Motown or Dart Block?
Le Mans Master
Joined: Feb 1999
Posts: 5,877
Likes: 1
From: Park Ridge IL
Re: Motown or Dart Block? (John Dirks)
If your big inch SBC is going to utilize a 4.00" stroke or greater, I'd go with the Dart Iron Eagle/GM Rocket block. The WP Motown blocks and the Dart Little M's are great aftermarket blocks which feature significant enhancements to improve their strength and durability in high performance applications, but they have a couple of compromises for the sake of economy.
WP and Bill Mitchell like to taut the Motown blocks as having an advantage over the Dart Iron Eagle/GM Rocket blocks becuase you don't need a special oil pan or timing chain/cover, but they exaggerate the difference in cost. The Dart Iron Eagle/GM Rocket block feaures a couple of unique enhancements which allow it to accomodate a 4.00"+ stroke much easier and without compromising the strength of the block and the rotating assembly.
The Iron Eagle/Rocket blocks feature spread pan rails, .400" each side, which allows you to run a 4.00" stroke without any blcok machining. You can run as much as 4.250" stroke if you notch the bottom of the cylinder bores as you'd do with a standard 383 stroker using a production 350 block. The oil pan to fit these spread rails are not that expensive. Jeg's and Summit sell steel Moroso pans, including an oil pump and the appropriate pcikup for around $275. Stef's makes nice aluminum sheetmetal oil pans for $300-$600, depending on feures such as windage screen, trap doors, crank scrpwer, etc. also including an oil pump and pickup.
The Iron Eagle/Rocket blocks also incorporate a raised cam location, .391" compared to stock. This eliminates interference between the camshaft and the connecting rods which is problematic in stroker SBC's using production blocks. Again, the cost of the special timing chain/belt/gear over a stock component is minimal. Cloyes offers a Tru-double roller timing chain for the rased cam blocks for $100, and you still use a standard timing cover and gasket. Belt drives and gear drives are also readily available with comparible costs to the standard components.
You will also need shorted pushrods since the lifter bores are higher in the block, but any valvetrain company does custom length pushrods for not much more than off-the-shelf pushrod lengths.
The Iron Eagle/ Rocket blocks do not have an integral oil filter pad, so a remote oil filter mount and plumbing is reguired. Depending on which oil filter adapter you chose to use, it could cost you $50 to $300. Jeg's/Summit offer several affordable cast aluminum remote oil filter mounts for around $50 or so, or you can use nicer, billet aluminum stuff from Barnes, SCE, CV Products, etc. You'll also have to factor in the cost of the AN plumbing but it's not necessarily cost prohibative, and depending on how you set it up, it can provide alot of advantages over a block mounted oil filter.
Some additional options that you can add to the Iron Eagle/Rocket block are talled deck heights, 9.325" (offered on cast iron and aluminum blocks) and 9.500" (only offered on the aluminum version blocks), as well as a choice of BSC, BBC, and 50mm roller cam bearings. You can also chose between 350 and 400 SBC main journals. The taller deck height will allow you to run a longer rod with the longer storkes so that your rod/stroke ratio and piston compression heights do not have to be compromised. Even with a 4.0" stroke, I run a 6.125" rod and a 1.17" compression height to maintain a good rod stroke ratio. My rod/stroke ration is identical to a 454 BBC, and slightly better than the commonly used 5.7" rod 383.
If you maintain a stock deck height, the difference between using an Iron Eagle/Rocket block and using a Motown, Bowtie, or Little M is potentially less than $500 or so, depending on the components you use. But that number is reduced further if you factor in the additional machining and clearancing that must be done to the Motown, Bowtie, or Little M to accomdate the 4.0"+ stroke.
The big cost increases start to come into play when you increase the deck height, since you now need a custom intake manifold or intake manifold spacers. But to do it right, it's a good way to go if the budget allows.
[Modified by Monty, 3:56 PM 3/6/2003]
WP and Bill Mitchell like to taut the Motown blocks as having an advantage over the Dart Iron Eagle/GM Rocket blocks becuase you don't need a special oil pan or timing chain/cover, but they exaggerate the difference in cost. The Dart Iron Eagle/GM Rocket block feaures a couple of unique enhancements which allow it to accomodate a 4.00"+ stroke much easier and without compromising the strength of the block and the rotating assembly.
The Iron Eagle/Rocket blocks feature spread pan rails, .400" each side, which allows you to run a 4.00" stroke without any blcok machining. You can run as much as 4.250" stroke if you notch the bottom of the cylinder bores as you'd do with a standard 383 stroker using a production 350 block. The oil pan to fit these spread rails are not that expensive. Jeg's and Summit sell steel Moroso pans, including an oil pump and the appropriate pcikup for around $275. Stef's makes nice aluminum sheetmetal oil pans for $300-$600, depending on feures such as windage screen, trap doors, crank scrpwer, etc. also including an oil pump and pickup.
The Iron Eagle/Rocket blocks also incorporate a raised cam location, .391" compared to stock. This eliminates interference between the camshaft and the connecting rods which is problematic in stroker SBC's using production blocks. Again, the cost of the special timing chain/belt/gear over a stock component is minimal. Cloyes offers a Tru-double roller timing chain for the rased cam blocks for $100, and you still use a standard timing cover and gasket. Belt drives and gear drives are also readily available with comparible costs to the standard components.
You will also need shorted pushrods since the lifter bores are higher in the block, but any valvetrain company does custom length pushrods for not much more than off-the-shelf pushrod lengths.
The Iron Eagle/ Rocket blocks do not have an integral oil filter pad, so a remote oil filter mount and plumbing is reguired. Depending on which oil filter adapter you chose to use, it could cost you $50 to $300. Jeg's/Summit offer several affordable cast aluminum remote oil filter mounts for around $50 or so, or you can use nicer, billet aluminum stuff from Barnes, SCE, CV Products, etc. You'll also have to factor in the cost of the AN plumbing but it's not necessarily cost prohibative, and depending on how you set it up, it can provide alot of advantages over a block mounted oil filter.
Some additional options that you can add to the Iron Eagle/Rocket block are talled deck heights, 9.325" (offered on cast iron and aluminum blocks) and 9.500" (only offered on the aluminum version blocks), as well as a choice of BSC, BBC, and 50mm roller cam bearings. You can also chose between 350 and 400 SBC main journals. The taller deck height will allow you to run a longer rod with the longer storkes so that your rod/stroke ratio and piston compression heights do not have to be compromised. Even with a 4.0" stroke, I run a 6.125" rod and a 1.17" compression height to maintain a good rod stroke ratio. My rod/stroke ration is identical to a 454 BBC, and slightly better than the commonly used 5.7" rod 383.
If you maintain a stock deck height, the difference between using an Iron Eagle/Rocket block and using a Motown, Bowtie, or Little M is potentially less than $500 or so, depending on the components you use. But that number is reduced further if you factor in the additional machining and clearancing that must be done to the Motown, Bowtie, or Little M to accomdate the 4.0"+ stroke.
The big cost increases start to come into play when you increase the deck height, since you now need a custom intake manifold or intake manifold spacers. But to do it right, it's a good way to go if the budget allows.
[Modified by Monty, 3:56 PM 3/6/2003]
