32/36 DGEV vs 38 DGAS for power AND economy

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Just started rebuilding a 250ci 6 which came with a Carter RBS on the standard cast inlet manifold.
The engine appears to be standard internally (but I've not checked the cam yet), but has exhaust headers. I intend to give the head a 3-angle valve job and equalise the chamber volumes, and I'm not ruling out sticking in a 264 cam.
According to this link:
http://www.webercarburetors.com/ppw/html/aplication_guide/making_the_right_choice_32.htm
a 38 DGAS would seem to be the obvious choice. Especially as they're common in UK as they were fitted to V6 Capri. But we also have to deal with gasoline that costs almost $4 per gallon :cry: so I don't want to stick on a juicy carb if the progressive DGEV can be made to work almost as well with the mods listed above but with better economy.
Anybody got any suggestions?

Also, I'd like to add that this is by far the most helpful & friendly forum I've ever been on...also one of the best to use!

cheers

Rob Okey
1969 250 engine. Shame there's no car to go with it...
 
Others are more able to talk about it than I, but I'd go for the 32/36 as it is able to produce up to 150 hp net if you modify it right. Follow David Vizards ancient SOHC Ford book of the mid 80's, and enjoy the ecconomy. Chances are the 250 you have has the earlier 1.5" hole in the intake part of the heat, so perhaps a 38 would be overkill.

I appreciate the economy angle. It's never an issue when you start, but suddenly the matter causes the sale of a good engine. Although 150 hp and perhaps 300 lb-ft of torque is not a lot, a six like that can twist the cobbles off any road from 600 rpm. The instantanoues torque they have is mighty.


We have no congestion here in Kiwiland. The thought of an 83 2.8 Granada Wagon with that engine in it as a tow car for a moto- cross bike is almost too much to pass up. If you used a US Toploader over drive manual trans, you'd get a car that could cruise at 2400rpm on the motorway. I think the early 73's ran a C4 auto as a 3.0 V6. That'd be a cool ride too. Then again, and old Vauxhall Carlton or Royale would swallow a 250 whole, and no-one whould be any the wiser.... :twisted:

Now that I know you're on the right track, I'll leave you to these fine gentlemen.

You have absolutely no idea what a buzz it is to see someone find an engine like that. In my 9 months on this forum, your 250 rates as one of the highlights!

Any one else got some ideas on the Right 'Juicer' for this engine?
 
Hi Rob,

One of the things I really like about my car is the strong torque curve. Takes very little throttle get the car rolling and has strong pull through the first half of the rpm band. Torque like this is helped by high intake velocity. The progressive carb helps maintain this condition. Also, the 32/36 will get better mileage. As far as performance, the 32/36 flows 320cfm vs 370 for the 38/38. With the rod ratio present in the 250 the car is better built with a 5000 top end. The 264 cam is just right for that. Assuming you can achieve 85% volumetric efficiency (VE) with your mods (stock approx 70%) the 250 can only pull 300cfm at 5000rpm. Another benefit of the 32/36 is that of intake bore area matching. The surface area of the 1.75" carb bore is 2.40 Sq. in. The surface area of the 32/36 is 2.92. The 38/38 is 3.63. So, I tend to think the 32/36 is a better fit.

I went with the Holley-Weber 5200 (26/27 & 270cfm) on my 200 with 1.5" carb bore head for this same reasons. Car pulls 231cfm @ 5000 (stock cam - 80% VE). Carb / bore area is good match at 1.77 / 1.77. Very happy with the results.

Enjoy - Steve
 
Your set up sounds great. For economy purposes (gas MPG + actual cost of the carb) I would go with the 32/36 - (the difference between the two carbs are: 32/36 vs. 38/38, and 320 CFM vs. 370 CFM). I have the 32/36 on mine and I couldn't be more pleased.
(www.geocities.com/levidodd7/65stang)
 
I drove a jeep with a 32/36 and then drove it later with a 38/38 DGES. In spite of the minor CFM difference, there was a big difference in the way the engine responded. The bigger synchronous carb seems to make much more power. I couldn't say if the economy was affected, but I'm sure it was.

Personally, I think a 32/36 is too small for a 250. If I could redesign the log, I'd incorporate dual DGV's.
 
I tend to agree with Jack. The 32/36 is as small as you would want to go on a 250. The Jeep is a 258, so that is a good example of the performance difference between these two carbs, i.e., you tried them both on the same car. I recommended the 32/36 on the basis that it will support the 250, and get better mileage. $4 a gallon is a sobering thought.

Steve
 
Just spoken to a major UK Weber dealer. They do the 32/36 DGEV in two calibrations for Jeep 2.5 and 4.2 (with quite a price difference), to replace the Carter 1bbl and 2bbl respectively.

My 250 has a Carter 1bbl. I expect fitting the one calibrated to the 256 Jeep 6 cylinder would give me pretty good performance without punching me in the wallet too hard.

Which brings me to my next question...

The standard inlet manifold has a single hole. I could make up an adaptor to fit a DGEV in the machine shop at work...or I could machine the manifold so the carb bolts straight on and has holes in the manifold matched to the carb bores. Is that a better idea? I really don't intend putting the Carter RBS back on if I buy a brand new Weber.
Also, why does the cast manifold curve up slightly towards the back of the engine?

It really is a nice engine to work on. I should buy more American stuff...
:)
 
What about for a 200 w/ the 1.75" intake hole? Would a 32/36 be a good carb. for it? Also, would you have to have headers to realize a performance gain w/ this carb and an otherwise stock engine?
 
Rob,

A direct mount of the 32/36 is a very attractive idea. However, I believe you would still need and adapter / spacer of some kind the get valve cover clearance. No big deal if you have access to a machine shop. Go for it and let us know how to duplicate it when your done.

Falcon64,

The 32/36 would work well on a 200 with the 1.75 carb bore head. Performance would be improved by a header. Intake efficiency is greatly improved by rapid exhaust flow. You will get better performance with the carb alone. A free flow exhaust system on a stock exhaust manifold would be better. A header with port divider would be best.
 
As long as we're talking about a 250, would a 252H cam from comp cams be good for gas mileage and a little bit of power for this engine or would it hardly be an improvement over the stock cam? The car is a 250 with a c4 and 2.79:1 gears. What cam would you suggest for good gas mileage and a bit of power?
 
steve is more hands-on than I.

General information, from non-other than Englishman David Vizard, is that over 270 degrees duration, the brake specific fuel consumption starts to take a hike. So don't go over 270 degrees. High lift cams, which are intense in there opening and shtting, are okay. The degrees at which both intake and exhast valves are 30 thou open is a critical point for a car with an auto.

Back to carbs. I have no doubt that a Cortina/Pinto carb looses over 10% on peak power to the 38 DGAS. But there is possibly an economy saving of 5 mpg with it, perhaps more. Our post 1982 Aussie 250 Falcons ran a Weber ADM carb, with a similar carb venturi area, and it could do 27 imperial mpg at 60 mph.

Example is a 351 (5.8 liter) V8. With a 600 Holley vac sec 4-bbl, there is, in venturi terms, about 5.2 inches at Wide Open Throttle (WOT). With the bigger 750 cfm vacum secondary 4-bbl, about 6.2 inches @ WOT ( aye wot, no more funnies, please). In cubic inches engine capacity per square inch of venturi, thats going from 68 cubes per square to 58 cubes per sqaure. A difference of 20%. Power goes up by 7%, from 290 hp to 310 hp. Fuel consumption, on the best of tunning for both carbs, overall fuel consumption drops from 16 imperial mpg to 11 imperial miles per gallon. A loss of over 45%!

In your case, with the 32/36 there is around 145 cubes for every inch of carb venturi. In don't know how wide the venturis are on a 38 DGAS, may be around 29 mm for a total of around 2.05 square inches of carby area. 122 cubic inches per square. An increase of almost 20% in effective carburation.

On a 4.1 liter engine, MPG's rule. Under carb it! One thing I'd do, is be aware that the two inner branches of the six inlet runners are spread further than the others. If you are placing the carby on, be sure the secondary and primaries are squirting into the centre branch. A case for leaving the 1.5" hole as it is.

I can see it now at car shows where Rob the Viking's Capri gets thronged by hundreds of Englishmen saying 'why doesn't it have a bigger carburettor!'
 
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