HI guys. I've learned a decent amount about the different head options, but I don't know much at all about the intakes. How do the stock lt1 and lt4 intakes flow? Are there any easy ways to port these for additional flow to increase their capabilities? How much hp are they good for before becoming a restriction?

I kind of took this stuff for granted since my car came with cnc'd heads and the intake appears to be a modified and ported lt1 intake.

I tried doing a search for the tpis mini ram for the lt1 and couldn't find much.... well anything.

I'm interested in the upper end of performance such as 500 hp+. I'm also curious to see if any of the other options allow me to get rid of the opti so I can run a 50 mm cog setup.

Thanks!

 

qwiketz,

the lt1 intake will make some good power with some boost behind it but if your heads have the taller ports ie..LT4 heads then the LT1 intake manifold will hold you back because the port height is shirter in the manifold then in the heads. if the heads are ported to a felpro LT1 gasket then your not going to gain much without adding heads with taller ports. Plenum volume increase would be a big help for guys like us who run alot of boost for the upper rpm band. I am seriously thinking of starting to fabricate sheet metal intake manifolds for the LT1 and L98 motors since I remember what a pain in the rump the tuned port was when I wanted to make some decent horsepower up in the higher rev range and the TPI just flat ran out of breath around 5000rpm.

Chris

 

As for getting rid of the optispark, I may be doing a little something with that as well that will work with the sheet metal intake manifold and make plug wire changes a breeze and allow the use of about any kind of blower drive you can think of

Chris

 

Some say you can really improve the LT1 heads and intake, but the potential is much greater with the LT4 head, intake and Hot cam package. Edlebrock has a LT4 intake that will maximize the worked LT4 heads. I'm not sure you can reach 500 hp and still keep it streetable, without a blower or NO2. I'm slowly gathering the parts for a change to the LT4 top end. My 92 runs very well now and is very good on gas mileage so it's hard to justify beginning the upgrade at this time.

 

For several years I ran an LT1 with stock intake and heads. Behind those I had a HotCam and fairly open exhast system. Althiough I never dyno tested that combo, the car would run 12.6's all day and once ran just under 12.50. Speed at the top, a better indicator of horsepower, ranged from 107 to 109 mph. Based on a weight of car + driver of 3500 lbs, I estimate the crank horsepower at 370-380. YMMV.

Now with a ported LT1 intakem ported LT1 heads and a stroker 383, I dyno'd 400 RWHP and it runs the quarter in 11.66 at 118. From these numbers, I estimate the engine HP around 470-490. So, this all shows that the LT1 intake is pretty good as it is and can be ported to achieve substantial horsepower.

 

depending on what cam you are running I would expect more then 400whp from a 383 with ported heads and intake. my 350 hot cammed car with ported lt1 heads and intake went 12.00@119mph regularly like a bracket racer with crap 1.8 60's.. power on it was 372/362.. the extra cubes should be good for more then 25 horsepower????

now the my fathers 96 LT4 with ported heads intake and cam made 410rwhp (stock shortblock 350cid) nand ran steady 11.5's@122-123mph both cars were full weight vehicles.

here is an overlay of the two cars, the 96 LT4 had a decent cam in it 235/242 similar to the comp cams CC306 cam.


Chris

 

If you are going to make a change, just switch to a single plane manifold with elbow, and call it a day. When you get to the higher HP levels, you will find that air distribution issues abound with the LT series manifolds (as well as the MR manifold).

My vote, single plane.
Aaron

 

Going to a single plane conversion may be a little premature, as people have made impressive power with LT1 (and LT4, MR, SR, etc) intakes. However, Aaron is certainly on to something...
My LT4/383 was over 500 HP (at the crank). I ported the snot out of my LT4 intake (TPIS ported LT4 heads), but still my spark plugs indicated that the rear cylinders were not getting equal air, and I could literally go from front to back and identify each cylinder that the plug belonged to by reading the plug's 'color'. I did have thoughts of some kind of centrally located throttle body/elbow/carb-style intake set-up, but the engine was not exactly lacking for power, so such an effort was not deemed a priority.
When you hear of port-ers cutting an intake in half, then welding it back together, this is much of what they are trying to address.
I have heard of a ported Mini Ram intake supporting 600 naturally aspirated HP atop a high revving 396 stroker.
A ported LT1/4 intake should make it to 500 HP, with a 58mm throttle body and 36lb injectors. Beyond that, EVERYTHING becomes an issue of compromise in driveability, cost, durability, exotic efforts, etc.

 

is the edelbrock lt4 exactly the same as the stock lt4 intake or slightly different? Is it an air gap intake similar to the tpis intake?

 

the LT4 edelbrock intake is an airgap unit. there are some subtle differences beyond that as well. I was less then impressed with the ports and they will certainly need some work if you are picky like I am. they CNC the first 1" or so to give you perfect gasket matching but past that the machine tool path leaves a sharp ridge where it just quits. in my opinion this creates a cross sectional difference that will effect the air movement too drastically for a nice seamless transition into the intake port of the cylinder head. I personally have had best results when my cross sectional area starts larger at the beginning of the intake port and slightly decreases in size to the mating point of the manifold and cylinder head and this is how I port my intake manifolds and have had alot of good success. gives it a kind of funnel or flushing effect where the port speed builds as it gets closer to the back of the intake valve. this has always shown better low lift flow numbers while still increasing peak flow numbers. the powers that be here on the oard may have different opinions or results, but my cars always performed beyond what most expected so I am settled with my own personal experience

but other then that I do like the air gap design, the plenum volume is a wee bit small for my tastes but for a street car with boost it will be fine. As Aaron stated, I would like seeing more plenum volume which in theory should help alleviate cylinder to cylinder variances in flow characteristics.

for the money.... if I had to do it all over again.... I may consider a single plane or I would have built a sheet metal and will likely still do this once the new 4 axis CNC machine arrives.. or I may even just make a two piece manifold machined from billet stock where I can truly play with the port design.

the DFI Gen VII I am running allows me to fine tune fueling for each cylinder so it is not as critical for hurting the motor.. if I have a leaner cylinder I can add some fuel there but I would prefer a more balanced power per bore then bandaid. for now helping keep the motor alive by tuning per hole will suffice on my street car.. for the 1985 drag car we will be building... alot of R&D will go into that one to build a better mouse trap...

some exciting things are happening in my life and while I am nervous and scared I am excited and more driven then ever before soo... gonna see what this drive can produce!

Chris

 

A few questions...

How would your rank the performance options:
-modified lt1 intake to fit lt4, ported
-lt 4 intake, ported
-edelbrock lt4 intake with port work
-tpis manifold, with or without port work

Will any of the single planes with elbow fit under the stock hood?

On a side note, the tpis intake has the option to run a standard dizzy. I've seen it done on an lt4 intake, but would it be about the same amount of work to get it to work on a edelbrock?

 

If emissions is a concern do an agressive port on what you have and call it a day. As hot as Vettes get under the hood I dont see how the air gap would do any SOTP good unless the design is just that much better.
Dont waste your time fooling with the LT1 intake if you already have ported LT4 heads (pretty sure you do?)

 

I converted an edelbrock just last night to work with a dizzy.. took about 30 minutes and the correct clamp and some thinking on how to locate the hole which I used a std sbc manifold and made a aluminum bracket bolted down and drilled the hole in the bracket through the sbc manifold then I transfered it over to the new edelbrock manifold and did the opposite, voila.. the clamp requires two holes to be drilled one for the stand off and the other for the tightening bolt to hold the dizzy.. this is about 5 minutes worth of drilling and tapping at best.

last thing to do is properly shim the dizzy so that it tightens and isn't in a bind, you want it set down so that the gear mesh is acceptable, nothing a little blue gear dye and a few shims and trial and error until you find the correct height then measure and cut the shim.. it will need to be angled to avoid oil leakage here.. so pretty straight forward and easy to do with a little thought!

I would go for the single plane like I said, but mine is a street car so 100% out of the manifold isn't the most important thing to me and I like the stock maifold layout and can accomodate any flow distribution issues so its not as a bbig of a deal to me and it will still make plenty of power.. my boost is on a ****

Chris

 

Chris,
How do you handle air flow differences when they become significant. The LT1/4 is similar to the MR type manifolds (even rumored that GM got the idea from design work from TPIS).

With that being said, there are enough people on this board making big power where there is a distinct flow difference from front to rear (lots of comments on here and the F body forums that detail this issue). I can vouch for several of my MRs in that I have cut open and done significant rework to equalize flow, and still as the HP gets up in the 600 range, the intake becomes a limiting factor.

I do not think there is any amount of tuning that will fix this issue. Basically if you equalized the fuel flow with the air volume, you might have some cylinders that are producing 20%+ more power than others. You know, as well as I, that this is no way to tune an engine.

This is when I made the move to the single plane.
Aaron

 

I was going to get the Edelbrock LT4 for my blower build, but now that I know my heads (AFR195's) will work with my LT1 I'm not going to bother.

 

Aaron,

I agree with you, for all out racing and power you can pull every pony out of the motor with a single plane intake manifold, but for ease of packaging for now I will stick with my edelbrock which has tried at least to overcome some of the flow differences.. I took a close look at it earlier today since it has been sitting during my mitsubishi build, and I noticed something that i hadn't at first glance which i am curious to see how it works... the runners are swept forward towards the throttle body at a pretty good angle at that.

but for the time being, with the turbo and big boost I have still seen a few F-body guys tip in at 850-1000rwhp on the stock ported intake manifold.... soo gonna give it a go!

Chris

 

For modest power levels, it would appear that the superram is a reasonable intake choice for a centrifugal supercharger.

The long runners increase the pre-boost torque and also flow reasonably well up top. My impression is that the large plenum permits the compressed air to expand and cool somewhat before being consumed.

I haven't seen too many supercharged superrams around here, but I don't see any serious downsides until the overall flow becomes a limitation. I haven't noticed any mixture distribution problems, and I don't recall reading about them either.

 

What gasket are you using?
I have a 1284 here and if you stick it up to the LT1 intake the bottom will need trimming, in fact enough to where youre better off making a gasket or using another one there Fel Pro I doubt will seal right.
When sticking it up to your 195 heads youll need to trim up top, there will be a nice mismatch and a LOT of grinding required to match the two pieces.

 

The single plane intake has been refined and refined for how many years? hard to argue against it. Have not heard anything mentioned as far as results for the new modified stealth ram offered that will fit under a stock hood?

 

Old thread... Anyone know of any solutions that will fit under the stock hood? The tpis intake looks is taller so I'm not sure if that'll fit. Are there any ways to correct or try to balance the flow per runner on the lt1 intake?