CFM for a 218?

[Powerhouse]

Anyone know what the cfm for the 218 is? I am considering putting dual 2 bbl prog holley webers on my 218. They are rated at 270 cfm each. Would the cfm be doubled if two are used? (Dumb Question but I don't know how that works) Would they be usable as stock or do the venturi thingamabobs need changin'?

[blueskies]

I have a pair of Holley/Webber carbs on my 230, bored 30 thousands over, which makes it about a 235 cu in engine. I also have a 3/4 cam, HEI, and dual exhaust through tube headers.

These carbs were originally used on Pinto motors with about half the cubic inches of the 230, according to Tom Langdon.

Mine are right out of the box, and it runs like greased lightning. Not sure what they would be like on a stock 218, but I would think maybe a little rich...

Pete

[Powerhouse]

SO...I'm guessing the 3/4 cam is a necessity. Eventually, I 'll be able to go that route. But that involves a rebuild...unless there's some way to take a cam out without removing anything else...

[greg g]

cfm is more or less determied by the air the pistons pump. puttin two hole through whifh the pump pulls actually lessens the air going through each.

A 218 is 3.7 liters, so looking at the pinto at 1.6 liters each, seems there is plenty of wiggle room. the rating on the carb is maximum the carb will flow, so if the pump is flowing more the carb will be the flow restrictor, if the engine is pulling less, the the carb should be comfy.

[1937 Dodge]

I would recommend 2 X 2 Carter Webers. Langdon has both but the Holly Webers are rebuilt while the Carter Webers are new from the factory. The Carter Webers come with an electronic choke and are designed for a 200 CI engine at 6000 RPM. Since we run our flatheads at a 4000-4500 RPM max., the Carter Webers would work well. You get matching numbers same color, brand new carbs etc.

It is hard to get new Holly Webers so what you end up with is rebuilds that may not match number or color wise. Pete is correct that the Holly Webers work well with larger sized engines.

You'd have to contact Langdon 586 739-9601 for the $$$ and get his opinion.

[Powerhouse]

cfm is more or less determied by the air the pistons pump. puttin two hole through whifh the pump pulls actually lessens the air going through each.

A 218 is 3.7 liters, so looking at the pinto at 1.6 liters each, seems there is plenty of wiggle room. the rating on the carb is maximum the carb will flow, so if the pump is flowing more the carb will be the flow restrictor, if the engine is pulling less, the the carb should be comfy.

neat...

I thought the 5200 Holley/Webers came off 2.3 liter ford engines? late 70s early 80s models?

[greg g]

Those may flow a bit more coming off the 2+ liter engines, but they have adjustable jets you may need to fiddle with.

[Powerhouse]

Those may flow a bit more coming off the 2+ liter engines, but they have adjustable jets you may need to fiddle with.

OH boy....sounds like a headache coming soon...

[Powerhouse]

so...according to my records so far...

The Carter Weber(???cfm) 2bbl prog comes out of a ??? liter 200 CI @6k rpm

the Holley Weber (270 cfm) 2bbl Prog comes out of a 2.3 liter 140 CI @ ?k rpm

Carter B&B(STOCK) is for a 218 CI 3.7 liter @3600 rpm

[TodFitch]

Don't know squat about aftermarket carburetors, but the CFM of a 218 at its rated max BHP is easy to calculate:

(218 cu.in.) / (1728 cu.in/cu.ft) * (3600 rev/min) / (2 rev/intake stroke) = 227 CFM.

At 4500 RPM that would increase to 284 CFM.

And if you are pushing more than 4500 RPM from an old Plymouth L-6 engine, it had better not be mine or I will get really, really upset.

[Powerhouse]

And if you are pushing more than 4500 RPM from an old Plymouth L-6 engine, it had better not be mine or I will get really, really upset.

HAHAHAHA! I never pass 3000...sometimes I get around 3500...but that's very abnormal.

Thanks much for the CFM! So my Holley/Weber is already too much at 270? Hmmm..

[greg g]

why not getcha one of those inexpensive ( don't pay more than 20 bucks for it) adapters and try it with one of the big carbs. Remember in 56 Plymouth had a 2bbl option for the 230. It added 8 hp I think. Just think you might pick up 6 on the 218 and put it over the 100 hp mark. summit used to have them for 16 bucks, Langdons has them also.

[Powerhouse]

I have 2bbl Holley Weber from langdon on the 218 now....it works ok. Just feels like I have more HP in reserve. It idles great and eventually gets up to speed...just feels like it has more power that's not getting used. Throttle opens all the way too.

[BeBop138]

For grins which set would you use on a 265 punched to 40 over and a 260-410 cam with split exhaust, T-5 with 3;50 gears..........thanks

[martybose]

I've got the Carter-Webers, and like them a lot. The only issue with them is to make sure that there is enough distance between the carb mounts so that the rather large electric choke on the front carb clears the rear carb. Mine didn't clear on my Edmunds manifold, which required some re-engineering to work.

My guess is that either carb will work fine, with the added benefit that both have vacuum-operated power valves, which really make a difference. I had previously tried the hotrod standard, dual Stromberg 97's, and despite lots of time invested, I could never get them to work well at all engine speeds. I couldn't get to the manual power valves before the engine started detonating rather severely. I bolted the Carter-Webers on, connected the fuel lines, and haven't touched them since I got the linkages synchronized. A far superior carburation system!

Marty

[Plymouthy Adams]

I believe by the formula that the 218 will need about 288 CFM for max substained air flow at WOT (air horn size) ..the throttle plate does two things..first it meters the air and by doing this we control the draft which siphons the fuel that is metered by the main jet (second by-product part)...CFM is really never been reported by most car makers for the one barrel carbs.. The jetting of the carb is the main player in fuel to air ratio..the air horn just need to be large enough for the max draft needed to fill each cylinder on intake...CFM slides up as the size of the engine goes up as the need to breath (fill the larger cyclinder with adequate air)...there is little need for a carb to exceed 660 CFM unless you have a big block with a deep breathing cam..

the BIG 2bbls on the common mopars were at 350 for the small block and the 383 was upped to 500 for the two barrel version of the engine..and we all know that the 290 horse 383 was not a slouch by any standard with the two barrel..

[48mirage]

Quick note in regards to the numbers. These are 100% numbers, we will never see this type of flow due to the friction/restrictions within the system. A number of about 85% volumetric efficiency would be more accurate for calculating your needs.

[Plymouthy Adams]

that is true but most builder think they are going to achieve that number when at best 92 would be top of line performance...actually the idealist number for this engine on base stock at 3600 RPM would have a CFM flow rate requirement of 228 ..

[Powerhouse]

For grins which set would you use on a 265 punched to 40 over and a 260-410 cam with split exhaust, T-5 with 3;50 gears..........thanks

probably the holley webers...according to Langdon

[48mirage]

For grins which set would you use on a 265 punched to 40 over and a 260-410 cam with split exhaust, T-5 with 3;50 gears..........thanks

For my 230 (D30) I found a holley 94 that came from the '56 ford 272 V8. The idle is a little high and I could probably do something with the idle jets to make it better but it is not enough to cause me any problems.

The reason I mention the Holley is that after I made an adaptor to mount it on the '54 Plymouth manifold all I had to do to make it work was adjust the length of 1 rod.