318/392 Stroker Motors

EWRice
Royal Aluminum Star
Posts: 319
Joined: Thu Feb 04, 2016 12:37 pm

Re: 318/392 Stroker Motors

Post by EWRice »

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
Site Admin
Posts: 885
Joined: Fri Jul 11, 2014 9:15 pm

Re: 318/392 Stroker Motors

Post by jralbert »

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
Royal Aluminum Star
Posts: 319
Joined: Thu Feb 04, 2016 12:37 pm

Re: 318/392 Stroker Motors

Post by EWRice »

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
Site Admin
Posts: 1521
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: 318/392 Stroker Motors

Post by Fastjeff »

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
Aluminum Star
Posts: 174
Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Post by Trowerpower »

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
Aluminum Star
Posts: 174
Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Post by Trowerpower »

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
Trowerpower
Aluminum Star
Posts: 174
Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Post by Trowerpower »

Happy New Year! Spring is just around the corner. In Tennessee. Our marina was building new docks, no place to park the boat in the yard until now. Hope to pull her out of the water to repair the port motor blown head gasket in the next few weeks. We believe something is not flat, head or block. While she is out of the water we will clean and paint the bottom as needed. Also will install the 4 blade props I bought a few years ago. I will update this post as we move forward.
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
Site Admin
Posts: 1521
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: 318/392 Stroker Motors

Post by Fastjeff »

Use a straight edge and a thin feeler gage across the block surfaces. If you see any gap you'll have to resurface it.

Good luck! (One of my favorite big M projects.)

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
Trowerpower
Aluminum Star
Posts: 174
Joined: Sun Dec 07, 2014 8:50 pm
Location: Northern Kentucky

Re: 318/392 Stroker Motors

Post by Trowerpower »

Hey Jeff! Thanks! Will post an update soon!
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
legendlc
Aluminum Star
Posts: 181
Joined: Tue Mar 01, 2016 6:50 pm

Re: 318/392 Stroker Motors

Post by legendlc »

Just about finished with a head job myself on a 440. Good luck. I purchased a project boat that had a apparently blown head gasket. Or at least the empty heat exchanger milky oil and a couple of cylinders full of antifreeze led me to that conclusion. I have everything back on except the exhaust bellow's. Getting the manifold on by myself was a chore. But as Jeff said a nice metal straightedge and feeler gauges are your friend. My deck and head both checked okay but I had some valves that needed reseating and one exhaust valve replaced. So I had the head machined while there. Good luck and I hope spring hits Kentucky soon as well.
1978 37 Double Cabin
Lake Cumberland KY
Post Reply