Single Plane EFI Intakes on LT1's, 4 bbl TB's VS LSx TB's

[B'klyn9C1]

I am not fan of of the stock LT1 intake with its short runners and uneven air distributiion.

I was thinking of using an Edelbrock or Professional Products carb single plane for EFI with a the long low profile Edelbrock elbow(for the increased plenum volume) and a 90mm LSx type TB. But I have been reading on the web that guys have been getting 50+ RWHP gains by switching their OEM style (LTx &LSx)TB's w/elbows for 4 barrel TB on their single plane intake. Besides the RWHP gains they say that they have been getting more HP and torque under the curve and also a much smoother running engine. Granted these are on built big cube motors but I think the principle still applies across the board.

So is this true??

If I am going to go the single plane intake route should I save up my pennies also for a 4 barrel TB with progressive linkage instead of the OEM type TB with an (90 +degree) elbow??

Grumpy what is your or any of your friends expericence with carb style single plane intakes on EFI motors such as the LT1 and experience with 4 barrel EFI throttle bodies like the ones made by Wilson, Holley and Accufab???

I really came to appreciate the elegance of the carb style single plane intake manifold with its ability to keep ramming air into the engine and not have the different cylinders to rob air from one another and also have all cylinders feed off of the plenum from a common point. I know this set up has been applied to an all out race application but I think that there is a high performance street application can immensely benefit as well with the longer intake runners helping in low to midrange torque production.

How much more plenum volume you think I would gain over a stock LT1/LT4 intake?

I want to put this on a quaility budget rebuild of my '96 LT1 longblock. My goal is to make 420 RWHP and 400 RWTQ but with better low to mid torque than what the LTx intake can provide. My 9C1 has 3.73 gears, a cold air intake and plan to put 4 into1 long tube headers on a 3" dia exhaust (with 2.5" tailpipes) and an "x" pipe. I am also thinking of going to EFI Connection's LS1 PCM and coil-on-plug conversion for better spark and tuning capabilities.

B'klyn9C1
Brooklyn, NY

 

[grumpyvette]

naturally the results vary with the components used and factors like cam timing, displacement, runner length and cross sectional area, and exhaust scavenging efficiency with tuned headers.
but yeah, the better single plane intakes with a 4 barrel throttle body, do have advantages, when your restricted by hood clearance as they tend to flow more and fuel distribution can be slightly better as the air is more evenly directed without the 90 degree elbow, which tends to direct air flow to the rear 4 cylinders with less restriction than the forward 4 cylinders, but keep in mind if your running a turbo or centrifugal supercharger it changes the flow dynamics, as youll have pressures in the intake runners that are far higher , and the former restrictive 90 degree elbow may no longer pose a significant restriction, but even then the 4 barrel throttle body design on a tall intake with longer runners can show some advantages

this style intake has several advantages, when your restricted by hood clearance issues

http://www.fuelairspark.com/ezefi/default.asp

http://www.holley.com/HolleyEFIBrochure/

but the taller tunnel ram intakes like the stealth ram have some advantages if properly designed

if hood clearance is NOT an issue the taller tunnel ram designs are superior like this one below, or a well designed throttle body/mpfi conversion of a tunnel ram style manifold similar to a Holley stealth ram

now Ive been asked many times if a STEALTH RAM, MINI RAM OR A single plane EFI intake is the best choice?
thats a good question, and Id say the answer changes with the amount of work your willing to do, and the application you use the intake in,a custom stealthram can easily provide more power potential than your average hot rodders looking for,for street use, (500hp or so)but in general Id say that the single plane intakes, with a 4 barrel throttle body design, once correctly matched to your heads will provide the best results, in the power range your looking for.(500 and less hp) simply because of clearance issues and ease of setting up the intake.
obviously if your trying to maintain a semi stock appearance theres other options

obviously theres other options

ID suggest you read thru the threads and sub links

viewtopic.php?f=55&t=431&p=1409&hilit=stealthram#p1409

viewtopic.php?f=55&t=1745&p=4381&hilit=stealthram#p4381

 

[B'klyn9C1]

Thanx for the quick reply Gumpy.

Thank God the B-Body does have the hood clearance like the 4th Gan F-Body. But in your travels which of the single plane EFI intake are best used on a 355 to 383 ci Gen II SBC(LT1)?????

Edelbrock' s Victor Jr.?? Holley??? Accel ProRam?? Professional Products' Hurricane Plus line???

 

[grumpyvette]

HEY GRUMPYVETTE
I noticed that the Holley EFI single plane vortec intake has a a cloverleaf opening to coincide with the throttle body openings on the top of the intake instead of the full "4150" opening you get with Edelbrock and other vortec single planes. Is this to promote greater port velocities than other single planes since it only flowing air in the EFI application??? Or is this just a marketing gimmick???


its just not all that critical either way, but yes at least in theory the cloverleaf inlet smooths the flow, in reality Ive yet to see a measurable difference

One more thing. What is your opinion as to the EFI nozzle location on these converted to EFI Carb style single plane vortec intakes?? Are they placed in the correct angle in relation to the intake valve and port??

naturally the location and angle varies with the guy installing the injectors and the fuel rails,etc. but generally the taller designs have a better angle on the injector spray pattern as it fogs the air stream in the intake runner so Id suggest the taller designs OR intakes designed as EFI intakes, like the HOLLEY single planes, the only problem with the holley sbc single plane efi is the runners need minor port clean-up as the injector bung sits into the air flow slightly and you need to port the exit area and thin the bung casting area and open the runner carefully to maximize the air flow. thats one reason that a carefully ported stealth ram has a direct spray pattern at the back of the intake valve and why if its correctly ported that it produces very good hp/tq

http://www.summitracing.com/parts/HLY-9901-107/

http://www.summitracing.com/parts/EDL-29135/?rtype=10

 

[grumpyvette]

vortec heads have port locations slightly higher than standard gen I sbc heads, like the LT1 heads so yes thats the style intake to use, on the conversion of an LT1
vortec

LT1

either intake will work, in many cases, if properly ported, but theres far less chance of a port mis-match with the vortec version, in your case

Id suggest the HOLLEY,
http://www.summitracing.com/parts/HLY-9901-107/
http://paceperformance.com/index.asp?Pa ... dID=204279

the edelbrock has slightly larger port openings but I think the runner design and plenum on the HOLLEY are a bit better, Ive used the holley intake designed for the standard gen 1 heads on my 383 with good results (made over 450hp)and the vortec version has larger ports

stealthram base

 

[grumpyvette]

Grumpy,

A few days ago I was in discussion with engine shop In Illinois RE: a 383 LT1 build. When I expressed my desire to ditch the stock LT1 intake manifold in favor of a carb style single plane intake the tech said to me that I will experience a big decrease in low and mid range torque in going to the single plane. I thought this was counter intuitive I was lead to believe that the shorter the intake runner the lower the low and mid range torque and the longer the runner are the greater the torque like the famous or infamous Tuned Port Intake on the L98.

He went on to say that though the runners on the LT1 intake are indeed extremely short (3") but the intake has a small plenum volume and this enables the engine to have very port velocities at low and mid range RPM's which aids in cylinder filling at such low RPM's hence the high torque even with short runners

Grumpy is this true??.

What is yours or anybody else who know's experiences with changes in low and mid range torque in switching out the stock LT1 intake for a carb style single plane or anything else(holley Stealthram, Accel Superram, etc.)????



you need to think ,every time you have someone tells you something, now look at the plenum volume of BOTH intakes, keep in mind the distance between cylinder heads doesn,t change and to get longer runners the plenum needs to be either higher or smaller ,and you tell me which ones got the smaller plenum and longer runners, if your confused you can measure, the lt1 plenum is an upside down triangular cross section
approximately 13" long and 3.2" wide and 3.2" deep=67 cubic inches

the single plane is about 4.2" x 4.2" x 3.9"=69 cubic inches

if you think that makes a significant change I can,t see it?

the increased runner length in the single plane is due to the plenum being placed higher in relation to the ports in the heads

now think about the stealth ram, its runners are longer and straighter and its plenum is about 5" wide x 3.7" tall and about 13" long INTERNALLY or about 190 cubic inches if you compensate for internal casting design for the thru bolt sleeves,a significant change, yet the stealth ram has only a slight loss of lower rpm power and some noticeable gains from about 3500rpm-6500rpm provided its matched to a cam that's designed to use the longer runners and larger plenum



viewtopic.php?f=52&t=333&hilit=+cross+section

http://www.wallaceracing.com/max-rpm2.php

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.bgsoflex.com/intakeln.html

viewtopic.php?f=52&t=322