318/392 Stroker Motors

EWRice
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Joined: Thu Feb 04, 2016 12:37 pm

Re: 318/392 Stroker Motors

Postby EWRice » Thu Sep 05, 2019 2:38 pm

It sounds to me like you have a warped head/block or are developing a hot spot in the head or block between those two cylinders. I have read that the later 318 blocks had substantially thinner cylinder walls compared to the early blocks. Can I assume you have a .040" over bore to get to 392ci? It is possible too that over torquing the head bolts has distorted the block in that area. A picture of the failed gaskets would be helpful. Also, do you have any pictures of the combustion chambers in the head that failed the gasket?
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

jralbert
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Posts: 677
Joined: Fri Jul 11, 2014 9:15 pm

Re: 318/392 Stroker Motors

Postby jralbert » Thu Sep 05, 2019 3:08 pm

I know you are not looking at overheating as an issue but the post above referring to a "hot spot" raises the question again - is it possible coolant isn't getting to that part of the engine? I recall that with engines on a slant, the fwd end doesn't get all the coolant it needs at times.
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

EWRice
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Posts: 304
Joined: Thu Feb 04, 2016 12:37 pm

Re: 318/392 Stroker Motors

Postby EWRice » Fri Sep 06, 2019 1:22 pm

About the only way coolant won't flow to a certain part of the block is if you develop steam pockets under the deck. The old 400 chevys had special steam holes drilled between block and head to minimize this. Coolant only enters the block through one spot on each bank, but flows around the cylinders and up through the deck into the head. Then out the front to the intake, t stat, etc. It is odd that a hot spot would develop between 1 and 3 as they get coolant first. Unless there is an issue with gasket or head port matching (which i have seen on chryslers using heads and blocks across different years). I would take a really close look at the deck and head surfaces with a VERY high quality straight edge and feeler gauges. Then triple check ALL ports, block and head, with a new gasket.

This is more interesting than an Olds 403 that had the cam installed 30 degrees off. Tore my hair out on that one for quite a while.

Good luck
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

Fastjeff
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Posts: 1198
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD
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Re: 318/392 Stroker Motors

Postby Fastjeff » Sat Sep 07, 2019 7:19 am

That 9.8:1 seems a bit high for 89 octane gas. I assume that's what you're running on (since only millionaires can afford the 92 stuff).

Also, look for light under the straight edge using a mini flashlight.

Good luck! Yours are my all time favorite Marinette repowers.

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

Trowerpower
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Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Postby Trowerpower » Sun Sep 08, 2019 10:10 pm

Most of the marinas on Norris Lake have 93 octane fuel made by Phillips 66. I believe they call it valvetech. It has no ethynol. Thanks for all the comments! Starboard engine is still running 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

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

Re: 318/392 Stroker Motors

Postby Trowerpower » Sun Sep 08, 2019 10:20 pm

The blocks were bored .030 over and there is a rotating assembly from Scat Enterprises including, pistons, rods and a forged crank. Custom ground cams and Scorpion roller rockers.
The valves were enlarged slightly to help it breath better. 750 edlebrock carbs stock intake.
My e mail address is gregstarks57@gmail.com i will share photos of the last time it was apart.
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