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Thread: New Dart big m

  1. #1
    Member JOURNEYMAN
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    New Dart big m

    What all is required when purchasing a new block?
    Any other machine work? I am looking at the big M 9.8 deck 4.5 bore. And the actual bore the way it is sent is 4.490? for part number 31263444
    Doug

  2. #2
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    Re: New Dart big m

    Quote Originally Posted by altereddoug
    What all is required when purchasing a new block?
    Any other machine work? I am looking at the big M 9.8 deck 4.5 bore. And the actual bore the way it is sent is 4.490? for part number 31263444
    Doug
    On the Dart blocks SBC and BBC the blocks need to be line honed, lifter bores clearanced, decked and plate honed, freeze plug holes chamfered along with the thrust on area on the rear main cap.

    The bore spacing on a BBC I thought was 4.480
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  3. #3
    Member JUNIOR BUILDER
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    bbc bore/bore spacing

    Carl, I think he is referring to the unfinished bore size as opposed to the bore center to center spacing.

    Skip

  4. #4
    Junior Member JOURNEYMAN
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    Re: New Dart big m

    Quote Originally Posted by hink
    Quote Originally Posted by altereddoug
    What all is required when purchasing a new block?
    Any other machine work? I am looking at the big M 9.8 deck 4.5 bore. And the actual bore the way it is sent is 4.490? for part number 31263444
    Doug
    On the Dart blocks SBC and BBC the blocks need to be line honed, lifter bores clearanced, decked and plate honed, freeze plug holes chamfered along with the thrust on area on the rear main cap.

    The bore spacing on a BBC I thought was 4.480
    i don't know about your dart blocks but my big M was right in the middle of the spec on the mainline.

  5. #5
    Senior Member DYNO OPERATOR
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    Odd'
    Carl,
    I find the Drat Blocks seem to be machined much better with higher quality than the World stuff is. I have never seen anyone's line honing that is truly the same on each main journal, Dart is no exception. I always have to use several bearing sets to get clearances I want no matter if it is new from Dart or fresh for Reher Morrison or other shops.

    Dart is using CNC Decking equipment. What is wrong with the decks? Most I am measuring are very close from one side's measurements to the opposite side's measurements, as close as .0002 . Not an error. That is three zeros.

    I am willing to be educated though.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  6. #6
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by edvancedengines
    Odd'
    Carl,
    I find the Drat Blocks seem to be machined much better with higher quality than the World stuff is. I have never seen anyone's line honing that is truly the same on each main journal, Dart is no exception. I always have to use several bearing sets to get clearances I want no matter if it is new from Dart or fresh for Reher Morrison or other shops.

    Dart is using CNC Decking equipment. What is wrong with the decks? Most I am measuring are very close from one side's measurements to the opposite side's measurements, as close as .0002 . Not an error. That is three zeros.

    I am willing to be educated though.

    Ed
    We have 6 Dart Little-M blocks in shop right now and the mains on the first 3 blocks are 2.640 after we clean and relube the bolts with CMD-3 and when we are done they are with in .0001 with no problems.

    As far as the decks on the blocks I have bought Dart can not sweep off the deck and the rear of the deck as there is always a small step in ALL the Little-M's we have in the shop and on the deck about an inch from where the intake bolts on there is also a step in the decks. Dart can not machine the whole deck in one cut as they do about 3 different cuts and with the amount they are taking of the decks I am sure its hard to match mill to .0000

    We probe out every block that goes through our shop and I know the probe does not lie as we have had some old Cup blocks in my CNC machine and between the decks and cylinder placement we have found those blocks well with in .0015 on both the Ford and Chevy blocks.

    Ed I hope you not one of those guys that throws a boring bar on a block and bores the cylinders to where they are located as we are set up to BLUE PRINT BORE OUR BLOCKS. On the last 3 blocks we ran through our CNC machine 2 of them were with in .0025 from intake to exhaust and were with in .001 from front to rear. On one of the blocks we found the cylinders off .0065 on one side and -.0055 on the other side and thats from intake to exhaust and front to rear was with in .001 now thats .012 over all (correct). Thats why we buy all small bore blocks and blue print bore them to spec.

    3 years ago I spent some time with Dick who runs the CNC shop for Dick Maskin and told him what I was finding when probing the blocks out and his reply was that we produce 150 blocks a week and we rough machine these blocks and its up to the engine builder to make sure that they are to BLUE PRINT and Dick also said that if any one wanted a truely blue printed block they could machine one for them but it would cost them.

    Thats why I spent 124,00.00 dollars on a CNC machine to blue print machine all the blocks we send out the door and the ones we use in our engine shop.

    Go over to the http://speedtalk.com/forum/index.php...89d986a2c13b80 and ask if I know how to line hone as we have done blocks for quite a few of those guys over there and I have got calls from a few of them saying the sizing is right on the money.

    Line honing is an art and not every one can line hone and have it come out right as we see this all the time and the Dart blocks we have seen right from Dart seem to be well with in .0001 but all seem to be under the low side.

    We have shipped a lot of blocks over the last 8 years and so far no complaints on the work we produce and I have some of the best measuring equipment at both my CNC shop and engine shop.

    Now on the Bowtie blocks we find the mains on those blocks in the middle to high side.

    Back to the decks on the Dart blocks maybe they send me all the messed up ones as they know I can straighten them out when I am done LOL.
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  7. #7
    Senior Member DYNO OPERATOR
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    Carl,
    The only Aftermarket Blocks I fool with or shall I say most of them are a version of the BB Chevy mostly. Most or almost all of my SB Customers are still stuck in the stock blocks. So when I am tootin Dart's Horn it is from experiences with BB Sportsman, Billet, and Race Blocks only.

    I do have a few customers with SB Little M and Iron Eagles, but they already had them before I began working for them. Same as the World Blocks I have to work with. I got burned and burned up several years ago by a deal they did me wrong on, so that soured me from ever buying from them again.

    I have another one of those big heavy monstrously thick 11.625 (actually this one is currently 11.629) World blocks here now that has taught me all over to not like World Blocks. It took me forever and a nightmare to make room in this thing for a 5.500 stroke, but World claims it is good for a 5.750 stroke.

    If we were closer, I would like to try your services. I know that I don't like the line honing or the Lifter Bore work from Reher Morrison. I guess it all seems to work ok in their engines they build though. Disapponited the heck outta me, I will tell you for sure and it wasn't cheap either.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  8. #8
    Senior Member MASTER BUILDER
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    I am with Ed. Dart usualy, I say usualy, as there are exceptions, do a pretty good job on the mains. We usualy install studs, and touch up the line hone, and, we always cut the decks, with the BHJ fixture, but, the are very close, its just the finish isn;t always that great. I like Cometic and MLS fel-pro's, and just like to put the correct finish on it.

    I did see a Dart block on Thrusday, that appeared to have only been line bored, or, an EXTREMELY smooth diamond line hone finish on the mains. It was very smooth, and very shiny, but, you could see some very fine angled lines, like from a honing process. Anyonw know if this is a recent change?

    Frank
    Advanced Performance
    www.get-ap.com

  9. #9
    Senior Member EXPERT BUILDER
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    Never said anything bad about the Darts main lines as we always find them under low side appox. .0005 and most of my customers want them in the middle to high side.

    We had a World block in the shop to plate hone the cyliders and what a peice of shyt compared to a Dart, Worlds main line was just a very coarse line bored finish and the lifter bore finish was ugly looking.

    On the 3 blocks we are machining the lifter bores are .0005 under the low side of the the GM spec and we have always had to hone .0002 to .0005 out to get them to spec. and I am sure the next three will be the same.

    We did get a block from Dart 2 months ago where the lifter bores had .0008 taper and one bore was totally messed up and Dart paid for a set of severe duty Crower lifter .875 lifter and we machined the lifter bores to .8755 for the custmer for 150.00 and it was a win win situation for everybody.

    When we had the deal on the Workd blocks it was costing us money as the last block we got was filled with epoxy up to the freeze plug holes and the customer didn't want it and they would not take it back so we sold it for 1300 dollars our cost to rid of it.

  10. #10
    Member JOURNEYMAN
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    On a budget what would be a better block to buy?
    I doubt if I could afford a new block that is cnced to exact specifications. In a perfect world I would love to have one, but the reality is that most bracket racers can't. The masses of older Gm blocks would probably fail miserably if you were to probe them.
    Basically what I am getting at is that this post really makes me wander what to do. Becasue on my limited budget I previuosly bought a short block from a east coast builder, complete 540 bbc with a merlin 3 block. And I ran it about 60-70 passes. Inspected the bearings a few weeks ago just to inspect it and found that it had some slight bearing damage. So I pulled it all the way apart and had the crank ploished. Then while cleaning the pistons off I noticed that they were wearing funny. So I measured the P/W clearance and it varied from .0075 to .0085 and spec from wiseco was .005. And #1 cylinder had a nice .003 scratch down the side. So it was eother bore it .030 ( because it was cheaper than going .010 for the pistons), buy new pistons,rings and have it rebalanced or sell the block and buy a new one and keep the rotating assembly.Which had just a very slight wear on the skirts and top ring land. Where as, I would still be almost the same in price for upgrading to a better billet main block. Unless I have to spend a additional 500-800 in block preparation.
    Decisions, decisions..


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