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  1. #1
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    Tech specs of late inlines.

    Donīt know if anybody is really interested in this kind of information but I think at least Mk75H indicated, some days ago in another thread, that he might be. So here are my numbers, porting and compression, taken some time ago while building a spare powerhead for my 1988 Merc 115.

    Exhaust ports opens / closes: 96 deg ATDC / 98 deg BTDC

    Exhaust open period: 166 deg

    Main transfer ports opens / closes: 114 deg ATDC / 116 deg BTDC

    Main transfer open period: 130 deg

    Blow down period: 18 deg

    Diameter of exhaust ports: 22 mm (7/8" nominal?)

    (Sorry to say I didnīt check the Power Port values or height of main transfers.)


    Geometric compression ratio: 10,15

    Trapped compression ratio: 6,84

    Geometric comp ratio with high deflector pistons: 10,47

    Trapped comp ratio with high deflector pistons: 7,04



    This will probably be a long posting, so in fear of loosing it all into cyberspace, I do it in parts.

    PL

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    Some notes on my previous post:

    The block in question used for my rebuild came from a 1984 115. Block p/n is 852-8310A4 and s/n is 6479527. These 8310A4 blocks were used from the first 1979 1/2 140 ADI engines and all the way up to the last 1988 115.

    My timing numbers are based on opening points where the ports are just about to open but have not yet opened (same with closing numbers). Perhaps my numbers could be compared to "advertised duration" for a 4 stroke automotive camshaft, where numbers for "duration at lash point" and "duration at .050" valve lift" etc are also often specified.

    Distance from the crankcase to block split line (crankshaft centerline) to top of exhaust port is 132,3 mm/5.209" and to top of main transfer 123,2 mm/4.850". Rod length center to center is 4.062" and distance from piston pin center to top of piston (flat portion, not deflector) is 1.5" and cylinder stroke is 2.562".

    With these figures known the opening/closing positions in crank degrees could be calculated with a formula easily found in the litterature. But such a calculation would only present a close to the real world approximation in this case. This is because there is (as well as in many other engines) a piston pin offset position with, in this case, the piston pin a bit closer to the transfer side than the exhaust side. The piston pin offset is also the reason behind the biased 96/98 and 114/116 opening/closing values.

    I am sure the piston pin offset could be taken care of by some amendment added to the formula, but as I could not find it anywhere, and it is then up to my brain capacity to figure it out myself, I did instead degree my flywheel and used a dial indicator in the number one plug hole to check real world timing of that cylinder. And pin offset impact on port timing is obviously only about one degree (earlier opening and closing of ports).

    to be continued in another post...

    PL
    Last edited by petlun; 02-27-2011 at 12:49 PM. Reason: spelling

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    Some notes continued:

    Diameter of exhaust ports was 22 mm in my block. It is tempting to believe they are 7/8" (22,2 mm) but my 22 mm drill bit was so tight in my ports I would say a 22,2 would have been impossible.

    Compression ratio figures are based on filling the combustion chamber with oil "scrutiny style" and was done on my never opened 1988 powerhead (so some carbon deposits are involved). Volume up to and including the spark plug hole was 31,5 cc which is about 29,8 cc with plug hole excluded. Volume of a low deflector seems to be around 13 cc and my guess, based only on visual impression, is a high deflector is 14 cc or maybe a fraction more. This would indicate around 30,5 cc with high domes (no carbon!) including the plug hole. The old APBA paper said 28,0 cc for the 1350/1150 which would mean a 9% margin for carbon build up or something else. (UIM papers had a 7% margin to actual volumes in two 2 liter XR2-engines I checked several years ago.

    I really tried to check combustion chamber volume on the bare block with tinted water from a burette, but capillary effects made sharp and reliable readings very hard. Volumes of different parts simply didnīt sum up to the scrutiny method with oil and I rate the oil method the more reliable in my case. So my comp figures could very well be challenged by somebody else who has done these checks. Or from somebody having Mercurys nominal specs!

    PL
    Last edited by petlun; 02-27-2011 at 12:52 PM. Reason: spelling

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    Thank you. We have been comparing them on another forum as well and the 1500 distributor motors appear to have the exact same measurements.

    The 1500XS exhaust ports turned out to be 5.245" (.045" higher) and the transfers 4.826" (.024" lower). The XS also had a wider more accessible window from the cover into the transfer port, making the machining easier to access the cylinder if nothing else involved in the flow.

    Looking at the 90/115 ported motors in person and pics of the 1500 & XS, the transfer porting is very intricate. There are at least 4 cuts to each cylinder and the outer edges appear higher like Dr. Spock's eyebrows on Star Trek. I don't have a motor apart to confirm this, maybe someone else can confirm both the angle and the XS transfer height.


    I doubt 90/115's can successfully be ported up to XS specs by hand, the transfer port cuts were done by milling type tools at the factory and the angle is very slight.
    Last edited by Mark75H; 09-28-2010 at 05:01 PM.

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    Thank you Mk75H for answering. I feared for some time the Forums threads were down recently due too my to many words posting! But maybe not so. I will re-read and consider your post for an answer (Swedish native language here), it is a bit late here and the 14 year old is calling for food.

    Thanks
    PL

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    Thanks for posting this imfo ,I'm moding my 1500 with minor porting and balancing .

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    Lots of food later...

    Mk75H:
    The 1500XS exhaust ports turned out to be 5.245" (.045" higher) and the transfers 4.826" (.024" lower).
    Exhaust ports in the XS was expected but the transfers being lower than std was a real surprise though.

    I would have thought the XS were the same in all but the exhaust ports sitting slightly higher. Or maybe having a slightly bigger diameter but if so material between ports would be very narrow, to say the least.

    A more conservative transfer porting (timing) would of course increase the blow down period even more, maybe beneficial for high rpm operation.

    Mk75H, in what aspect wuold the XS have a wider more accessible window into the ports? (See pics of my std transfer ducts below.)





    (Why can I not preview my post?)

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    Mk75H:
    Looking at the 90/115 ported motors in person and pics of the 1500 & XS, the transfer porting is very intricate. There are at least 4 cuts to each cylinder and the outer edges appear higher like Dr. Spock's eyebrows on Star Trek. I don't have a motor apart to confirm this, maybe someone else can confirm both the angle and the XS transfer height.
    Here comes an old patent paper on a method for machining the main transfers of the Direct Charge engines.









    If you look at the pic of my transfer ports below I think you can see evidence of the ports having been done as explained in the patent paper. Namely with a flat end mill coming in at an angle but paralell with piston top. It goes in just far enough to create the "hook" that mates with the eyebrow shape of the piston deflector, then the mill is just backed out the same way (same axis) as it went in.

    A result would be a port shape as they are in the ordinary Direct Charge inlines. At the left port opening in my picture I think you can clearly see traces from the mill in the aluminum and liner, with it just coming in and going back out as described above. (When pic was taken I had just started to remove these traces in the right port opening.)



    Do the transfers look different in a J/XS block? (I know T2īs are a completely different animal though.)
    Last edited by petlun; 02-27-2011 at 01:00 PM.

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    dale robertson:
    Timing numbers based on light check through the ports and plenty of Budweiser special measuring fluid.
    He he, that was funny indeed. Similar kinds of measuring fluids available here to (even Bud nowadays) but I did my checks more than two years ago so I canīt say if any fluid was involved.

    But I do remember expecting readings of timing numbers should be a bit of a "dim and fuzzy" experience (like taking the volumes for compression calculations for instance!), so I was prepaired to do them perhaps ten times over and over again to get a good enough impression of correct values. But they came in surprisingly sharp at the exact same numbers each time, so I did just a few repeats. Which is to say I am a bit stubborn about the timing numbers on my 8310A4 block.



    PL
    Last edited by petlun; 02-27-2011 at 01:02 PM.

  10. #10
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    2 shots of my 115





    Milkdud's XS


  11. #11
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    He he, that was funny indeed. Similar kinds of measuring fluids available here to (even Bud nowadays) but I did my checks more than two years ago so I canīt say if any fluid was involved.
    My checks were done 35yrs ago. I am just looking at old notes. I don't use the special measuring fluid any more as it makes my head hurt too bad the next day.

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    Thanks for posting up the patent papers Petlun. I never was quite sure how the ports were cut into the block.

  13. #13
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    Thank you Mk75H for some unusually good and clarifying photos.

    One immediate reflection is the big (may I say huge?) difference also in transfer port timing between the lower hp inlines and the std 1500īs et al. The "Height difference between 115 and others" must correspond to a whole bunch of crank degrees difference in transfer port timing.

    From the two pics of your 115, I now see what you mean with ports being machined in four (2+2) steps. It definitely looks as if there has been another (or the same) mill applied at another angle. If so I presume there must have been some specific technical reason for this additional "secondary factory porting angle." to defend the cost of the extra machining manoeuver in production.

    Not necessary a disbeliever, but when I look at the upper port in your first picture I would say it looks very much like a mill has been applied in only one direction there. The low position (to the right in the pics) of the port in combination with the mill diameter chosen (size of ports), makes it eat a bit into the aluminum of the transfer opening though.

    But maybe I am just fooled by the angle of view. What would it look like with a drill bit of proper size pushed into position in the "primary hole/channel"? If done I guess the result of the secondary machining would be clearly exposed.


    On the pic of Milkdudīs XS I think it looks like the main transfers is at least as high (left in pic) as in an ordinary 1500/late 115, perhaps and maybe even a fraction higher. From this angle it also seems the passage before the ports to be as cast, indicating an ordinary as cast transfer passage. It seems unlikely Mercury would have spent money on expensive changes in die cast mould patterns for the limited production of J-blocks and XS engines (donīt think that was done even on the T2, only sand casted crank case fronts in low numbers there, right?). But of course I donīt know. Transfer port covers on XS engines were ordinary pieces though, according to parts lists.


    Thank you for taking your time Mk75H. I know you are answering a zillion of different questions on a daily basis in postings here and elsewhere. There is no rush for an answer here on my behalf. I am just very curious.
    Last edited by petlun; 10-05-2010 at 03:00 PM. Reason: spelling

  14. #14
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    side bar.....

    Does anybody know the difference between a 140 block and a 150 block (non xs) ?
    20 Foot Switzer Wing 2 X S3000 (Dust'n the Wind II)
    !6 foot Wood Eltro Vee (2X Merc 1500's) (Dust'n the Wind IV)
    15 foot Powercat 15C (2 X Merc 1500) (Dust'n the Wind III)
    (Single engine boats are lacking something)
    15’ Wooden Switzer Shooting Star...
    16 foot Lee Craft Merc S 3000-(Gold Dust II)
    (The exception proves the rule)
    Obsolete and Proud of it

  15. #15
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    Quote Originally Posted by petlun View Post
    Not necessary a disbeliever, but when I look at the upper port in your first picture I would say it looks very much like a mill has been applied in only one direction there. The low position (to the right in the pics) of the port in combination with the mill diameter chosen (size of ports), makes it eat a bit into the aluminum of the transfer opening though.

    But maybe I am just fooled by the angle of view. What would it look like with a drill bit of proper size pushed into position in the "primary hole/channel"? If done I guess the result of the secondary machining would be clearly exposed.
    I took that first picture to show how straight in the tool went; pretty much showing it had to be a mill bit. The second picture is the same cylinder from a different angle.

    Here are some more angles of the same cylinder as above. Looking at larger views of the XS, it has the same kind of second angle cut, just less pronounced. That is why I predict this can not be done with hand tools. I agree, there must be some fairly dramatic results from this or Merc would not have done a second machining operation. Every step left out is money saved, to add in a operation means it is really required for some result.





    I would also like to see a second and third XS apart for measurement and inspection ...
    280
    Last edited by Mark75H; 10-05-2010 at 05:07 PM.

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