3,200 spring, lost bottom end!

[JimmieD]

Hi, friends, been a while...

Running a 4BT with VE pump, NV4500, 4.1 gears in '67 Dodge Town Wagon. Used stock stepvan donor's exhaust, 3.5"? Got the last HTT Turbo Stage II and installed on my H1C with 16cm2 exhaust. Gave better bottom end to midrange, smoother power, boost now up to 20. 10-15% more power I'd guess.

Just installed 366 spring, had a 386 in it. OH NO! I lost the bottom end and low midrange! When I was done idle sounded exactly as before, maybe 25-50 rpms lower but I doubt it. The throttle indexing seemed to be correct but had a hard time with it. Noticed yesterday that instead of just letting out clutch slowly in 2nd to start, then giving some throttle, I now have to feed it fuel to get rolling.

What can restore stronger bottom end? Live in the mountains and REALLY need it.

If I re-index throttle to try to turn it for earlier fuel, will I be in danger of runaway? Just wondering if I should pull turbo intake apart and be ready.

I know advancing timing kills some bottom end, and mine's dead-on stock setting now. No fuel adjustments have been made. What fuel tricks contribute most to bottom end power? Rather not have smoke.

Thanks for any tips & hints!

JimmieD

[CumminsPride]

Full power screw!

[KTA]

Did you move the fuel screw when you did the spring?

[JimmieD]

Thanks for replies!

No, all fueling settings were left alone.

I did my best to return idle screws to original. I've heard from others since posting and they suspect I got the throttle indexing off one notch. Does that sound like something that would cause the lack of bottom end power and other problems?

[c12h26]

I had the same problem when i had my spring put in,put the index on the stock notch and fabricate a new throttle linkage to get all the throttle travel out of the pump.here is a pictrue of the new linkage

[cummins king]

prety simple, and i like the pipe bracket, whats the blue cross over tube that i can only part of
CK

[c12h26]

It is for the water to air intercooler

[DTanklage]

you did something wrong with your fuel screw adj

had to have

installing the tighter spring changes the fueling all the way thru the curve

makes it better

the indexing thing is just for getting your throttle linkage back to the same spot is was when you took it apart

as long as it idles and still gets full throttle it doesnt matter what lines you had to use to get that

from the pix it looks like you have your linkage clockwise compared to a lot of stock ones

that is where i have mine

you are on the second to last line clockwise, right?

[JimmieD]

Well now I don't know what to think! Took apart the linkage, re-indexed, put it back together and no start. Cranked and it tried to start but wouldn't stay running, tried it 8 or 10 times. Then I noticed fuel leaking beneath linkage. Took it all apart again, pulled throttle shaft, fought linkage back on, reindexed. Indexing is correct.

Now it won't start without 1/2 throttle, any less and it dies. 1/2 throttle is about normal idle. Haven't got a clue in the world what the problem is and don't even know where to begin to look.

Really don't want to take the whole blasted thing apart again.

In the instructions at Den's site, where he gets into re-assembly, he shows that lever that you have to 'Click back..." according to him. Reading Bosch text and looking at a cutaway that seems to be the 'reverse lever'.

Well, mine moved back but there was no spring tension or any pressure or detent to keep it from swinging anywhere it wants when I invert the pump top to reinstall! It's impossible for me to hold back throttle lever [Denny says to use wire loop], plus hold back this reverse lever, and put the pump top on and start screws with only 2 hands.

No real idea how to know that lever is in right place with pump top right side up and on top of pump! Don't know what the right place is.

Truck ran fine but lacked power right after first install of new spring. Didn't remove pump top to re-index throttle lever. Still, it now wants 1/2 throttle to even idle. Doesn't make any sense.

[KTA]

My guess is you either bent or broke the lever in the bottom of the pump that the fuel screw pushes against. That is why I always say to take the fuel screw out when taking the top off and putting it back on, it is just too risky to bend or break that lever if it isn't aligned perfect and you get to pushing pretty hard on things or using screws to tighten the top down.

[JimmieD]

Well, if that's the case I'm thoroughly screwed. I'm on top of a mountain over 20 miles to town and over 75 miles to Bosch/Cummins shop or any kind of help.

This is the first I've heard in dozens upon dozens of posts about 366 spring installs about removing the fuel screw. Never heard it on any of 4 Dodge Ram or Cummins sites, just how marvelous easy it is to install and what a great upgrade it is. Totally screwed here.

Den's Dodge website needs to lose those 'Easy Instructions', there's about 1/2 missing. I'm dead in the water for a l-o-n-g time, screwed.

[JimmieD]

Can't find anything broken, all looks like it did when I had it apart before. Are you talking about the lever that sticks up slightly above pump body, the one you're supposed to hold back with a wire loop according to Den's instructions?

I see nothing wrong with anything from what little I know. Far as I know I had indexing correct, as only other choice is 180 degrees from where I was.

So, it's apart but no idea why it didn't work last time. Therefore no idea what to do differently this time. Stuck at square one.

The lever that's supposed to be 'clicked back' according to Den's instructions, which I referred to as the 'reverse lever' from Bosch text, pushes the fuel pin that rides against the fuel cone below diaphram. The fuel pin itself holds lever in position, unless fuel pin slips over into diaphram housing when fuel cone isn't in there.

[JimmieD]

Anybody know if the throttle lever shaft's O-ring can be replaced with a natural rubber O-ring of correct size? That is does it have to be some super scientific stuff, or just an ordinary O-ring?

[PToombs]

What do you mean "ordinary o-ring"? If it's rubber, it won't work. I think most cheap kits are buna-n, might be ok.
On the big problem, unscrew the fuel screw, until the inside end is flush with the housing. Using the wire to hold the lever off the screw is almost impossible!
The lever on the throttle shaft goes towards the engine. It's easier to hook up the spring, etc, then push the shaft thru the cover as you put it on. When the cover is tight, turn in the screw to where it was, or close to. Put the throttle arm on. If it won't start, then starts when holding down the pedal, the index is off. Turn the shaft counter clockwise 1 notch and try again.
I honestly can't remember how I held the shaft when I put the lever on.
I hope this helps!

[JimmieD]

Thanks for the tips, Pete, KTA also if I didn't mention it!

Sorry to get a little testy in my last posts, not famous for patience and the thought of a dead truck was just too ugly.

Got it back together and all's well. Didn't find anything wrong or incorrect with first install, have no idea what went wrong when I re-indexed, not a clue.

Took a test ride but all I have is some wild mountains so no town testing. Very bottom end, first couple of hundred off idle, lost some oomph, still weak. Starts to come on a little better as it climbs and by low midrange it gets to fueling pretty good, plus good boost starts kicking in. Midrange and top end definitely stronger, EGT's climb much more quickly.

Overall I'd say midrange and top end, thumbs up, but a slight loss of off-idle torque. May have more to say after I get more miles with it. On the throttle lever I used a skinny screwdriver to push it back, like you said the blasted wire thing is impossible. Oh, and yeah, I figured out to remove throttle lever from pump top to do the tophat & spring, lots easier.

Didn't use the O-ring, it was just the plumbing type, 'ordinary' in that sense.

Thanks for the tips guys, back on the road again....