44mm IDA Venturi, jetting suggestions

[leec]

Hi guys,

Know this is a tricky one, but can anyone suggest base jetting for my motor. I currently run 40 vents in my IDA's (48 carbs) but want to up the Venturi size to 44 to match the inlet valve size, purely to see if I can extract a touch more go and better my pb at UK Drag Day.

Brief motor spec

2276cc
FK87
10.3:1 CR
44x37.5 Wedgeports with quick clean up

I already have 40mm vents and jetting to suit that, I don't have a huge amount of time to test various jets and cost with that, can anyone suggest a tried and tested jetting?

Thanks,
Lee

[richie]

Hers the nearest i got

2332
48 idas,44mm vents
fk89,
untouched wedgeports,44x37,cb650 springs
just flycut for compression


thought you were going to dyno it?

cheers richie

[leec]

Hi Richie,
You know everything
Was going to dyno but to be honest I've not got a lot of free time due to work and 2 year old commitments!!
What CR is Jo's car running. The jetting you list above seems very similar to what I already have iirc!

Thanks
Lee

[Shane Noone]

Hi Lee,

I sent a message to Matt re valve guides so just waiting for him to reply. Ta

Re your chokes and jetting. What is your current mains / emulsions / airs ? on the 40 vents.....
Dyno / Rollers is the only way as you know but going from a 40 vent to a 44, I would imagine your main jet will need to go up a fair bit. The airs may not really need to change that much. F2 emulsions are suggested by many once you go to a 42V and that's what I now have in mine with a 44V. As for the rest my jetting probably not much use due to differences in head setup.

Hope you get it sorted and see you at drag day ( I won't be racing now so plenty of time to chill absd watch you guys ! )

Shane.

[richie]

Different engine Lee, high 11s compression so a little more than yours,and no I dont know it all,not by a million miles,but if I got some actual facts that I did myself I am happy to share


cheers Richie

[leec]

Assumed you meant Jo's. I'm going to see what jets I have already and go from there. Will do a few runs on the set up you mention and go from there. Might owe you a tea if it goes quicker

Lee

[Neil Davies]

I'll have a look in the attic when I've got a spare minute for my old logging book, it should have a list of the jets I used in my motor, it was a 2276 with an Fk87 and around 10.6:1 comp IIRC, definitely used 44 vents tho. You've already gone quicker than I did so I might not be any help at all!

[neil68]

My 2332 cc has the following 48 IDA jets, after some test and tune:

F7's then F2's
65 idles
180 mains
210 airs
45 vents

10.7:1 CR
Raptor camshaft 06908 (10.8 mm/0.425 lift, 274 degree @ 0.050"/1.27 mm)
1.4:1 rockers

[adrian]

I had a 2442 with fk87, 10.5:1, 42mm vents, 185 mains, 200 airs. 46 x 37 wedgies, made more power with the 42 s than 44 s ( on an engine dyno).

[leec]

Thanks for the replies.

Going to see what happens at drag day. Going to use an LM1 and see what happens to the E.T's with the 44 vents.
The motor is very streetable at present so can't help but think with bigger vents/jetting a sacrifice in low down performance may increase horsepower at the top end.

Lee

[Shane Noone]

Lee, when my motor was first dyno'd at JMR with 46 vents to match the intake valve size, it made the most power as you are thinking but wasn't nice to drive on the street. We then switched back down to 44 vents so one size smaller than intake valve and lost 3 bhp but drivability was improved on the street. Than main jet also came down from a 190 with the 46 to a 180 on the 44.

Trial and error with the LM1 sounds promising. Good Luck.

[leec]

Hi Shane,

It may not work out any quicker, I'm just concerned I haven't ever changed the set up of the motor since I built the car (mainly because it did better than I ever expected) and just curious

Lee

[Shane Noone]

Hi Lee, I know, it's the what if ? scenario 

As we've talked about before, I agree think your bug / motor / tranny combo exceeded expectations based on the spec. Which is awesome. I'd be well chuffed at sneaking an 11 out of my street driven / street legal ride. How cool is that.

I hope get deeper into the 11's mate at Drag Day  see you there bud.

[leec]

Right, in order to try and beat my mate Harv, I am considering trying the 44mm vent set up again. When I tried it a few years ago I broke my gearbox so never got to fully test the set up.

Lee

[herbieharv]

This looks like fighting talk
 

[leec]

This looks like fighting talk
 

Looking forward to it

[herbieharv]

We might try the 44 vents at dragstalgia Lee , I've got my old time sheets to do we can compare what they are doing compared to the 42s in the car now

[leec]

We might try the 44 vents at dragstalgia Lee , I've got my old time sheets to do we can compare what they are doing compared to the 42s in the car now

Copy cat 

[Martin Greaves]

Harv have the new Rockers and Vents turned up yet.

[neil68]

I'm experimenting with the IDA's on my 2332 cc and the current jet stack is as follows:

44 mm Raptor vents
F4 emulsion tubes
185 mains
215 airs
65 idles
120 idle airs
3.0 mm needle valves
9.5 mm fuel lines
Raptor cam similar to FK47

[Jim Ratto]

I'm experimenting with the IDA's on my 2332 cc and the current jet stack is as follows:

44 mm Raptor vents
F4 emulsion tubes
185 mains
215 airs
65 idles
120 idle airs
3.0 mm needle valves
9.5 mm fuel lines
Raptor cam similar to FK47

Hi Neil
any hard numbers in running the F4 vs what you were running (F2)?
thank you

Jim

[leec]

..

[Martin Greaves]

Lee it's not just about changing the idle jet you also need to think about the idle jet holder as well.

[leec]

I see. Not clued up with this. How does that work then?
Lee

[DaveN]

I used 65s on my 2332cc

[leec]

I used 65s on my 2332cc

But Martin said I can't just change to 65's?
Lee

[Martin Greaves]

No I didn't say that Lee.....

The idle jet controls how much fuel you get and the idle jet holder controls how much air you get for emulsification.

Best I call you over the weekend about it as it going take me all day to write it out on here. 

[leec]

I'm with you! Thanks 
I think I will stick to my current set up and when I actually get some time do some proper testing on a rolling road
Lee