I am getting ready to order my motor. It is a turn-key 540ci 695hp. The standard block is a Gen VI, but there is a $475 option for a Merlin III block instead. Is it worth the extra money? I like the idea of not having to use an electric fuel pump, but it isn't that big of a deal. The few local people I have talked to said the Merlin is a much better block. What do you guys think? Is it worth the extra $475?

Yep, Go with the Merlin.... Not sure about the Gen VI, but the Merlin has priority oiling passages, blind head bolt holes, so less chance of a water leak, and is a heavier, more durable block. Its also pre-notched for a longer crank, I think up to 4.75 inches of stroke. My 540 was based on the old "Bowtie" Gen IV block. It was a good block, but needed to be machined for crank clearance,etc. The machine work alone makes the Merlin a better overall buy. IMO, go with a 4.5 inch crank while you're in there for 572 inches. Why stop at 540? You can get more cubes,brute torque,etc from the short deck 9.8 block,and the price is the same. The Merlin block will take the 4.5 crank with no problem.

Niether ;)

Dart Big M or GM Bowtie would be my choices if building a BBC

Merlin

Niether ;)

Dart Big M or GM Bowtie would be my choices if building a BBC

Just curious, why? My Bowtie block needed machining, and did not have priority oiling for the bearings. Also needed to use sealer on my top head studs to prevent a water leak. The Merlin and Dart blocks have blind holes at the heads to prevent needing to seal bolts and studs for water. Is the Gen VI block improved over the Gen IV?

Just curious, why? My Bowtie block needed machining, and did not have priority oiling for the bearings. Also needed to use sealer on my top head studs to prevent a water leak. The Merlin and Dart blocks have blind holes at the heads to prevent needing to seal bolts and studs for water. Is the Gen VI block improved over the Gen IV?

I'm not speaking for him, but there has been a lot of negative feedback on the Merlin blocks on many of the boards I'm on. Poor machining, deck heights all over the place, etc. A friend bought one and sent it back after looking at a Dart block. He was extremely disappointed in the look of the Merlin and had his engine shop do some measuring which confirmed his suspicions. The Dart he bought was spot on. I would opt for Dart definitely.

Jody

I'm not speaking for him, but there has been a lot of negative feedback on the Merlin blocks on many of the boards I'm on. Poor machining, deck heights all over the place, etc. A friend bought one and sent it back after looking at a Dart block. He was extremely disappointed in the look of the Merlin and had his engine shop do some measuring which confirmed his suspicions. The Dart he bought was spot on. I would opt for Dart definitely.

Jody

Thanks for the input. Was not aware of the issues you mentioned...:o

Thanks for the input. Was not aware of the issues you mentioned...:o

I would agree with you, the Merlin on paper is a better design that the stock factory offering. But the feedback has me wary, leaning towards the Dart instead.

Jody

Even a Merlin III is better than the factory block because of stronger main webings, thicker deck, and thicker cylinder walls. Both the Merlin and the Gen VI block have moved the oil feed off of the pan rail (used by the Mark IV blocks) to allow more grinding to clear stroker cranks. I also have to say given a choice of a Merlin or a Dart Big M there is no choice, Big M every time. Better quality and I believe they use a higher nickel content to make the block even stronger. (Though I may be mistaken because the Merlin may also be a high nickel content block, which the factory block is not).


Larger Dave