RE: new longblock in 1990 454 Mercruiser fresh water cooled gas 330hp 7.4l - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-14-2010, 06:23 AM
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RE: new longblock in 1990 454 Mercruiser fresh water cooled gas 330hp 7.4l

ok, here goes-I confess I'm a boater with a Sea Ray 350 Sundancer 40' LOA with twin Mercruisers. But I'm having a real problem that maybe you guys who really know engines can help me with anyway since I'm getting nowhere with fellow boaters!

I went ahead and had new reman longblocks installed last year, did the 10 hour break-in and had them adjusted and checked. Now with 16 hours on them one of the holes in the port engine is not getting oil to the push rod (only a little spurt now and then).

Had a new push rod assembly and lifter installed and still doesn't work. No one can figure out why.

I suppose it could be something like an obstruction or a lifter that was not adjusted properly to begin with?

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Old 05-14-2010, 06:18 PM
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Welcome to the site, We have several boaters on here post in the engine section or check out our lounge.


Cole
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Old 05-15-2010, 04:08 PM
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Quote:
Originally Posted by express cruiser
ok, here goes-I confess I'm a boater with a Sea Ray 350 Sundancer 40' LOA with twin Mercruisers. But I'm having a real problem that maybe you guys who really know engines can help me with anyway since I'm getting nowhere with fellow boaters!

I went ahead and had new reman longblocks installed last year, did the 10 hour break-in and had them adjusted and checked. Now with 16 hours on them one of the holes in the port engine is not getting oil to the push rod (only a little spurt now and then).

Had a new push rod assembly and lifter installed and still doesn't work. No one can figure out why.

I suppose it could be something like an obstruction or a lifter that was not adjusted properly to begin with?
Did you see the lifter that came out? I'm suspecting that if the problem remains on the new lifter that the cam wiped a lobe. The oil that moves up to the rocker is pulsed by the movement of the lifter, if the lobe is wiped there is little to no movement, thus little oil.

My opinion, for what its worth, is that the Remain rebuilds are just not up to my quality standards, they're usually OK for a grocery getter car, but a boat is a whole 'nother deal. Boat engines work hard all the time even when cruising, therefore, automotive type rebuilds just aren't strong enough. But that aside, flat tappet cams these days are a PIA, the changing chemistry in motor oils has reduced or eliminated ZDDP for environmental reasons. This chemistry is what made high loading between the lobe and flat lifter possible. It's loss is why the OEMs went to roller cams starting back in the 1980s. This is a message that should be taken to heart. The best you can do is run aftermarket additives in the oil, but where most people get burnt is too much ZDDP isn't a good thing. About 400 to 700 parts per million is the proper mixture, less than 400 too little, more than 700 too much and your problems reappear when you think you're doing right by the camshaft. Moly additives are nice and do good work but the filter eventually snatches 'em so it's an additive with a fairly short useful life. Still if you increase the filter replacements to maybe 2 or 3 to an oil change period and keep doping the oil with moly at the filter change, this can be made to work.

Boat engines, especially those using pond water for cooling vary operating temps too much, again my opinion. The Delta T is much greater than that seen with closed cooling systems which too often results in too little flow thru the engine such that while total coolant temps look OK, in specific hot places there is boiling which allows for local overheating. I much prefer to see a closed cooling system and a coolant to water heat exchanger on the hull. Yes it costs a couple knots but the engine's are lot happier as you can really rope the op temp to tight band around 180-200 degrees and keep it uniform in detail. On the other side of cooling is that boat engines run quite a bit of heat in the lube oil. Having an engine oil temp gauge is a good thing and if they hold over 220 in the sump adding an oil cooler adds a lot of life to the motors.

Bogie
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Old 05-15-2010, 05:14 PM
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Possible causes:

Exccessive distributor body to engine block distributor hole clearance.

Blocked lifter oil gallery. Excessive lifter bore clearance, another faulty lifter.
(after market flat tappet lifters seem to be getting crappier since OEM's no longer use them in OEM engines.) OEM's have the volume buying clout to insist on a certain quality on these critical OEM parts or make their own in house.
Many of the replacements are made off shore now. Many of the off the shelf replacement and popular high volume high perf cams that are sold in volume are also made offshore now. EG: Comp cams sells more XE cams than it could ever hope to produce in house. Someone is makeing all these XE 268 cams and most likely at the cheapest cost.
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Old 05-17-2010, 05:22 AM
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many thanks

Thanks guys for the suggestions. I'm taking them to my yard owner and see where we get with this problem.
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Old 05-17-2010, 07:05 AM
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Quote:
Originally Posted by express cruiser
Thanks guys for the suggestions. I'm taking them to my yard owner and see where we get with this problem.
A vacuum gage check will show you if there's a wiped lobe. You DO have flat tappet cam and lifters, and not an OEM roller, right? Is there any noise like ticking associated w/the rocker/p-rod?

I'd also suggest you see what the oil pressure is under varying conditions/RPM to see if there's a problem w/how much pressure is being supplied. And for peace of mind.

If you have an adjustable valve train (net lash started in 1991, I believe), you can try using a different preload setting. Sometimes increasing the preload is all that's needed to restore flow. It could possibly have too much preload, for that matter.

Has the oil flow been checked w/the engine at 2000- up RPM to see if the flow increases w/RPM?

If you have a "net lash" valve train, the preload isn't adjustable. If the preload is incorrect, you will need either different length push rods or convert the valve train to an adjustable set-up.

I would also check to see what the geometry looked like. This is adjusted w/different length p-rods, like the preload on a net lash system. If the valve train's adjustable, the preload doesn't require a p-rod length change, but to adjust the geometry, the p-rod is still changed.

Last edited by cobalt327; 05-17-2010 at 07:14 AM.
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