rect port bbc intake on oval port heads?naturally aspirated
#1
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Join Date: Jan 2005
Posts: 4
rect port bbc intake on oval port heads?naturally aspirated
i have a friend that told me after dyno time on 2 different engines ,a square port intake was installed on both ,and both had oval port heads ,,,engines made 30 or so more hp at the same rpm,,,i know it should'nt matter on a blown motor cause i've done it ,,,but just seems impossible that it could make more hp with that kind of port mismatch,,,anyone ever heard of this ?
i,m a doubting thomas !
i,m a doubting thomas !
#3
On a carb motor, you can run a oval intake with square port heads (causes an anti reversion step). Will never work opposite.
Blower motor - I just don't know but think you are losing efficiency.
Blower motor - I just don't know but think you are losing efficiency.
#4
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Join Date: Jan 2004
Location: central Illinois
Posts: 459
rect port
Back in the early 70's, when there were alot of 396 oval port engines with cast iron intakes from the factory, we all pulled them off and put factory 375 horse rectangular port aluminum intakes on the 325 and 350 horsepower engines.
I swear we thought they were faster even with the port mismatch. Maybe it was just losing the weight of the iron intake?
I can also remember using the wrong intake gaskets the first time and having a hell of a big vacuum leak. Took a couple beers to figure that one out.
I swear we thought they were faster even with the port mismatch. Maybe it was just losing the weight of the iron intake?
I can also remember using the wrong intake gaskets the first time and having a hell of a big vacuum leak. Took a couple beers to figure that one out.
#5
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RACING JUNKIE
Join Date: Jan 2012
Posts: 628
Hmmmm, If there was anything gained by "Port Mismatch" either way, do you suppose CNC matching would be the business it is today?
I'll go with the matched ports everytime . . I might not be 100% right but 55 years of conventional wisdom tells me that I'm close . .
Heheheheheheheheh . . .
And I'd guess, on the Dyno Runs and during the changes, they did something else that offset their results . . Depending upon the total output, 30 HP could be 20% or 2% . .
I'll go with the matched ports everytime . . I might not be 100% right but 55 years of conventional wisdom tells me that I'm close . .
Heheheheheheheheh . . .
And I'd guess, on the Dyno Runs and during the changes, they did something else that offset their results . . Depending upon the total output, 30 HP could be 20% or 2% . .
#7
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Join Date: May 2006
Location: Pikeville KY
Posts: 109
I have done it myself, had a set of 781 GM ovals with a team g intake "oval", pulled engine out of car to put rear main seal in. Hoist hooked to carb pad and cracked about 1" under carb pad.......... Had a team g square port on the shelf with a set of gaskets, I wanted to go racing that coming weekend so I put it on. The car did pick up from 6.09 to 6.04. Cant swear the intake done it, but Im sure it wasent the rear main seal.
#8
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Join Date: Jul 2006
Posts: 184
That is/was a common deal on super stock engines. Its about velocity. It slows the air speed down, letting the engine go up in rpm, which, will make the car et better if its making more power at higher rpm.
Super Stock engines are very velocity limited. Basicay, its telling you your heads are to fast. Its a crutch, and if you addressed the situation correctly, correct air speed in heads, it would run even faster.
Frank
Super Stock engines are very velocity limited. Basicay, its telling you your heads are to fast. Its a crutch, and if you addressed the situation correctly, correct air speed in heads, it would run even faster.
Frank