hey guys, i know a lot of people are upgrading their intake manifold for their L98s and that it isnt as neccesary for the lt1/4s. but hopefully you can answer a question for me. the intake manifold that came stock on the LT4 was a little bit high performance version of the one that came stock on the LT1 correct? so the LT4 intake manifold can use even higher amounts of horsepower? even so would that be somewhat of a barriar when you are running LOTS of hp through an LT motor? i mean if you are running say over 400-450 to the wheels will getting somebody like LPE's ported and polished LT4 intake manifold help your power? how much do you think it would help a mostly stock LT4?

 

A LT4 intake will not fit on a LT1. The intake runners has been raised .100+ over the standard LT1 intake ports. So that means that the ports won't match. But if you install a set of LT4 heads on your engine then you could benefit from the HP improvements. Without the macthing heads the LT4 intake is of no benefit.

 

wow i didnt realize they were not easily interchangeable. however i have an LT4 to start with. would it benefit me much to get the LPE professionally ported and polished one? or would i not see much gain cause im mostly stock? i wonder if i would see much gain if i was pushing over 400 rwhp?

 

thre is a how to on the gs registry site on how too port match it your self it will save you a couple of dollars http://www.grandsportregistry.com/te...ke_porting.htm

 

:iagree: I agree 100% do it yourself using Jims tips and save yourself a lot of money over what LPE will charge you. I had LPE' so called super porting on my intake, it cost me $350 back in the days when I didn't know much about port work and what it meant. Let me tell you, it can be done with ease. This intake there isn't much work to it at all. I did the port work on the next three LT4's I worked on and they all turned out fine. Cost, about $35-40 worth of bits and sanding cones, and of course some time.

You may see some gain, but its going to be at the upper end of the RPM band.


[Modified by tjwong, 9:51 AM 9/22/2003]

 

tjwong:......
your bio says you have a blown LT4. how much hp are you putting out? did you put the ported intake manifold on as you were doing everything else? if you did it would be hard to say if you felt any difference. please let me know. not many ppl talk about porting intake manifolds. my guess is your right and that it would only make a difference under high rpms and makes me wonder if a ported and polished intake manifold would benefit even more if it had a high revving cam to back it up ie hotcam or even more aggressive around 7k rpms. i also wonder how this compares to porting and polishin heads. i know there are ppl on this baord that have had a stage 3 port and polish job done on thier stock LT4 heads with little or no other mods and picked up over 20rwhp! thats a lot of power. im curious what kind of power a P&P intake would do. it might help it breath even more if you had a good exhaust system to help it exhale that extra air

 

I did everything all at once. It is always a good idea to at least port match the intake to the heads. I have some CNC machined AFR LT4 heads. Back when I first got these heads in 96 these were some of the first offerings that AFR had for the LT4. I had them do some additional CNC work on the ports and these heads were made custom for my engine with 70cc chambers if I remember correctly.

So I can't tell you if the intake port work made much difference or not. Surely it couldn't have hurt matters as the stock runners in no way matched the CNC ports of the new AFRs. When I had LPE do this, they asked what heads I was installing and they were advised to speak with Rick at AFR at that time. Between LPE and AFR the porting was right on the money when I got the intake back. The ports on the heads and the ports on the intake matched nearly perfect. I touched them up just a tad but not much. Besides that the blower made up for any inefficiencies.

There has been alot of talk lately about porting the L98 TPI base and what it could flow versus changing it out to a TPIS MINI-RAM or even going to a LT1 intake conversion which is about the same design as the Mini-ram. The tried and true TPI setup of the L98 was a low end torque monster but it ran out of breath after 4000 RPM or just after that. So most people either go with lots of port work and large tube runners, or if they can afford it they change it out with a LPE/Accel Super Ram set up or the Mini-Ram from TPIS. It is all about air flow, making it a simple input equals output. The more air and fuel you can stuff into the engine the more HP you get out of it.

Most street engines won't be revved over 6500 RPM. I know a few guys here on the list that routinly puts their 96 LT4 GS's through the paces at 6500+ but these are the exceptions. Sure my engine can do that and maybe a bit more. The internals inside of it and the cam surely can handle it but there isn't too many places where I can do that here and not get a ticket other than a drag strip. But it sure is fun to blast it from time to time. I am putting out over 500 Hp easily, I can run 11.15's in the 1/4 at 5000' above sea level on a 90* day and that is traction limited from a couple years ago.

If you want that LT4 to really run, have Pete at CNC heads give them heads a CNC port job. There are others out there as well but Pete does a fine job and is reasonable with his costs. He can also supply you with a matching cam or you can go with the hot cam which is a good all around performance and street cam. Doing so will give you a real good rush when you step on the go pedal. But remember now that she breaths in a lot better you better do something about the exhaust to really take advantage of them new heads.


[Modified by tjwong, 8:49 PM 9/22/2003]

 

I thought they sold LT4 intake manifolds for LT1s? I can't think of the guys who offered it, but it was in a magazine. Thing looked damn near identical to the LT1 manifold except the color.

 

They do, you just need to buy the heads to mate to the intake manifold. If you use the LT4 intake with LT1 heads you will have a severe intake leak, as the ports will not match and properly seal against the gasket.

 

On hwy 26 westbound from sylvan area and past the 217 exit is a good place at around 2am. Nowhere for cops to sit and its good for 170mph, dont ask me how I know :D