Need close to 500 RWHP with heads/cam, which and what? help
03-31-2006, 09:04 AM
#21
Melting Slicks
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See my post here.
http://forums.corvetteforum.com/show...5&postcount=66
Now, I've made some pretty quick passes in some H/C cars also. I've also had the opportunity to test various parts and pieces along the way. I've also been drag racing for quite some time.
So, lets look at ported ls6 heads vs AFR 205's. First, if you look at the flow numbers that Tony has posted up, you'll find that many of the quoted numbers fall WELL short of what shops quote. Unfortunately in this game shops that "fudge" the numbers a bit sell products. So, in many cases, it drives the whole market to "fudge" just a little. In fact I've seen the results of flow testing of most of the heads out there. All I can say is most of the talk of small volume ls6 heads making big flow number is all hype. If you aren't modifying the runner, then all that leaves you is the bowl and the short turn. So, short of epoxying up the bowl you can't add material back in, you have to take it out... Thus the volume has to get bigger in a ported ls6...
I'll give you my own personal example...
The heads on the H/C I drive were "supposed" to flow around 330-335 according to Jay @ Absolute Speed, and were supposed to be around 220-225 cc's.
In reality the ports were 237cc's, and they flowed as follows:
Intake side
….200….300….400….500….550….600
….146….208….264….301….314….323
On the exhaust side they were a bit soft, and we had Greg Good touch up the exhaust side. Thus we picked up some exhaust volume. They poured at 90CC which is pretty big for an ls6 port on a 346.
Exhaust side
...200….300….400….500….600
….114….155….214….238….252
With these heads, a stock ls6 shortblock, FAST90, and a LGM G5X3 package we made ~503RWHP. Its pretty well known what the car ran, and where it ran it at. So, we'll just leave that as it is...
We've tested a Nick William Throttle Body, a TPIS throttle Body, and a GM 90. The GM cost us peak HP (5-8HP), but the low speed drivability was much better with it in place. Since we street drive the car, we took that hit.
So, that gets us to where we are today... We had planned on using an AFR 225 on the car to see how it might fare against the ported ls6 heads that are on there now. See, my belief is that velocity makes power.
But, the AFR 225 wasn't avaliable, so we decided to try an AFR 205 head. For those who aren't up on what AFR quotes on their heads.
….200….300….400….500….550….600
….145….210….257….290….301….308
So, lets compare that with my ported ls6 heads
….200….300….400….500….550….600
….145….210….257….290….301….308
….146….208….264….301….314….323
....-1.....-2.....+7....+9....+13...+15
Wow, just going on flow numbers alone it looks like clearly the AFR heads are just simply inferior to the ported Ls6 heads. In fact our AFR numbers may have even been a bit worse as I milled the heads, and shrouded up the chamber a bit more than most. But, I think this is pretty close to what we can consider accurate.
But, like peak dyno numbers, peak flow numbers are only one point in the curve. Again, you have to look at things like velocity, cross section area, etc... when taking flow numbers into consideration.
Anyhow, we decided to do an A to B test of the AFR heads vs our Ls6 heads on our current combo. It should be noted that the current combination is an custom cam from Flowtech induction. Also, we're running a forged 347. The additional reciprocating mass of the 347 cost us a few Hp over the much lighter cast piston 346. The 347 is still a flat top motor, so we aren't doing anything creative with super high compression. Its basically as close to duplicating a stock 346 as we could with a set of forged pistons. This combination dyno'd around 503 RWHP after it was put together which is shown in the charts above. This was done with an Exedy dual disc. Since that time we switched to a Textralia single disc.
The problem was, something was up with the car. Having changed nothing on the car we were down on power from our previous dyno runs. The best the car would pull was 452.7. Obviously that is quite a bit down from the 490-500RWHP numbers we were expecting as a baseline that we had seen before.
Before the question is asked, all my dynos are done at an independant 3rd party location who has no vested intrest in either side, and no agenda to promote.
After spending two day sorting the car out. We were still in the 450's. So, it was decided to go ahead with the swap and see where we were at. We were quite happy to see the car find its lost power. With final tuning on the car completed we had recorded a best of 492 RWHP with the AFR heads in place.
The one thing that is really noticeable with the AFR 205's is the drivability. The part throttle response is much better, the low speed drivability is much better. In other words for a street head, to me it is a much better choice.
Having had a bunch of other obligations we really had no time this past year to make it to the track and make many runs in the car. So, we wanted to get a chance to run the car in decent air before the summer heat and super positive DA's skewed our results too bad. On the car's first pass it sheared 9 teeth off the ring gear, and destroyed the pinion. The new clutch hits much harder than the clutch it replaced, so we're going to have to adjust the launch style in the car to keep the rear in it.
Since then we've had the car out street driving, road racing with LG, and this past weekend had planned to take it to the Texas Mile Top Speed shootout (but again, other obligation prevented this). The car pulls like a freight train, and if we can stop breaking rears in the car I feel pretty certain in good air (read that as negative DA) we can record a 10.40. The car has already gone 10.90's @129 in +1100 DA with traction issues.
Here are some dyno graphs for anyone who cares...
Peak numbers belt on vs belt off.... 503 vs 487
Before and after the head swap with a 50HP delta... 452 vs 492
Peak to peak ported ls6 vs AFR 205
As you can see the AFR was as good or better than the "superior" ported ls6 head throughout the range. Heck, if we wanted to "fudge" a bit about it, it would have been really easy to post up that AFR heads picked the a car up 50HP over ported LS6 heads.
You can make 500 RWHP with a 346. But it's going to be a max effort car with all the bolt ons.
If I wanted 500RWHP I'd look at this as a good starting point:
AFR 225 small chamber heads
FAST90 ported by Tony Mamo
LG Race series Headers
Meziere WP
Ed Curtis Custom cam
Textralia OZ700AB clutch
With the current setup we have I know I have power sitting on the table.
We're at ~492 where the car sits currently, but have been at 503.
First off, the dyno run was stopped at 6900 the cam carries to 7400 so thats an easy gain, I see probably 5 or more HP by carrying the dyno run further.
Secondly I can swap out the heavy stock iron flywheel for Aluminum and pick up 8-10 HP.
Third, I can port the stock GM90MM TB. We know it cost us 5-8 HP when we swapped over from the Nick Williams TB, but we had Nick Willams TB#2, and Nick learned a lot about TB's since those first few. The Gm gave us better low speed drivability, but Nicks had more flow, and we definitely picked up power...
Fourth, we making 492 with AFRT 205's. We'd probably pick up some power by swapping the 205's for a small chamber 205, but the 205's picked up the low speed drivability so much, I don't know that we're going to swap them out any time soon.
http://forums.corvetteforum.com/show...5&postcount=66
Originally Posted by J-Rod
Now, I've made some pretty quick passes in some H/C cars also. I've also had the opportunity to test various parts and pieces along the way. I've also been drag racing for quite some time.
So, lets look at ported ls6 heads vs AFR 205's. First, if you look at the flow numbers that Tony has posted up, you'll find that many of the quoted numbers fall WELL short of what shops quote. Unfortunately in this game shops that "fudge" the numbers a bit sell products. So, in many cases, it drives the whole market to "fudge" just a little. In fact I've seen the results of flow testing of most of the heads out there. All I can say is most of the talk of small volume ls6 heads making big flow number is all hype. If you aren't modifying the runner, then all that leaves you is the bowl and the short turn. So, short of epoxying up the bowl you can't add material back in, you have to take it out... Thus the volume has to get bigger in a ported ls6...
I'll give you my own personal example...
The heads on the H/C I drive were "supposed" to flow around 330-335 according to Jay @ Absolute Speed, and were supposed to be around 220-225 cc's.
In reality the ports were 237cc's, and they flowed as follows:
Intake side
….200….300….400….500….550….600
….146….208….264….301….314….323
On the exhaust side they were a bit soft, and we had Greg Good touch up the exhaust side. Thus we picked up some exhaust volume. They poured at 90CC which is pretty big for an ls6 port on a 346.
Exhaust side
...200….300….400….500….600
….114….155….214….238….252
With these heads, a stock ls6 shortblock, FAST90, and a LGM G5X3 package we made ~503RWHP. Its pretty well known what the car ran, and where it ran it at. So, we'll just leave that as it is...
We've tested a Nick William Throttle Body, a TPIS throttle Body, and a GM 90. The GM cost us peak HP (5-8HP), but the low speed drivability was much better with it in place. Since we street drive the car, we took that hit.
So, that gets us to where we are today... We had planned on using an AFR 225 on the car to see how it might fare against the ported ls6 heads that are on there now. See, my belief is that velocity makes power.
But, the AFR 225 wasn't avaliable, so we decided to try an AFR 205 head. For those who aren't up on what AFR quotes on their heads.
….200….300….400….500….550….600
….145….210….257….290….301….308
So, lets compare that with my ported ls6 heads
….200….300….400….500….550….600
….145….210….257….290….301….308
….146….208….264….301….314….323
....-1.....-2.....+7....+9....+13...+15
Wow, just going on flow numbers alone it looks like clearly the AFR heads are just simply inferior to the ported Ls6 heads. In fact our AFR numbers may have even been a bit worse as I milled the heads, and shrouded up the chamber a bit more than most. But, I think this is pretty close to what we can consider accurate.
But, like peak dyno numbers, peak flow numbers are only one point in the curve. Again, you have to look at things like velocity, cross section area, etc... when taking flow numbers into consideration.
Anyhow, we decided to do an A to B test of the AFR heads vs our Ls6 heads on our current combo. It should be noted that the current combination is an custom cam from Flowtech induction. Also, we're running a forged 347. The additional reciprocating mass of the 347 cost us a few Hp over the much lighter cast piston 346. The 347 is still a flat top motor, so we aren't doing anything creative with super high compression. Its basically as close to duplicating a stock 346 as we could with a set of forged pistons. This combination dyno'd around 503 RWHP after it was put together which is shown in the charts above. This was done with an Exedy dual disc. Since that time we switched to a Textralia single disc.
The problem was, something was up with the car. Having changed nothing on the car we were down on power from our previous dyno runs. The best the car would pull was 452.7. Obviously that is quite a bit down from the 490-500RWHP numbers we were expecting as a baseline that we had seen before.
Before the question is asked, all my dynos are done at an independant 3rd party location who has no vested intrest in either side, and no agenda to promote.
After spending two day sorting the car out. We were still in the 450's. So, it was decided to go ahead with the swap and see where we were at. We were quite happy to see the car find its lost power. With final tuning on the car completed we had recorded a best of 492 RWHP with the AFR heads in place.
The one thing that is really noticeable with the AFR 205's is the drivability. The part throttle response is much better, the low speed drivability is much better. In other words for a street head, to me it is a much better choice.
Having had a bunch of other obligations we really had no time this past year to make it to the track and make many runs in the car. So, we wanted to get a chance to run the car in decent air before the summer heat and super positive DA's skewed our results too bad. On the car's first pass it sheared 9 teeth off the ring gear, and destroyed the pinion. The new clutch hits much harder than the clutch it replaced, so we're going to have to adjust the launch style in the car to keep the rear in it.
Since then we've had the car out street driving, road racing with LG, and this past weekend had planned to take it to the Texas Mile Top Speed shootout (but again, other obligation prevented this). The car pulls like a freight train, and if we can stop breaking rears in the car I feel pretty certain in good air (read that as negative DA) we can record a 10.40. The car has already gone 10.90's @129 in +1100 DA with traction issues.
Here are some dyno graphs for anyone who cares...
Peak numbers belt on vs belt off.... 503 vs 487
Before and after the head swap with a 50HP delta... 452 vs 492
Peak to peak ported ls6 vs AFR 205
As you can see the AFR was as good or better than the "superior" ported ls6 head throughout the range. Heck, if we wanted to "fudge" a bit about it, it would have been really easy to post up that AFR heads picked the a car up 50HP over ported LS6 heads.
You can make 500 RWHP with a 346. But it's going to be a max effort car with all the bolt ons.
If I wanted 500RWHP I'd look at this as a good starting point:
AFR 225 small chamber heads
FAST90 ported by Tony Mamo
LG Race series Headers
Meziere WP
Ed Curtis Custom cam
Textralia OZ700AB clutch
With the current setup we have I know I have power sitting on the table.
We're at ~492 where the car sits currently, but have been at 503.
First off, the dyno run was stopped at 6900 the cam carries to 7400 so thats an easy gain, I see probably 5 or more HP by carrying the dyno run further.
Secondly I can swap out the heavy stock iron flywheel for Aluminum and pick up 8-10 HP.
Third, I can port the stock GM90MM TB. We know it cost us 5-8 HP when we swapped over from the Nick Williams TB, but we had Nick Willams TB#2, and Nick learned a lot about TB's since those first few. The Gm gave us better low speed drivability, but Nicks had more flow, and we definitely picked up power...
Fourth, we making 492 with AFRT 205's. We'd probably pick up some power by swapping the 205's for a small chamber 205, but the 205's picked up the low speed drivability so much, I don't know that we're going to swap them out any time soon.
Last edited by J-Rod; 03-31-2006 at 09:09 AM.
