Capacity Limited Road Race Engine
Thread Starter
Teching In
Joined: Aug 2014
Posts: 7
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Capacity Limited Road Race Engine Hi All,
I have the following class restrictions for building an engine for road racing.
-6000cc capacity limit, naturally aspirated
-8000rpm rev limit
-2480lb minimum vehicle weight with driver
-Gearing that typically keeps the car in the 4000-7500rpm band on most tracks I race on occasionally dropping to 3500 on slow corners
- Budget max $20,000 doing my own build
This is going into a highly modified Porsche 944 which has previously raced with a 430hp supercharged 4 cylinder motor. The new race category has a mix of cars but the most competitive are running ex NASCAR SB2.2 motors or turbo 20B rotaries so I need similar power levels to compete. i.e. 650- 750hp.
I can of course follow the crowd and look at a rebuilt SB2.2, but the LSX is an easy catered for conversion for the 944 and I need to keep the weight down as much as possible to target minimum weight.
I am new to LSX motors so my question is, from the collective wisdom on this forum, can an LSX realistically achieve this power level with those restrictions and budget, and if so what is the most viable block configuration to start with, LSX version, bore, stroke etc that would optimise power and give me that type of torque band?
Cheers
Steve
I have the following class restrictions for building an engine for road racing.
-6000cc capacity limit, naturally aspirated
-8000rpm rev limit
-2480lb minimum vehicle weight with driver
-Gearing that typically keeps the car in the 4000-7500rpm band on most tracks I race on occasionally dropping to 3500 on slow corners
- Budget max $20,000 doing my own build
This is going into a highly modified Porsche 944 which has previously raced with a 430hp supercharged 4 cylinder motor. The new race category has a mix of cars but the most competitive are running ex NASCAR SB2.2 motors or turbo 20B rotaries so I need similar power levels to compete. i.e. 650- 750hp.
I can of course follow the crowd and look at a rebuilt SB2.2, but the LSX is an easy catered for conversion for the 944 and I need to keep the weight down as much as possible to target minimum weight.
I am new to LSX motors so my question is, from the collective wisdom on this forum, can an LSX realistically achieve this power level with those restrictions and budget, and if so what is the most viable block configuration to start with, LSX version, bore, stroke etc that would optimise power and give me that type of torque band?
Cheers
Steve
What are your hood dimensions? Can you run a single plane intake? If so your off to a good start already. I would go straight to a solid roller setup because your on a budget and wouldn't have to spend so much on lightweight valves and other things and could put more money into a set of heads and oiling system. Since this is a road racing car I would opt for the aluminum block whether you go with a stock ls2 block or aftermarket. I don't think 20,000 goes far when the block costs 5,000 after machine work. If you go dry sump on an ls2 setup you will save money and have a better system for lubrication for high Gs. This goal is very realistic of 650hp to 750hp if you spend the money once and skip right over the many conventional methods used on this forum like a fast intake or hydraulic roller.
Obviously as much as possible, but If I can get 650 or better at the wheels I should be competitive at the minimum weight.
What type of gas can/are you allowed to use? That will tell you whether or not you are even close to achieving that goal or not.
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Banned
Joined: Mar 2013
Posts: 1,137
Likes: 2
From: Studewood/Acres-Homes TX.
Both can get 700fwhp but heads, cam, compression are what are going to get you there with the limited amount of CID and RPM. The bores and crank sizes will all be close, so they are all really the same as far as rod and stroke combos DECK HT included. So now its all about how well it is able to breathe. Heads and induction. I would refer to Proline - Vengence - HKE -LME they may have done a class limited race engine.. The closest head to the SB2 would be Mast PXR inline head- WCCH ALL PRO -2- or the LSX DR or CT - circle track heads all need shaftmounted rockers.. None of these heads have a canted valve lay-out like the SB.2 inline head. Throw in a solid roller with some ***** for lift and made 2 get around 8000 RPMS.. Also if you can run the ECU fine tune-ing included.
Thread Starter
Teching In
Joined: Aug 2014
Posts: 7
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Thanks to all for the info posted.
Being a road race car I need to maximize the torque band in the 3.5-7.5 range as well as achieving the right power levels. I realize head, valve train and cam choice is going to be critical, but how much impact would different bore stroke combinations for the same 6.0 capacity have on the outcome. Am I better to stick with the typical LS2 dimensions or is it worth considering a bigger bore/shorter stroke combination? Bigger bore presumably helps flow, but as the capacity is limited and I can only go to 8000rpm anyway I presume I can't get much benefit from a shorter stroke. Thoughts?
Being a road race car I need to maximize the torque band in the 3.5-7.5 range as well as achieving the right power levels. I realize head, valve train and cam choice is going to be critical, but how much impact would different bore stroke combinations for the same 6.0 capacity have on the outcome. Am I better to stick with the typical LS2 dimensions or is it worth considering a bigger bore/shorter stroke combination? Bigger bore presumably helps flow, but as the capacity is limited and I can only go to 8000rpm anyway I presume I can't get much benefit from a shorter stroke. Thoughts?
TECH Fanatic
Joined: Aug 2009
Posts: 1,845
Likes: 255
From: Coast of San Mateo County Between Pacifica & HMB
ERL or RED Sleeved Block
4.185 Bore X 3.28 Stroke (4.8) = 361 CI
4.155 Bore X ". " = 357 CI
LS7 Block
4.125 Bore X 3.40 Stroke. = 364 CI
6000cc=366CI
The following rotating is pricey but bullet-proof
To 8K RPM & 800 crank HP
Callies Magnum XL lightened crank W/ Honda journal
Ultra I beam long rod 6.35"
Custom pistons Diamond, Ross,JE etc.
check out Dyno results section Jackson did destroked LS3
W/ 4.8 crank 333 CI 620 crank HP @ 7700 RPM W/
TFS LS3 Heads 12.5:1 on E85 relatively small cam
I would look at the smallest square port heads that flow
~ 380+ CFM by .650 with good mid lift flow and custom
cam.Holley Ram Intake.
All of above + plus a good dry-sump (not factory gm)
Probably $17-18K in parts and machining maybe more.
Anyway just my .02 alot more experienced guys in here then I.
Food for thought.
Good Luck!
4.185 Bore X 3.28 Stroke (4.8) = 361 CI
4.155 Bore X ". " = 357 CI
LS7 Block
4.125 Bore X 3.40 Stroke. = 364 CI
6000cc=366CI
The following rotating is pricey but bullet-proof
To 8K RPM & 800 crank HP
Callies Magnum XL lightened crank W/ Honda journal
Ultra I beam long rod 6.35"
Custom pistons Diamond, Ross,JE etc.
check out Dyno results section Jackson did destroked LS3
W/ 4.8 crank 333 CI 620 crank HP @ 7700 RPM W/
TFS LS3 Heads 12.5:1 on E85 relatively small cam
I would look at the smallest square port heads that flow
~ 380+ CFM by .650 with good mid lift flow and custom
cam.Holley Ram Intake.
All of above + plus a good dry-sump (not factory gm)
Probably $17-18K in parts and machining maybe more.
Anyway just my .02 alot more experienced guys in here then I.
Food for thought.
Good Luck!
Last edited by NAVYBLUE210; Aug 12, 2014 at 11:48 PM.
The SB2.2 is not an inline valve head. It is a canted splayed setup like a BBC. You will have a hard time building a 6.0 LS for 20k that will make 750hp in a road race application reliably. The rules are forcing you to an unusual bore stroke combo that drives the cost up. You need quality cylinder heads and valvetrain. If you're really road racing then you need a dry sump system. I'm not saying that it can't be done as it has been done. I just don't see it happening for $20k. I think you'll be pushing near $30k depending on a few things. I think you might be able to build your longblock for $20k. Those SB2.2 heads/valvetrain were easily $15k when new and are very capable. Thanks to NASCAR they can be bought rebuilt with Jesel rockers for a 1/4 of what they cost, and that's just heads.
Thread Starter
Teching In
Joined: Aug 2014
Posts: 7
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Yes I am getting that impression, just pricing parts and with the absence of any similar examples of 6.0 LS's putting out similar levels. I guess that's why most in this series are simply opting for rebuilt NASCAR motors.
Banned
Joined: Mar 2013
Posts: 1,137
Likes: 2
From: Studewood/Acres-Homes TX.
Navy Blue combo looks good but a TFS or any other LS3 head WILL not keep up with the SB.2 with 11ºx4º intake and 8ºx0º exhaust head its just better. You use to be able to get used SB.2 heads for around 2 grand from Racing Junk or if you know some1 on a CUP team. Call PROLINE and ask for KERRY he may be able to give you the difference in cost and performance.. Anyway you cut it 20,000 is your bottom line SB.2 or LS. I'm sure that the LS platform can do it but no 1 has done this combo for CLASS SPEC RACING..I'll make a few calls and see what I can find out.. Give me a sec. My truck harmonic balancer split TUES. so let me set this up and I'm on it.
TECH Fanatic
Joined: Aug 2009
Posts: 1,845
Likes: 255
From: Coast of San Mateo County Between Pacifica & HMB
Thoughts & Questions LS3 Block 4.070 Bore Destroked 3.50 = 364.3 CI
14.0:1 Comp E85 is it possible/practical?
TFS LS3 Head can be ported to ~390CFM@ .600 lift with good
Mid lifts w/ less than 260 CC Intake Ports.
How big are SB2 Ports? can big ports with huge flow (400+ CFM)
be utilized by 366 CI below 8K RPM? Would a bigger torque curve
Perhaps 40-60 lbftBetween 4-7K be worth
trading 30-50 HP @ 7500-8000 RPM?
Is a smaller cam (lift wise) more reliable in a endurance application?
How much tire can you fit and power can you utilize in a 2500lb
Chassis? 650-700 crank might be more easily reached w/ less cost
Leaving more for Dry-Sump.
14.0:1 Comp E85 is it possible/practical?
TFS LS3 Head can be ported to ~390CFM@ .600 lift with good
Mid lifts w/ less than 260 CC Intake Ports.
How big are SB2 Ports? can big ports with huge flow (400+ CFM)
be utilized by 366 CI below 8K RPM? Would a bigger torque curve
Perhaps 40-60 lbftBetween 4-7K be worth
trading 30-50 HP @ 7500-8000 RPM?
Is a smaller cam (lift wise) more reliable in a endurance application?
How much tire can you fit and power can you utilize in a 2500lb
Chassis? 650-700 crank might be more easily reached w/ less cost
Leaving more for Dry-Sump.
Thread Starter
Teching In
Joined: Aug 2014
Posts: 7
Likes: 0
I am pretty much stuck with the tires and gearing I have which are 310/655/18 Dunlop slicks. The Porsche rear end and box with Guard diff, Motons and 1000+ springs with sticky slicks has been very good at getting power down at my previous levels the way it is setup, and there are several 944 race cars running around with 600hp turbo engines and similar setups that get the power down very well. Main thing is to keep torque in the 4-8 range which is where I am 98% of the time with current gearing. Getting out of corners is critical.
A fat mid to high range torque curve is more important than outright power, but the power also needs to be there. I have to say that just based on info collected so far I am starting to be doubtful about being able to match the horsepower levels with an LS and my budget.
A fat mid to high range torque curve is more important than outright power, but the power also needs to be there. I have to say that just based on info collected so far I am starting to be doubtful about being able to match the horsepower levels with an LS and my budget.