wanting to boost LS7

parker@gearone

parker@gearone

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So I completely rebuilt my new to me dunebuggy.com car last summer. And I had my engine gone through by a shop here in phoenix  but it is a rebuilt LS7 with stock bottom end with heads cam and intake. I know this engine isn't the best to boost just wondering what my options are. depending on my options might just put it on a bottle 🤪

 
what RPM do you drive that engine.?  great power in the 4-5k rpm range on those engines.  If  you like duning with this engine stick with it and throw some NOS on there.  Do at least a 250 if you really want to feel it.  Adding a blower is very costly and lots of stuff to add and buy.  single turbo with no intercooler on 5lbs of boost would be my second choice.   That or sell you engine and buy a complete blower engine package if you have better than a S4 trans. I have a buddy with a brand new complete Redline 440 with whipple for sale.  Never installed.

 
I wouldnt recommend putting nitrous on your LS7 with stock internals. And nitrous is fun for the drags or going up Olds but you want the power all the power all the time.

We basically have the exact same car and I had a Turnkey built LS7 putting 500hp to the tires. Great engine and it had 9 seasons on it between my friend/client@SuperHunky (RIP buddy) big prerunner and my car.  

I built myself a stoker LS2 with Magnacharger making 5-6psi and now have 629hp at the wheels. It woke my db.com car up big time. So much more fun to drive! It was like getting back on a two stroke bike. 

Building myself a twin turbo RHS now and will have it for next season. 

 
Squatcher said:
what RPM do you drive that engine.?  great power in the 4-5k rpm range on those engines.  If  you like duning with this engine stick with it and throw some NOS on there.  Do at least a 250 if you really want to feel it.  Adding a blower is very costly and lots of stuff to add and buy.  single turbo with no intercooler on 5lbs of boost would be my second choice.   That or sell you engine and buy a complete blower engine package if you have better than a S4 trans. I have a buddy with a brand new complete Redline 440 with whipple for sale.  Never installed.
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Isn't the old saying spend 10k to make the car worth 20k more? 🙂

Whats he want for the 440?

 
Squatcher said:
what RPM do you drive that engine.?  great power in the 4-5k rpm range on those engines.  If  you like duning with this engine stick with it and throw some NOS on there.  Do at least a 250 if you really want to feel it.  Adding a blower is very costly and lots of stuff to add and buy.  single turbo with no intercooler on 5lbs of boost would be my second choice.   That or sell you engine and buy a complete blower engine package if you have better than a S4 trans. I have a buddy with a brand new complete Redline 440 with whipple for sale.  Never installed.
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Interested, is it listed somewhere?

Also they car has an albins just gone through by Kevin McMullen, so I'm not to worried about the trans.

L.R.S. said:
I wouldnt recommend putting nitrous on your LS7 with stock internals. And nitrous is fun for the drags or going up Olds but you want the power all the power all the time.

We basically have the exact same car and I had a Turnkey built LS7 putting 500hp to the tires. Great engine and it had 9 seasons on it between my friend/client@SuperHunky (RIP buddy) big prerunner and my car.  

I built myself a stoker LS2 with Magnacharger making 5-6psi and now have 629hp at the wheels. It woke my db.com car up big time. So much more fun to drive! It was like getting back on a two stroke bike. 

Building myself a twin turbo RHS now and will have it for next season. 
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Engine runs awesome and makes 552 on the hub dyno, feels like I want another 200 hp these db.com cars are awesome but heavy.

 
My buddies engine is a brand-new Redline 440 with a Whipple 4.0. It's sitting at Kevin McMullen shop Kevin picked it up from Red Line. My buddy hurt his back so he's out for a couple of Seasons engine brand new sitting there he said he wants $33,000 for it. he has an S4 D sitting there also I believe

 
parker@gearone said:
maybe sandwich this intercooler in my hi ram and throw some turbos on it with low boost like 6-8 psi

https://www.tickperformance.com/tick-1400hp-low-profile-billet-air-to-water-intercooler-for-all-holley-ram-intakes/

View attachment 23201
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Where do you like to sit, RPM wise, most of the time?  Wherever it makes power or "keep it in 3rd" type duning?  Hi-ram on an LS7 making 552hp at the hubs says you've been on the limiter a few times, but just making sure... :biggrin:

 
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Rockwood said:
Where do you like to sit, RPM wise, most of the time?  Wherever it makes power or "keep it in 3rd" type duning?  Hi-ram on an LS7 making 552hp at the hubs says you've been on the limiter a few times, but just making sure... :biggrin:
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I like to cruise at around 3k but on fast runs it definitely sees limiter more than once, usually runs from 4-7 k kicking the clutch and all. my driving style is exactly what keeps the transaxle builders in business.

 
parker@gearone said:
I like to cruise at around 3k but on fast runs it definitely sees limiter more than once, usually runs from 4-7 k kicking the clutch and all. my driving style is exactly what keeps the transaxle builders in business.
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Turbo will give you more power, but there will always be some lag.  Whipple will give you basically the same powerband...  Just 200whp farther up the graph. :biggrin:

 
Supercharger is easier to retrofit IMO and more fun if you dune.  the Turbos require lots of hot and cold side plumbing. the SC requires a heat exchanger radiator (maybe an expansion tank - not always) (pretty small) a  pump (12volt)  and a new Serp belt. (or more pulleys depending on what SC).

Heavy cars always need more TQ throughout the RPM range and thats where the SC is great. Boost done right is not hard on the bottom - RPM is ... The stock Ls7 engine is pretty stout and structurally better than any other LS, even the stock rods are OK -  the issue with Boosting ANYTHING stock is Ring gap - start pushing Turbo boost on that engine without re-gapping the rings and even at 10Lbs you will be in a world of hurt.  Anything less than 10Lbs of turbo is wasting your money - the lag will erase the gains and you Should limit the redline at 6000, so your usable power range will be 4000-6000  thats not a lot, you might get down to 3500 but you will need a big intercooler to keep the IATs down when you spin the smaller snails up around 150k rpm to get boost that low, but back pressure will not be an issue if you keep Redline down at 6000.

With a reasonable SC  - and on a 427 where you want the most power under the curve  say 2500-6000 you can get away on pump at 10-11 lbs boost and not touch the internals (although I would gap the rings personally) and you can get timing back to make it smooth and safe .. The problem is with Ls7 heads you are pretty stuck with Whipple (Whipples are not bad at all, but really shine when you crank up the boost, not efficient on low boost applications) and really the 4.0 is a good size for a few reasons although the parasitic loss is Horrible close to 150HP to turn it- so when only using 10Lbs of boost its a boat anchor on a 427.  the 2.9 is being mostly replaced by the Gen 5  3.0  which has a lot of advantages. No jackshaft - although the drive snout runs through the middle of the Intake air tube and heats the air coming in (dumb IMO)  but that cools the bearings of the shaft so it lives longer.  And the 3.0 takes way less power to turn .. So far I have nit put one on a car but I like the design overall.  The 2.9 was IMO and Interim design to get a bigger SC  with a too large diameter rotor pack under tight car hoods - the designb is compromised by a jackshaft and a smaller in manifold heat exchanger . While the 2.9"should" only take 80-100HP to turn the Jack shaft screws that up - Kenne Bell measured that at 130HP to the turn,  the 3.0 is closer the KB 2.8 which is 65HP  no one publishes the number though I would guess its around 90- 100HP based on the rotor pack being similar to the 2.3 and 3.3  that Whipple used before (Lysholm).   There is not a Roots (not twin screw like Whipple) Eaton-based (magnuson, Harrop etc) 2300 or  2650 alternative they are just too small the HP numbers are not what worth the spend - . although it is very efficient at low boost  and the TQ curve makes them feel fast (think wheelies) and they takes less than 60HP to turn ... the 2300 is basically a waste today - the 2650 is completely replacing it on anything over a 5.7L/ They are good to keep in mind for 383 or 406 .... the numbers 2500-5500 RPM are very impressive.

The problem on a 427 is that now you have to use a really small pulley on the 2.9 even to get 11lbs and you need almost 300 degrees of pulley wrap - thats hard top do ... and due to the rotor design of the Whipple  it has a lot of twist on that pulley and you have small heat exchanger as faster rotors build more heat  (IAT) if you don't go to a 10 rib belt you will likely have issues unless you go with a separate pulley on the crank like the 10 rib (shorter belt). You could go to a bigger lower pulley and therefore a bigger upper pulley  but that again is more spend  (ATI balancer and pulleys are not cheap).

In the end like sizing turbos - sizing SC's is similars - it is the difference between "this is nice"  and "this thing hauls A$$"  for the spend you need to think very carefully on what you choose. I have "upgraded" a few SC cars and most often moved them to smaller SC's and it was night and day, but personally anything with a Jackshaft IMO should not be on a sand car. And SC boost because of the way its delivered is far easier on the ring gap issue (instantaneous heat)  than a same boost turbo.   Their are many stock 427's running around on pump and 10-1Lbs boost for 100,000 miles and plenty of 427's with TT's running around with 7lbs turbo boost as well.  HP is about the same, but the TQ curve on the SC is flat (if done right) with the stock cam from 2500 to X-over  vs the Turbo  where its peaky like HP ...

Either choice done right will wake up yout car....

 
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Not that I wanted to write a book here  ... But Power wise the SC will make the engine feel 50% larger - so whatever HP you make NA  at 14.7Lbs of Boost you should expect to double it and double the TQ - minus the parastolic loss of turning the SC (thats why you want the smallest SC that makes the target boost you are considering - it takes way less to turn it, and why you see small 2300 Eatons on factory cars)  .  At 10Lbs its nearly linear  but I usually see 50% gain  - so 500HP becomes 750HP and 400 Ft Lbs TQ becomes 600 Ft Lbs.  Minus turning losses.  Turbos are about the same by the math, but better in general due to the "peaky nature" of the boost curve - average the curve and its about the same, without the turning loss (yeah backpressure takes some HP...).  And thats why its so important to size the SC correctly.  I always shoot for 22RWHP per lb of boost on a well design SC car with no HP loss from heat soak after long drives.   I verify on the Dyno and its always right there - Turbos are closer to 35HP ,,,,

 
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Fullthrottleguy said:
Supercharger is easier to retrofit IMO and more fun if you dune.  the Turbos require lots of hot and cold side plumbing. the SC requires a heat exchanger radiator (maybe an expansion tank - not always) (pretty small) a  pump (12volt)  and a new Serp belt. (or more pulleys depending on what SC).

Heavy cars always need more TQ throughout the RPM range and thats where the SC is great. Boost done right is not hard on the bottom - RPM is ... The stock Ls7 engine is pretty stout and structurally better than any other LS, even the stock rods are OK -  the issue with Boosting ANYTHING stock is Ring gap - start pushing Turbo boost on that engine without re-gapping the rings and even at 10Lbs you will be in a world of hurt.  Anything less than 10Lbs of turbo is wasting your money - the lag will erase the gains and you Should limit the redline at 6000, so your usable power range will be 4000-6000  thats not a lot, you might get down to 3500 but you will need a big intercooler to keep the IATs down when you spin the smaller snails up around 150k rpm to get boost that low, but back pressure will not be an issue if you keep Redline down at 6000.

With a reasonable SC  - and on a 427 where you want the most power under the curve  say 2500-6000 you can get away on pump at 10-11 lbs boost and not touch the internals (although I would gap the rings personally) and you can get timing back to make it smooth and safe .. The problem is with Ls7 heads you are pretty stuck with Whipple (Whipples are not bad at all, but really shine when you crank up the boost, not efficient on low boost applications) and really the 4.0 is a good size for a few reasons although the parasitic loss is Horrible close to 150HP to turn it- so when only using 10Lbs of boost its a boat anchor on a 427.  the 2.9 is being mostly replaced by the Gen 5  3.0  which has a lot of advantages. No jackshaft - although the drive snout runs through the middle of the Intake air tube and heats the air coming in (dumb)  bbut that cools the bearings of the shaft somit lives longer.  And the 3.0 takes way less power to turn .. So far I have nit put one on a car but I like the design overall.  The 2.9 was IMO and Interim design to get a bigger SC  with a too large diameter rotor pack under tight car hoods - the designb is compromised by a jackshaft and a smaller in manifold heat exchanger . While the 2.9"should" only take 80-100HP to turn the Jack shaft screws that up - Kenne Bell measured that at 130HP to the turn,  the 3.0 is closer the KB 2.8 which is 65HP  no one publishes the number though I would guess its around 90- 100HP based on the rotor pack being similar to the 2.3 and 3.3  that whipple used before (Lysholm).  

The problem on a 427 is that now you have to use a fairly small pulley on the 2.9 even to get 11lbs and due to the rotor design and you have small heat exchanger as faster rotors build more heat  (IAT) if you don't go to a 10 rib belt you will likely have issues unless you go with a separate pulley on the crank like the 10 rib (shorter belt). You could go to a bigger lower pulley and therefore a bigger upper pulley  but that again is more spend  (ATI balancer and pulleys are not cheap).

In the end like sizing turbos - sizing SC's is similars - the difference between "this is nice"  and "this thing hauls A$$"  for the spend you need to think very carefully on what you choose. I have "upgraded" a few SC cars and most often moved them to smaller SC's and it was night and day, but personally anything with a Jackshaft IMO should not be on a sand car
Click to expand...


Fullthrottleguy said:
Not that I wanted to write a book here  ... But Power wise the SC will make the engine feel 50% larger - so whatever HP you make NA  at 14.7Lbs of Boost you should expect to double it and double the TQ - minus the parastolic loss of turning the SC .  At 10Lbs its nearly linear  but I usually see 50% gain  - so 500HP becomes 750HP and 400 Ft Lbs TQ becomes 600 Ft Lbs.  Minus turning losses.  Turbos are about the same by the math, but better in general due to the "peaky nature" of the boost curve - average the curve and its about the same, without the turning loss (yeah backpressure takes some HP...).  And thats why its so important to size the SC correctly.  I always shoot for 22RWHP per lb of boost on a well design SC car with no HP loss from heat soak after long drives.   I verify on the Dyno and its always right there - Turbos are closer to 35HP ,,,,
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Should I throw some dish style pistons in there to lower the compression, Lowering the compression should allow me to turn the boost up safely. by the way I am already tuned and set up for e85 and there is e85 on the pump 2 miles from my shop (tests at e80 - e90) $3-$4 a gallon 

 
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