When do you really need a LT4 intake???
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Re: When do you really need a LT4 intake???
Originally Posted by chads97z
as a LT4 owner... i will say the LT4 and LT1 intakes if not the same.... very close to the same... my LT4 intake (only mod: port matched to heads) flowed 483cfm - a bone stock lt1 intake on the same flowbench within 2 hours flowed 476cfm - 7cfm difference
flowed from throtle body openings to cylinder #3 port - all other ports blocked
the only difference is the port locations
now my heads flow just over 300cfm per intake port - and most after market heads wont go above 350cfm
so... i will say the lt1 intake is more than enough for any application
now.. aftermarket intakes w/ different runner volumes may make a difference in performance and where peak power/tq is... but the basic design of the LT1 and LT4 is the same
now - lt1 heads to lt4 heads... different - very different
flowed from throtle body openings to cylinder #3 port - all other ports blocked
the only difference is the port locations
now my heads flow just over 300cfm per intake port - and most after market heads wont go above 350cfm
so... i will say the lt1 intake is more than enough for any application
now.. aftermarket intakes w/ different runner volumes may make a difference in performance and where peak power/tq is... but the basic design of the LT1 and LT4 is the same
now - lt1 heads to lt4 heads... different - very different
You can't simply look at a single intake runner and say because the intake outflows that one runner (at some unstated pressure loss) it is more than adequate for that head.
The total pressure loss on the system is the sum of the intake and the head runner, and you can increase filled cylinder pressure by minimizing the loss in the intake. They don't both have to "lose" 28"Hg.
Last edited by Injuneer; Aug 21, 2006 at 03:03 PM.
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From: western, Massachusetts
Re: When do you really need a LT4 intake???
Originally Posted by Injuneer
Your analysis is flawed. The intake manifold has to simultaneously support varying stages of air flow to 4 of the 8 cylinders (+/- depending on intake duration). The average air flow in a stock 350 at 6,000rpm with only an 80% VE is going to be around 485cfm.
You can't simply look at a single intake runner and say because the intake outflows that one runner (at some unstated pressure loss) it is more than adequate for that head.
The total pressure loss on the system is the sum of the intake and the head runner, and you can increase filled cylinder pressure by minimizing the loss in the intake. They don't both have to "lose" 28"Hg.
You can't simply look at a single intake runner and say because the intake outflows that one runner (at some unstated pressure loss) it is more than adequate for that head.
The total pressure loss on the system is the sum of the intake and the head runner, and you can increase filled cylinder pressure by minimizing the loss in the intake. They don't both have to "lose" 28"Hg.
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Joined: Aug 2006
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From: San Diego, CA
Re: When do you really need a LT4 intake???
i have the flow#'s for each port and if all the ports @ the same time at my old house
i was just using the numeber i had written down to compare the same measuement on two different intakes... under the same conditions - and i beleive #3 had the lowest cfm that is why i wrote that one down...
i was just using the numeber i had written down to compare the same measuement on two different intakes... under the same conditions - and i beleive #3 had the lowest cfm that is why i wrote that one down...
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Joined: Nov 2003
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From: Under The Hood
Re: When do you really need a LT4 intake???
You don't buy an LT4 intake to make power, you buy it because it's the piece that matches to the LT4 heads, which can be ported to out match the LT1 Heads. The intake is just an accessory piece. BTW if you don't portmatch the intake to the LT4 Heads, you wont be seeing full potential of the combo.
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: When do you really need a LT4 intake???
Ya have to measure an intake when it is BOLTED TO THE HEAD. Free flow doesn't mean anything. Most LT1 intakes will lose ya 12-15% of your head flow. A good sheet metal is about 10%,and a custom is about 2-5%. The LT4 intake won't match ANY custom but is capable of making HP in the 425-475RWHP range. It's main drawback is the short runners.
Last edited by 1racerdude; Aug 21, 2006 at 06:31 PM.
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Re: When do you really need a LT4 intake???
Originally Posted by Built LT1
Don't forget that the LT4 manifold and heads have a raised valve angle of 7 degrees.
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From: SoCal
Re: When do you really need a LT4 intake???
Originally Posted by 1racerdude
The valve angle is the same-23* the port runner is just higher.
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Re: When do you really need a LT4 intake???
Originally Posted by Built LT1
Yes, I should have said runner angle; but this angle does match the LT4 or AFR 195 and larger head.
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From: SoCal
Re: When do you really need a LT4 intake???
Originally Posted by 1racerdude
Yep,and can be made to fit a bunch of others.
It seems that a lot of people do not realize that the LT1 manifold can be altered to have a 7 degree raised angle, so the lack of an LT4 manifold shouldn't hold anyone back. To name one business, I know Advanced Induction does this process at a reasonable cost.
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: When do you really need a LT4 intake???
Originally Posted by Built LT1
It seems that a lot of people do not realize that the LT1 manifold can be altered to have a 7 degree raised angle, so the lack of an LT4 manifold shouldn't hold anyone back. To name one business, I know Advanced Induction does this process at a reasonable cost.
An LT1 will never flow with an LT4 without so much work it can't be done cost effectively.
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