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Size of R500 roller bodies


edmandsd

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Dave,

 

I think they are 46mm. Its not possible to machine them larger either as the barrel circumference is only aboout 188mm.

 

It would be nice if you could make them larger - I even explored the psooibility with Titan (who make them), and even machining the housing and a new barrel is a no go.

 

I think the luminition bodies mihgt come in 48mm, but SFAIK there is nothing bigger in a roller barrel design.

 

Fat Arn

 

Slay the K.

 

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Thanks.

 

I'm not thinking of going this route or Jenvey for that matter, but simply getting some comparisons in size having recently measured my slide.

 

I'm surprised to hear that the R500 roller throttle bodies are 45-46mm at their narrowest point as my slide is only 42mm - The body of the slide is 45mm but taperes down to 42mm at the slide face.

 

I was looking at Mike Barnby's 2lt Hart engine recently and his set up is virtually identical to mine although the slide is bigger - being 48mm at the slide body and 45mm at the slide face. This makes sense though considering the valves and ports are a fair bit bigger than the already big bd (38mm inlet v 35.5mm on the bdx), the stroke's shorter and the exhaust primaries are 2.25 v 2.125 on my bd.

 

This extra 3mm results in c 15% more area which is significant ....but may well be detrimental to engines which have much lower torque peaks and don't maintain the torque at high rpm like a purpose built race engine.

 

There is scope to increase the bore size on my slide to c 44m which I think I'll do as this results in less than a 10% gain in area at the narrowest point and should theoretically push up the peak power/rpm points.

 

Home of BDR700

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The other thing to consider here is carbs.

 

My old all singing and dancing crossflow had 48's with 43.5mm chokes. HT Racing's Pinto's use 50's with 46mm chokes. My experience would suggest that 8v engines prefer larger chokes to their 16v equivalents. One must then consider that the butterfly and Aux vent absorbs a proportion of the area so 46mm chokes in a pair of 50's will probably equate to a 44.5mm slide.

 

Home of BDR700

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Graham - On Sanspeed's rolling road HTR's 2.2lt Pinto's with 50's show 230-240 flywheel bhp @ c 7,500-8,000 rpm (Sanspeed's rolling road has always read very similarly to Dave Walker's) On HTR's new Superflow dyno only 200- 210bhp (SAE) is being recorded - it isn't just Pinto's that are reading lower either as an all singing and dancing 2.3lt n/a cossie engine on 45mm slide throttle injection only showed 260bhp on the dyno. That said the injector duty indicates how powerful this really is with over 80% duty being recorded using 4 Cosworth light blues (437cc/min) at 3 bar fuel pressure. Julian Godfrey recently claimed 297bhp from a 2.1lt BD on another type of dyno using 4 Bosch 803's (dark greens) at 3 bar but these injectors (350 cc/min) simply wouldn't provide enough fuel to give that sort of power on a Superflow dyno. HTR's 2.2LT Pinto's are running under 12 seconds at over 110mph on the drag strip in Mk1/2 Escorts, which is as fast as an R500 but with twice the weight, so this may be an indication as to their comparative output.

 

Home of BDR700

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