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Flathead Deck Height Help Needed....

Discussion in 'The Hokey Ass Message Board' started by Sixcarb, Mar 24, 2009.

  1. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    I just talked to the machine shop so I could get the new deck height on my block to order pistons and he told me the deck height is 10.160 I'm wondering if this sounds ok since the stock height is about 10.435, about a 1/4 difference. I'm concerend about the valve lift since the cam has a lift of .460. I'm really gonna be cutting it close on the heads that I'm using. Any thoughts if this deck heigth is ok would be great.
     
  2. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    I don't think deck height 1/4" less than stock is really possible...there would be nothing strong enough to work with left up top?
    Could this be a straight measurement without reference to the offset crank?? I think without an offset you would measure from main bearing bore to top then add in half the diameter of bearing saddle. I can't quite imagine what the offset would do to this.
    Dimensions would I think be in the Service Bulletin cutaways and on Blown 49's posters, but I don't have them in my office, alas.
     
  3. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    Thats why I was asking.....it just didn't seem right. It's measured from crank center.
     
  4. banjorear
    Joined: Jul 30, 2004
    Posts: 3,788

    banjorear
    Member

    Joe:

    That is an awful lot material to remove from a deck. A few more questions need to be asked.
     
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  5. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    I know I started looking into it after I got off the phone with him and was thinking it's not right.....I'm hoping he's measuring wrong off the mains.......just got off the phone, he said he didn't have the right ring size for the main so he was just going off the center of the shaft. I really wish I had the equipment to learn how do to certain machine work on my own and wouldn't have to deal with this. I had/have a lot of faith in this shop since DJ (Flatdog) had the same work done that I need.....decking and line boring.
     
  6. banjorear
    Joined: Jul 30, 2004
    Posts: 3,788

    banjorear
    Member

    Wait, the measure he gave you was wrong or he set it up in the decking machine wrong and it's done? I hope not the latter.
     
  7. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    no he said there's no way he took off a 1/4....there wouldn't be much of a valve pocket left.....I think he winged the measurement which doesn't help since I have to have the pistons made, this has been going on since early october....I ended up having 2 bad aftermarket rear main caps, they were offset so far they could'nt even be line bored.
     
  8. banjorear
    Joined: Jul 30, 2004
    Posts: 3,788

    banjorear
    Member

    Hhhmmm, not good. I hope this gets you get it all straight soon.
     
  9. As long as it looks right and the value pockets look correct, I wouldn't worry about it. The easiest way to order custom pistons is to put the crank in the block (obviously with bearings), with a single rod and pin - then measure from the top of the pin to the deck surface. Then subtract 1/2 the pin diameter. This will give you the 'compression height' which is what your piston manufacturer will want anyway. This takes the question of deck height off the table and also uses your actual lower-end to measure everything - which is the safest way in my book.

    Hope this helps!

    Dale
     
  10. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Just like an SBC and most production engines, deck is thinner than you'd like stock. I think they should only be decked if warped beyond spec. Another reason to use a torque plate too.
     
  11. flatjack
    Joined: Feb 13, 2007
    Posts: 893

    flatjack
    Member

    What kind of cam are you using that has .460 lift?
     
  12. Sounds like a big ass roller, with a base circle of about 5/8" -- just a guess!
     
  13. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,834

    Mike51Merc
    Member

    Not to ring alarm bells, but I've heard from many sources to NEVER deck a flattie. Your headbolts will pull that sucker up and you'll never get your gaskets to seal. It's possible your machinist may very well have ruined your block.

    Anybody else hear/read this, too?
     
  14. blown49
    Joined: Jul 25, 2004
    Posts: 2,213

    blown49
    Member Emeritus

    I tried to make my CAD posters as accurate as possible when I made them in 2006. I show 10.4337 on right side and 10.4365 on the left side, from the crank center, as stock.

    Jim
     
  15. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Everybody with a flathead needs that poster. It is a great aid to thinking about this stuff! AND a set of Service bulletins!
     
  16. Bruce,
    Where can we get one? Also, is it the later blocks or does it cover all. I'm going to be picking up that 32 pretty soon and it sounds like something good to have. ;)
    JK
     
  17. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,409

    Kevin Lee
    Super Moderator
    Staff Member

    I've heard so many stories like this I am afraid to let anything go to a machine shop.
     
  18. banjorear
    Joined: Jul 30, 2004
    Posts: 3,788

    banjorear
    Member

    Kevin:

    I was about to say the same thing. WTF! Can someone who acutally machines these things on a regular basis step up and give us some facts.

    I need to bring my block back to the machine shop for final machining and he wants to deck my block. I'm kinda reluctant to let him do it.
     
  19. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    That's the one ! I'm still waiting to hear back on the new measurement and the thoughts of having a shitted block weighs in the back of my mind but I'll be hoping for the best. When I brought it there I told the guy 5 times that I want the smallest possible clean up done on the deck work as possible.
     
  20. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,409

    Kevin Lee
    Super Moderator
    Staff Member

    Unless he gave an actual reason, this is the kind of shop that worries me the most.

    I dropped by a shop with a good reputation with some heads and before I had even set them on the counter the first thing out of the guy's mouth was, "We're going to need to true those up."

    Thanks anyway.

    Don't think I would ask to have the surfaces decked unless there was a real problem. And would you really want to use a block that was that far out?
     
  21. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,409

    Kevin Lee
    Super Moderator
    Staff Member

    I hope it turns out alright for you, but I am done dropping stuff of and hoping for the best. If I can give a clear explanation of what I hope to accomplish and have to explain it more than once or argue to get what I want, I'll be packing my things and finding another shop.

    This isn't to say I'm not open to other options, but I need to hear some thinking behind it.
     
  22. I believe we may be worrying too much about something that has probably NOT been done. I can see no way that any reputable machine shop would take a big cut on a deck surface of ANY block - unless they were instructed to do so. Hundreds of thousands of material removal - can't see it.

    On my last blown flathead, I did have the block just lightly decked (think it was less than 10 thou.) - cleaned the surface up really nice and I do believe it helps head gasket sealing (especially with higher boost engines).

    Many of these old flathead decks have quite a bit of wear and corrosion around the valves, water passages, etc -- IMHO a minimal decking won't hurt a dang thing. Obviously if it doesn't need decking - then don't do it!

    Same goes for align boring - take the absolute minimum if it needs it. I've typically done an align bore/hone when changing main caps - which is something you just have to do. The machinist should know that the absolute minimum is the goal - so that crank gear to cam gear relationship doesn't become too tight.
     
  23. Most of the piston manufacturers that I have contacted are stating the deck height that they are using for a stock replacement piston is 10.438"

    It is a fact a smoother finish on the surfaces does aid in the seal of any gasket, especially a head gasket; think of floating a paperclip on water the minute you break the surface tension the paperclip sinks the same goes for a gasket, a high or low spot in the surface causes a void which makes it easier for compression, coolant, or oil to leak through. It is absolutely imperative to have a flat surface as well (within .002") for copper or steel gaskets as uneven torque load will lead to leaks too.

    I am going through the same process building my flattie and luckily my machine shop is very willing to work with me and has taken a huge interest in the project, and asks a lot of questions about it as well as contacts others who have done more flatheads than he has for questions I cannot answer or he cannot find on his own.
     
  24. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,410

    Flat Ernie
    Tech Editor

    I'm with Kevin on my mistrust of most machine shops. We have a very good one who has been doing flatheads since they were popular here in town. I always ask for the old man & explain anything I want/need done. He always calls if there's anything he thinks is unusual or needs doing...he will use torque plates too.
     
  25. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    I agree with Kevin as well but since "Flatdog" was the guy who sent me there I was feeling pretty confident, DJ had machine work done there on a couple of his blocks for things he wasn't set up for. I went there to have it line bored for aftermarket caps, cut for larger valves, and my words were a very small cleanup on the deck, luckily I have a great guy to help me on the other stuff as far as boring and assembly who has done tons of great work but he's not setup for the line boring or decking. I'm going to give the guy until mid next week before I start hounding him on some measurements.
     
  26. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    A sigh of relief.......after waiting another couple weeks for the machine shop to give me a new measurement I gave up and went and picked my block up, I brought it to the guy who does some other work for me(he doesn't have a line bore) so thats why the motor was elsewhere, anyway we remeasured the deck height and came up with 10.430 which is great considering the first measurement the first shop gave me was 1/8" different....good news and I'm off to order up some nice pop up pistons.
     
  27. Cool! Are you running Navarro High-Dome or Baron pop-up style heads? I have both - was wondering who is making your pistons, what type of rings you'll be using (don't put those POS Grant's in there!), what pins and what the approximate costs are?

    Thanks and best of luck on your motor. If I can ever help with anything, let me know.

    Dale
     
  28. Sixcarb
    Joined: Mar 5, 2004
    Posts: 1,503

    Sixcarb
    Member
    from North NJ

    I have the Navarro heads, I have to call Ian at Ross and discuss ring openings.....I'm not going to use the Grants, and thats something I have to look into as well. Ross gave me a price of $775 including the pins.
     
  29. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,410

    Flat Ernie
    Tech Editor

    Ross will sell them with millimeter ring packs...many builders prefer those.

    Have heard Total Seal will make some for you as well...
     
  30. HotRodMicky
    Joined: Oct 14, 2001
    Posts: 1,763

    HotRodMicky
    Member


    Whats the advantage of millimeter rings(other than it's easier to measure for me :))
     

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