[383Eliminator]

Hello everyone. I would like to pick everyones brain. Last year I got my blown 383 put together and running in my boat with a ton of help from this forum. I broke the snout off my crankshaft at the end of last season. I currently have a Chevy small block 383 with a stock block, AFR heads, and a 6-71 blower. Now I need a new crankshaft, and was working with Bob Madera of Marine Kinetics for a custom ground cam shaft. He is telling me that with the amount of boost that i want to make that the main caps are not going to last. Well this made me think about what other options are out there. I have read the the Vortec 6.0 truck engines have really stout bottom ends and the heads from what I can tell flow pretty good as well. I want to do a stock Vortec 6.0 long block with a refresh and forged pistons. Then install the 6-71 blower, custom cam, and run dual 750 carbs and E-85. Will the LQ9/LQ4 bottom end hold up to 700-800 HP?

[sprayed99]

Originally Posted by 383Eliminator

Hello everyone. I would like to pick everyones brain. Last year I got my blown 383 put together and running in my boat with a ton of help from this forum. I broke the snout off my crankshaft at the end of last season. I currently have a Chevy small block 383 with a stock block, AFR heads, and a 6-71 blower. Now I need a new crankshaft, and was working with Bob Madera of Marine Kinetics for a custom ground cam shaft. He is telling me that with the amount of boost that i want to make that the main caps are not going to last. Well this made me think about what other options are out there. I have read the the Vortec 6.0 truck engines have really stout bottom ends and the heads from what I can tell flow pretty good as well. I want to do a stock Vortec 6.0 long block with a refresh and forged pistons. Then install the 6-71 blower, custom cam, and run dual 750 carbs and E-85. Will the LQ9/LQ4 bottom end hold up to 700-800 HP?

It is a dice roll at best. If you are going to spend the time to do pistons just do the rods. The crank will hold no problem. Many people have made north of 1000 with the factory crank.

[Hogg]

The factory GM rating on the block is 500hp, the LSX block is 1500+ or over 2000+hp in a drag race app.

The GEN 1 SBc's sure do like to snap the snouts of the cranks in blown apps. Even the forged 4340 3.80" GM stroker cranks have been busting off when driving a blower..

peace
Hog

[sprayed99]

Originally Posted by Hogg

The factory GM rating on the block is 500hp

Not sure where you found this information, but it has been proven false by many. Hell I have only owned one LS based engine that made under 500 and never once have I had a block failure.

[383Eliminator]

I have have a great deal on a LS1, but after reading it seems that the LQ9/ LQ4 iron blocks are a lot stronger then the aluminum LS1/LS2 versions. My Gen 1 block held up so far with the abuse. I would rather try this then to hold onto the old school small block forever.. Right now I plan to use the block and crank and use forged rods and pistons with L92 heads..

[1Gary]

Originally Posted by 383Eliminator

I have have a great deal on a LS1, but after reading it seems that the LQ9/ LQ4 iron blocks are a lot stronger then the aluminum LS1/LS2 versions. My Gen 1 block held up so far with the abuse. I would rather try this then to hold onto the old school small block forever.. Right now I plan to use the block and crank and use forged rods and pistons with L92 heads..

The aluminum blocks are the ones with limits of HP.In fact the aftermarket speaks to that in how they have addressed that in their design.The cast iron is a stronger part.
There is two thoughts that come to mind given you build plans.

First,the 6.0 isn't known for good gas mileage.It's better than a 383,but still isn't as good as the 5.3.So I am thinking if your plan is because you think your going to gain in that department,you might be disappointed.

Second,I know the LSx's have been turbo'ed with good success.I don't recall one with a roots type blower.I do know crank companies in the first Gen's offering a bigger snout to address the problem you have,but I don't think I've seen that for the LSx's.With the turbo it wouldn't be a issue and turbo's have a solid mid and not so much so for a bottom or top end.But I would think for a boat that would be ideal for a constant run mid rpm having a power curve right where you want it and use a EFI system for throttle response.

In general I sure wish Chevy hadn't build the c.i. sizes they did in the LSx engines in a attempt to save on gas mileage and then tried to compensate with power train gear ratio's/electronics.Most of it seems they turned back the clock to the days of 327 first gens.Certainly the mod'ed first gens out shine the LX's in the bottom end range.

[cobalt327]

Using a sbc crank w/a bbc snout should have held up, along w/splayed 4-bolt caps. But at some point, the caps will begin to move, regardless.

The iron LSx blocks are tough- and crossbolted. The LS crank snout is a bit over 1.48" (sbc is about 1.245", bbc is about 1.6”), the wrist pins are bigger, has a bigger main journal size (about 2.56"), even the cam is bigger in diameter.

Stock LS cranks have been used to make more than the power you're aiming for, but a Roots blower will impart more load than NA or even a turbo application, so aftermarket forged is a good insurance policy if it's in the budget.

[sprayed99]

Originally Posted by 1Gary

I know the LSx's have been turbo'ed with good success.I don't recall one with a roots type blower..

Magnacharger (Eaton), KenneBell, and Whipple all make a roots blower for the LS engines.

The TVS 2300 has made the numbers he is after on pump gas with a forged 6.0 block. With the newer Whipple 4.0 blower those numbers will be really easy to get.

The Magnachargers are the best priced for what you get IMO.

Then you also have the centri blowers like the paxton, vortec, and pro charger. I personally like the procharger. In fact the 2 fastest stock rotating assembly SS Silverados In the country are D1 procharged both with stock heads.. They are running 11.0X 1/4 and weigh in at 5200+ lbs.

Turbos are cool but a total pain in the ***** to tune and get running right unless it is a full out race effort, but on a budget the blowers just down right work!

[383Eliminator]

I have seen some of the articles about the newer blowers making a ton of power. I just picked up a blower shop billet blower and love the look of a jet boat with a nice blower and long tube headers.. Kinda mixing both worlds together. I really want the strength of the LQ9 block and the efficiency of the L92 heads.. Should be a fun spring project and hopefully I put some big blocks in there place...

[sprayed99]

Originally Posted by 383Eliminator

I have seen some of the articles about the newer blowers making a ton of power. I just picked up a blower shop billet blower and love the look of a jet boat with a nice blower and long tube headers.. Kinda mixing both worlds together. I really want the strength of the LQ9 block and the efficiency of the L92 heads.. Should be a fun spring project and hopefully I put some big blocks in there place...

Only advise I can give you on the L92s is find someone that knows what they are doing to spec a cam. The major difference in port sizes makes it a different animal compared to the cathedral port heads.

Your boat should run good as long as the parts work well together.

[Hogg]

Originally Posted by sprayed99

Not sure where you found this information, but it has been proven false by many. Hell I have only owned one LS based engine that made under 500 and never once have I had a block failure.

read my post again, ITS THE FACTORY GM RATING. 500HP rated by GM. Just because you CAN do something, doenst mean that the manufacturer will rate the product at that level. The surce of that info is GM literature.

peace
Hog

[Hogg]

Originally Posted by 1Gary

The aluminum blocks are the ones with limits of HP.In fact the aftermarket speaks to that in how they have addressed that in their design.The cast iron is a stronger part.
There is two thoughts that come to mind given you build plans.

First,the 6.0 isn't known for good gas mileage.It's better than a 383,but still isn't as good as the 5.3.So I am thinking if your plan is because you think your going to gain in that department,you might be disappointed.

Second,I know the LSx's have been turbo'ed with good success.I don't recall one with a roots type blower.I do know crank companies in the first Gen's offering a bigger snout to address the problem you have,but I don't think I've seen that for the LSx's.With the turbo it wouldn't be a issue and turbo's have a solid mid and not so much so for a bottom or top end.But I would think for a boat that would be ideal for a constant run mid rpm having a power curve right where you want it and use a EFI system for throttle response.

In general I sure wish Chevy hadn't build the c.i. sizes they did in the LSx engines in a attempt to save on gas mileage and then tried to compensate with power train gear ratio's/electronics.Most of it seems they turned back the clock to the days of 327 first gens.Certainly the mod'ed first gens out shine the LX's in the bottom end range.

1 reason the 6.0 has a bad wrap for fuel economy is because a mjority of 6.0's are found in 3/4 and 1 ton trucks and use the 4l80e trans. Apples to apples comparison with a 5.3 in a 1/2 ton truck and a 6.0 in a 1/2 ton truck reveal that fuel consumption is on par for the displacement difference. Its not like the GEN 3/4 6.0's are gas hogs by design.

I agree 100%, the new 6l80e/90e and their 4.0:1 1st gears are in use to make up for the lack of low rpm torque the GEN 3/4 engines possess. The GEN 4 LY6 is a 6.0 installed in the 3/4 and 1 ton trucks and it is a dog at low rpm, even with its VVT.
In my Vortec 350 truck I can put along 1400rpm in OD with the torque converter clucth locked up. If I apply throttle will accelarate as is. Same scenario in a GEN 3/4 engine power truck results in a downshift or TCC unlock.

peace
Hog

[Hogg]

Originally Posted by 383Eliminator

I have seen some of the articles about the newer blowers making a ton of power. I just picked up a blower shop billet blower and love the look of a jet boat with a nice blower and long tube headers.. Kinda mixing both worlds together. I really want the strength of the LQ9 block and the efficiency of the L92 heads.. Should be a fun spring project and hopefully I put some big blocks in there place...

Just look at the GEN 4 LSA from the Cadillac CTSV V2, and later the Camaro that GM has relasedd for marine use.

530hp@5400rpm and 545lb/ft@4000rpm. It uses the 1.9 liter Eaton TVS blower with a single element integral intercooler.
-LSA 1.9 blower runs 9 psi boost, 2.3l LS9 blower runs 10.5psi

-The LSA and LS9 run an aluminum block and oil squirters that coat the bottoms of the pistons and cylinder walls with oil.
-The LS9 in the ZR1 Vette uses a specific block that is machined differently to enhance durability, the LSA is different than the LS9's block but is an upgrade over the "standard" GEN 4 6.2 aluminum block
-12mm headbolts vs 11 for the LSA and other GEN 4 engines(new GEN 5 LT1 uses 12mm headbolts exclusivley).
-LS9 runs forged titanium con rods, LSA runs powdered metal forgings
-LS9 runs forged pistons LSA runs cast hypereutectic (high silicon) pistons
-LS9 runs 2 smaller intercooler elements for Vette hood clearance while LSA --runs 1 single element
-both run a forged steel crank

If you look at the differences between these 2 OEM supercharged engines, it will give you indications of where you may need to pay extra attention during your own GEN 3/4 marine engine build. If you start boosting these GEN 4 L92/LS3 heads you can build a TON of power. Even in NA form, an GEN 3 LQ4/9 with GEN 4 L92/S3 heads or a GEN 4 LY6(truck engine with L92/S3 heads) has easily over 500hp potential. 550hp with attention to details.

Another cue to observe, is that when GM did the COPO Camaros, you could get a 2.9 or 4.0 displacement Whipplecharger on a 5.3 engine.
GM never offered a blown LS7. This block is at the high limit at 505hp stock. GM wanted the extra stiffness of the smaller 6.2l bore for the LS9 Corvette and 69 GEN 5 COPO Camaros.

We have to be careful using the LSx reference esp. when talking about blocks. Some people call the GEN 3 and GEN 4 engines LSx, but now Gm has their GEN3/4 iron racing block that they called the LSX block.

Many of the GEN 3 and GEN4 engines weren't actual LS engines. There were the truck engines which were LR4, LM7, LQ9, LY6 etc etc.

Good luck and keep us posted.

peace
Hog

[sprayed99]

Originally Posted by Hogg

read my post again, ITS THE FACTORY GM RATING. 500HP rated by GM. Just because you CAN do something, doenst mean that the manufacturer will rate the product at that level. The surce of that info is GM literature.

peace
Hog

Okay I get it... but bottom line if we all followed GM's information none of us would be running these engines past 1000hp. We wouldn't even see them running Heads and cam swaps and making north of 400rwhp. So If the 500hp statement needs to be made it also needs to be followed with the source as we all know its just GM doing the good ole CYA.

[Hogg]

Originally Posted by sprayed99

Okay I get it... but bottom line if we all followed GM's information none of us would be running these engines past 1000hp. We wouldn't even see them running Heads and cam swaps and making north of 400rwhp. So If the 500hp statement needs to be made it also needs to be followed with the source as we all know its just GM doing the good ole CYA.

To imply that 1000hp using a stock 6.0 block esp. in a marine environment will be be durable is risky.

GM marine engines have to pass the 300 hours "dock test". And engine is in a boat that is tied to a dock. The engine is held at WOT for 55 minutes at a time, and let idle for 5 minutes, then returned to WOT for another 55 minutes for 300 hours straight. BTW 300hrs is 12.5 days. A 18,000 minute test length with 1500 minutes at idle and 16,500 minutes at WOT.

Other GM engines have to pass the 200 hour test, the engine on a dyno is cycled from the rpms at which peak hp and peak tq occur at WOT for 200 hours.

Your 1000hp scenario would be for 10 seconds at a time MAYBE. Hold that 1000hp for a minute of 2 and see what happens. Maybe it will take it, but for how long is anyones guess. Without proper engine validation it is simply conjecture.

My point here is that even though GM is obviously conservatively rating some of their performance parts, simply taking performance parts and having them stay together for short periods of time doesnt meake the factory ratings invalid, just conservative. just because an engine block has survived 1000hp, doenstmean it shoudl be rated ta 1000hp. A perfect example of this is the LSX iron block, GM rated at 1500hp sustained, and over 2000hp short term(less than 10 seconds ina drag race scenario).

With a 500hp factory rating and claims of 1000hp short term surviveability, in a marine environment, sustained durability would be somewhere in between, but again this is again conjecture on my part.

The GEN 3/4 engines are great powerplants and will survive dozens or dyno pulls at WOT over 1000hp. Simply amazing engines with many many examples of NA daily drivers running 500-600 hp at the crank and forced induction running even more.

peace
Hog