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DP 570 antifreeze in Bilge

Q

quint

Contributing Member
91 DP 570 FW cooled. leaking antifreeze into bell housing assume its rear freeze plugs or worse cracked block..will only leak under load...no coolant in oil. wont know til haul out and engine pulled. Other problem is port side head notice antifreeze coming from 2 bottom head bolts above engine mount. Used dye test with uv light to verify this. Once again only under load. I had my heads redone by machine shop this summer because a intake valve on Cyl #1 failed. Heads were not warped prior to this and machine shop they were flat not warped. Boat runs and sounds great just pissing coolant from bellhousing and these 2 head bolts not gasket mating area. Could let cool down add more coolant and make short run again before losing to much coolant..nothing in oil, never overheated it, no smell of coolant from exhaust or sheen in water?? Marine mechanic put heads on used proper torque specs and pattern..new gaskets..Any ideas? Advice?
 
The head bolts on a Chevrolet small block should get sealer on the threads because some of them dead end into cooling passages, you can use Merc Perfect Seal, Evinrude gasket sealer or Permatex Aviation. The other problem could be a rusted core plug...too bad you have to pull the engine to fix but if so then you can attend to a number of other things at the same time...
 
louc said:
The head bolts on a Chevrolet small block should get sealer on the threads because some of them dead end into cooling passages, you can use Merc Perfect Seal, Evinrude gasket sealer or Permatex Aviation. The other problem could be a rusted core plug...too bad you have to pull the engine to fix but if so then you can attend to a number of other things at the same time...
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we did use thread sealer on all bolts black RTV. What is a core plug?
 
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all used new head bolts too. I questioned black RTV my self put me made sore all passages and dead ends where head bolts go were wire brushed out and cleaned..im just at a lost here. Since engine will be yanked I do need more torque and hp was pondering vortec long blockbut would like the D cup pistons and pressed in satellite exhaust seats. Saw option form Michigan Mortorz for 96 and up that will says it will work..but im worried about my DP-A gear ratio of 1:95:1. I want to achieve maximum bottom end torque and hp while not blowing out drive. Whats a re-gearing option of drive to handle this?
 
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quint said:
all used new head bolts too. I questioned black RTV my self put me made sore all passages and dead ends where head bolts go were wire brushed out and cleaned..im just at a lost here.
In my opinion, RTV was not the best choice for this.

Since engine will be yanked I do need more torque and hp was pondering vortec long blockbut would like the D cup pistons
With the Vortec cylinder heads, the correct piston would be a LCQ style and of the correct dish volume.

and pressed in satellite exhaust seats.
Saw option form Michigan Mortorz for 96 and up that will says it will work..but im worried about my DP-A gear ratio of 1:95:1. I want to achieve maximum bottom end torque and hp while not blowing out drive. Whats a re-gearing option of drive to handle this?

Stay with the 1.95:1 with the 5.7L SBC.
You could do the 1.78:1 with a properly build 6.3L SBC.

It is typically NOT cost effective to change the gears/bearings out for a change in reduction.
Best option is to find a good used lower unit in the ratio that you need.

What is a core plug?
That is in reference to the plugs that seal off the casting holes.
Technically these are casting core plugs or welsh plugs.
In a misnomer fashion, they are sometimes called "freeze" plugs.
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quint said:
Thanks Ricardo...do you know what a max hp rating would be for 1:95:1 gears?
The 1.95:1 gear set uses a smaller drive gear, of which makes them not quite as stout as the 1.78:1 set.
As for max rating... no, I do not know that. Rest assured that they are correct for a small block engine.

this vortec small block says is rated for 315 hp if using the edelbrock intake. I just bought edlebrock 1409 carb this season.
The first of the Marine version 5.7l SBC Vortec engines were rated at/near 5,300 RPM.
That's an RPM that we would never cruise at.
Realistically, and with these using the GM Full Dished pistons, your usable horse power will be near 260.
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