Darton Sleeved 5.3 Blocks
Joined: Apr 2006
Posts: 3,909
Likes: 1,158
From: Grand Rapids, Michigan
Pretty simple - Certain 5.3 blocks, from the factory, have siamese bores and a LOT of material around the factory sleeves. Siamese bores are stronger, as they are supported fore to aft in the block instead of having a water jacket between the bores. This also makes the block more suited to be sleeved with a much larger sleeve for more cubes.
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Joined: Apr 2006
Posts: 3,909
Likes: 1,158
From: Grand Rapids, Michigan
Maybe on an unbored iron 5.3 you might have more strength in the bottom end, but iron 5.3s don't have siamesed cylinder walls. Iron 6.0s are notorious for radial cracks in the bores, which is partially due to the lack of siamesed walls. Under immense cylinder pressures, the bores try to expand like a balloon ( relatively speaking ) and eventually crack. In the aluminum 5.3s case ( siamesed versions only ), they have the wall thickness AND the support from metal between the bores. A lot of people seem to be using them for high boost, big power builds. I'm building one myself (stock sleeves), for a much more modest power level. Price-wise, I don't think you're going to get an aluminum aftermarket block for what it costs to sleeve one of these. An iron one, sure. That weighs 150+ lbs. more. All depends on your plans and desires for your build. I'm certain there's a crossover point that an iron block makes more sense.
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5.3L iron truck blocks tend to be used because they are readily available and inexpensive. And the truck engines don't have any bay-to-bay breathing holes in the main webbing so there is added strength for high power applications. Downside is you don't have bay-to-bay breathing which helps with oil control & return.
Also, I think the builders prefer iron blocks from a manufacturing process perspective because it is much easier to modify for sleeves. The block is machined to accept the sleeve and then the sleeve pressed in. Aluminum blocks have sleeves from the factory that have to be removed, and then the block is prepared to accept the new sleeve. The process with aluminum block is more difficult and time consuming, but it gives similar benefits of stronger liners and capability for larger bore and longer stroke.
For everyday builds they're going to use the most economical block as a starting point. That's the 5.3L for iron block, and the LS3 for aluminum block. If you have your own LS2, LS7, or aluminum 5.3L then they'll use it if you ship it. You'll have a tough time finding somebody to sleeve your LS1 because the block is thinner in critical areas and typically don't have such a good outcome.
What is also nice about sleeving a 5.3 is the sleeves are longer and you can run more stroke comfortably (less piston rock). The Darton sleeves are 5.80 inches long and the OEM are like 5.600 inches.
The draw is more bore, stroke, and there’s some stronger material strength from the sleeves.
I know that Dart blocks have .375 longer cylinder barrels than OEM so that is probably in-line with the sleeves.
A quick search says a Gen 4 aluminum 5.3 weighs 121lbs. (Claim was more than Gen 3 aluminum block), 6.0 iron weighs 211lbs., and the Dart iron Pro next block comes in at 227lbs. Not sure what a sleeved 5.3 block weighs but I’d think a few lbs. more than what it started as.
I mean if you wanted to really prep a sleeved block for forced induction and RPM, your talking a 1/2” head studs, perhaps block/head hoops, and pinned billet mains but you’d be awfully close or over the cost of a final machined Dart block at that point. If you are class racing and aftermarket blocks are not allowed then that is your option. Dart block you get better oiling, billet mains, and additional head bolts.
I know that Dart blocks have .375 longer cylinder barrels than OEM so that is probably in-line with the sleeves.
A quick search says a Gen 4 aluminum 5.3 weighs 121lbs. (Claim was more than Gen 3 aluminum block), 6.0 iron weighs 211lbs., and the Dart iron Pro next block comes in at 227lbs. Not sure what a sleeved 5.3 block weighs but I’d think a few lbs. more than what it started as.
I mean if you wanted to really prep a sleeved block for forced induction and RPM, your talking a 1/2” head studs, perhaps block/head hoops, and pinned billet mains but you’d be awfully close or over the cost of a final machined Dart block at that point. If you are class racing and aftermarket blocks are not allowed then that is your option. Dart block you get better oiling, billet mains, and additional head bolts.
Thread Starter
Joined: Jan 2013
Posts: 143
Likes: 22
From: Largo , Florida USA
I'm a bracket racer where all-out engine build efforts aren't necessary . My current 421 Gen One piece has a Dart Little M block that was chosen for durability and it has delivered . I was getting ready to build a replacement for it due to over 4 years of racing , etc and untold thousands of 1/8th mile WOT runs ... I had never really investigated the LS platform but decided to check it out before proceeding with parts collection . When I saw the flow numbers of the LS7 heads , I was sold ... my Brodix 227's are about 40cfm behind the factory LS7 and about 60cfm behind everyone's porting or aftermarket heads . I also learned that the LS7 block was not a durable piece . While the weight saving of an aluminum block is enticing , my C4 is already having some front end anti-gravity issues off the line and my machinist cautioned against the aluminum architecture from a long term reliability angle . (Too much flex and expansion) . I have decided on and purchased a Dart LS Next Pro block for my next powerplant . Meanwhile , the Gen One is still running strong and will likely stay in place until it loses it consistency or its guts .... 3360# 1.34 60's 6.50-6.60 in regular 2000'+ Florida air ... 6.40's in under 1000' DA's @103mph
I'm a bracket racer where all-out engine build efforts aren't necessary . My current 421 Gen One piece has a Dart Little M block that was chosen for durability and it has delivered . I was getting ready to build a replacement for it due to over 4 years of racing , etc and untold thousands of 1/8th mile WOT runs ... I had never really investigated the LS platform but decided to check it out before proceeding with parts collection . When I saw the flow numbers of the LS7 heads , I was sold ... my Brodix 227's are about 40cfm behind the factory LS7 and about 60cfm behind everyone's porting or aftermarket heads . I also learned that the LS7 block was not a durable piece . While the weight saving of an aluminum block is enticing , my C4 is already having some front end anti-gravity issues off the line and my machinist cautioned against the aluminum architecture from a long term reliability angle . (Too much flex and expansion) . I have decided on and purchased a Dart LS Next Pro block for my next powerplant . Meanwhile , the Gen One is still running strong and will likely stay in place until it loses it consistency or its guts .... 3360# 1.34 60's 6.50-6.60 in regular 2000'+ Florida air ... 6.40's in under 1000' DA's @103mph
Last edited by grinder11; Feb 5, 2023 at 11:20 AM.
Thread Starter
Joined: Jan 2013
Posts: 143
Likes: 22
From: Largo , Florida USA
Flow on a head isn't everything. It may be everything once over 5,500rpm, and peak power. However, velocity is just as important. I'm a guy who's had AFR 225 cathedrals on a 427 LS, because thats all there was in 2005. I now have LS7 heads on it. The 225s were about 40hp down on peak power. From idle to 5,500 rpm, they were up by 40-50hp almost everywhere on the curve. They started losing their advantage after 5,000-5,500 rpm. BUT, the 225 heads were so much snappier, and felt faster. Period. Also got 4-5mpg better mileage. Also, LS7 blocks are plenty durable, up to a point, say 1,000hp-up. The LS7 has a problem with the heads far more often than the block. Put a good set of Brodix BR7 heads on an LS7 block, and stuff it with a Callies crank, rods, and good pistons, and the LS7 is very reliable. I'd trust it to at least 800-900hp. Thomson (now Lingenfelter) Automotive cracked the 1,000hp level with an FI LS7. They were selling complete 1,000hp LS7 engines for $40,000. Nobody is gonna pay $40,000 for an engine that goes boom every year.....
GM Gen IV aluminum 5.3 The 5.3 12571048 and 12601900 are the strongest of the GM aluminum production blocks that can be dry sleeved with Darton ductile iron sleeves. These castings are the only two castings with siameesed bores. Can't dry sleeve a non siameesed block. These also have solid main bearing bulkheads, no breather holes which weaken the blocks. Breather hole blocks can crack between the breather holes and cam bearing bores when highly stressed. Weight is around 110 pounds with main caps. I don't think you would want the weight of an after market iron block in the front of a Vette. An aluminum Dart block costs more than double what it costs to sleeve a 5.3 if you can get one. Great if you are looking to make 2000 plus horsepower. I'm a Dart dealer as well. I can sleeve any make block that can be sleeved.using Darton off the shelf or custom sleeves I design for the application.
__________________
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
