stocker low lift flow

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.

03-03-2013, 11:37 AM	#1
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,137 Likes: 172 Liked 719 Times in 220 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	#2
R. Thorne Member Join Date: May 2009 Posts: 183 Likes: 75 Liked 101 Times in 34 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.