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  1. #1
    rabzman's Avatar
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    Newbie 1390 BB questions

    Hi All,

    Well its about that time I start my first 1390 build. I would like to stick with stock carbs, ignition, and pump gas. While I don't have any of the parts yet, I do have a few questions as to what I need to buy for the bones of the project.

    While I would like to start with a set of 1200 cases, I know I can add pulse lines to a set of 1300's if needed.

    But while reading Group K's web site I saw that they "delete" the power valves on their 1390's is that correct? If so should I start with a set of 06-08 cylinders? Is group K the only ones doing the 1390 mod? Also, what are my other options? If a PV1390 is the way to go then I would probably want to use a bellows actuated PV's as I really would like to eliminate any potential servo gremlins. And are all of the 1390's using plated or iron sleeved cylinders?

    Ultimately I would like for this build up to be a no frills, mid 70's rec boat that I can beat the crap out of it for at least 150+ hours between rebuilds.

    I would like to thank all of you here at GH as there is a lot of good info here and apologize in advance for all of my newbie questions!

    Thanks,
    Mike


  2. #2
    spdracr's Avatar
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    Smile

    I have a Lowell Horning 1390 and I had my power valves blocked, no more dropped valves or leaking. I sent him 1200 cylinders and he took care of it from there. I have since swithed over to EFI from the carbs and haven't looked back. So far 84.9 is the best it has done and 83 to 84 all day long. I will tell you that a lot of work needs to be done to the bottom, My friend danny has his stock 1300 power valve at 78.6 so it is all how you set it up, but extra horsepower is nice to have.

  3. #3
    Moderator OsideBill's Avatar
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    I would give Lowell Horning a call and discuss your project with him. He did a 1390 motor for me that runs on 91oct pump gas and incorporates the benefits of the power valves. The stock carburetors will flow more than enough fuel for these motors with some simple re-jeting. As for ignition you will not realize the true benefit of porting without some type of improvement here.

  4. #4
    YudLuz2's Avatar
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    I would stick with a power valve 1200 cylinder. Bored and replated.
    If you are looking for something that is going to last, why not
    just run a 1300 setup with oem pistons. You can get 75 mph from
    a stock 1200 motor. A ported 1300 would bring even bigger numbers
    with great acceleration. Keep the power valves, if you like the gas
    valves then thats fine too. Ben

  5. #5
    rabzman's Avatar
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    Thanks for everybody's input so far. There is just so many engine/hull mod combos out there my head is spinning!

    I kind of have 3 projects right now and my funds are running tight, but I really would like to build up something from scratch even if it just sits around until I find a hull that I can molest the heck out of with all of the truing, ride plate and intake mods.

    Right now I have decided to finish my 1200 PV motor repair with a T&W Crank I just bought from Jim(Thanks again) and a #3 cylinder replate & piston just so I can get my stock 2000GPR up and running again. I am also picking up a 2002 next week which I'm just going to do the basics to like PPK, Wave Eaters, D-plate, solas 13-19, ferchos & leo's hole shots, and a few other low dough mods. I also have the twitches to buy a FSR or an RXP!!! If only that damn money tree would just start growing!

    All of my friends either ride X4 SD785 Limiteds and SSs or Lightly modded RXPs, and Ultra250xs. So all I need to do is have a reliable mid 70's GPR that handles up to a 2-3 ft chop to be happy!

    I also want to go to the next Mud Bug to try and see some of these die hard 2 strokers run against the conversions.

    So, I'll keep trying to read all of the great threads and try to get at least one project done for our annual April 1st ride.

  6. #6
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    Quote Originally Posted by rabzman View Post
    Hi All,



    Ultimately I would like for this build up to be a no frills, mid 70's rec boat that I can beat the crap out of it for at least 150+ hours between rebuilds.

    I would like to thank all of you here at GH as there is a lot of good info here and apologize in advance for all of my newbie questions!

    Thanks,
    Mike
    Ok from this statement a Group K motor would be your ticket.
    Harry builds a DAMN fine "CHEAP" kit. On the other hand L.HORNING BUILDS a DAMN Fine More expencive kit. LH kit has power valves and will give you better profomance with power valves.
    But GK kit is a done deal. he rejets blocks and sets the carbs for all around riding. YOU will not even have to buy a tack with his kit. It is like a "snap together" model you get as a kid. just follow the directions and go
    I have one of these and they are TOUGH! But I do have my regreats. Power valves give a slightly better hole shot, and 1mph on top end (from what I hear). But The group K kit can be modded for some real nice proformance, Mine does well, very well.

    If you do the jet works mod, d-plate, and MOST OF ALL...... A 3* keyway and VF-3 reeds, you will be IMPRESSED. this can be done for under 3500.00 the kit is 2000.00, reeds are 500.00. key is 50.to 60 ....
    A modded plate form JIM, a good CONCORD impeller for your late model ski (i have one if you need one,I run a Dyna fly) .
    3000.00 and some tricks you will have a single pipe ski that runs 75MPH everyday all the time, and more if you add to it.
    everyone can go 75mph with money, form there on up it's skill.

    but if you get a LH motor you have more to build with in the future. and LORD KNOWS YOU WILL GET ADDICTED!!! MAY the force have mercy on you

  7. #7
    rabzman's Avatar
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    There is a guy in the classifieds selling 1200 pv cylinders which he states can be used as cores. He said that most of them have grooves/gouges from running dry with no oil presumably.

    So, my question is can I use these cylinders for my 1390BB project? What should I ask of the seller if I am considering buying these?

    Thanks, Mike

  8. #8
    Moderator OsideBill's Avatar
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    Quote Originally Posted by rabzman View Post
    There is a guy in the classifieds selling 1200 pv cylinders which he states can be used as cores. He said that most of them have grooves/gouges from running dry with no oil presumably.

    So, my question is can I use these cylinders for my 1390BB project? What should I ask of the seller if I am considering buying these?

    Thanks, Mike
    The important thing's are the gasket sealing surfaces, port damage, depth of any gouging, stripped bolt holes and any cracks. Ask for pictures, I sent Lowell 5 cylinders when I did my 1390 and asked him to select the best three, I figured there was a few that would not clean up, he told me he could of used any of them.

  9. #9
    I got 3 1200pv core cylinders from WFO for my LH 1390 that's currently in the works.... They cost me less than that guy is asking in the classifieds... Might want to ask around before jumping on those.

  10. #10
    dhoad's Avatar
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    If I was doing a BB GPR over again I would do a Lowell Horning 1390 with locked PV and 160 lb compression. First time round I did a ported 1300 from Lowell and was very happy with it, but with the bigger displacement there is less need for PV. just my 2 cents

    also, I would contact WFO re cylinders. he is a great source for parts and could help you with the BB also

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