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Confused about 351W Reverse Rotation

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g13davis View Drop Down
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    Posted: April-24-2017 at 1:19pm
Alright, Here Goes :
   Some years back I bought my 1980 SN from an Estate Sale Auction. The Auctioneer stated the engine was stuck so I bought it cheap hoping for the best. I was able to talk to the previous owner who told me he had replaced the motor with a new Jasper LongBlock the previous year. He took it out once @ the end of the season and forgot to drain the water. He put it in his basement, his wife kept smelling gas ( from an apparent fuel line leak ) so to keep the peace he placed it outside in his barn for the winter. I'm sure everyone who reads this knows what happened. Yes the water froze in the block, and cracked the engine in the lifter galley from # 1 to # 4 cylinder.
    So once I determined the extent of the problem I proceeded to look @ my options for getting the boat back in the water. By the way the engine only had ( 5 ) hours on it.

1) Go to Jasper, offer to send the Engine back pay the charges for a rebuild if they could use my engine internals since they were essentially New. ( Didn't Work, was told they " Sell " engines Not " Rebuild " them, thought that was kinda funny ).

2) Buy a New Short Block

3) Find a Motor & Rebuild it

I ran across a 1986 Martinique that had a gash in the hull ( comparable to the Titanic ) because it had been run aground by some intoxicated folks. It had a PCM 351W Reverse Rotation just what I needed. I did the math and felt this was a viable option. So, I proceeded this winter to dismantle the boat, save what I could sell, and start the engine swap process. I did some tests ( Compression & Oil Pressure ) and decided while I had it out I would just go ahead & rebuild it. Here's what all this has been leading up to. I have had the engine @ the Machine Shop, Punched it .040, Hot Tanked, Pressure Tested, Crank Polished, Decked, Cam Bearings, etc. I'm ready to start my reassembly, and I started running into issues The parts house I ordered the rebuild kit from told me they didn't have kit for a one piece rear main marine engine, the timing chain was different, wasn't sure about the oil pump, and I would need special marine gaskets. So I'm Digging for answers now.   I have been researching this Website for answers, but thought it might just be easier to ask. Sorry All that just to get to my questions.

1) I have looked and measured the Crank, no swirls on rear main area, and I cant see anything that would require some sort of directional seal.

2) I know the camshaft gear & distributor gear are reverse, but does this affect the timing chain ?   The timing chain gear does have a different casting # than an automotive gear.

3) Oil Pump ( Standard Automotive or Some Special Reverse Rotation )
      The Kit I ordered came with a Melling ( M 83 )

4) I bought Sealed Power ( H336CP ) Hypurtectic Flattop Pistons & Steel Rings
   I saw people saying the Ring Gap Clearances are different because the cooling system isnt Closed Loop. ( Truth or BS )       

5) I had the Pistons pressed on the Rods in the Normal Orientation, but I've read Posts   were people say they need to be pressed on reversed because of the Wrist Pin Offset.

I'm a Tool & Die Guy by Trade & have worked on Engines All my life, but this is my 1st Reverse Rotation boat engine & quite possibly my last.

Sorry for the Long & Exhausting Post, but I need some answers from People who know.
The River here in Tennessee comes up the first of May so my Family is Pressing on me Pretty Hard. Thanks for Advance any Advice, Opinions, Posts for Reference or Comments.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote GlassSeeker Quote  Post ReplyReply Direct Link To This Post Posted: April-24-2017 at 1:39pm
You've come to the right place... I don't know the answers but all of your questions will be answered,..Be patient
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flyweed Quote  Post ReplyReply Direct Link To This Post Posted: April-24-2017 at 4:02pm
Welcome....Glad you posted your questions..the guys here will NOT lead you astray. Take the advice that comes your way...you'll have that engine up in no time. The guys here are awesome!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-24-2017 at 5:31pm
Hi I'll give you my thoughts on your engine

1   Since that's an 86 engine it has a one piece rear main seal. The helix or wick lines are in the seal, so you need a one piece RR main seal. They're about as common as hen's teeth

2   The timing chain and gears are the same no matter which way your 351 rotates

3   That's a standard Melling oil pump. Works for either rotation also

4    Here's where you'll get all kinds of answers/opinions. Some people will tell you that a marine engine has looser clearances than it's automotive counterpart, others will say they're the same. A Ford manual for an automotive 351 and a PCM, Mercruiser, and Volvo Penta manual all have the same specs for piston clearance, ring gap etc with a range on those specs. I'd check with your piston manufacturer to get their specs for clearances since they're not OEM pistons and use their numbers. Plenty of people running same clearance as an auto engine and just as many running loose and they both run.

5    I've had PCM 351's of both rotations apart and the pistons were oriented the same way.
In a picture of your pistons the reliefs look the same, but there's nothing like an up close personal look to verify that the reliefs are the same. You could also ask the manufacturer when you ask about piston clearances.

Good luck with the reverse rotation 1 piece seal, do a search on here and you may find a recent post about somebody finding one that's actually in stock. You can find some on websites and when you try to order they may be out of stock (for a long long time)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fl Inboards Quote  Post ReplyReply Direct Link To This Post Posted: April-24-2017 at 6:06pm
Right hand rotation Ford 5.8 /351-W rear seal, PCM # RO47041A 1983 on $109 Each. How many do ya want??
Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-24-2017 at 6:10pm
Originally posted by Fl Inboards Fl Inboards wrote:

Right hand rotation Ford 5.8 /351-W rear seal, PCM # RO47041A 1983 on $109 Each. How many do ya want??


Now that's fast help right there
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g13davis Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 6:45am
Dang, now Ain't that some service. A same day post to answer my questions, and a same day post with a source for the part I need. Like Flyweed Posted, you guys are Awesome ! Keno, Thanks for the much needed info. it is much appreciated. Its all becoming a bit clearer now, I take it the seal is made directional to persuade the oil back into the sump due to the engine angle I assume.
Whatever the case, Fl Inboard, Thanks to you also for the response, I will be contacting you hopefully tomorrow to get one of those Seals on the way here to Tennessee. Thanks Again to everyone, Awesome Site, And there WILL be more Questions !
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 8:47am
Originally posted by g13davis g13davis wrote:

Dang, now Ain't that some service. A same day post to answer my questions, and a same day post with a source for the part I need. Like Flyweed Posted, you guys are Awesome ! Keno, Thanks for the much needed info. it is much appreciated. Its all becoming a bit clearer now, I take it the seal is made directional to persuade the oil back into the sump due to the engine angle I assume.
Whatever the case, Fl Inboard, Thanks to you also for the response, I will be contacting you hopefully tomorrow to get one of those Seals on the way here to Tennessee. Thanks Again to everyone, Awesome Site, And there WILL be more Questions !


With oil being splashed in the area of the seal, even if the engine was level you'd still need the lines in the seal. A normal rotation engine has the lines in the seal going in the opposite direction.

But like you said, it helps keep the oil in the sump and out of the bilge
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldcuda Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 9:47am
Ring gap is different but not because of cooling system. The engine is under more load thus more expansion so running auto specs on rings will cause taking out top ring landing. Check with ring manufacturer for proper ring gap for marine use.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 10:37am
These guys are all over it.   Piston to wall clearance is also important, but don't get too crazy. Generally the piston manufacturer should provide a range of recommended clearances for marine use, depending on the type of piston and its design it will expand/warp differently under consistent loading.   In my experience unless you run towards the low side of the automotive specs you tend to be ok. It is rare to stick a piston, but I have scuffed them up pretty early - I have also had the ring end gap close up enough to score a line in the cylinders.   With conservative tuning even a tight engine might break in and run well forever, a looser engine might let you survive a tune that is a bit more lean or with a bit more advance. - its a balance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmasariu Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 11:44am
Is this what he needs, seems applicable and affordable @ $27.99...

RR Rear Main Seal
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g13davis Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 12:11pm
Man its amazing how much clearer the Muddy water gets when you get the right answers from the right sources. Thanks again for all the info. Things are beginning to add up now.
I was thinking along the lines that if the Ring Gaps were different they would lean to the looser side because of the load a boat sees vs. automotive. I guess I need to get in contact with Sealed Power about my Piston to Wall Clearances in a Marine Application, Mahle about recommended Ring Gaps, and go back and check all my clearances. I guess the only thing I still have to decide on is Timing Chain. Since it is Standard, and I'm NOT a big fan of the Plastic Gear OEM Chains, what about a Double Roller Indexable Chain like used in Automotive ?

1) Will it physically fit ?

2) Does it have any advantages, like advancing the timing +4 deg. to improve Low End ?
    ( Isn't that the goal for these boats anyway, Torque )

3) Or is it overkill and not worth the money or effort ?

As Always Thanks in Advance, and Man I wish I had used this site ( 5 ) years ago when I registered. I've got more info. in ( 2 ) days than ( 4 or 5 ) years of feeling like an idiot trying to do it on my own.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-25-2017 at 1:04pm
Originally posted by mmasariu mmasariu wrote:

Is this what he needs, seems applicable and affordable @ $27.99...

RR Rear Main Seal


Sure looks right, if it's in stock

My Ford manual and the marine manuals mentioned earlier had the same specs for piston to cylinder clearance and for ring gaps also just as a point of interest. In other words there was no difference in specs .Like everybody says check with the manufacturer on clearances.

Double roller chain and gears are no problem at all but if you start playing with advance and retard keys etc. remember things are turning backwards. I'd say don't get fancy just a decent double roller chain and gear set or a silent gear and chain set without the nylon coated teeth.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g13davis Quote  Post ReplyReply Direct Link To This Post Posted: April-26-2017 at 10:58am
M Masariu, Thanks alot for the Seal Link, I will definately check that out and let everyone know.
Keno, once again Thanks for the Info. Simple Double Roller it is.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shierh Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2017 at 3:51pm
The one piece seal is available. I found a source and its on one of my prior posts when rebuilding mine.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2017 at 4:07pm
[QUOTE=shierh] The one piece seal is available. I found a source and its on one of my prior posts when rebuilding mine.   [/QUOTE

You're about a month late, the place you referred to in previous posts was Alex's Parts and mmasariu put up a link to the same seal a handful of posts back in this thread
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shierh Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2017 at 4:18pm
Not been on for a while.

The seal from Alex's Parts was also a quality part.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2017 at 4:25pm
Good for people to know it was a quality part from somebody who's actually used it.

At that price I'd have a spare hanging around if I had a later RR Ford.

Don't know if g13davis ever got one
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