Jetting for 40 IDF with stroker?

Arnolds64 · Post by **Arnolds64** » Sun Feb 12, 2006 2:08 pm

Going to build a 78.4 x 90.5 motor, 120 Engle, 40 x 35 heads Dual Springs with a Cal- Look forum DIY P&P chambers as well.

Anybody with this combo that has set up te A/F jetting? Like to get a base to start with for first start up.

Recommedations? Thanks!

500LbGorilla · Post by **500LbGorilla** » Sun Feb 12, 2006 2:34 pm

For DUALS, with 32 vents or so, I'd say 125-130 mains, with 180 airs, and 55 idles.

Arnolds64 · Post by **Arnolds64** » Mon Feb 13, 2006 7:12 am

I should look see what size the vents are. They are the originals that come with the Empi kit. I was told they come with 115 jets?

500LbGorilla · Post by **500LbGorilla** » Mon Feb 13, 2006 7:34 am

Oh, are these HPMX's?

Maybe 28 vents, in which case 115 is close, with some 160-180 airs.

You need to check the floats, those are key to proper tuning, as is correct fuel pressure.

Arnolds64 · Post by **Arnolds64** » Mon Feb 13, 2006 10:12 am

Yeah the 28's & 115's sound right and I believe they are MX's. I'll take a look tonight at them. They are only 2 years old. I just bolted them on got the linkage even on both sides adjust the idle mix and the timing and they ran smooth as silk. Even in 20 degree weather. It did run a little rich though. Of course I was told it had a larger cam and it was a 1776. Look at my sig. I was suspect when it just did not idle and run like it should.

So your combo would be a good start point or is this what you have done and it works?

500LbGorilla · Post by **500LbGorilla** » Mon Feb 13, 2006 10:22 am

It's a good starting point from what other folks and I have found. Out of the box the 200s are a little lean for top end power, but those carbs are really not going to let you wind it to the moon with a lot of power anyway. Not to worry.

What's going to work for you specifically is going to be a factor of how your engine performs, and altitude. No one can give you the jet sizes you'll NEED, you just have to dial it in. 115's will get you running well, and if you want perfect, you'll get a AF meter.

You may find that going a size down on the idles will improve economy but will mean some leaner running during warmup.

If they are two years old, they are regular IDFs (not EMPIs new HPMX line).