70s (Olds v8 is a perfect example of this. Less nickle in the iron and started casting windows in the main webs, thinner cyl, deck, etc.).

I have been reading some of the technical info on the stroker builds for a 318. There is some very detailed info on what goes into building these engines and what it changes about the engine. The questions above will give me a better idea of what could be going on inside your engine.
Muskegon Lake
1972 32' Express flybridge
"AL13"
Twin 318s
On board air & prime 920
1963 Thompson Super Sea Lancer
Graymarine 327
1961 Alumacraft 12'
'55 10hp Johnson

Trowerpower
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Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Tue Sep 03, 2019 8:58 pm

Yes I have pictures, 9.8 to 1 is the compression ratio., it's failing between no. 1 and no.3. The plugs are rich, running a HE I type distributor will have to check my file on timing. Starboard motor is doing great. Gapping plugs at .055. 93 octane marine gas. RAP HEAD BOLTS NEW THE LAST TIME ASSEBLED the heads. Fel Pro marine gaskets.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set

Trowerpower
Aluminum Star
Posts: 158
Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Tue Sep 03, 2019 9:01 pm

155 was the highest cylinder pressure in the starboard motor that still runs great.
Trower Power
1987 32ft Marinette Sedan Flybridge
Blue Sky
twin 392 Chrysler Stroker Motors
Performance Distributors
750 Edlebrocks
fresh water cooled
1.5 to 1 velva-drives
Onan 6.5kw gen set