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Lost tq with cam and ported heads?

Shibby50

TCG Elite Member
Mar 30, 2008
5,005
74
Braidwood, IL
So I finally had my car dyno'd at the dyno day and I'm sort of at a loss/ confused. When i first got the car I had it dyno tuned after basic bolt ons
Slp intake headers catback etc. dyno jet

Made 343hp 363tq.
Now after a custom cam and ported 241s the car put down 389hp 346tq.
Is it normal to lose tq? This was 3 identical back to back pulls on a dyno jet as well.
 

ajdereicup

Measly little 4.6 2v in a boat
Oct 30, 2012
5,234
261
Lombard
Different dynos put out different numbers? And I'm thinking depending on what kinda cam and heads you got they may lean more towards the HP not the TQ but not positive. Some are setup for more TQy things like tractor pulls or whatever and then some more for HP like certain racing?
 

rocket5979

Gearhead
Nov 15, 2005
6,576
18
Round Lake, IL
So I finally had my car dyno'd at the dyno day and I'm sort of at a loss/ confused. When i first got the car I had it dyno tuned after basic bolt ons
Slp intake headers catback etc. dyno jet

Made 343hp 363tq.
Now after a custom cam and ported 241s the car put down 389hp 346tq.
Is it normal to lose tq? This was 3 identical back to back pulls on a dyno jet as well.


Post up both sheets so that was can see what dyno, what correction factor, smoothing, torque curves look like, etc. There are a multitude of variables that could be at work in skewing the numbers to "appear" lower than what you hoped for. Did the heads change compression; if so then did it drop? How aggressive was the ECM tune before and after the hardware mods, etc?
 

Pressure Ratio

....
TCG Premium
Nov 11, 2005
20,303
11,728
Glen Ellyn
Looked like han's was hanging out STD numbers. Were the earlier runs made with SAE or STD numbers?

And yes, when you increase the cross section of the port you can lose torque. Especially if the cam moves the power band higher. MANY thing factor into it as you can imagine. Was it re tuned after the install? Many times revised timing tables can gain some of what was lost.
 

Shibby50

TCG Elite Member
Mar 30, 2008
5,005
74
Braidwood, IL
Dyno with bolt on's
bhgchu.jpg


Dyno after ported heads/cam
6p6z5c.jpg


The car was tuned, by 2 different shops. Not sure on the timing, but both seem to be right at 13.0 AFR. The power band did move higher with the cam, and this isn't a bashing thread or anything. I was just unsure as to whether or not this is a normal thing or not.
 

Turk

Lt. Ron "Slider" Kerner
TCG Premium
Jan 21, 2008
28,484
7,874
Well, I've been preaching since 2008 that HP is much more important than torque. I wouldn't worry about it, your car is much faster under this setup. Peak torque doesn't matter at all really, if you're going to look at torque, look at area under the curve as someone already mentioned. Look how much harder the motor pulls at high rpms which is all that matters cause that's where you are when you race!
 

Shibby50

TCG Elite Member
Mar 30, 2008
5,005
74
Braidwood, IL
my buddy had a 00 SS cam/headers/ stall and made more than when he installed an LS6 intake and had it retuned.

is your car an auto ? could it be with / without the TC locked?

Didn't think about that. I don't think the converter was locked yesterday when it was done. The first time it was dyno'd it had a stock converter in it so it was most likely locked
 

Pressure Ratio

....
TCG Premium
Nov 11, 2005
20,303
11,728
Glen Ellyn
Just for your info, your first dyno is posted in SAE numbers. The second is in STD numbers. There is a 2.6% difference there. Your new peak numbers converted to SAE are more like 378 / 338.

Does it feel lazy down low compared to before? See how it runs at the track. If the ET drops and the MPH comes up that is all that really matters.
 

rocket5979

Gearhead
Nov 15, 2005
6,576
18
Round Lake, IL
Didn't think about that. I don't think the converter was locked yesterday when it was done. The first time it was dyno'd it had a stock converter in it so it was most likely locked


If the TC is locked then it will show higher average hp but lower average torque because it is not torque multiplying but is also not slipping as much (if at all) in the upper RPMs. But, if the TC is unlocked then it will show lower average hp because it is not 1:1 during any portion of the dyno run but higher average tq will result because it is still able to torque multiply; mainly in the lower rev range.
 

rocket5979

Gearhead
Nov 15, 2005
6,576
18
Round Lake, IL
Track can vary so much based on weather etc. I remember on my SS I gained 20rwhp and ran 4 tenths SLOWER because of the weather.

Yeah, DA, traction/launch, and the amount of burst knock retard set up in the tune can have huge effects on your ET. Sure DA calculations will add some of that lost ET back in, but there are other losses such as with knock retard and track conditions that a DA calculator cannot add back in. So, like Turk implied, it's all relative to the conditions at hand.
 
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