Weber 48 IDA - Show me your linkages

[John Fitzpatrick]

Doc-
Looks very interesting, and I'd be interested. Could it be used for experimenting with suspension geometry too?

[Doc Watson]

John,

I was thinking that myself actually, and with a little more work I could work out all the geometry of the suspension. I would then probably go to far and use a genetic algorithm to optimise the suspension.... finally a use for my PhD.....

Andy

[John Fitzpatrick]

Sounds like it would make a good class project for Mech. Eng. students, if you teach. When I was a Junior (back in the day), we tried something like that for aircraft landing gear using an analog computer. Wasted enough graph paper to repopulate a forest and never did get it right. Don't mean to go off-topic, so PM me if you get it working- I'm curious how you go about optimizing with non-linear components and variables.
John

[Rick]

I found this some time ago, it may be of some use to you fellows:

From Kinslers site: pg 23

[Earl J. Castillo]

Hello you guy’s, I’m new here. I know this reply is a bit late as there hasn’t been a response in over 3 months. I’ve read thru the post, very entertaining…a few punches get thrown around here but fortunately nothing too damaging. Anyway, I’m in the acquiring parts stage of my engine build. I am for the most part done with the exception of pistons, flywheel/clutch and possibly a new cam selection. A quick run down: 331 C.I new BOSS 302 block, Steel Scat crank, Manley H beam rods, C7ZE HP289 heads 1.94/1.60 Mondello ported (I know I’m limiting myself with these heads) with Weber 48 IDA’s. I’m in search of a new cam. I was original going to run this NOS C7FE 2350-A (LeMans cam) but from what I hear and read isn’t wise for the street. My targeted HP is in the 380 range which I think is realistic. I wish I could say I was putting this into a GT40 (RCR or CAV) or maybe into a Cobra, It’s heading for a 65 GT350 replica. I know there are other forums for these but a good majority (including the Shelby American Automobiles Club SAAC forum) tend to discourage the use of Webers.
My feeling is; if there is any group of people that has the knowledge and first hand expertise with Webers on V8’s it would be you guys. So here I am, go ahead throw a punch. By the way here’s the linkage for my set up it’s comprised of Enderle hardware, Inglese (bell crank and plate) and Carr McMaster rod ends (holding center shaft) the manifold is an original (carbs all facing the same way, fuel line will terminate behind the Dist.) I need help…

[dave harris]

Hi Earl, Where are you in N. Calif? I'm in the Santa Rosa area.

No comments on the webbers (Can't afford them myself - - ), but I would ask a question regarding your engine - How do you plan to use it? If you are going to mostly run street / drag strip the H-beam rods are suppose to be a good choice. If you plan to run road track use I've heard from some very knowledgeable engine guys that the I-beam rods work better for the rapid / constant rpm changes. You might ask others to chime in on that or send a PM to Gorden Levi -

Cheers

Dave

[Earl J. Castillo]

Hello Dave, I'm down in the Bay Area (Berkeley) answering your question, basically I plan to use it as a weekend toy. Mostly on the street, minimal track time with the Nor Cal SAAC group. It’s an accurate GT350 replica of an early 2 digit car with webers. With the exception of the block and the webers it’s dead on.fficeffice" />

[Cliff Beer]

Earl, please feel free to ignore this, but, it looks to me like you may have unequal rates of butterfly progression from idle to WOT. With all the Webers oriented in the same direction, you will have the 2 carbs on one side with a faster initial rate of opening of the butterflies than on the other side because of the geometry of the longitudinal pull. This unequal phenomenon would reverse it's effect as you progress to WOT. Kind of hard to describe with words alone here and it's late so I may have this wrong.

A balanced and equally progressive butterfly opening is definitely achieved in the attached pic.

[Big-Foot]

Originally Posted by BundleOfSnakes

I’m in search of a new cam. I was original going to run this NOS C7FE 2350-A (LeMans cam) but from what I hear and read isn’t wise for the street. My targeted HP is in the 380 range which I think is realistic.

Hi Earl and welcome to gt40s...

My engine is not that different from yours. I chose the more aggressive of the two cams now offered by Inglese / Comp-Cams (Inglese is now owned by Comp-Cams). It's a hydraulic roller cam made specifically for our engines to be used in a street/track venue with Webers. Since Webers are so finicky to tune with cams that have a broad overlap, these actually have a lot less.

Engine is a 331 with Dart Pro1-170 Heads, 10:1 compression, Weber 48IDA carbs 37mm chokes, Inglese "Weber grind" Roller cam with 115LC, 222/224 duration @ .050, .571 Intake, .565 Exhaust. Dyno long primary headers.

After a bit of Jet tuning (Thanks Jac-Mac you really helped out a bunch here) we threw down some pretty good numbers although a bit shy of the hoped for 450 HP the Torque was well above expectations.

414 HP / 430 TQ

We need to revisit the valve springs and/or push rods as she had valve float at 5900. The power band started nosing over around 5700 anyway..
Either way - the engine idled very well - not real choppy but enough of a lump to let you know that something stronger than the family station wagon is lurking...
Throttle response was very crisp.

Final Jetting / Air Correction was;

F7 Emulsion tube, 145 Main Jet, 120 Air Corrector, 120 Idle Holder, 70 Idle Jet

It was interesting that this engine does not like a lot of timing. The power started dropping off at 31 degrees and a lot more at 32 degrees. No detonation present or noted. The fuel used was 92 Octane pump gas. 3.5 PSI fuel pressure.







I hope this is of some help to you Earl...

[Earl J. Castillo]

Hello,fficeffice" />

You guys are amazing. This was the type of feedback/info I was looking for. I’m no where near done as there are still a number of decisions to address. I thought I was ready to order pistons and decided to keep the compression ratio in the 10.3–10.5 range assuming I was to run the deck height .015 in the hole. Then I was introduced to a Neil R. who told me run the deck height .006 out (above) assuming I would run a Felpro gasket that has a crushed thickness of .041, run the longest rod possible (in my case 5.400) adjust me CR accordingly, Dump my Crower rockers in favor of a T&D shaft arrangement and a custom solid roller cam specifically ground for Webers with a 112 degree centerline? He had just finished a good friends CSX4000 series 427 Cobra with a 427SOHC with Webers! HP and torque was staggering. His previous engine builder is the person I was having build mine, until I saw the improvements he did on his flow bench. Not that my builder was/is some backyard guy, Tim M. has built some championship winning engines. Neil told me to stop reading that Hot Rod Car Craft magazine crap. Another consideration was Tony Jr. at Tony Otto Engineering (TOE). My pockets are not that deep.
Anyway back to this linkage, of the little small things that I can do I want to really understand Webers and how to tune them properly. As well as what combinations work and ones that don’t.

Cliff, Thank you in regards to your post I’m well aware of the different carburetor arrangements/orientation in regards to throttle positioning (idle/part throttle – WOT) air/fuel flow characteristics and parallel vs. over-under linkage setups. This is a “we will see”, if not adjust accordingly. I saw the post here on the GT40 forum “Webers the ffice:smarttags" />Right Way” Interesting arguments.

Randy (Big-Foot), your specs are somewhat similar to what I’d hoped for. I know I won’t be able to reach your HP level due to the heads I’m using. A number of friends have been telling me to use a modern head. I was considering using that very same cam because it was specifically designed for Webers strong vacuum signal and all, until I was told hydraulic rollers were good to 6000. I’m partial to a solid lifter flat tappet and open to suggestions regarding a grind that works well with Webers. Custom mechanical rollers would let me rev to god knows what, but do I need to on the street. I’d be very interested in hearing your input on your cam and its drivability. Unfortunately I’m pushing around 2850-2900 lbs in overall weight, with a final drive gear ratio of 3.89.

In reading posts from Doc Watson (Andy), Canuk40 who run this orientation, I’d want to know if my linkage would work correctly. I don’t understand Andy’s geometry diagrams. Granted he’s building it on top of the air box floor covering vacuum lines, but intentionally arranged the carbs this way. Due to the differences in the throttle positioning is there a way to compensate flow rates by adjusting arm lengths or starting point locations?

~Earl

The people in the cheap seats always boo the loudest.

[Jac Mac]

To late now but you could have run a 5.625" rod with a 0.950" piston--next time maybe