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What are your choices for a block? The project will be for a 19' jet boat primarily used for the river, but will see time at the track as well. Would like to run 10.0 and stay on pump gas. Looking at a 540 aluminum head roller motor and we want to start with a new block.

What are your thoughts? Dart, Merlin? I'd really like to try and get the owner to step up to an aluminum block, but I'm not sure if that's in the cards. As usual, price is important, but not everything.
 

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TEN THIRTY ONE
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Dart makes a nice product. I've seen a few out of the box nightmares with the Merlin stuff.
 

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Dart makes a nice product. I've seen a few out of the box nightmares with the Merlin stuff.
X2..... I have had good luck with a Dart (Iron 496 ),Blown alky Hydro.........Eric:)hand
 

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Village Idiot
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The Dart is a good all around block. Do not assume that just because it says Dart it is ready to run. I have had to straiten out the decks on the last three I have got. The last five all needed the mains fixed since they were way out of whack and you have to check the threads on every bolt and plug hole. None of the oil gallery plugs were tapped deep enough. Now don't expect any of the other blocks to be much better. The last CNC Bowtie blocks I got were a little better, but I have not got one of them in a while. I know the Merlin's were "hit and miss" over the last few years but I guess they went to a new foundry recently. It would be nice to see them putting out a great product again like they had with the Merlin Pro blocks.

Moral of the story, expect to pay more since there will be machining you did not expect. I have no experience with the aluminum blocks so I can't say what they are like.

Paul
 

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Here is what we do to a Big-M block when we machine them
I deck all of them to a finished number depending on gasket & desired piston height
Block needs to be honed with a plate or bored & honed depending on bore
Bottoms of bores need to be chamfered
Most need the lifter bores honed, at the least checked
Most need line honing
All pipe threads need to be retapped
Oil return from fuel pump cavity needs to be done
Core plug holes need deburiing
CHECK THAT THE DISTRIBUTOR GEAR DOES NOT CONTACT THE BLOCK BY THE CAM. There is a big cast blob down there you may want to relieve.
 

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Brodix aluminum is fairly cheap and good.
Have you seen problems with rings sealing because of cylinders moving around?
 

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Have you seen problems with rings sealing because of cylinders moving around?
not really and mine is at 4.600..
have talked to guys running big n20 hits with bores larger than that and they are claiming not to have problems.

the only extra machine work mine needed right from the get-go was on the mains. they were .003 undersized.

other than that, i've been totally happy with my block.
 

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Village Idiot
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I can see bore and hone to get the size you want but to align hone and square deck a BRAND NEW block is just unacceptable.
Many people think the same thing and don't check the stuff. Needless to say they end up blaming everything else because they knew the block was NEW so it had to be right. I thought the same thing when I saw my first Dart was way out. I was as mad as a hornet. Needless to say I have come to expect it now and move on. Its all a part of the fun.

Paul
 

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not really and mine is at 4.600..
have talked to guys running big n20 hits with bores larger than that and they are claiming not to have problems.

the only extra machine work mine needed right from the get-go was on the mains. they were .003 undersized.

other than that, i've been totally happy with my block.
Interesting. I have an Oldsmobile with a Rodeck block that's 4.560" I believe and when my oldman ran it we had problems with the inner cylinders sealing.. Heard it's not uncommon for them to move around.. I guess I'll have to look into the Brodix.. Do you know what deck heights are available off hand?
 

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Unless you are a full on racer and need the weight savings I would pass on aluminum. No matter which other block you choose it will have to be prepped some, out of all of them my choice would be either the Bowtie CNC or Dart.
 
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