stocker low lift flow

R. Thorne · 02-28-2013, 09:42 PM

I have improved intake flow by 20%@.100, 5%@.200, 1%@.300, BUT high lift flow decreased by 1.5%. Max lift is .400. Because the camshaft ramps are so steep and the nose of the cams are so long would this be a wash as far as improved performance? In other words, how important is low lift flow in a stock eliminator car? PM if you prefer. Thanks, Ron.

Billy Nees · 03-01-2013, 08:57 AM

It all depends on the combo. IMHO, if you can improve the low lift #s that much and only lose 1% at peak, you're going to find an improvement. High RPM lots of valve lift and carb are going to want to see better peak #s. Low RPM limited valve lift and restricted carb are going to want to see all of the low lift flow that you can give it.
Now find a cam to take advantage of it.

R. Thorne · 03-02-2013, 11:44 AM

Thanks, Billy and Myron. Engine is low rpm Pontiac 350 (6300 rpm max). Ron.

Mike Taylor 3601 · 03-02-2013, 02:03 PM

If you can average #'s, I worry more about average flow than big #'s,usaully the heads that have highest average will out perform a head with better high lift #'s
Will have flatter and wider hp/tq #'s which equals faster and more consistent car,will be less sensitive to weather,shifts etc.
Mike Taylor 3601

Adger Smith · 03-02-2013, 05:35 PM

I'm with Mike on the average flow. I've had engines pick up big time when I change the valve job to one that provides a fatter bell shaped flow curve.By big time I mean in the operational torque curve. I would much rather see a flow curve that was way fat at low & mid lift than one that was a few points higher at peak and was linear. If you can do that you are usually going to see more tq and better down track performance, esp pulling off a gear change & hitting the converter leaving the line.
Now leave the seat angles you have on it alone and go to work on the shape of the valve, esp at the margin. Watch what happens!! :~)

gmonde · 03-02-2013, 08:24 PM

low lift numbers are the ones you want to improve on ,, on a stocker you might be able to get those numbers to be good past .500 lift and them some but most of us if not all have to work below that number ,, also valve train comes into play, the valve train has to do it's job to keep the lifter on the cam ,or it will act like a governor ,, small chevys have the lightest valves but have a small lifter diameter witch causes cams to go bad ,,, some of the a/sa and b/s-a chevy cars buzz real high at the end ,,lots of mass to be running gmonde

Greg Reimer 7376 · 03-03-2013, 11:37 AM

Seems to me that various engines would like various things. A case in point, one that i have 20 or so years experience with, is a '68 327 250 horse engine. It is identical in all aspects to the 275 horse unit, but for the heads. The 250 horse unit has 8.5 to 1 compression on a GOOD day, 1.72' intake valves, and 1.500 exhausts. The ports are not as generous as the #462 or the 041 casting on the 275 horse, the intake is the same, the Q-jet is the same,the short block and the cam are the same, but it seems to me that the lower HP engine has a serious limitation of max horsepower dictated by compression ratio and high rpm breathing.The 275 by virtue of the 10.00 or so c/r and the better sized ports and intake valves, will make way more horsepower, all other things considered equal. This leads me to believe that the 250 horse needs a cam that isn't' as radical on the max lift, since the engine can't use it as well, and more effective at filling cylinders at lower to medium range use. Make all the torque you can,since you can't turn it with the same effect( mine saw a max rpm of 7000 at Winternationals) The other thing affecting that engine combo is the car that it came in. It only was put in Chevelles, Bel Airs, Impalas, and wagons, as well as a few trucks. These were heavier cars, which aggravated the need for more torque. Since C/R affects torque,(more is better,)as well as horsepower, the low compression unit needs to be thought out a bit differently. In the case of the Pontiac 350-400, it's not a high RPM type of thing, so the more low speed volumetric efficiency and cylinder filling you can get, the better off you are. You didn't say what year your Indian was,but I assume it's low compression like the 250 horse 327.
I envision that an all out effort on the 327 would see it with a different cam profile between the two horsepower versions ,as well as different operating characteristics of each engine. Good luck on your project!

R. Thorne · 03-05-2013, 06:21 PM

Thanks, guys. Your replies are much appreciated. The next phase (valve seat area) and some other stuff (thanks, Thomas)should increase low lift flow even more. We'll see. Ron.

02-28-2013, 09:42 PM	#1
R. Thorne Member Join Date: May 2009 Posts: 182 Likes: 64 Liked 100 Times in 33 Posts	stocker low lift flow I have improved intake flow by 20%@.100, 5%@.200, 1%@.300, BUT high lift flow decreased by 1.5%. Max lift is .400. Because the camshaft ramps are so steep and the nose of the cams are so long would this be a wash as far as improved performance? In other words, how important is low lift flow in a stock eliminator car? PM if you prefer. Thanks, Ron.

03-01-2013, 08:57 AM	#2
Billy Nees VIP Member Join Date: Oct 2002 Location: On a hilltop in Pa. Posts: 4,499 Likes: 3,601 Liked 7,780 Times in 1,743 Posts	Re: stocker low lift flow It all depends on the combo. IMHO, if you can improve the low lift #s that much and only lose 1% at peak, you're going to find an improvement. High RPM lots of valve lift and carb are going to want to see better peak #s. Low RPM limited valve lift and restricted carb are going to want to see all of the low lift flow that you can give it. Now find a cam to take advantage of it. __________________ Billy Nees 1188 STK, SS I'm not spending 100K to win 2K

03-02-2013, 11:44 AM	#3
R. Thorne Member Join Date: May 2009 Posts: 182 Likes: 64 Liked 100 Times in 33 Posts	Re: stocker low lift flow Thanks, Billy and Myron. Engine is low rpm Pontiac 350 (6300 rpm max). Ron.

03-02-2013, 05:35 PM	#5
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: stocker low lift flow I'm with Mike on the average flow. I've had engines pick up big time when I change the valve job to one that provides a fatter bell shaped flow curve.By big time I mean in the operational torque curve. I would much rather see a flow curve that was way fat at low & mid lift than one that was a few points higher at peak and was linear. If you can do that you are usually going to see more tq and better down track performance, esp pulling off a gear change & hitting the converter leaving the line. Now leave the seat angles you have on it alone and go to work on the shape of the valve, esp at the margin. Watch what happens!! :~) __________________ Adger Smith (Former SS) Last edited by Adger Smith; 03-02-2013 at 05:38 PM.

03-02-2013, 08:24 PM	#6
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: stocker low lift flow low lift numbers are the ones you want to improve on ,, on a stocker you might be able to get those numbers to be good past .500 lift and them some but most of us if not all have to work below that number ,, also valve train comes into play, the valve train has to do it's job to keep the lifter on the cam ,or it will act like a governor ,, small chevys have the lightest valves but have a small lifter diameter witch causes cams to go bad ,,, some of the a/sa and b/s-a chevy cars buzz real high at the end ,,lots of mass to be running gmonde

03-02-2013, 02:03 PM	#4
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,372 Likes: 357 Liked 308 Times in 103 Posts	Re: stocker low lift flow If you can average #'s, I worry more about average flow than big #'s,usaully the heads that have highest average will out perform a head with better high lift #'s Will have flatter and wider hp/tq #'s which equals faster and more consistent car,will be less sensitive to weather,shifts etc. Mike Taylor 3601

03-03-2013, 11:37 AM	#7
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	Re: stocker low lift flow Seems to me that various engines would like various things. A case in point, one that i have 20 or so years experience with, is a '68 327 250 horse engine. It is identical in all aspects to the 275 horse unit, but for the heads. The 250 horse unit has 8.5 to 1 compression on a GOOD day, 1.72' intake valves, and 1.500 exhausts. The ports are not as generous as the #462 or the 041 casting on the 275 horse, the intake is the same, the Q-jet is the same,the short block and the cam are the same, but it seems to me that the lower HP engine has a serious limitation of max horsepower dictated by compression ratio and high rpm breathing.The 275 by virtue of the 10.00 or so c/r and the better sized ports and intake valves, will make way more horsepower, all other things considered equal. This leads me to believe that the 250 horse needs a cam that isn't' as radical on the max lift, since the engine can't use it as well, and more effective at filling cylinders at lower to medium range use. Make all the torque you can,since you can't turn it with the same effect( mine saw a max rpm of 7000 at Winternationals) The other thing affecting that engine combo is the car that it came in. It only was put in Chevelles, Bel Airs, Impalas, and wagons, as well as a few trucks. These were heavier cars, which aggravated the need for more torque. Since C/R affects torque,(more is better,)as well as horsepower, the low compression unit needs to be thought out a bit differently. In the case of the Pontiac 350-400, it's not a high RPM type of thing, so the more low speed volumetric efficiency and cylinder filling you can get, the better off you are. You didn't say what year your Indian was,but I assume it's low compression like the 250 horse 327. I envision that an all out effort on the 327 would see it with a different cam profile between the two horsepower versions ,as well as different operating characteristics of each engine. Good luck on your project!

03-05-2013, 06:21 PM	#8
R. Thorne Member Join Date: May 2009 Posts: 182 Likes: 64 Liked 100 Times in 33 Posts	Re: stocker low lift flow Thanks, guys. Your replies are much appreciated. The next phase (valve seat area) and some other stuff (thanks, Thomas)should increase low lift flow even more. We'll see. Ron.