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Merc. 420 eng. ?

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Old 12-14-2004, 09:41 PM
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Question Merc. 420 eng. ?

What's the scoop on them? Did they have a crank case PSI. problem?,I was told it is normal for them to blow the dip stick up about an inch at WOT.

I have a friend that is looking at a set for his 90 Scarab that has about 1000 Hrs on old 454 mags. For the price he can get the motors for it will be cheaper that rebuilding his, he may have a crack somewhere ( milky oil ) in one motor.
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Old 12-15-2004, 08:27 AM
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Default Re: Merc. 420 eng. ?

nobody knows anything?
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Old 12-15-2004, 08:32 AM
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Default Re: Merc. 420 eng. ?

I had one in my old Formula and never had any problems what so ever. They have all the good parts in them (internals) and historically were great reliable engines.

Craig
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Old 12-15-2004, 08:32 AM
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Default Re: Merc. 420 eng. ?

No big block should have that much crankcase pressure. It's usually caused by blowby past the rings. That engine would have to be torn down and inspected, possibly rebuilt.
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Old 12-15-2004, 08:33 AM
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Default Re: Merc. 420 eng. ?

Mine are 420's. 19 years and going strong.
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Old 12-15-2004, 08:54 AM
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Default Re: Merc. 420 eng. ?

I had this problem on my 454ci 400's that was about 3 years ago ... they dont do it now but they are pretty tired. hope that helps
-Brad
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Old 12-15-2004, 09:10 AM
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Default Re: Merc. 420 eng. ?

Lapse...

Rings were obviously worn or some restriction must have been
present in the vent system to have oil out the dipstick. I have seen
oil present in the bottom of a distributor upper housing before, but
it was due to the owner having changed the valve covers and not
installed proper breathers.

I just freshened a set of HP 420'Sfor a person that had one wipe a cam
lobe out, but everything else was in great shape at 600 hours. Cam shaft
was just a random case since the lifters looked acceptable, and the other
motor's cam was re-used after all the lobes were inspected.

These are great pieces for what they were designed to do.

OR
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Old 12-15-2004, 10:24 AM
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Default Re: Merc. 420 eng. ?

These were great motors! The 454 cubes and the internal performance upgrades to produce this Merc 454/420 hp was a perfect mate to the TRS.The Gil Exhaust, and Crane guts along with the raspy sound of healthy power, is absolutely awesome. I am sure Arronow was proud to be running the iron.
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Old 12-15-2004, 01:28 PM
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Default Re: Merc. 420 eng. ?

The guy told him Merc. said they all do it and to put springs on the dip stick to hold it down they only have 206 hrs on them he says, but I don't tink they should be doing this or that merc. would say to put springs on to hold them in.
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Old 12-15-2004, 02:02 PM
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Default Re: Merc. 420 eng. ?

Quote:
Originally Posted by Lapse of Reason
The guy told him Merc. said they all do it and to put springs on the dip stick to hold it down they only have 206 hrs on them he says, but I don't tink they should be doing this or that merc. would say to put springs on to hold them in.
My Formula 357 did that and it did have the springs on the dipsticks to hold them down. I eventually had to replace the engines with 454/425's from GM after I filled one of them full of water from a cracked head and leaking head gaskets
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