intake porting just a question
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Elder User
Joined: May 2007
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From: Sparks, NV
intake porting just a question
im watching horsepower tv, and this guy was porting a SBC intake manifold and it got me thinking; if you can get a noticable gain in power by gasket matching intakes, why did ford make their truck intakes SUPER small? i have a cast iron 2bbl intake and the runners are really small compared to the gasket, though the SBF head ports are as big as the gasket. any idea why this is? low rpm power since the air runs faster like a venturi?
So if i port my stock 4bbl aluminum intake on my truck right now, will i lose the low end? im confused since the horsepower guys talk about high-rpm power
So if i port my stock 4bbl aluminum intake on my truck right now, will i lose the low end? im confused since the horsepower guys talk about high-rpm power
More Turbo
Joined: Jul 2003
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From: SC
Broadly speaking, the more velocity you have through the ports the more torque you make. More or less, sorta. Torque is "seat of the pants" power, what you need to get a heavy truck moving and what makes it more fun to drive in traffic.
When you're going after big ports you're generally after more flow for more horsepower and torque characteristics are a secondary consideration. Probably what they were doing. Not really what you're after in a truck that you use to drive every day.
Chevys are different too. The older V8's are well known to have port problems on the intake sides of the heads. Our Fords are the reverse. Many folks port the heck out of the exhaust side and barely do a little cleanup on the intake side. Matching the intake is worthwhile if only because you'd hate to have one side of the port of the head sticking out into the passageway coming from the intake. I've seen people check for this sort of thing by simply running a coat hanger down into the installed intake to see if the end of it catches anything at the port. Most folks just gasket match though.
When you're going after big ports you're generally after more flow for more horsepower and torque characteristics are a secondary consideration. Probably what they were doing. Not really what you're after in a truck that you use to drive every day.
Chevys are different too. The older V8's are well known to have port problems on the intake sides of the heads. Our Fords are the reverse. Many folks port the heck out of the exhaust side and barely do a little cleanup on the intake side. Matching the intake is worthwhile if only because you'd hate to have one side of the port of the head sticking out into the passageway coming from the intake. I've seen people check for this sort of thing by simply running a coat hanger down into the installed intake to see if the end of it catches anything at the port. Most folks just gasket match though.
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Joined: May 2007
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From: Sparks, NV
ok so lets take the 351C 4v head, HUGE ports, but you have to rev it high to make any type of power right? so if i take a truck intake manifold, with gasket matched ports and such, how would that affect the airflow characteristics? I think it would need more rpm to keep the fuel suspended since there is greater volume, but less pressure/airspeed yet makes more torque? sorry i am a little confused.
I may just have to go to a machine shop and ask them to teach me about this stuff.
tell me this; would i be even interested in porting a 302 for torque? or would i just raise the powerband?
i know the 351 is better suited for torque but i have to make do with the 302 til i get a 351 block the way i want it
I may just have to go to a machine shop and ask them to teach me about this stuff.
tell me this; would i be even interested in porting a 302 for torque? or would i just raise the powerband?
i know the 351 is better suited for torque but i have to make do with the 302 til i get a 351 block the way i want it
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Power is all about filling the cylinders.
For low-end grunt, smaller ports and manifold runners will keep the air/fuel moving, prevent pooling, and help fill the cylinders better an low revs. As the revs climb, there comes a time when the small ports/runners hurt you.
For max HP, you need revs and you need more air/fuel. Hence, big ports, valves, runners, carbs, valves etc. Do it right and it will be only a little soft on the low end and build with the revs. Do it wrong and it idles at 1500....(not that that's is wrong for some applications)
Dual runner intakes, variable cam timing and dohc with variable valve timing can conspire to give you solid bottom end and wild top end power--too bad you can't really retrofit that stuff....
For low-end grunt, smaller ports and manifold runners will keep the air/fuel moving, prevent pooling, and help fill the cylinders better an low revs. As the revs climb, there comes a time when the small ports/runners hurt you.
For max HP, you need revs and you need more air/fuel. Hence, big ports, valves, runners, carbs, valves etc. Do it right and it will be only a little soft on the low end and build with the revs. Do it wrong and it idles at 1500....(not that that's is wrong for some applications)
Dual runner intakes, variable cam timing and dohc with variable valve timing can conspire to give you solid bottom end and wild top end power--too bad you can't really retrofit that stuff....
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