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Fri Aug 21, 2009 8:34 pm

I'm having a lot of trouble leaning this thing out. On the dyno the jetting was fine using the LM1 and Lm 3 but it's a different story in the car.

Engine: 2007, K10, 40x 37.5 highly modified welded heads hemi cut with 50cc chambers, 9.6:1, 48 IDF with 38 mm vents. Mallory hyfire and vacuum advance distributor with grey / grey springs.

With 45 idles the AFR is 13.5 at idle and runs 12.4 or so up to 3K. From 3 to 5500 it's 14 - 15 under WOT using 145 mains and 180 airs. from 5500 to 7K its high 14's.

Timing is set at 10 initial and 34 total, elevation is 4980 feet.

I haven't messed with the mains yet but the idles are a problem. I tried 40's and it wouldn't run period. I had to change to 45's just to get home. At cruise around 3k it's in the high 12's . Next I took a set of 40's which actually measure 37 and made them 39's using a 1/64th bit and it's still rich both at idle and crusie. Besides it pops like crazy through the exhaust. Even with the 45's it's popping out the exhaust. Yes the carbs are synch'd and the linkage works perfectly both carbs open at the same time. The floats are set at 10 mm

I'm thinking that perhaps changing the springs my help. Any ideas?

Sat Aug 22, 2009 3:16 am

Maybe it's just late and I haven't taken my meds, but isn't the hemi cut chamber designed to lower compression ratio? 9.6 sounds awful high for a hemi cut chamber, and I've also heard that hemi likes more timing. This may explain why you're getting pops out the exhaust- overly lean mixture, combined with hemi chambers, lots of compression, and not enough timing....

Sat Aug 22, 2009 4:57 am

That cam likes compression. It's got .050 deck. The heads have been flycut to get back some of the quench. I wish the heads were not hemi cut but that's another story.

Sat Aug 22, 2009 6:18 am

So what total advance are you running?

Sat Aug 22, 2009 6:27 am

10 initial 34 total

Sat Aug 22, 2009 9:35 am

What are u trying to get the A/F ratio to?

What I find is 12.8 to 13.4:1 is the window, you can cruze at 14:1+ but its hard to get there some times..

Average set of IDFs run .52 or .55 idles... on bigger engines..

I have seen engines that just dont tune well.. Bad combo of cam exhaust and carbs to big..

Make sure you dont have Platium Plugs.. Use reg NGK or Bosch plugs for the heads you have..

This Manifold is just cool lookin...

Sat Aug 22, 2009 9:51 am

Thanks Art that is a cool looking manifold - nice welding. I'm using NGK B6HS. The exhaust is 1 5/8 with a magnaflow.
I know the hemi heads aren't the best but that's what I got.

I've read here on the samba that the crusie AFR should be 15 or greater but from what I'm seeing that isn't going to happen. I'm at 4900 feet any suggestions on mains and airs to get 12.75 or so under WOT. My emulsion tubes are F15's.

Sat Aug 22, 2009 10:32 am

Bones 53 wrote: 10 initial 34 total

Ok have you tried changing that to 36 or 38 to see how it reacts?

Sat Aug 22, 2009 11:18 am

the initial dyno numbers look right on. Was this a lab setup or wheel dyno?

If it was a wheel dyno did you take temperature and humidity into consideration? My experience with jetting engines is mixture should be 1 main richer if it was hot outside when you were running it. This is because hot air is thinner and when it is cooler in the morning you will be too lean.

It is behaving as if you knocked a vacuum hose loose.

Sat Aug 22, 2009 11:38 am

This was on a stutska. We did monitor the EGT and it was at 1300 or so. It has a mallory vacuum advance distributor but all is connected

Sat Aug 22, 2009 2:14 pm

F-11 is what I have the best luck with..

1300 is HOT!!!!!

Sat Aug 22, 2009 3:18 pm

The EGT temp was taken after several WOT pulls out of a bung at the #3 J tube about 1.5 inches from the head Cylinder head temp in the car runs 325 under #3 plug. I't never gone over 350 even on a 100 degree day.

Sat Aug 22, 2009 4:46 pm

Art Thraen wrote: 1300 is HOT!!!!!

No its not...

Sat Aug 22, 2009 5:13 pm

all i can say is if your making a pull and the 02 shows anthing above 13 under a load at any time i would stop and make a change! :shock:
With 9.6:1 why 34* timing? you should not need that amount?
1300 is not hot?
take timing out, up on the mains, what brand of fuel or is it pump?

Sat Aug 22, 2009 5:27 pm

A.J.Sims wrote: 1300 is not hot?

No, it's not. Full boost mine normally sits at 750*C, idle is around 580~600.

Sat Aug 22, 2009 6:02 pm

AJ I'm at 4900 and have hemi heads. I'm thinking less advance up top and I'm going to need to read how to take some advance out of the mallory while retaining the initial advance. This would certainly richen up the top end. I tried the high speed retard on the hyghfire but didn't notice any real difference. The gas is 91 octane pump gas. Remember I'm at nearly 5000 feet so the CR here is 8.6 static and with the cam and the program I used the dynamic is 7.9. The AFR on the dyno at WOT when we had 1300 degrees at # 3 J tube was 12. 4 with 60 idles and 145 mains but in the car the AFR's were in the 10's and 11's with the same jetting.

I have some 44 IDF's that I'm going to try instead of the 48 IDF's. I think the 48's are too big and besides I want to save those for another project. These are older 44's - where can I drill for the vacuum advance line? Should the vacuum be drilled into the manifold instead of the carb.

Thanks for all the help guys

Sat Aug 22, 2009 7:34 pm

Quote: was 12. 4 with 60 idles and 145 mains but in the car the AFR's were in the 10's and 11's with the same jetting.

Is there anything restricting airflow into the engine bay? The air was coming freely from 360 degrees and above and below when off the car. You no longer have the luxury of air all around the engine -

Do you have a fuel vapor recovery system that is hooked up in the car but not off the car?

What about the chokes? Make sure the elements are getting the correct voltage. Could they be partially closed?

Did you make any other changes like add an air cleaner back whereas when you dyno'd it was off?

What did you use to deliver fuel when off the car? Same pump or another? Could your pump and regulator be set too high?

What about gas? Did the run use the same 91 octane that you are running on the street or were you running racing fuel or avgas?

Sat Aug 22, 2009 8:07 pm

miniman82 wrote: A.J.Sims wrote: 1300 is not hot?

No, it's not. Full boost mine normally sits at 750*C, idle is around 580~600.
1300 IS hot,bro.Aluminum turns into silver paint at about 1420 F.How close do you want to get?Lets assume your egt gage is accurate?

Sat Aug 22, 2009 8:39 pm

Is there anything restricting airflow into the engine bay? The air was coming freely from 360 degrees and above and below when off the car. You no longer have the luxury of air all around the engine -

No actually there is a scoop under the car directing air into the fan

Do you have a fuel vapor recovery system that is hooked up in the car but not off the car?

No

Did you make any other changes like add an air cleaner back whereas when you dyno'd it was off?

yes 6 x 9 Kn

What did you use to deliver fuel when off the car? Same pump or another? Could your pump and regulator be set too high?

both the dyno and the car use a 110 GPH mallory pump and holley fuel pressure regulator set at 3PSI

What did you use to deliver fuel when off the car? Same pump or another? Could your pump and regulator be set too high?

On the dyno we did use some 110

Sat Aug 22, 2009 9:11 pm

The Noof wrote: miniman82 wrote: A.J.Sims wrote: 1300 is not hot?

No, it's not. Full boost mine normally sits at 750*C, idle is around 580~600.
1300 IS hot,bro.Aluminum turns into silver paint at about 1420 F.How close do you want to get?Lets assume your egt gage is accurate?

Let's not pollute: http://www.thesamba.com/vw/forum/viewtopic.php?t=373809
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