PCM 351 Cracked intake manifold |
Post Reply ![]() |
Author | |
stevejuststeve ![]() Newbie ![]() Joined: July-13-2018 Location: Edmond, OK Status: Offline Points: 5 |
![]() ![]() ![]() ![]() ![]() Posted: July-05-2024 at 1:43pm |
My friend inherited 79' MasterCraft S&S and asked me to help get it going. When I opened the motor cover the first thing I noticed is 3 of the 6 freeze plugs were sitting in the bilge
![]() I've never seen freeze plugs actually save a block from being cracked. Is it possible that replacing only the intake will fix it? Also I don't think I was able to fully seat the freeze plugs, as getting a good purchase on them is hard with the motor mounts in the way... Any suggestions are greatly appreciated. Thx!
|
|
![]() |
|
Jonny Quest ![]() Grand Poobah ![]() ![]() Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2937 |
![]() ![]() ![]() ![]() ![]() |
If the intake has cracks that go all the way through...then water intrusion into the lifter valley is very likely. At the very least, the intake should be removed and inspected. If you want to replace the intake, I would go with an aluminum (not cast iron) intake -- such as the Edelbrock Performer manifold. Should even pick up a few HP with a better intake.
Also...the term "freeze plug" my be incorrectly used. Those are really core plugs. Core plugs (aka Welch plugs) are used to fill the sand casting core holes found on water-cooled engine blocks. The term "freeze plug" was coined many decades ago out of ignorance of the true purpose of the core plugs - they were never designed to be displaced by water freezing inside the block. Displacement of a core plug is merely coincidental if water freezing inside the block does occur. JQ
|
|
Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
|
![]() |
|
stevejuststeve ![]() Newbie ![]() Joined: July-13-2018 Location: Edmond, OK Status: Offline Points: 5 |
![]() ![]() ![]() ![]() ![]() |
Thank you JQ. I appreciate the clarification on the welch plugs. I was thinking no water was entering the valley because of the condition of oil after running it, but perhaps it's a very small leak and hasn't emulsified the oil yet? The intake 100% needs to be replaced, I just wanted to try and be rather sure that this block was still good before putting any more money/time into it. Do you think that is a reasonable assumption being that the oil is still good after 30 mins of run time? Thanks a ton for your insight.
|
|
![]() |
|
KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 11015 |
![]() ![]() ![]() ![]() ![]() |
Whatever Jonny wants to call them.......... core, casting, freeze, frost, welch, multipurpose, butt plugs,.in non technical terms, they may have saved that block from freeze damage
![]() New brass ones are readily available and pretty cheap and will stay in better than a reused one that popped out. The ones with an engine mount or a starter motor in the way are easier to replace if you disconnect the driveshaft coupling halves and lift the front of the engine just enough to remove the mount. Then you've got yourself some working room The one above the starter is a lot easier if the starter is removed. Put the plugs in good and get some time on the engine so it's good and heated up, watching the oil and look for cracks on the exhaust manifolds along the bottom edges, since if somebody didn't drain the engine, maybe they didn't drain the manifolds either. Check the cylinders for any water by pulling the plugs and turning it over with the starter to see if any water comes out of any cylinder and look at the plugs too for water drops/wetness.
|
|
![]() |
|
MrMcD ![]() Grand Poobah ![]() ![]() Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3733 |
![]() ![]() ![]() ![]() ![]() |
Good advice so far Ken and JQ. As far as the term Freeze Plugs, In the engine aftermarket ALL of the suppliers identify them as freeze plugs. Our old Buddy Pete, who I hope is still tuning in always corrected us on the proper terminology. Sealed Power, Pioneer, Melling , Clevite all call them Freeze plugs. All the engine rebuilders I called on who buillt over 3000 engines per month used the same term so don’t feel like you called them wrong. Technically we are all wrong but in the industry EVERYONE UNDERSTANDS FREEZE PLUGS WHEN YOU ASK FOR ONE. Hope that helps. The new intake will be better looking, weigh much less and perform better. Running 30 minutes with zero oil in the water is a good test. Hope your block is good. If it takes 20 hours use to cause milk in the oil, change the oil and fix it someday when you are bored. Not mid summer when the boat should be in service. Just do not park it over the winter with water in the oil.
|
|
![]() |
|
stevejuststeve ![]() Newbie ![]() Joined: July-13-2018 Location: Edmond, OK Status: Offline Points: 5 |
![]() ![]() ![]() ![]() ![]() |
Thanks guys!
|
|
![]() |
|
MourningWood ![]() Gold Member ![]() Joined: June-13-2014 Location: NorCal Status: Offline Points: 915 |
![]() ![]() ![]() ![]() ![]() |
With first hand experience I second J Q's recommendation for the Edelbrock Performer intake. It adds a lot of much-needed pep to the bottom end.
|
|
1964 Dunphy X-55 "One 'N Dun"
'I measured twice, cut three times, and it's still too short!" |
|
![]() |
Post Reply ![]() |
|
Tweet
|
Forum Jump | Forum Permissions ![]() You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |