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spoolin4life

DHLA 40 question. Running pig rich!

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Posted (edited)

I recently jetted my triple dhla 40s for a standard N42 L28 and the car felt like it was running great. Basically no hesitations and clean acceleration throughout the the rev range. Carbs are all in sync more less and very responsive.

I wanted to do some fine tuning and put on a wideband o2 sensor. The car according to my gauge is running absolutely rich as it gets. I can set it to idle around 14-15afr but as soon as I touch the gas it goes right to 7-9 afr and cruises at 9. The jets/chokes I know are around the proper size. 32 mm chokes, 130 mains, 35 pumps, 7772.5 emulsion. 50 idles, 195 air correctors. 

What would possibly be the cause of it running super rich?? I'm still very new to this so any help would be appreciated.

Thanks!!

Edited by spoolin4life

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I don't think it can run well at afr 7-9. my experience is it'll bog down once your down to 10 and lower.
what do the spark plugs look like?

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Posted (edited)
7 hours ago, jonbill said:

I don't think it can run well at afr 7-9. my experience is it'll bog down once your down to 10 and lower.
what do the spark plugs look like?

They look a little darker than the regular brownish colour. I'm kinda stumped unless my wideband is reading off. Would you check fuel pressure next or look to the float level? I haven't touched the float needle valve yet. 

Edited by spoolin4life

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they'd be very black I think if it was running 7-9. what kind of afr kit is it?
fuel pressure is probably not relevant as long as its not overcoming the inlet valves. 2-5 psi should be fine.

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10 hours ago, jonbill said:

they'd be very black I think if it was running 7-9. what kind of afr kit is it?
fuel pressure is probably not relevant as long as its not overcoming the inlet valves. 2-5 psi should be fine.

I checked again today and they were much darker. It's an innovate mtx-l. Also the oil stank of fuel so that's scary. Don't wanna wash my cylinders. Could it be the floats? 

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mtx-l I think should be accurate. How do the AFR values change as you drive around?
what do you get cruising on steady throttle below 2500 rpm?
and what is it at full throttle above 3000?
when you're just off idle and it goes rich, it's on the progression holes and I'm not sure the float level is influential there. I'd guess its just the combination of idle jets and idle jet holder is too rich.
unless the choke is on of course. have you got a choke cable connected? is it definitely all the way off?

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just a comment on that choke size. I know that there's lots of advice around to use chokes that small, but I think that's mainly driven by ease of setup. if you want to use all the rev range then those chokes will be limiting it's performance. changing the choke sizes however invalidates all your jet choices so if you do want to get the most out of the engine ever, best to change the chokes first.

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15 hours ago, jonbill said:

mtx-l I think should be accurate. How do the AFR values change as you drive around?
what do you get cruising on steady throttle below 2500 rpm?
and what is it at full throttle above 3000?
when you're just off idle and it goes rich, it's on the progression holes and I'm not sure the float level is influential there. I'd guess its just the combination of idle jets and idle jet holder is too rich.
unless the choke is on of course. have you got a choke cable connected? is it definitely all the way off?

I'm almost positive the choke is off. But anytime I even touch the gas it goes right to 8-9 afr - doesn't matter how much gas i give it. (Full or partial) Im using a 7850.1 idle holder. What would you suggest as idle jets? 

I've spoke to some people and they've said 32 chokes are a nice low end/high end balance.

Again I'm a novice to this stuff so trying to learn 

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do check that the chokes are completely off.
I think 34mm would be a better choke size than 32, but it's not a big difference and I don't want to go spending your money :)
I'd go with 40 idle jets as the next step. idle jets are reasonably cheap so that's where I'd start. maybe check your float heights while you wait for them since it's easy.
there's a very good book "how to build and power tune weber and dellorto dcoe and dhla carburettors" by Des Hammill which is full of useful info. we'll worth getting a copy.

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4 hours ago, jonbill said:

do check that the chokes are completely off.
I think 34mm would be a better choke size than 32, but it's not a big difference and I don't want to go spending your money ?
I'd go with 40 idle jets as the next step. idle jets are reasonably cheap so that's where I'd start. maybe check your float heights while you wait for them since it's easy.
there's a very good book "how to build and power tune weber and dellorto dcoe and dhla carburettors" by Des Hammill which is full of useful info. we'll worth getting a copy.
 

I've actually read lots of the info in that book but it makes suggestions for tuned l series engines so it's tricky to know the right info on a stock l28. Lol

Would you get leaner idle jet holders too? 

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I tend to compare the L28 to 2.0 Pinto engine. they've got a lot in common and the size per cylinder is close.
I wouldn't at this point go for leaner holders. I'd just go for 40 jets and see what difference it makes.

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2 hours ago, jonbill said:

I tend to compare the L28 to 2.0 Pinto engine. they've got a lot in common and the size per cylinder is close.
I wouldn't at this point go for leaner holders. I'd just go for 40 jets and see what difference it makes.

I may just order them just in case, cause as you know international shipping is currently horrible with Covid; especially since these little parts all seem to come from the UK.

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I may just order them just in case, cause as you know international shipping is currently horrible with Covid; especially since these little parts all seem to come from the UK.
if you were in the UK I could lend you my box of spares. :)

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2 hours ago, jonbill said:
4 hours ago, spoolin4life said:
I may just order them just in case, cause as you know international shipping is currently horrible with Covid; especially since these little parts all seem to come from the UK.

if you were in the UK I could lend you my box of spares. ?

That would be amazing haha. I'm in Canada unfortunately! I have a few assorted sizes already.

Would you go one size down with the jet holder or two if the 45 idle jet isn't lean enough? .4 is a level below and .9 is two lower I believe 

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On 5/24/2020 at 7:14 PM, jonbill said:

I only have two idle holders, .2 and .1, so I work with them.

 

 

I'll see if the 45 idle jets fix it if not ill make another order and wait lol. Thanks for the help Jon!

I'll keep you posted. 

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Posted (edited)
On 5/24/2020 at 7:14 PM, jonbill said:

I only have two idle holders, .2 and .1, so I work with them.

 

 

So it helped a little bit I found it still went rich when I tap the gas but super lean when idling. My larger issue is now that I have a multiple misfire on 3 cylinders (2, 3 and 4) ? I did 4 full throttle pulls and afrs were 11ish which was way better but as soon as i went to park it i noticed the misfiring. I feel I have done engine damage somehow. I replaced the plugs and didn't make a difference. So compression testing later. Hoping its something basic and not internals.

Edited by spoolin4life

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did you adjust the idle screws? I would expect you'd need to open them a bit to keep the mixture right.

the "idle" jets supply both the progression holes and the idle screw. the idle jets alone determine mixture during progression, the idle jet and idle screws together set the fuelling at idle.

whe you go full throttle, the fuelling is determined by main jets and emulsion tubes so isnt a good test of your new idles!

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7 hours ago, jonbill said:

did you adjust the idle screws? I would expect you'd need to open them a bit to keep the mixture right.

the "idle" jets supply both the progression holes and the idle screw. the idle jets alone determine mixture during progression, the idle jet and idle screws together set the fuelling at idle.

whe you go full throttle, the fuelling is determined by main jets and emulsion tubes so isnt a good test of your new idles!

I did open them just a bit. I opened them up roughly half a turn but when I tapped the throttle it would still go to 9ish. Although the holding throttle was much better around 13-16. So I left it there. The driving was quite good also.

The reason I did the pulls was because my engine builder asked me to do a few full throttle pulls to see how the engine was as i had just finished breaking it in and afrs seemed safe. Sadly I don't feel so great now. ?

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12 hours ago, jonbill said:

did you adjust the idle screws? I would expect you'd need to open them a bit to keep the mixture right.

the "idle" jets supply both the progression holes and the idle screw. the idle jets alone determine mixture during progression, the idle jet and idle screws together set the fuelling at idle.

whe you go full throttle, the fuelling is determined by main jets and emulsion tubes so isnt a good test of your new idles!

Engine is toast. Compression was 110, 90, 110 120, 120, 130

Bigger problems now 

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Engine is toast. Compression was 110, 90, 110 120, 120, 130
Bigger problems now 
that doesn't sound good. engine out then.

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"Toast" doesn't sound right.  If it's freshly built it seems like the rings just didn't get seated correctly or are wrong for the cylinders.  Might just need new rings.

Just being positive.  

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2 minutes ago, Zed Head said:

"Toast" doesn't sound right.  If it's freshly built it seems like the rings just didn't get seated correctly or are wrong for the cylinders.  Might just need new rings.

Just being positive.  

Ya I'm not sure. The cars compression was good prior to doing the few full throttle pulls. The car still runs but I'm obviously not driving it now. I'm hoping it's just head issues. 

More datsun problems 

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You might check other things before you take it apart.  If you didn't hear detonation or rev to 8 grand there's no reason for something to break.  Could be something simple like valves getting loose.  Rings on one side, valves opening and closing correctly on the other.  That's all there is to creating pressure.  I'd give it a good inspection and "re-tune" before taking it out.

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1 hour ago, Zed Head said:

You might check other things before you take it apart.  If you didn't hear detonation or rev to 8 grand there's no reason for something to break.  Could be something simple like valves getting loose.  Rings on one side, valves opening and closing correctly on the other.  That's all there is to creating pressure.  I'd give it a good inspection and "re-tune" before taking it out.

If I had to guess it's valves as I didn't hear any detonation.

I'm going to do a better inspection tomorrow night. I may just pull the head off and see from there. Hoping it's nothing in the bottom end. 

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