Converting An Ls7 To 6 Litres With A 96.9mm Bore
02-13-2007, 09:23 AM
#41
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knightec,
I actually did read the thread beginning with your initial post when I submitted my response on February 8. However, you were sufficiently vague in your approach to this quest that I wondered (as have others) what exactly was going on. I did not mean any disrespect but things did not seem quite right to me.
I agree that the LS designs (including the LS7) have tremendous structural rigidity. However, to toss every component except for the block, crank and caps (and perhaps the dry sump oiling system) seems a real waste. Maybe you should consider something like the L76 long block and work from there. You could resell the crate engines and have a better starting point.
All my best,
Steve
I actually did read the thread beginning with your initial post when I submitted my response on February 8. However, you were sufficiently vague in your approach to this quest that I wondered (as have others) what exactly was going on. I did not mean any disrespect but things did not seem quite right to me.
I agree that the LS designs (including the LS7) have tremendous structural rigidity. However, to toss every component except for the block, crank and caps (and perhaps the dry sump oiling system) seems a real waste. Maybe you should consider something like the L76 long block and work from there. You could resell the crate engines and have a better starting point.
All my best,
Steve
02-13-2007, 09:47 AM
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steve - no offence taken 
........yes it was a bit vague - I just tried to keep to the main question in hand, rather than complicate things with the history of the ptroject......... most parts will need to be sold on / binned as the aim is for in the region of 650bhp with 620lb-ft of torque .....ish.......believe me its going to take quite some work to bring it up to spec.........
yes there is the option of forgetting the LS7 bottom end and just buying aftermarket parts........all depends on how the team owner wants to progress the matter......he currently spends about £250,000 on his yearly engine supply, which is about 1/2 million dollars, either way it will work out cheaper.
I probably wont hear anything for a few months, as they are comitted to their current race progremme, I just want to use this time to clarify my proposal......regarding head selection - the information from this forum has been top quality
........yes it was a bit vague - I just tried to keep to the main question in hand, rather than complicate things with the history of the ptroject......... most parts will need to be sold on / binned as the aim is for in the region of 650bhp with 620lb-ft of torque .....ish.......believe me its going to take quite some work to bring it up to spec......... yes there is the option of forgetting the LS7 bottom end and just buying aftermarket parts........all depends on how the team owner wants to progress the matter......he currently spends about £250,000 on his yearly engine supply, which is about 1/2 million dollars, either way it will work out cheaper.
I probably wont hear anything for a few months, as they are comitted to their current race progremme, I just want to use this time to clarify my proposal......regarding head selection - the information from this forum has been top quality
02-13-2007, 12:21 PM
#43
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Originally Posted by knightec
steve - no offence taken ........yes it was a bit vague - I just tried to keep to the main question in hand, rather than complicate things with the history of the ptroject......... most parts will need to be sold on / binned as the aim is for in the region of 650bhp with 620lb-ft of torque .....ish.......believe me its going to take quite some work to bring it up to spec.........
yes there is the option of forgetting the LS7 bottom end and just buying aftermarket parts........all depends on how the team owner wants to progress the matter......he currently spends about £250,000 on his yearly engine supply, which is about 1/2 million dollars, either way it will work out cheaper.
I probably wont hear anything for a few months, as they are comitted to their current race progremme, I just want to use this time to clarify my proposal......regarding head selection - the information from this forum has been top quality
........yes it was a bit vague - I just tried to keep to the main question in hand, rather than complicate things with the history of the ptroject......... most parts will need to be sold on / binned as the aim is for in the region of 650bhp with 620lb-ft of torque .....ish.......believe me its going to take quite some work to bring it up to spec......... yes there is the option of forgetting the LS7 bottom end and just buying aftermarket parts........all depends on how the team owner wants to progress the matter......he currently spends about £250,000 on his yearly engine supply, which is about 1/2 million dollars, either way it will work out cheaper.
I probably wont hear anything for a few months, as they are comitted to their current race progremme, I just want to use this time to clarify my proposal......regarding head selection - the information from this forum has been top quality
I don't think you are being realistic expecting 650/620 from a 6L LS series engine breathing thru 2 x 33-34 mm restrictors, with a sub 4 inch bore. If you use 6500 rpm as power peak, you are at a BMEP of 14.7 Bar @ power peak rpm. If the 620 lb-ft arrives closer to 5500 rpm, the BMEP there is about 17.4 Bar. If it were 7L not 6L, you'd be right about where the C6R engine is. It doesn't seem possible to me without valves around 2.18 and 1.6 (1.36 int/exh ratio), and those aren't going to work in the small bore.
Half a million US$ sounds like a lot, but it's way low if you are developing an engine like you envision. What is your time frame for having the engine ready?
02-17-2007, 06:28 PM
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Originally Posted by GrannySShifting
In a race application there is never one good reason to shrink bore size unless you can exceed the mechanical rpm limits of the rotating assembly. F1 car, maybe, everything else give me bore, unshroud my valves and let the heads breathe.
well, the problem is that the restrictor can be a bigger restriction than the head/shrouding.
It means your flow is going to go supersonic through the restrictor, as many do.
02-18-2007, 10:17 PM
#47
Originally Posted by treyZ28
well, the problem is that the restrictor can be a bigger restriction than the head/shrouding.
It means your flow is going to go supersonic through the restrictor, as many do.
It means your flow is going to go supersonic through the restrictor, as many do.
i would think the best cylinder filling arrived at by letting the port and valve and bore do the work would be most efficient and would make power with a higher degree of efficiency - ie make the most use of available air.
The caddys used CxR stuff, destroked and run restrictor plates correct?
02-19-2007, 01:49 AM
#48
Originally Posted by FastPacedGTO
i may have missed this, but what are these going into? Left over Vauxhall Monaros? (since you're from the UK)
i think the caddys run in a class where you get to run 7ltr. for a 2 valve per cylinder engine (4 vlavers get to run 6.0 ltr and turbos get 4.0ltr i think).
have you any more news on this knightec???
thanks CHris.
02-19-2007, 07:35 AM
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Originally Posted by GrannySShifting
To deliver x amount of hp with any given cubic inch its going to take x amount of airflow to support that correct, irrlevant of the bore size, with some changes due to efficiency but largely a given amount of air correct?
i would think the best cylinder filling arrived at by letting the port and valve and bore do the work would be most efficient and would make power with a higher degree of efficiency - ie make the most use of available air.
The caddys used CxR stuff, destroked and run restrictor plates correct?
i would think the best cylinder filling arrived at by letting the port and valve and bore do the work would be most efficient and would make power with a higher degree of efficiency - ie make the most use of available air.
The caddys used CxR stuff, destroked and run restrictor plates correct?
02-19-2007, 08:54 AM
#50
Yeah I forgot the rpm factor. With the same CID, RPM and HP targets I think bore helps every time. Regardless your going to have the same volume of a cylinder to fill at 8000 rpm, and a bigger bore easier working head would have a better time doing it no?
02-21-2007, 01:35 AM
#53
FormerVendor
Knightec,
Actually you aren't that far off in what you are trying but you need to stay with heads designed with the smaller bore in mind and look at the ETP and TFS and AFR small bore heads. If you don't need the airflow then the bore will not necessarily help you. with the LS series heads you can make very good power as well even with the small bore as evidenced by Joe and Ambers 3.900 bore engine now going 147 in the quarter at 3300 pounds. Like Oldstroker says it will be hard to make that much power that low in rpm at 6 liters though and with those restrictors. What are people really supposed to be making? Do these have to be V8 engines?
Actually you aren't that far off in what you are trying but you need to stay with heads designed with the smaller bore in mind and look at the ETP and TFS and AFR small bore heads. If you don't need the airflow then the bore will not necessarily help you. with the LS series heads you can make very good power as well even with the small bore as evidenced by Joe and Ambers 3.900 bore engine now going 147 in the quarter at 3300 pounds. Like Oldstroker says it will be hard to make that much power that low in rpm at 6 liters though and with those restrictors. What are people really supposed to be making? Do these have to be V8 engines?
Originally Posted by knightec
guys, thanks for your great replies, I have now learnt a great deal about the LS heads available to me......just to throw some light why I'm headed down this troute, two reasons:-
1) V8 2-valve push-rod LMP1 motors have been tried before by chrysler (John Caldwell), and by Panoz (Elan technologies) - in short, they failed on track.......these motors have been NASCAR motors, derived from thier 358" (5.8 litre) base capacity........they have been very short stroke, wide bore motors, as per the NASAR engine rules around max bore and valve spacing........I know the cross-sectional area of the NASCAR restrictor plates compare well to the LeMans restrictors - but it just dosent work like that......the lemans motors just dont rev like their Nascar alternatives......the 6.0 lemans restrictors, really limit revs to about 7500rpm.....and in short the motors listed above dont make the power or torque of the competitors, as they cant rev as high as they would like, Chrysler were quoting 590bhp, Panoz were 620bhp......their on-track performances would appear to indicate this too - in otherwords - they were not competitive motors......in todays world you need to be in the region of 650bhp for a good LMP1 motor........hence to do this with a 6.0 2-valve motor, the bore and stroke are important factors in making low down power before the restrictors take effect at high revs.
2) 2.0 Litre F3 motors are a classic example of how to make a good restrictor motor, very long strokes of about 93mm with bores of about 82.5mm.......they make about 215bhp at 5500rpm.......which is well before the restrictor takes effect = more area under the power curve......yes all F3 motors are 4-valve heads - but the principle is still the same for a any valve amount & layout........F3 valves are heavily shrouded, but still flow OK
I agree that the small bore I am initially evaluating (96.9mm) may be pushing it a bit......I dare say I may have to back it off a little and start to consider an equal bore and stroke - otherwise known as square.......the long stroke is a fundamental part of producing low down power.......this is not me speculating - its been proven in many forms of motorsport.........the main problem here is that V8 pushrod motors follow a traditional tuning route derived from the likes of Nascar, drag racing, outlaws etc......the ACO regulations for a 6.0 2-valve LMP1 LeMans engine are a different ball game - as John Caldwell and Panoz found out the hard way.
1) V8 2-valve push-rod LMP1 motors have been tried before by chrysler (John Caldwell), and by Panoz (Elan technologies) - in short, they failed on track.......these motors have been NASCAR motors, derived from thier 358" (5.8 litre) base capacity........they have been very short stroke, wide bore motors, as per the NASAR engine rules around max bore and valve spacing........I know the cross-sectional area of the NASCAR restrictor plates compare well to the LeMans restrictors - but it just dosent work like that......the lemans motors just dont rev like their Nascar alternatives......the 6.0 lemans restrictors, really limit revs to about 7500rpm.....and in short the motors listed above dont make the power or torque of the competitors, as they cant rev as high as they would like, Chrysler were quoting 590bhp, Panoz were 620bhp......their on-track performances would appear to indicate this too - in otherwords - they were not competitive motors......in todays world you need to be in the region of 650bhp for a good LMP1 motor........hence to do this with a 6.0 2-valve motor, the bore and stroke are important factors in making low down power before the restrictors take effect at high revs.
2) 2.0 Litre F3 motors are a classic example of how to make a good restrictor motor, very long strokes of about 93mm with bores of about 82.5mm.......they make about 215bhp at 5500rpm.......which is well before the restrictor takes effect = more area under the power curve......yes all F3 motors are 4-valve heads - but the principle is still the same for a any valve amount & layout........F3 valves are heavily shrouded, but still flow OK
I agree that the small bore I am initially evaluating (96.9mm) may be pushing it a bit......I dare say I may have to back it off a little and start to consider an equal bore and stroke - otherwise known as square.......the long stroke is a fundamental part of producing low down power.......this is not me speculating - its been proven in many forms of motorsport.........the main problem here is that V8 pushrod motors follow a traditional tuning route derived from the likes of Nascar, drag racing, outlaws etc......the ACO regulations for a 6.0 2-valve LMP1 LeMans engine are a different ball game - as John Caldwell and Panoz found out the hard way.
02-21-2007, 01:40 AM
#54
race7088, good point!
what are the rules regarding turbos?? is there any chance you could go for a 2.0ltr turbo? the new EVO unit is all ally and should make VERY nice power! or you could go for the scooby unit (lower cent. of gravity??), again all ally and can make big power.
Chris.
what are the rules regarding turbos?? is there any chance you could go for a 2.0ltr turbo? the new EVO unit is all ally and should make VERY nice power! or you could go for the scooby unit (lower cent. of gravity??), again all ally and can make big power.
Chris.
02-21-2007, 08:13 AM
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racer7088 - nice to hear someone being polite for a change.......this has to be the most hostile forum I have ever visited........anyway, I'm interested to know more about the heads you reccomend - what are the general specifications of the "ETP and TFS and AFR small bore heads"........with regard to valve size, valve angle, bore size etc.......head selection for this study was always going to be a problem, hence I asked the LS community.
I'm only interested in a low revving 6.0 V8 push-rod 2-valve motor.......along the lines of a cost effective LMP1 motor.......because the other engines available are not exactly cost effective to say the least.
I know I'm pushing it with a 96.9 bore, the way its looking at the moment it will have to increase to something like a 3.9" or 4".......my initial bore to stroke ratio plan was around 0.95........looks like I now need to be around 1.1
I'm only interested in a low revving 6.0 V8 push-rod 2-valve motor.......along the lines of a cost effective LMP1 motor.......because the other engines available are not exactly cost effective to say the least.
I know I'm pushing it with a 96.9 bore, the way its looking at the moment it will have to increase to something like a 3.9" or 4".......my initial bore to stroke ratio plan was around 0.95........looks like I now need to be around 1.1
