JPM Raptor Venturies in 51.5 mm IDA?

[neil68]

Question:  Do the JPM Raptor venturies also fit the 51.5 mm Weber IDA carbs that are most commonly sold?  I'm not sure whether the IDA body is opened up only below the venturi in the butterfly area, or the entire bore from top to bottom...thinking probably the latter.  Thanks.

[T11964]

I've bored  a few sets to 51,5 and you only do it at butterfly bore , if done all up you're in trouble fitting venturi 

[neil68]

Thank you.  I was looking to have my IDAs enlarged locally, using this mail-order kit:  http://www.jayceevw.com/store/p87/51.5_Weber_Conversion_Kit.html

[spanners]

There's always two ways to skin a cat, there are gains by boring just the lower throttle area, but you are still stuck with stock size vents if you just fit oversize throttle plates, a gain is a gain but are minimal compared to a full over bore to 51.5 which allows 48 vents and a huge gain in cfm. So it depends on your motor spec, valve size and cam etc and wether or not a bigger carb will translate to quicker times, it may be just the bigger throttle plates and gas flowing them and the spindles gives you enough, I did a fair few cup motors where we had a spec centred 40 drla, and I upped them to 45 throttles, lots of work and disappointment, they break out in the progression hole area, I think the gas flowing alone would have been better.

[neil68]

I was hoping to keep my JPM 44 mm venturies and stacks, with the assumption that a 51 mm bore would provide better venturi effect.  If the whole carb bore is enlarged to 51 mm, then I assume the vents and stacks would not fit or seal properly anymore, correct?

I noticed on the JPM facebook page they are showing a 10-second kit with 51 mm IDA's, etc, so I was going to go that route since I already have JPM heads and Wasp Stage 2. I would be happy to run an 11.90 some day.

[Taylor]

But you can make 250hp with 48s.

[spanners]

I was hoping to keep my JPM 44 mm venturies and stacks, with the assumption that a 51 mm bore would provide better venturi effect.  If the whole carb bore is enlarged to 51 mm, then I assume the vents and stacks would not fit or seal properly anymore, correct?

I noticed on the JPM facebook page they are showing a 10-second kit with 51 mm IDA's, etc, so I was going to go that route since I already have JPM heads and Wasp Stage 2. I would be happy to run an 11.90 some day.

Yes, proprietary over the counter 51.5s such as Berg etc would need the special oversize chokes which go up to 48, you can fit 44 or a special thin wall 45mm choke in your stock 48s, as Taylor quoted tho, 250hp is on with these, can your motor pull enough air for more? What's the spec at the moment?

[neil68]

2332 cc, MS230 heads 48 x 38, JPM Raptor 06908 cam (274 degrees/10.8 mm lift), 15.2 mm lift with Scat 1.4, Italian IDAs with enlarged bowls and 3.0 mm needle valve, Raptor 44 mm vents & stacks, 10.7:1 CR, stock '68 Beetle 925 kg with driver, front dropped spindles, Rancho pro comp close ratio gearbox, SAW short race swingaxles, stock 21 mm torsion bar/Z-bar/suspension, M&H drag radials.

[Udo]

Your car is very heavy 
You need a good gearbox with that weight and 11's
Udo

[neil68]

Yes, Udo...you are correct!

Using a drag racing calculator, a vehicle weight of 925 kg with 204 HP gives an estimated 12.5 second ET, so that matches my best ET.

If I drop the weight to 800 kg, then the calculator predicts 11.95 seconds.  So, I might have to give some thought to reducing weight this winter.  However, this is an original condition Beetle that has never been cut or welded, so I'd rather confine any weight reduction to removing parts that can be reinstalled later.

[jim martin]

Hey Neil hope your doing well.
I cannot remember your gearing ,but if you really want to get things moving you need to take
Advantage of your heads and cam potential by getting some rpm in all gears
Your car is heavy and need to get it up and moving .
I would recommend 3.88 ring , 4.11/2.74/1.74/1.31
This will get the heaviest car up and going out of the hole and keep it in the
7500 rpm range

[neil68]

Hello Jim.  Hope you are doing well.  We missed the GCVWS this year, but will try to race next summer!

My Rancho gearbox is currently:  3.875 with 3.78, 2.26, 1.65, 1.31 (I'm not 100% certain about 2nd gear, I'll have to find the receipt from many years ago).

[NoBars]

I use those vents with 51s Neil. I believe the 44 vents are recommended by JPM to be used with 51 mm throttle bores.

[neil68]

Anthony,

Do you know if Raptor 44 vents are identical for both 48 & 51 IDA applications?
Will they only work in IDAs that are enlarged below the vent in the butterfly area?
Or does the rubber O-ring seal sufficiently in a 51 mm bore?

I can't seem to find any info on the JPM website or Facebook page as to whether there are two sizes of 44 vents for the 48 OD and 51 OD. Thanks.

[NoBars]

I believe JPM only makes one version. They hang off the aux venturi counterbore, so they will work with either carb. I pulled them out of my 48s and dropped them right in a set of 51s I bought and tricked up a little more. When I bought the JPMs it was always my intention (and JPM's recommendation) to use the 44s with 51 carbs.

I wouldn't be concerned with going real big on vents, as Udo says you have a heavy car you have to get moving.

I'd advise you just send your carbs to Jack and have them cut for 51s. Any cost savings you might get from having them done locally is not worth the risk of having your carbs ruined IMO. Give the job to the man with the most experience.

[neil68]

Thank you, for answering my questions.

I might send my IDAs back to Jaycee (they did the float bowl enlargement and third progression hole for the previous owner).

[PPRMicke]

Ms 250
EMPI 51.5
 JPM Raptor Venturies 44
  283 hk  10.64 @ 199.45  / 10.66 @ 201.12
Gardermoen 
/// M

[hotstreetvw]

Yes!  Do tell more.

Ms 250
EMPI 51.5
 JPM Raptor Venturies 44
  283 hk  10.64 @ 199.45  / 10.66 @ 201.12
Gardermoen 
/// M

[PPRMicke]

Yes!  Do tell more.

Ms 250
EMPI 51.5
 JPM Raptor Venturies 44
  283 hk  10.64 @ 199.45  / 10.66 @ 201.12
Gardermoen  
/// M

Engine OXY Boxer     
Rapror Cam
Raptor Power Jet  on  cab  
Wasp Exhaust
Gearbox  Finnish gear  
RLR clutch  
Driver/owner    Andreas J
/// Micke

[NoBars]

I now find that power jet intriguing:

[neil68]

I'm thinking about installing the JPM Power Jet as well.

[PPRMicke]

Hi Neil68
Have a few questions
Have you tested your flow with intake
Intake Cb / scat / bugpack ?
/// Micke

[neil68]

CB manifold, but no flow testing was done.  Only chassis dyno testing was completed, with various jets.

[PPRMicke]

Ok

did you adjust your intake down 4-5 mm
/// M

[AJ]

Ms 250
EMPI 51.5
 JPM Raptor Venturies 44
  283 hk  10.64 @ 199.45  / 10.66 @ 201.12
Gardermoen 
/// M

Small correction, 10.59@ 201.12kmh