Car Craft LT1 Build
#1
Car Craft LT1 Build
Anyone see the latest issue of Car Craft where they build an LT1 out of a Caprice and do various tests with Edelbrock heads/intake and a single pattern cam? I understand it is an advertisement for Edelbrock, but you'd think they would employ some known concepts and better-known parts to improve the outcome.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
#3
Anyone see the latest issue of Car Craft where they build an LT1 out of a Caprice and do various tests with Edelbrock heads/intake and a single pattern cam? I understand it is an advertisement for Edelbrock, but you'd think they would employ some known concepts and better-known parts to improve the outcome.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
Edlebrock LTX heads are garbage no matter what cam its feeding . Those aren't exactly numbers I would be proud of for a H/C setup, but I bet they just pulled the "huge increase in power from the stock 275hp rating!!" .
#6
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Anyone see the latest issue of Car Craft where they build an LT1 out of a Caprice and do various tests with Edelbrock heads/intake and a single pattern cam? I understand it is an advertisement for Edelbrock, but you'd think they would employ some known concepts and better-known parts to improve the outcome.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
Anyone know why they stuck with single pattern cams? Their best was 414hp/405tq IIRC. Yes, that's at the flywheel.
It sure makes me look forward to my 408 LQ9 build this winter.
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#8
With modern aftermarket heads, the exhaust port is much stronger and you can run a single pattern cam with success and make more tq then a split pattern cam to boot.
Don't take my word for it though, the genious minds at Isky said it best:
Tech Tip - 2003
Longer Exhaust Duration: Is this really necessary?
Most stock camshafts from American production V8, V6 and 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration. Or, another way of looking at this is that they are ground with shorter intake durations! The former embraces the viewpoint that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and is in need of an assist. The latter suggests that the intake system is rather efficient and cam timing can be trimmed back a bit with out much sacrifice in power, in order to maximize throttle response and cruising efficiency.
Take your pick here. There is no absolutely correct viewpoint - because both are probably true! In a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.
However, High Performance is another thing entirely. Change one factor, let's say in this case, the exhaust system (installing headers and larger pipes) and you have just negated in most cases, the need for that longer exhaust lobe. Now couple this change with a different intake system and camshaft and you have really scrambled the equation. But, wait just a moment. Why is it that so many people (racers & cam grinders alike) insist on running a cam with longer exhaust duration regardless of what equipment is employed? The answer is "habit". Most of them have been somewhat successful in doing it their way and will probably never change unless virtually forced by circumstances to do so.
Before we go any further however let's review what it actually is we are trying to do with an engine when we attempt to make more power. Our best result comes when we are cognizant of the fact that an engine is basically an air pump. We pump it in and out (although in a different form) and we have problems when one side or the other is restricted. Balance or the equilibrium or flow should be our objective, unless of course we are not trying to make more horsepower!
Example #1 (Oval track racing) Here, I have often observed that the most experienced drivers are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat always make more torque! These veterans have a more educated foot and greater experience in feathering the throttle in the corners. They can therefore, utilize the benefit of added torque, in the lower to mid RPM range, to their advantage.
Their counterparts, the younger drivers on the circuit, generally are not as experienced and may at times actually get "crossed up" in the corners especially with a lighter car or when they are learning the ropes. In their case, a longer exhaust duration is often the more appropriate choice. It will often help them to drive better, more "flat footed" if you will, without consequence. But please for the sake of accuracy, let us be truthful. The benefit comes from an actual bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened, not from any improvement. The improvement, (if any) would come because of an improvement in scavenging at the extreme upper end of the power curve and would usually be marginal at best. Yet the so-called "extra power" potential of a longer Exh. Duration cam is most often why they are touted - power most people are backing away from at the end of the strait away!
Example #2 (Drag Racing) At the drag strip it's a little different and I feel more honest. Here, racers have long enjoyed longer exhaust and longer durations across the board (If I may add specifically for the purpose of "killing" low-end torque) to keep the tires from too easily breaking lose. This has been successful and sometimes actually results in a slight increase in top end power - something you can actually use in drag racing since it is a full throttle endeavor through the lights. Keep in mind here though, it's quite possible that a longer duration cam overall would have done just as well or better. In other words if you needed that longer exhaust for top end, perhaps the intake could have benefited from such a lengthening as well.
One of my favorite expressions is how "The Drag Racing mentality has infiltrated the ranks of Oval Track". Many have crossed over and made the switch in the past 10-15 years and some have brought their preconceived notions about how to cam an engine with them. A few may actually read these concepts and if they do so will at least come away with a better understanding of what they are doing. On the other hand they also could find that this information might actually help their cars to run just a bit faster!
Note: Readers may find Camfather Ed Iskenderian's Top Tuners Tip #33 "Can an Exhaust System Over-Scavenge the Combustion Chambers" to be a relevant precursor.
From: http://www.iskycams.com/techtips.php
Longer Exhaust Duration: Is this really necessary?
Most stock camshafts from American production V8, V6 and 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration. Or, another way of looking at this is that they are ground with shorter intake durations! The former embraces the viewpoint that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and is in need of an assist. The latter suggests that the intake system is rather efficient and cam timing can be trimmed back a bit with out much sacrifice in power, in order to maximize throttle response and cruising efficiency.
Take your pick here. There is no absolutely correct viewpoint - because both are probably true! In a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.
However, High Performance is another thing entirely. Change one factor, let's say in this case, the exhaust system (installing headers and larger pipes) and you have just negated in most cases, the need for that longer exhaust lobe. Now couple this change with a different intake system and camshaft and you have really scrambled the equation. But, wait just a moment. Why is it that so many people (racers & cam grinders alike) insist on running a cam with longer exhaust duration regardless of what equipment is employed? The answer is "habit". Most of them have been somewhat successful in doing it their way and will probably never change unless virtually forced by circumstances to do so.
Before we go any further however let's review what it actually is we are trying to do with an engine when we attempt to make more power. Our best result comes when we are cognizant of the fact that an engine is basically an air pump. We pump it in and out (although in a different form) and we have problems when one side or the other is restricted. Balance or the equilibrium or flow should be our objective, unless of course we are not trying to make more horsepower!
Example #1 (Oval track racing) Here, I have often observed that the most experienced drivers are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat always make more torque! These veterans have a more educated foot and greater experience in feathering the throttle in the corners. They can therefore, utilize the benefit of added torque, in the lower to mid RPM range, to their advantage.
Their counterparts, the younger drivers on the circuit, generally are not as experienced and may at times actually get "crossed up" in the corners especially with a lighter car or when they are learning the ropes. In their case, a longer exhaust duration is often the more appropriate choice. It will often help them to drive better, more "flat footed" if you will, without consequence. But please for the sake of accuracy, let us be truthful. The benefit comes from an actual bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened, not from any improvement. The improvement, (if any) would come because of an improvement in scavenging at the extreme upper end of the power curve and would usually be marginal at best. Yet the so-called "extra power" potential of a longer Exh. Duration cam is most often why they are touted - power most people are backing away from at the end of the strait away!
Example #2 (Drag Racing) At the drag strip it's a little different and I feel more honest. Here, racers have long enjoyed longer exhaust and longer durations across the board (If I may add specifically for the purpose of "killing" low-end torque) to keep the tires from too easily breaking lose. This has been successful and sometimes actually results in a slight increase in top end power - something you can actually use in drag racing since it is a full throttle endeavor through the lights. Keep in mind here though, it's quite possible that a longer duration cam overall would have done just as well or better. In other words if you needed that longer exhaust for top end, perhaps the intake could have benefited from such a lengthening as well.
One of my favorite expressions is how "The Drag Racing mentality has infiltrated the ranks of Oval Track". Many have crossed over and made the switch in the past 10-15 years and some have brought their preconceived notions about how to cam an engine with them. A few may actually read these concepts and if they do so will at least come away with a better understanding of what they are doing. On the other hand they also could find that this information might actually help their cars to run just a bit faster!
Note: Readers may find Camfather Ed Iskenderian's Top Tuners Tip #33 "Can an Exhaust System Over-Scavenge the Combustion Chambers" to be a relevant precursor.
From: http://www.iskycams.com/techtips.php
Last edited by Puck; 07-23-2009 at 09:56 PM. Reason: clarifying
#10
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#11
I'd generally agree, but that statement assumes then that the new LS7 head has lazy exhaust ports. It has a crazy split, and obviously it works, but I don't believe it's due solely to horrible flowing exhaust ports. I know very few guys running single pattern cams - and it seems the dual pattern cam guys run just as fast with less. Just an observation.
#12
no, other than getting prices on parts and trying to decide how wild to go with it. After twisting 33-spline strange axles (0.018" runout on both) with my LT1, I'm going to have to really go backwards changing other parts first. This racing **** is expensive - I'm going to need a third job.
#13
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no, other than getting prices on parts and trying to decide how wild to go with it. After twisting 33-spline strange axles (0.018" runout on both) with my LT1, I'm going to have to really go backwards changing other parts first. This racing **** is expensive - I'm going to need a third job.
I thought kidney's would be in higher demand so I may have to move onto lungs or something!
That's pretty crazy twisting both axles. Those M6s are really hard on parts. I'm on my third th400 and my new setup will probably find all my other weak links. It bothers me when I destroy parts that shouldn't have broken or were upgraded.
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I'd generally agree, but that statement assumes then that the new LS7 head has lazy exhaust ports. It has a crazy split, and obviously it works, but I don't believe it's due solely to horrible flowing exhaust ports. I know very few guys running single pattern cams - and it seems the dual pattern cam guys run just as fast with less. Just an observation.
Alot of the Gen 1 and LT1 aftermarket heads flow really well on the exhaust, and thats what I thought we were talking about, the LS motors seem to be a whole different animal.
#17
I'd generally agree, but that statement assumes then that the new LS7 head has lazy exhaust ports. It has a crazy split, and obviously it works, but I don't believe it's due solely to horrible flowing exhaust ports. I know very few guys running single pattern cams - and it seems the dual pattern cam guys run just as fast with less. Just an observation.
In the real world though I would still just give the flow numbers to a pro and see what they say. Getting deep into cam specs and valve timings attempting to spec a cam to a set of heads and a cars setup just makes my head hurt.
#18
Apologies for the double post, here are the LS7 flow numbers from Texas Speed's flowbench:
The first thing I think is holy ****, thats a STOCK factory head flowing those insane numbers . The second thing is that the exhaust flows from ~70% of the intake @ .200 down to only ~60% of the intake flow @ .700, and going by the old rule it should run a split duration cam for best performance.
Too bad that is still SBC theory and all that goes out the window with anything newer then an LTX.
Code:
Lift Intake Exhaust cfm: cfm: .200 161 114 .300 227 171 .400 291 193 .500 330 203 .600 351 209 .700 359 214
Too bad that is still SBC theory and all that goes out the window with anything newer then an LTX.
#19
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no, other than getting prices on parts and trying to decide how wild to go with it. After twisting 33-spline strange axles (0.018" runout on both) with my LT1, I'm going to have to really go backwards changing other parts first. This racing **** is expensive - I'm going to need a third job.