Correct Manifold for Comp Cars with Hi Rise Heads?

[Byots]

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[computerworks]

Dick Thompson ran the Essex car at Elkhart Lake USRRC in Sep. 1965, Laguna Seca USRRC in Sep. 1965 and Riverside L.A. Times GP in Oct. 1965...

...in OA class, not AP

[Anthony]

Originally Posted by Byots

Here is a picture of a high riser equipped engine in CSX3002 at Silverstone in late '64: http://www.clubcobra.com/photopost/s...0&ppuser=18204 The carb was an 850, as evident from the different shape of the airhorn relative to the 780. Period Ford documents list the 850 for the "7000 rpm" high riser.
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What was (is) the Holey List # for the 850 cfm carb?

[Cobra #3170]

Originally Posted by computerworks

Dick Thompson ran the Essex car at Elkhart Lake USRRC in Sep. 1965, Laguna Seca USRRC in Sep. 1965 and Riverside L.A. Times GP in Oct. 1965...

...in OA class, not AP

I looked at the car in 1965 at Laguna and it had a single 4 barrel, I was quite interested because I already had a deposit down on my car at the time. Although I am not positive, I think the car ran in both production and OA classes.

[Byots]

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[computerworks]

Uploaded a resized version to your Gallery....

..original, at ~3.5meg was too large. Gallery likes 2 meg or less; 600-800k is optimum.

[Cobra #3170]

I had a good friend who was also a Cobra affectionado at the time and he attended the Times Grandprix at Riverside. He told me that the Essex Wire car entered both races, production and the CanAm. What really impressed everyone was that the car was pretty competitive in the CanAm race.
I suppose they could have swapped manifolds between races, but I don't know.

Was there ever a 427 car sold by Shelby American equipped with Webers?

My take, Webers look really cool, do they belong on an original 289 or it's replica, absolutely. Do Webers belong on an original 427 or it's replica, hell yes if you want to look cool, if you want authenticity or horsepower NO.

A single plane open plenum manifold will produce more horsepower than an I/R set up because of the volume available to it, at least at 58 mm Weber flow rates.

[Excaliber]

Seems to me the data I've seen suggests the Holley carb makes more horse power at the upper end of the rpm band than the Webers. But the Webers did better at low and mid range rpm. Single four produced 'enough hp'? An effective way to dismiss the Webers question if you ask me. Shelby went to 2X4 intake for Le Mans in an effort to increase hp over a single four! On THAT track, with it's demand for max hp I could see not using the Webers.

Dry sump because of reliability issues and not required on the small blocks? Balderdash I say! If your looking for max hp it's logical to go dry sump, and the small blocks would have benefited to that end as well.

That motor in CSX3002 (the Turd?) pictured above was the first 'experimental' all alloy 390 side oiler.

[Michael4yah]

Ernie, Hows it. It would depend on the course. At Le Mans they have that long straight called "The Mulsanne that can make you or break you time wise. The fastest car on that part of the course had a distinct advantage and was usually a front runner or winner. If your talking 48s then a 4bbl seems to be the way to go. But many road courses the Webers have an edge. Their throttle response and torque gives them an edge especially in passing. Thats why Ken Miles begged for them to be put on his car. Here ya go Ernie, wanna see what the Mulsanne Straight looks like in a Porsche 956 doing 246 mph down the straight?
http://www.youtube.com/watch?v=iQbmv12s-Yk&NR=1
Enjoy, Michael

[Excaliber]

I agree, throttle response would be a significant factor on the shorter courses, hence the desirability of Webers in such a case. No question Shelby was seeking max mph and thus hp for Le Mans. I think the target speed that MUST be achieved in 1965 or so was around 185 mph minimum. Two chicanes have been added to Le Mans in recent years to lower max mph on that long straight!

Hmmmm, I wonder what the Cobra drag race cars (289-427) preferred for the best time? No doubt they used a variety of intakes in the search for optimum performance.

[Michael4yah]

Ernie, did you watch the Le Mans video? Man that guy was flying. The trees really bring it all into perspective. I just bought that single 4bbl manifold in the photo near the top of the page. I think Im going to put my Tunnel Wedge Hi Riser intake and carbs up for sale. Havnt made up my mind completely. I may use it to rig some webers. You cant find a Hi Rise Weber manifold to save your life! Yup that Mulsanne Straight Changed the Cobra forever. The little sports car body was no match for the streamline bodies of the Gt 40 and the Daytona Coupe. I wonder how fast they had the Daytona Coupe going on that straight. I'll bet it was near 200. After watching that video I cant imagine going that fast on that course in a Cobra!! Yikes.

[Byots]

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[Cobra #3170]

Originally Posted by Byots

You would need a modern worked/ported spider intake with max prepped dominator carb to match the top end power of the webers, and your low speed performance would then be terrible - and it wouldn't be period correct/original. Hofstaedter dyno tested all the factory HR inductions and the 58mm webers made notably more power at every engine speed, including in excess of 7,000 rpm. Dyno testing back in 1964 at SA showed the 58's to make significantly more top end power than the 1x4. It is a widely known fact that webers in general will give you significantly better mid range power, one reason why in a road race the webers give lowest lap times and why SA used them on all the factory race cars. F1 used webers and even today still use IR in what is essentially the evolution of webers, fuel injection. If the most sophisticated race series in the world uses IR, it must have some ideal attributes.

Bottom line, the 58mm webers were the top of the line available option from SA for the big block Cobras back in the day and was planned on being used on team race cars, especially at Lemans, had there been a factory effort (the big block configured coupe was even sent to Lemans in '64 with this induction: http://www.clubcobra.com/photopost/s...47492&cat=500). Anyone can interpret that as they may. More modern inductions are not of interest to me.

How many cars did they sell with Webers? Using your logic you could also install a dual 4-barrel single plane tunnel port in your Cobra because it was available "in the day" and someone thought about putting one in a Cobra and actually did.

You are dead wrong about your contention that a single plane manifold equipped with a Dominator has no low-end performance. I had one and have the dyno sheet to go with it. It produced more low-end torque than an 850 that was also dynoed on the same engine. The engine was very responsive on both road courses and autox events, which would be difficult if not impossible for 58 mm Webers. All this talk is cheap though, why don't you get your engine finished and share the dyno results with everyone and then demonstrate drivability at some open track events.

This is a video of my car with a single 1150 cfm dominator, does it sound like there are any low speed response problems? http://www.youtube.com/watch?v=mZaMFyZpKlo
H

[Excaliber]

Michael, yes, and impressive video!

It is quite possible the 58's do much better than the 48's. The dyno reports I've seen Webers vs Holley did show the Holley making more power at the top end. No doubt those were 48's, a much more common application.

All this 'number crunching' raises another question. The typical math formulas used to calculate the size requirements of a carb don't always apply, especially when it comes to race engines. I suspect the basic problem with the carb cfm math would be found in the VE area. Volumetric Efficiency, which is incorrectly ASSUMED in many cases. Using that formula one could easily conclude a single four of modest size is optimum, as far as CFM goes. I think it is clear, certainly for an FE, that 'more is better', like 2X4 or monster 58's when it comes to absolute power.

Work the CFM numbers for a 427 and I think you will find some where around 800 max cfm comes up! A number I just don't believe. From personal experience at the drag strip with three different size carbs (both carbs matching) I've found the best performance was around 1200 cfm (twin Holley 660's).

[Cobra #3170]

1600cc Formula Atlantic's used to run 50mm DCOE Webers feeding a 24.4 CID cylinder. A 58 mm Weber feeding a single 53 CID cylinder seems a little under carbureted, the more area the better to a point where velocity suffers.
A single cylinder that has a large plenum available to feed it along with multiple throttle blades will be less restricted and produce more power.

[Michael4yah]

Ernie, Yeah Im thinking that that 850 single 4bbl is going to be maxed out with the stroker I was planning. Already bought the manifold though. When you add up the flow from all ports you can see why they invented the Dominator etc.
That video was a good one. Showed the braking of an all out racer too, Did you see how much speed he was able to scrub off while approching that white porsche and just before that switchback? I mean he went from over 200 to less than 40 in no time. And it was so smooth too. Just amazing stuff. Not the best cinematography and could have used a cleaner windshield and without the glare from the dash but still it was almost like being there. What did the Hot Rod Lincoln song say ? Telephone poles passing bye like a picked fence". Thats what those trees looked like. You could sense that if you left the track at that speed, youd end up a 1000' from the pavement. I can see why people come back year after year to Le Mans. I wonder if the old cars still get a chance to use that course during the year?

When it comes to setting up a car If I had my choice of anyone living or dead, I'd choose Ken Miles. If he said Webers work better than carbs Id take it to the bank. Ken passed more people than almost anyone and knew what it took to get the jump on the other driver and the choose the right angle of pursuit. I bet he used the quicker response and low end torque from those webers to edge out a lot of drivers. He was truely an amazing man and one of the worlds best drivers. Not nearly enough is ever said about him. Ok... Im off my soap box now.
Michael

[Anthony]

Originally Posted by Cobra #3170

1600cc Formula Atlantic's used to run 50mm DCOE Webers feeding a 24.4 CID cylinder. A 58 mm Weber feeding a single 53 CID cylinder seems a little under carbureted, the more area the better to a point where velocity suffers.
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Weber has a published graph recommending a specific size carb based on cylinder size and max rpm. For any given cylinder volume, the higher the rpm, the larger the carb needed, and the reverse is true, the lower the rpm, the smaller carb. I'll look tonight for their recommendations.

Originally Posted by Cobra #3170

1600cc Formula Atlantic's used to run 50mm DCOE Webers feeding a 24.4 CID cylinder. A 58 mm Weber feeding a single 53 CID cylinder seems a little under carbureted, the more area the better to a point where velocity suffers.
A single cylinder that has a large plenum available to feed it along with multiple throttle blades will be less restricted and produce more power.

The benefit of a weber, IR type intake, is the "ram tuning" effect, of getting greater than 100% cylinder filling from a specific runner length. Also, IR intake systems generally are easier to get equal fuel distribution as opposed to an opne plenum intake, which may not get as ideal air-fuel distribution.

[Excaliber]

I'm currently running twin 450 cfm Holleys with vacuum secondary. While a bit slower than the 660's, mpg and streetability are vastly improved over the 'full race' 660's.

[Byots]

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[Michael4yah]

Byots, Excelent coverage of the topic. You explained it within its historical context which to me is the most Important and interresting issue. You had to be around back in those days to understand how fluid the change was. Certainly the SA employees must have resented somewhat the intrusion of Fords execs into what was before a basicly free wheeling and open minded shop. It sounds to me those guys were encouraged to tinker with anything and everything attached to a Cobra. Can you imagine being part of that effort? I have lived here in So Ca. since '67 and no matter where you traveled back then you could see the enthusiasm and energy being poured into projects of almost every shape and size. The small shop was king and the industrial parks were their playgrounds. The Company that I worked for then dealt with lots of small machine shops throughout LA. Nearly all of them were involved in some sort of R&D. It wasnt unusual for me to be sent to pick up parts from these shops and while there youd see the employees huddled around their latest creations tinkering with them. It was Truely the golden age of manufacturing in America. We need to bring those days back. Its one of the keys that made our country great. I would have loved to see that big block Daytona run at Le Mans. I bet it would have done well. Peter Brock, you did yourself proud.
Michael