Which one would you buy? Dart has a special going where they will ship any iron block anywhere in the 48 states for $1, so the price is now comparable to the World Products Merlin II. I had decided on a Merlin for the price, then this Dart deal came along...

I believe the Dart can support a larger bore (4.6"), but I can't find much information about this block. It's not even on Dart's web page yet!

-Joe

 

I can't speak from firtst hand experience about either block, but I would point out that Dart makes excellent products and is a subcontractor for GM. Alternatively, the Merlin blocks have been around for a long time and are a proven commodity.

Why not just call Dart. I've spoken to them a few times and they have always been very helpful. If the price benefit is worth it, I wouldn't hesitate to use the Dart block. My SBC 427 uses a Dart block, and it's a work of art. My general impression has always been that Dart is more race oriented than World. WHile you may not be building a race engine, the features that Dart incorporates into their blocks translate into excellent durabilty on the street. Not that the World stuff isn't though.

 

I'm sure they are both great. I have the Merlin II and It's also a beautiful piece. Lifter bores were straight etc etc. No issues. The bore issue is a long standing one and changes depending on who you talk to. Since Bill Mitchell is a primary part of World it surprised me to get different stories from both of them. World officially says the Mrlin II will only go 4.560. Unofficially they say the bore thickness of the Mrlin and Merlin II are the same. They say they use the same casting molds for the bores. They say that they are encouraged to sell the billet capped high $$ Merlin for anyone who discusses the 4.600+ issue. Unofficially they say the Mrlin II can go 4.625 with no problem. Bill Mitchell's guys say the same thing. They say they have built many of them.

Sadly I didn't sonic check my block so I can't verify it all. I wish I had.

And way back when wasn't Dart and World the same Co? Then they split up during the iron head wars? It became World for iron heads and Dart for aluminum. Now they both do each.

Jim

 

As a side note.. you might check some of your local race shops. I bought mine from a shop in Dallas and picked it up at the shop for less $$$ than were being advertised in all the trade publications with no shipping charges.


Jim

 

Monty, thanks for the idea. Maybe Dart has some literature they can send me. I'll give them a call. Info about this block is definitely scarce.

Jim, that clears up the confusion about the bores. I've seen a few World blocks with HUGE displacements, so they're probably using the original Merlin. I wonder if anybody on the forum has bored a Merlin II to 4.6"?

I think I know the answer to this, but I'll ask anyway: You guys don't think steel caps are required in a BB street engine, do you? They want quite a bit more money for them. I'm trying for the biggest bore I can get so the rest of the engine can stay relatively mild. That's the benefit of the Dart block, it's guaranteed for .3" wall thickness at 4.625"! You can build one heck of a short deck motor with slugs that wide. I'm thinking 3.76" stroke and 4.6" bore for a 500 or 4" stroke for a 532. I'm not sure if I could actually find pistons for the 500 combo, but it would sure be a revver!

One other benefit of the Dart is that it's factory clearanced for a 4.5" stroke. The Merlin II is set up for 4.25". Is a 4.5" stroke practical for the street in a Vette? I'm picturing a BIG oil pan to clear that stroke. Probably overkill for my goals.

I guess the main thing I have to decide now is: How much power is too much? This car is a street cruiser that only sees the track two or three time a year (it's a convertible, so they'd send me home anyway:)), and I have no plans for suspension modifications or slicks (although I may have to beef up the rear with Tom's parts or similar). I have a Richmond road race 5-speed to go in with the new engine. Jim, since you've already been down the big displacement road, what displacement would you do next time?

Thanks! -Joe

 

Well, I guess it all comes down to what you want to do. My whole project started out because a buddy had bought a new 4.25 crank and .250 long rods and wanted to sell them. I toyed with making a 496 originally but the big bore idea appealed to me.

If you are really going racing then the big bore/short stroke idea is definitely the way to go. I know of some guys running NMCA stuff with 4.500/3.76 setup in 3500 lb cars twisting 8200 rpm with flat tappets. They are bumping 800 hp at the top end. Run 9's on radials. make sure you have some ungodly flowing heads to make it work.

But my plan was to drive it on the street and the valvetrain had to live a long time. That means that anything that will feed that many cubes at high rpm cam wise is out of the question. So I assembled the 540. I love the torque it makes. I guess it would be nice to see it make more power at 7000+ rpm than it does, but there goes driveability. All I need is more cam and maybe compression if I get crazy and I'm there. My other choice might be to build the 509 or 522 setup to kill some bottom end and twist a little tighter, but it needs to last along time too. My setup seems to make 40-60 ft lbs more in the midrange than the short stroke ones.

I'll keep my setup. When and if I get it to hook up it's gonna be killer. For the street it's great. It's like having a Nitrous bottle that is never empty! If you are never going to put slicks on it it's never going to really hook, so you might build the smaller one to help. I'd rather have the extra and use my right foot and clutch to make it work.

Jim

 

I went with the Dart Big M Block.
Jim Oddy Built my motor and he felt the Dart was a better block.
It is lighter than the Merlin.
My Motor has a 4.56" bore and 4.25 stroke.
The Dart does go out to 4.60".
To see my motor check my web site.

 

noelga, how much lighter is the Dart? Anything significant? I can't find that information anywhere. Actually, the Dart will go to 4.625", but I wouldn't want to bore a brand new block to the max, just in case...

Jim, I may have misspoken a bit. I do plan to take it to the track a few times a year, but I'm not what you would consider a racer. I only go there when I'm meeting other Vette owners for some fun. I'm not a bracket racer by any stretch! Like you, I'm really only concerned with street performance. I'm not going with a solid roller or really high lift (probably a mech. solid or possibly a hyd. roller), so longevity should not be an issue. My main reason for going with a shorter stroke would be to keep the car controllable on the street. My wife drives it quite often, so I don't want to make it a hassle to drive, although she is a very good driver (for a girl!;))

Realistically, I know I could build a motor with the type of power I'm looking for with a cheap used 454 block and GM iron heads, but I'm looking at this engine as a long term investment in fun. Everybody's got a 454. This is just the beginning...

Thanks for your input!


[Modified by Flareside, 11:24 AM 12/12/2001]

 

Flareside
I don't know the exact weight deference but I could find out from
Oddy. When I ordered my motor the Dart was not available and Jim was going to use a Merlin.. Jim saw the Dart at
SEMA last year and liked it. He ordered 6 and I got the first production block Dart made. Jim is famous for high hp blown BB and when he built mine he
said that the and block and bottom end were good for 1,800 hp with out any other mods.
You are rite about the 4.625 but then you would not have much left for a rebuild.

 

Finally found some info on the big Dart block. It's very impressive! The Dart is 240 lbs, and the World is 270 lbs. The 30 lbs savings is much more that I though it would be, the equivalent of replacing one of my iron heads with aluminum. The Dart block is looking better all the time! Where did I put that credit card...:lol:

[B]Dart has reinvented the Rat motor! Our new cast-iron Big M big-block is a no-compromising design that solves the problems that have plagued big block racers for years. Working with top builders and Dart's own championship-winning Pro Stock engine department, we designed a user-friendly block with the features you need today.
For example, we redesigned the lubrication system to create a true "priority main" system that oils all the main bearings before the lifters for extra reliability. Our stepped main oil gallery (9/16" to 1/2" to 7/16") increases the flow of oil to the crank at high rpm, and our front oil crossover eliminates internal oil leaks around the distributor shaft. The result: more oil at the bearings and pushrods where it's needed, and less power-robbing crankcase windage.

Big-blocks are prone to head gasket failure in the long spans between head bolts. We added two head stud bosses on both sides of the lifter valley to take the place of the "missing" head bolts. The bosses are slotted so you can use studs instead of the hard-to-install bolts.

We machine Big M blocks in-house on precision CNC equipment to ensure quality and to eliminate the need for expensive "blueprinting." We engineered the Big M to be the strongest, most reliable, and easiest to build big-block on the market. Ask your engine builder about Dart - and then step up to the Big M!



Material: Superior Iron Alloy
Block Height: 9.800" & 10.200"
Bore: 4.250" or 4.500" unfinished
Bore & Stroke: 4.625" x 4.750" max recommended
Main Bearing Size: Std. BBC
Main Caps: All 4-Bolt Steel or Ductile Iron
Weight: 240lb.
Largest Recommended Bore: 4.625"
Camshaft Bearing Diameter: Std. BBC
Camshaft Position: Std. BBC
Cam Drive: Std Timing chain, gear drive, or belt drive
Cylinder Wall Thickness (min): .300" @ 4.625" Bore
Deck Thickness (min): Adequate for all apps
Torque Specs/Main Caps: 1 - 5 1/2" bolts/2 - 4 1/2" splayed
Cubic Inch: 632" max recommended
Fuel Pump: Mechanical Fuel Pump provision
Freeze Plugs: Press-in cup plugs
Oil Filter: Std. oil filter location
Rear Main Seal: Std. 2-piece seal

Siamesed extra-thick cylinder walls resist cracking and improve ring seal (minimum .300" thick with 4.625" bore).
Scalloped outer water jacket walls improve coolant flow around the cylinder barrels to equalize temperatures.
Standard 9.800" and extra-tall 10.200" deck heights available for stroker engines.
Four-bolt main bearing caps in steel or ductile iron have splayed outer bolts for extra strength.
Crankshaft tunnel has clearance for a 4.500" stroke crank with steel rods without grinding.
True "priority main" oil system lubricates the main bearings before the lifters.
Oil filter pad is drilled and tapped for an external oil pump.
Rear four-bolt cap uses standard oil pump and two-piece seal - NO adapter required
Lifter valley head stud bosses prevent blown head gaskets between head bolts.
External block machining reduces weight without sacrificing strength.
Mechanical fuel pump boss, clutch linkage mounts, and side and front motor mounts simplify installation in any chassis
Dual oil pan bolt patterns fit standard and notched oil pans.
Bellhousing flange and rear main bearing are reinforced with ribs to resist cracks



[Modified by Flareside, 7:54 PM 12/12/2001]

 

That Dart looks like a nice piece. But where did the 30 lbs go? Still a tough piece!

Don't worry about streetability on it. My wife regularly drives mine to cruise nights. I promised her i wouldn't make it drive any more "radical" than the old 427. I believe it's almost milder with all the cubes.

Just be careful not to underhead or cam the dude. It will kill it. It's hard to go to big on them. Typical .650 lift cams idle under 1000 rpm. You gotta forget everything you ever thought about as being "big".

I also counted on being able to get a few rebuilds in if necessary. But who am I kidding... the 427 was 20 years old and still has a std. bore and crank!


Jim

 

Flarside,

I received an e-mail from Scoggin Dickey that they are running a special Merlin II blocks. They are selling the fully prepped block with a 4.5" bore for $1695. Both standard and tall deck blocks are the same price.

I have been looking into building a 540 stroker myself. http://www.sdpc2000.com/

John

 

Darn John, I had just decided to go with the Dart block, since it's lighter and the price was comparable. Now the Merlin is cheaper, and it's pre-bored... Thanks, I think ;)

What's a bore and plate hone worth these days? $200?

-Joe


[Modified by Flareside, 9:24 AM 12/15/2001]

 

Well John, I just couldn't resist at that price. A brand new Merlin II 4.5" fully prepped block is on it's way to me for $1764 including shipping. Thank you very much!

-Joe

 

Joe,

Congratulations on your purchase. :cool: I think that you will be happy with it. I will probably order one on Monday after I check with one of my distributors to make sure that it is OK to have it delivered to their warehouse. I travel quite a bit for work , and I don't think my wife would be much help in getting it off of the back of a truck. I also don't want it delivered to a freight terminal.

Have you made a decision on your rotating assembly. I found that Flatlander Racing out of New Hampshire has excellent prices. http://www.flatlanderracing.com/

John

 

Thanks again for the tip John. Don't procrastinate too long, the salesman I spoke to said they're selling pretty quickly, and that once their inventory is gone, so is the sale price. A friend of mine runs the loading dock at my office, so I'm having it shipped there.

My rotating assemble will have to wait until after the holidays. I think my wife would kill me if I spent more money right now :blueangel: I have looked at Flatlander, but the more affordable assemblies on their site use "cast in China, machined in the US" Scat connecting rods, and they don't include balancing. Everyone in the business seems to recommend that Chinese cranks are ok in a street engine, but that you should go with a higher quality connecting rod. Apparently World Castings also thinks so, since they use Scat cranks and Manley rods. I found that the Bill Mitchell Hardcore (The maker of World Castings/Merlin) assemblies are pretty reasonably prices, and available through Summit racing. They are high speed balanced from the factory. I have a 10% discount code for Summit that's good through Dec. 31st if your interested. Email me off-line at 6brl427@optonline.net

The other setup I'm considering is a 509 using a forged GM 4" 454 crank, GM LS7 rods with 7/16" bolts ($360 per set!), and forged pistons. This would be the cheapest option, and some say it's the strongest with the shorter stroke and all US parts.

Are you going to run the 3x2 on a Merlin? Should be nice!

-Joe

 

Joe,

Yes I am going to use the tri-power setup. It flows a lot of CFM and I have it matched to a set of Chev. aluminum rec. port heads that have been ported and cc'ed. The 3x2 also has a nice Wow factor when you open the hood.

I have a Edelbrock 2x4 intake with carbs that I was thinking about using but there is not enough clearance to use a decent air cleaner with a stock BB hood.

Thanks for the offer on the Summit discount but I don't need it. I have the pistons plus one of the guys from my company's performance division has a line on the crank and rods for me.

John

 

So John, did you get your Merlin ordered? :D

 

Joe,

After thinking about it over the rest of the weekend I ordered a Dart Big M block for $76 more than the Merlin II. I know that the Merlin has been honed while the Dart is not, but I like the idea of being able to fit each piston to each bore. Through my company(I work for Federal - Mogul) I have some contacts at machine shops where I know I can a good deal on the labor. I am also thinking about sending it out to our Training Center in St. Louis. I could have it put together when they run a Performance Engine School. The freight out and back would be more than covered by what I would save on the labor. Plus any FM parts that are used during the build up would be no charge. It would also be fun to assemble it myself. I just need to decide what I want to do.

It was allegedly shipped out on Tuesday, so with luck it might be here by Friday. I've got my fingers crossed.

John.

 

Congrats John! It's good to work for FM, huh? Can't beat free parts and labor.

So are you going to use a 4.6" bore in that Dart? 565 just has a nice sound to it... Heck, it seems like everybody has a 540 these days!

Thanks again,

Joe