engine ?
+ Reply to Thread
Results 1 to 10 of 10

Thread:
engine ?

  1. #1
    Junior Member
    Join Date
    Dec 2007
    Location
    Boron Ca.
    Posts
    16

    Default engine ?

    Hi guys I don't post much but follow the forum.I have gen 5 454 in my boat. I've got a set of pistons I'd like to put in it with a new cam also. I'll have to change my heads to because It has peanutports that I port matchedto my ovalport manifold. I have a set of 990s for a mark 4,have any of ever used these on a gen5 ? If so what gskets did you use? thanks for you're help Roy

  2. #2
    Senior Member jetboatperformance's Avatar
    Join Date
    Dec 2007
    Location
    Atascadero Calif
    Posts
    7,463

    Default

    Quote Originally Posted by fujimo View Post
    Hi guys I don't post much but follow the forum.I have gen 5 454 in my boat. I've got a set of pistons I'd like to put in it with a new cam also. I'll have to change my heads to because It has peanutports that I port matchedto my ovalport manifold. I have a set of 990s for a mark 4,have any of ever used these on a gen5 ? If so what gskets did you use? thanks for you're help Roy
    Roy the short answer is yes on the heads , but you might want to read this info first Tom
    http://reviews.ebay.com/Big-Block-Ch...AT:-1:SEARCH:4

  3. #3
    Junior Member
    Join Date
    Dec 2007
    Location
    Boron Ca.
    Posts
    16

    Default

    Thanks for the link Tom. I'll probably be giving you a call I got a few more questions. I don't want to put alot of money in this engine would like to get a little more out of it with some parts I have. roy

  4. #4
    Cas
    Cas is offline
    Angry American Cas's Avatar
    Join Date
    Jan 2008
    Location
    NorCal
    Posts
    3,103

    Default

    Quote Originally Posted by jetboatperformance View Post
    Roy the short answer is yes on the heads , but you might want to read this info first Tom
    http://reviews.ebay.com/Big-Block-Ch...AT:-1:SEARCH:4
    good read! thanks for the link

  5. #5
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
    Join Date
    Dec 2007
    Location
    Newton Ks.
    Posts
    6,834

    Default

    Quote Originally Posted by fujimo View Post
    Hi guys I don't post much but follow the forum.I have gen 5 454 in my boat. I've got a set of pistons I'd like to put in it with a new cam also. I'll have to change my heads to because It has peanutports that I port matchedto my ovalport manifold. I have a set of 990s for a mark 4,have any of ever used these on a gen5 ? If so what gskets did you use? thanks for you're help Roy
    Going from "peanut" port ovals to rectangles is, IMO, not the greatest deal, but, it is what you have available.
    You're going from a case of too small a head port to feed at RPM, to too large a port to feed at good velocity at RPM, unless the RPM climbs significantly higher. The middle ground may have been better.

    Get your compression as high as you can, I think 10.5 in an iron-headed jetboat is safe enough (run 91 octane premium only) to help and put the right fitting cam in there to try to minimize the flow issues of the heads under 6-grand and you ought to be a good deal ahead of where you are currently.

    What is the casting number of your current head? I've seen lots of people mistake a large oval port head for a small oval port (peanut) unless they get the 2 side by side. Obvious visual difference, but both are known as "oval ports" and folks sometimes expect the worst and are mistaken (another thread on here right now).

    What oval port manifold are you keeping?
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

  6. #6
    Senior Member kdub's Avatar
    Join Date
    Jan 2008
    Location
    Houston
    Posts
    221

    Default

    990's will work on a GEN 6 but I dont think they will on a 5 due to the water jacket changes they made unless somebody knows how to correct that

  7. #7
    Junior Member
    Join Date
    Dec 2007
    Location
    Boron Ca.
    Posts
    16

    Default

    Thanks for the input. I understand about the rectangle verses oval port. I've got the LS-6 pistons 10.5-1 I think and manifold to go with them. I don't want to put alot of money into this engine just trying to use some parts I have. Probably get a new cam tho. Roy

  8. #8
    [email protected]
    Join Date
    Feb 2008
    Location
    Ohio
    Posts
    1,011

    Default

    Mark IV heads can be used on a GEN V, but you need a special head gasket to do it so there won't be an internal water leak. Gotta love these up and coming engineers trying to make their mark by trying to reinvent the wheel.

  9. #9
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
    Join Date
    Dec 2007
    Location
    Newton Ks.
    Posts
    6,834

    Default

    Quote Originally Posted by kdub View Post
    990's will work on a GEN 6 but I dont think they will on a 5 due to the water jacket changes they made unless somebody knows how to correct that
    The links posted above tell, and I read the other day, but, if I recall right, it is use a Mk-IV gasket, not anything "special".
    The passage in the block deck is bigger, and oblong, and a Gen-V gasket won't seal properly to the head surface. A Mk-IV gasket blocks off part of the re-shaped cooling jacket port, but causes no problems, and seals up right to the head.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

  10. #10
    [email protected]
    Join Date
    Feb 2008
    Location
    Ohio
    Posts
    1,011

    Default

    I've never messed with a GEN 5, but I know Apple Chevy in York, Pa. did sell a special gasket to put MK IV heads on. Think Dick-Sorggins(sp) do also.

    Tim

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in


Tags for this Thread

Digg This Thread

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •  
 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95