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Discussion Starter #1
So I am starting from scratch on a LS for my 1200 - 1300 hp twin turbo project. I know guys on budgets are going to say I can do this with a junkyard 5.3, but I am fortunate enough to afford to do it right. Not looking to go totally overboard but don't want to cheap out also

So what is the block of choice? Block has to be aluminum and for 6 bolt heads.
What crank and rods?
 

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i did a stock 5.3 iron block and crank, dss forged pistons and compstar rods. made 1300 on 25 pounds
 

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Factory iron block and crank. Good rods and pistons. Factory square port heads and even an LS3 intake/TB would probably get you to 1200. I run stock 5.3 truck parts (good rods and pistons) with cast manifolds and an 80mm turbo, and a comfortable tune up (with room to grow ) is at 1000
 

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This is an iron block... but has great heads!
https://ls1tech.com/forums/market/1904188?highlight=block

I ran an LS9 block, LS1 $100 crank, Compstar rods, Wiseco pistons, MAST LS3 heads (4 bolt), baby hydraulic cam, LS3 stock intake and nice Precision T4 88mm billet/BB turbo making 1000-1200rwhp+ for 3 years. never lost a head gasket and did probably 100 1/2 mile pulls in it pushing 21-22psi in 5th gear (no idea on power level). On 14psi it made 1060rwhp with $2/gal e85. After showing off doing a massive 1st-4th gear burnout it hooked up showing an indicated 150mph on the speedo (I was going maybe 70-80mph) and I snapped the crank at the 7/8 rod journal clean through. I rebuild it with a K1 crank, 2 new rods, rings/bearings and plan to do all over again this year. I like the billet main caps, piston squirters, and 12mm head bolts/studs from the factory. it is also cast from a better grade alum and rotocast (shaken when molten making it denser due to less air bubble). LS9 block is a great bang for the buck.

I would say at the 1200rwhp mark is the threshold for switching over to a 6 bolt block. It is also the turning point from a $6-8K built 4 bolt alum shortblock to double that or more going with alum 6 bolt.
 

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Discussion Starter #9
This is an iron block... but has great heads!
https://ls1tech.com/forums/market/1904188?highlight=block

I would say at the 1200rwhp mark is the threshold for switching over to a 6 bolt block. It is also the turning point from a $6-8K built 4 bolt alum shortblock to double that or more going with alum 6 bolt.
These builds always impress me so much. I have not short cut anything on this project yet, I am prepared to spend the money. I will sell this car at some point, the parts list is / will be impressive, it will be expensive when I market it (when I am finished playing), so I don't want to start cheating now. But with that said I do not think I need a $4000 crankshaft or $1700 rods either
 

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factory iron block,crank with gen 4 rods and pistons with truck heads ...makes about 850 on a dyno but goes 141 to the 1/8 at 3250lbs :confused:
 

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So I am starting from scratch on a LS for my 1200 - 1300 hp twin turbo project. I know guys on budgets are going to say I can do this with a junkyard 5.3, but I am fortunate enough to afford to do it right. Not looking to go totally overboard but don't want to cheap out also

So what is the block of choice? Block has to be aluminum and for 6 bolt heads.
What crank and rods?
If you mean you want an aluminium block, and also to actually use 6 bolt heads with the full compliment of studs...then it must be an aftermarket block, very expensive.

If you're happy to run a factory alloy block, say an LS9, with 6 bolt heads, albeit without the additional studs....then there are more options.

But LS9 block with the 12mm studs, or LSA drilled/tapped for 1/2" studs should be quite fine.

Whilst not needed and there are many many options...it'd be interesting to hear peoples thoughts on Callies new Compstar CCW crank ?
 

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Discussion Starter #16
I do want a aftermarket block and want aluminum. I am going to call and see about oil squirters, is it a option? But was hoping to find some real world feedback from someone running low 20 LBS boost range
 

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I do want a aftermarket block and want aluminum. I am going to call and see about oil squirters, is it a option? But was hoping to find some real world feedback from someone running low 20 LBS boost range
You arent making 1300hp on 20psi unless you've a big motor and pretty large turbos.

LSA and LS9 blocks come with oil squirters. Not essential, but good to have. Although to a degree that also depends what your intended usage is.

You've had real world feedback from people making the power with other and factory blocks. Although many favour iron as it's cheap/strong, and they arent worried about weight.
 

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Discussion Starter #18
Really do not want to challenge fate with a factory block, I only want to do it once, this is not the kind of build I want hang over fenders to swing multiple motors in and out, nor do I want to bust a block, oil the tires and wade it up. I know a aftermarket block is no guarantee, but always try to do it right. I am fully aware there are plenty of other ways to wade it up, trying to eliminate a motor explosion! So the real world experience with those factory blocks is no good to me, as impressive as it is what has been done.

I wondered about optional squirters because I did a RHS block supercharge motor and the piston squirters were added option. As for boost and power, LOW 20s I meant under 25? Will see. I guess I am trying to say NOT 40lbs. Will have plenty of cubes, It will be 427 CI so it it no a 5.3

The iron is just to heavy, the 100LB + can really affect weight balance, getting very close to 50 / 50 on this project, so weight balance is important. Already got some heavy ass turbos and intercoolers for counter balance. Going to try and mount those turbo near the firewall, but fat front tires most likely wont allow that. Will see.

I thought I would find guys here that used different aftermarket blocks, different combos, but it looks like everyone uses stock blocks.
 

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I thought I would find guys here that used different aftermarket blocks, different combos, but it looks like everyone uses stock blocks.

Some do use aftermarket...but most choose the likes of Darts Iron blocks.

But in the range you're asking for, a well built factory aluminium block can handle it just fine.

RHS and Warhawk used to be two names of alloy blocks that people used. There always seemed to be less than favourable reviews about them though. I think RHS are still on the go, no idea if things have improved with their stuff or not.

I think Dart offer an alloy block too ? But their cheaper iron seems to have taken over.

The TSP one has potential and isnt too insanely priced, but their web page does lack a lot of information.

Steve at RED always gets a mention for sleeved factory blocks, and many might say that is a good route to take, although it still leaves you with 4 bolts, if you feel 6 bolts are essential...which they probably are not.
 

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No need for aftermarket block, heads, or crank at only 1200hp. You don't need a more then factory CI to make 1200hp on 20psi with well matched turbo/turbos. Factory parts are very good and reliable.
 
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