40 IDA 3C webers 2.4

[kucharskimb]

i have a 2.4 with 10:1 compression, E heads, E cams, crane cams electronic ignition and webers on top...

1. the car hesitates with rapid throttle application. noticeable in neutral, significant underload. the carbs have been set up by my local dyno. he is experienced with VW's and porsches as his main business is dune buggies. the accelerator pumps squirt, but not till about 1/6 - 1/4 throttle. all squirters activate evenly and steadily when they come on. no visible leaks on the outside. is this an accel pump rod adjustment problem, an internal leak, or a float adjustment problem.

2. what is the leanest air/fuel mixture you can run in the idle and intermediate phases with this aircooled engine.

thanks for your replies.
matt

[RoninLB]

Originally posted by kucharskimb
i have a 2.4 with 10:1 compression, E heads, E cams, crane cams electronic ignition and webers on top...

1. the car hesitates with rapid throttle application. the accelerator pumps squirt, but not till about 1/6 - 1/4 throttle. is this an accel pump rod adjustment problem,

2. what is the leanest air/fuel mixture you can run in the idle and intermediate phases with this aircooled engine.

1] why can't the mechanic fix the acc rod ?

2] a tech answer, imo, is a EGT deviation between the coolest and hottest of about 70deg is fine.. 150deg deviation will cause operating problems when on the idle or main circuit. An o2 reading at idle could be adjusted low enough to pass smog, then re-adjusted richer afterwards. Forget about gas millage much above 15mpg at a steady 65 mph for good operation imo.

[Halm]

Originally posted by RoninLB
Forget about gas millage much above 15mpg at a steady 65 mph for good operation imo.

Not so sure about that. I have a 2.7, S cams and Webers. Driving the 1,000 + miles round trip to Rennsport II, I averaged 22+ MPG at speeds 10 - 25 mph faster. FWIW, I have 65 idle jets and only 140 mains, but it runs well on the street with a solid idle and pulls strong to 6800 rpm in 3rd (actually hit 7,000 by accident during the "parade lap").

HTH

[RoninLB]

Originally posted by Halm
I averaged 22+ MPG at speeds 10 - 25 mph faster. FWIW, I have 65 idle jets and only 140 mains,

GREAT.. I'm still tweaking these carbs. You've given me hope.

I'm running 60 idle. The mains don't seem to come on till 3.2k, which is around 70mph. There is a definate EGT change around that rpm.. whatever, trivia

[Halm]

Ron, My bad. I am running 60 idles, not 65's. Richard at PMO says the 2.7 should have 160 mains, but the 140's seem great around town so I adopted the theory that if it ain't broke, don't fix it!

[RoninLB]

Originally posted by Halm
I am running 60 idles,

Richard at PMO says the 2.7 should have 160 mains, but the 140's seem great around town

Me bad about infering the 15mpg at a steady 65mph. It's 90/10 with the off hy street being run around 3k-3.5k in 2&3.

I can't give you helpful hard info Hal 'cause we're running different cams.
So anyway for trivia.. I told Rich I want carbs for a cross country go cart.. so it started as 55 idle, then the 60s. Rich's install of the 140s produces an incredibly stable air fuel mix with my act. Naturally his art is the main reason. The point being that too much fuel for conditions creates an unstable combustion between the cylinders.. In your situation I guess your ears will be needed to tune the mix when on the mains.. as for as the idle mix setting a 1/2 turn is a Noticable effect on combustion.. The unbelievable situation I'm in is that his carbs are so dam perfect that if I'm testing, let's say, the 2 1/2 turn area that all cylinders will be stable equally at the 2 1/2 [within a good deviation].. ie: a 1/4 difference than the others will cause that cylinder to be out of sync with the others. and I have the info to confirm this. I'm not sure if you can use that info?

[Steve@Rennsport]

Originally posted by Halm
Ron, My bad. I am running 60 idles, not 65's. Richard at PMO says the 2.7 should have 160 mains, but the 140's seem great around town so I adopted the theory that if it ain't broke, don't fix it!

Hal:

Richard at PMO offered you VERY good advice and unless you wish to buy pistons in the near future, I'd kindly suggest that you adhere to that. I know it "ain't broke" now, but it sure will be soon if you keep those 140's,...

140 main jets are FAR too lean for any 2.7, no matter what cams or compression it has.

After almost 30 years at this, I've found that the combo of 60 idles, F3 E-tubes, 155-160 mains and 180 AC's work very well for 2.7's with 34-36mm venturies.

The rest is all about setup: excellent fuel filtration, fuel pressure, float levels, accelerator pump volumes, etc.

[Halm]

Steve, thanks for the advice. I had no idea that the 140's could cause a problem like that. New jets will be ordered Monday!!!

[RoninLB]

Originally posted by Steve@Rennsport
140 main jets are FAR too lean for any 2.7, no matter what cams or compression it has.

After almost 30 years at this, I've found that the combo of 60 idles, F3 E-tubes, 155-160 mains and 180 AC's work very well for 2.7's with 34-36mm venturies.

Steve.. I'm trying to sort out new PMOs for my street routine.

As delivered 55 idles, F11 E-tubes, 140 mains, 190 AC's. That 190 AC's. I requested parts for a street engine.

I had to change to 60 idles due to leaness with 55's. If I'm correct the E-tubes affect the progression circuit. The progression circuit is now smooth so I should or should not change the E-tubes ?

If the higher AC's of 190 lean out the main circuit 140's more than AC's of 180 would this affect acceleration from 3k in 4th gear ? Or is this Only controlled by the accelerator pump ? Presently 3.4k+ EGT's appear stable around 1,250deg. So your suggestions is confusing me..

Bottom line is that it appears that I should change to your suggestions.

What I'm trying to accomplish now is a faster acceleration from 3k in 4th gear... And not blow up the engine.
Thanks.

PS: Stock CIS & cams produced stable EGT's of appx 1,350deg among all cylinders with O2 of 3.5-4.0.

[kucharskimb]

steve
any advice on my original questions?
matt

[kucharskimb]

bump

still looking for info regarding the accelerator pump adjustments. does lengthening the rod change where the squirters come on, or just the total squirt volume.

thanks
matt

[Halm]

Matt, Have you faxed Richard Parr at PMO with this question? He has been very helpful with my issues.

[1974carrera]

Matt,
I know your original post said that they all squirt evenly, but have you checked the volume of fuel delivered from each of the accelerator pump nozzles? First, you want to confirm that each nozzle is delivering the correct amount and that all nozzles are delivering the same amount.

I hope this post will help get your thread back on track, but since it has been repetitively hijacked by others (not a criticism, just an observation )you may want to give up on this one and just start a new thread.

[RoninLB]

PMO 40s