installing and adjusting dual 44 hpdx's

[JHHeiger]

I finally got my T4 2056 together, installed it in my 62 Beetle and worked through the initial WebCam 86 cam break in. It sounds crisp and healthy and it pulls very well.

It idles well, make 70 psi oil pressure when cold and the pertronix ignition goes from 8 BTDC to 32 easily when revved.

When my foot is in it a little it runs great, but when doing 40 in 4th it bucks and gets real rough.

And when it's revved up and i let off of it, the engine shakes the car until it's idling.

Any suggestions? Who it the best source for tuning information? Are they enough like a Weber to use the REDLINE product information and low speed circuit tuning?

thanks

[Dale M.]

Best initial set up and tuning advice available is procedures in WEBER TECH MANUAL by Bob Tomlinson from CB Performace...

One of the critical things is linkage adjustment... Both carbs have to move off idle at exact same time and open exact same amount... IF one carb leads or trails the other in opening, you will never be happy with their performance... Always adjust the rods with a little care so carbs are the same in the geometry of motion and always use center arm to move cross bar to check throttle linkage action as if it were being pulled by throttle cable, if you move throttles at tuning time by arm on end of shaft, motion will be distorted and other carb on other side of motor will not open the same.... Its not rocket science, it just simple motion and it has to be same on both sides, it takes time, patience and tinkering, when you have it, dual carbs will be a joy to drive...

Other consideration is "lean best idle adjustment procedures" available on almost any carb site on net...

http://www.piercemanifolds.com/category_s/313.htm
http://www.piercemanifolds.com/category_s/311.htm

Best lean idle procedures is best done with at least one side linkage disconnected (then set rod lengths accordingly) ...

EMPI HPMX's are "exact" copy of Weber IDF's so anything that works for Webers works for HPMX's....

Keep in mind that the low speed circuit (idle mixture screws and idle jets) is in effect up to about 2500 to 3000 rpm when the carbs then "transitions" to main jets.... You need to know what rpm ranges you are having problems with so you know where to tinker with adjustments.... Also IF you are running a 009 distributor, there are issues there also with a advance operation right off the low end idle speeds...

At 40 MPH in 4th you should be just under 3000 rpm so you are probably dealing with idle jets and idle speed screws or you are actually at transition and low speed circuit (Idle) are not handing off to main jetting nicely.......

Dale

[JHHeiger]

thanks for the feedback. I changed the jetting, and set the idle circuits as shown in several sites and installed a SVDA distributor. It runs well, without hesitation, and has great acceleration.

But, if I leave it sit for a few days it will turn over, but just won't start until I give it a little jolt of starter fluid sprayed through the aircleaner.

[Piledriver]

thanks for the feedback. I changed the jetting, and set the idle circuits as shown in several sites and installed a SVDA distributor. It runs well, without hesitation, and has great acceleration.

But, if I leave it sit for a few days it will turn over, but just won't start until I give it a little jolt of starter fluid sprayed through the aircleaner.

Boiling the carbs dry after shutdown?
Mechanical fuel pump?

How's your CHT? Engine seals all in place? air moving through any HX?

[Dale M.]

With no chokes or fuel enriching valves you have to pump the throttle well till it starts to fire not necessarily because float bowls are dry, but you have to get a rich enough mixture into cylinders to fire.... Any engine with HPMX or Webers IDF will take a bit of pumping throttle to get it to light off if its COLD.... Do NOT use starting fluid... Its to volatile and can actually damage engine, if you need assist use lesser volatile carb cleaner....And hit both carbs.....

Dale

[Piledriver]

Good point, was so used to pumping fuel in that you don't think about it after awhile...

[JHHeiger]

thanks for the advice about how the carb's work, and the carb cleaner.

But Piledriver - What does CHT and HX mean? i'm not that bright.

[Piledriver]

CHT==Cylinder Head Temperature
HX==Heat eXchanger (so as not to confuse with HE==high explosive)

[Steve Arndt]

Nice combo. Have you tried more like 10 to 12 degrees at idle and 28 full advance?

Sorry for the side track, but the jetting and timing are linked. You have a nice setup, I doubt it needs 32 at full load.

[Dale M.]

I use 009 distributors and run 28-30° at 3000rpm and let idle timing fall where it may....

Dale

[Piledriver]

Typical T1 chambers "like" a tad more timing than T4s, T4s' usually like ~ stock spec at 27 BTDC.
If you have a ton of deck or are "semi-hemi" cut it may want 45 BTDC.
This entirely down to plug location, chamber shape and squish.

[JHHeiger]

The SVDA is a pertronix model. It was suggested to be set at 28-30 degrees, and let the idle fall where it may. It ended up being 7-8 degrees at idle. At 2000 rpm the vacuum advance kicks in and it tops out a 45 degrees. It's pretty durn fast and pulls the .82 4th gear easily. BTW I ran vac from both carb bases.

thanks for everyones interest.