LT-4 Intake Manifold
Thread Starter
Racer
Joined: Nov 2002
Posts: 320
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From: Bradenton Florida
LT-4 Intake Manifold
Is the LT4 Manifold a regular LT1 manifold just powder coated or is it ported or something, also if it ported or anything, do you need to modify your heads to put one on. Also how much of a HP gain can you expect from just bolting it on. :steering:
Melting Slicks
Joined: Aug 2001
Posts: 2,047
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Re: LT-4 Intake Manifold (C4kid94)
I am/was under the impression that the castings are the same. However, let's see where this thread goes. The main obvious difference between the LT1/4 manifolds is obviously the fuel crossover tube close to the throttle body. More flow, more equalization from rail to rail, more go! :steering:
Advanced
Joined: Nov 2002
Posts: 77
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From: Chicago Suburbs
Re: LT-4 Intake Manifold (EricVonHa)
Here is all you need to know about the LT1 vs LT4. http://home.tir.com/~steveher/lt4.html
hope it helps..... :chevy
hope it helps..... :chevy
Burning Brakes
Joined: Oct 2002
Posts: 1,152
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From: Wichita KS
Re: LT-4 Intake Manifold (weracemo)
The LT4 intake casting is completly different than an LT1, it is cast to match the revised port configuration of the LT4 heads. (read raised runners).
It was never intended to be a direct "bolt-on" for LT1 heads.
:seeya
It was never intended to be a direct "bolt-on" for LT1 heads.
:seeya
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: LT-4 Intake Manifold (superlund)
The LT4 intake casting is completly different than an LT1, it is cast to match the revised port configuration of the LT4 heads. (read raised runners)
The funny side fact is that you can bolt the LT4 manifold to LT1 heads with no internal port mismatch. And you can bolt an LT1 manifold to LT4 heads with no loss of performance.
Eric
Melting Slicks
Joined: Jan 2000
Posts: 3,418
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From: NW Chicago Suburbs
Re: LT-4 Intake Manifold (EricVonHa)
...The main obvious difference between the LT1/4 manifolds is obviously the fuel crossover tube close to the throttle body....
Eric
Burning Brakes
Joined: Oct 2002
Posts: 1,152
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From: Wichita KS
Re: LT-4 Intake Manifold (silver & red CE)
I had LT1 heads and intakes & the LT4 equivalents here at the same time. I hand fit every conceivable combination. I even made templates to use in blueprinting/exact matching of the head-intake port interface.
The top of the LT4 intake ports hit way high on the LT1 heads. You could physically look & see how they revised the internal ports/passages on the LT4 intake & heads to decrease the sharp bend in the floor area that was required to enter the bowl area on the LT1 heads.
It really has very little to do with what you "see" at the port opening the actual flow gains are made inside the ports.
Why would GM cast the outside of an intake manifold differently?
The LT4 heads & Intake were engineered as a package to increase the horsepower in 96' from 300 in the LT1's to 330 in the LT4's.
Which also shows how much work is actually required to gain a "real" 30 HP.
:eek:
[Modified by superlund, 12:25 AM 12/23/2002]
[Modified by superlund, 12:37 AM 12/23/2002]
The top of the LT4 intake ports hit way high on the LT1 heads. You could physically look & see how they revised the internal ports/passages on the LT4 intake & heads to decrease the sharp bend in the floor area that was required to enter the bowl area on the LT1 heads.
It really has very little to do with what you "see" at the port opening the actual flow gains are made inside the ports.
Why would GM cast the outside of an intake manifold differently?
The LT4 heads & Intake were engineered as a package to increase the horsepower in 96' from 300 in the LT1's to 330 in the LT4's.
Which also shows how much work is actually required to gain a "real" 30 HP.
:eek:
[Modified by superlund, 12:25 AM 12/23/2002]
[Modified by superlund, 12:37 AM 12/23/2002]
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Safety Car
Joined: Jun 1999
Posts: 3,570
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Re: LT-4 Intake Manifold (C4kid94)
The LT4 intake manifold is a different casting. If you remove the heat shield, here is what you see:
Melting Slicks
Joined: Jan 2000
Posts: 3,418
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From: NW Chicago Suburbs
Re: LT-4 Intake Manifold (superlund)
...internal ports/passages on the LT4 intake & heads to decrease the sharp bend in the floor area that was required to enter the bowl area on the LT1 heads.
Why would GM cast the outside of an intake manifold differently?
The LT4 heads & Intake were engineered as a package to increase the horsepower in 96' from 300 in the LT1's to 330 in the LT4's.
Which also shows how much work is actually required to gain a "real" 30 HP.
Which also shows how much work is actually required to gain a "real" 30 HP.
:cheers:
Eric
Le Mans Master
Joined: May 1999
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From: Louisville,KY
Cruise-In I Veteran
Cruise-In II Veteran
Re: LT-4 Intake Manifold (superlund)
The LT4 intake casting is completly different than an LT1, it is cast to match the revised port configuration of the LT4 heads. (read raised runners).
It was never intended to be a direct "bolt-on" for LT1 heads.
:seeya
It was never intended to be a direct "bolt-on" for LT1 heads.
:seeya
Drifting
Joined: Jul 2001
Posts: 1,296
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From: Largo Florida
Re: LT-4 Intake Manifold (Zora)
Odd thing about the LT4 intake. I spoke to Pete at CNC Heads and he said the LT4 manifold is more restrictive than the LT1. This was done for emissions at idle and right off idle. He also said that his intake port job is good for 10 rwhp on a stock LT4 setup.
He says that with an LT4 you need to port the intake because there is a 12% flow restriction unlike the LT1 and won't do a head port job without the intake getting ported as well.
I still find myself not believing what I wrote above but that is what he said. Maybe I am mistaken? Call him to confirm if you like. Pete is "the man" at CNC Heads.
727-527-8866
He says that with an LT4 you need to port the intake because there is a 12% flow restriction unlike the LT1 and won't do a head port job without the intake getting ported as well.
I still find myself not believing what I wrote above but that is what he said. Maybe I am mistaken? Call him to confirm if you like. Pete is "the man" at CNC Heads.
727-527-8866
Instructor
Joined: Apr 2002
Posts: 105
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From: Charlotte NC
Re: LT-4 Intake Manifold (ericcer)
Will it bolt onto LT1s? Sure.
Any reason to do it? Nope :)
As Eric said, it does not match the raised runner LT4 head, not by a long shot, and requires porting to do so.
IMO, this isn't the place to be looking for power, not for the $ anyway :)
Any reason to do it? Nope :)
As Eric said, it does not match the raised runner LT4 head, not by a long shot, and requires porting to do so.
IMO, this isn't the place to be looking for power, not for the $ anyway :)
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Re: LT-4 Intake Manifold (silver & red CE)
Here is a photo of across section of the LT4 intake manifold and cylinder head I found somewhere. Probably the http://www.LT4.com website.
After I pulled my intake and heads, I can say the cross section is accurate. The mismatch on the port roof to intake varies from .25" to .375". The reason its not constant is the injector boss starts in the intake and finishes just inside the head port.
I did the port matching myself to the intake to gasket #12367777. Trevor Johnson Cylinder Heads did the port matching on the head side. For more pictures see:
http://www.corvetteforum.net/c4/tmezger/heads.shtml
After I pulled my intake and heads, I can say the cross section is accurate. The mismatch on the port roof to intake varies from .25" to .375". The reason its not constant is the injector boss starts in the intake and finishes just inside the head port.
I did the port matching myself to the intake to gasket #12367777. Trevor Johnson Cylinder Heads did the port matching on the head side. For more pictures see:
http://www.corvetteforum.net/c4/tmezger/heads.shtml
Melting Slicks
Joined: Jun 1999
Posts: 2,872
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From: Wilmington NC
Re: LT-4 Intake Manifold (superlund)
agreed with superlund... the intakes and heads are from two different sides of the block. LT4 does have a raised roof runner, but also has a more efficient floor slope! I have ported many of them and can tell ya first hand. as for the LT4 not being as flow friendly as the LT1.. well i suppose thats one of those things to debate about... but if your going to do a combo... the LT4 castings have more meat and require less work then the LT1 manifold to fit on the LT4 heads. but either can be used with either with the correct porting done. the LT1 head will be significantely thinner on the roof if you are matching to the revised gasket from GM and have port matched both head and intake to the new gasket. the injector bosses will need some work in the manifold and the roof of the head at the mating surface will also need some special attention to get them perfect but once ya do... you have one hell of a combo!
Chris
Chris
