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NZXD's XD money pit

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Was it a particular kind of 600 vac or just your garden variety 4160? I have heard that in that particular squarebore design, the 750 was just right. Either side of that size carby had some compromises that you could never get around.

In any case, I think also that they're more careful with air bleed selection on any given size carby compared to the old days. It's much easier to play with jet/bleed combos with the screw-in bleeds available now, making different size carbys less of a compromise.

How is the fuel consumption when compared to the old one?

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Was it a particular kind of 600 vac or just your garden variety 4160? I have heard that in that particular squarebore design, the 750 was just right. Either side of that size carby had some compromises that you could never get around.

In any case, I think also that they're more careful with air bleed selection on any given size carby compared to the old days. It's much easier to play with jet/bleed combos with the screw-in bleeds available now, making different size carbys less of a compromise.

How is the fuel consumption when compared to the old one?

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Hey mate, it was a dual feed Proform carb 600vs, which a few years ago had great reviews. It’s a shed ornament now.

Not sure on what the fuel economy is going to be like, not overly bothered as it’s just a toy.

I’ll be interested in seeing what the AFRs are like, and then I’ll wonder whether it’s worth trying a 600/650dp.


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What extractors did you use on the Weezer Bud?


Hurricane 4 into 1 suit XA-XF.

They are an easy fit and even easier if you use the slip joint on the drivers side rear cylinder (as intended by the manufacturer as I later found out).




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I have been struggling with a rich idle on this thing for some time.

So I splashed out and brought a decent AFR digital gauge and I fitted it up over the weekend. Had the exhaust shop weld in the bung because I can’t weld or have a welder...yet.

So plugged it all up and have it nicely mounted so it’s not all out in my face.

I then read up on idle mixtures and mucked around with that using my new vacuum gauge.

I have a quickfuel 450 mechanical secondaries so have the four corner idle screws. It has between 13-14hg vac with the screws all about 3/4 out.

It still idles pretty rich at 11.5 - 11.8.

At cruise say 60kmh in third it’s 14.2 - 14.4, at 100kmh in 4th gear it’s drops to around 14.0

When you nail it and go WOT it bounces to 17.0 - 19.0 for a split second until the secondaries kick in and it drops the afr down to pretty much 12.8 - 13.0

So apart from the rich idle I think the carb is doing what it should. I will look at slightly bigger idle air bleeds as currently it has the factory 0.070 size.

Apart from the idle can anyone see any issues I should address urgently?



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What squirters are you running? Sounds like you need to cover that lean spot as the secondaries open, or go to a firmer secondary spring to have them open a tad later and come in more solid.

Do you not have enough adjustment in the idle screws to get the mixture right? Seems odd that you need to change bleeds just to lean out the idle.

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What squirters are you running? Sounds like you need to cover that lean spot as the secondaries open, or go to a firmer secondary spring to have them open a tad later and come in more solid.

Do you not have enough adjustment in the idle screws to get the mixture right? Seems odd that you need to change bleeds just to lean out the idle.

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It has the factory 25 squirrels in the front and rear.

If I wind the idle mixture screws to much further it doesn’t want to run and I have to have the idle wound in quite away and the afr stays in the 11s.

I have been reading and reading and seems a common issue with the idle mixture. Frustrating.

So with the lean dip when you floor it, would you up the squirter sizes or change the rod to make the mechanical secondaries kick in earlier?


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It has the factory 25 squirrels in the front and rear.

If I wind the idle mixture screws to much further it doesn’t want to run and I have to have the idle wound in quite away and the afr stays in the 11s.

I have been reading and reading and seems a common issue with the idle mixture. Frustrating.

So with the lean dip when you floor it, would you up the squirter sizes or change the rod to make the mechanical secondaries kick in earlier?


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Sorry I wasn't on the same page. I was assuming it was a vac secondary carb.

OK, if you have a lumpy cam, you have to have the throttles wider open to get it to run due to less vacuum to pull air past the blades. The trouble is, the more you open the throttle, the less influence the idle screws have. Holleys and most other carbs with transfer slots have a rule of thumb that requires 20 thou of slot to show at idle, and as the slot is also 20 thou wide, make a square when doing the adjustment off the car.

Any more opening of the throttle draws more fuel through the slot, which has fixed metering, rather than the idle discharge, which the idle screws control. So the dilemma is that you need more air in but opening up the throttles loses your mixture adjustment.

BG carbs used to come with something called idle-eze, which was a trick borrowed from hot rodders of yore that used the air cleaner stud hole as an air bleed with an Allen key screw to adjust the air through it. The thread was slotted down one side so the air cleaner stud could go in without blocking the passage.

Another simple but more drastic trick was to drill out the throttle blades with a 1/8" drill to allow air in with the throttle backed down to where it should be (as mentioned).

The problem with enlarging idle air bleeds is that they serve both idle and transfer circuits. If you bleed more air to correct the idle, you're going to lean out the cruise mixture (which looks pretty good). You'll be chasing your tail there.

The ideal adjustment for mixture is 1.5 turns out from locked up. Anything more than a turn in or out from this means something isn't right.

So maybe look at the fixes I suggest above.

OK now the lean spot... I haven't owned a DP carb but it sounds like the secondary acc pump needs to come in harder/quicker to cover the throttle opening. First things first, either one should shoot fuel at the slightest touch of throttle for the corresponding barrels. Make sure that the pump linkage is adjusted correctly so this happens.

Changing squirters doesn't change the amount of fuel pumped in, it changes the duration of the shot. A lot of people go swapping them and make the problem worse because the shot doesn't go for long enough. Having said that, you might need to go up to 28s or 31s to dump it in quicker initially. Anyway, check the secondary pump cam and make sure that it's adjusted to achieve full stroke and pumps straight away. I assume that they're both pink?



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Sorry I wasn't on the same page. I was assuming it was a vac secondary carb.

OK, if you have a lumpy cam, you have to have the throttles wider open to get it to run due to less vacuum to pull air past the blades. The trouble is, the more you open the throttle, the less influence the idle screws have. Holleys and most other carbs with transfer slots have a rule of thumb that requires 20 thou of slot to show at idle, and as the slot is also 20 thou wide, make a square when doing the adjustment off the car.

Any more opening of the throttle draws more fuel through the slot, which has fixed metering, rather than the idle discharge, which the idle screws control. So the dilemma is that you need more air in but opening up the throttles loses your mixture adjustment.

BG carbs used to come with something called idle-eze, which was a trick borrowed from hot rodders of yore that used the air cleaner stud hole as an air bleed with an Allen key screw to adjust the air through it. The thread was slotted down one side so the air cleaner stud could go in without blocking the passage.

Another simple but more drastic trick was to drill out the throttle blades with a 1/8" drill to allow air in with the throttle backed down to where it should be (as mentioned).

The problem with enlarging idle air bleeds is that they serve both idle and transfer circuits. If you bleed more air to correct the idle, you're going to lean out the cruise mixture (which looks pretty good). You'll be chasing your tail there.

The ideal adjustment for mixture is 1.5 turns out from locked up. Anything more than a turn in or out from this means something isn't right.

So maybe look at the fixes I suggest above.

OK now the lean spot... I haven't owned a DP carb but it sounds like the secondary acc pump needs to come in harder/quicker to cover the throttle opening. First things first, either one should shoot fuel at the slightest touch of throttle for the corresponding barrels. Make sure that the pump linkage is adjusted correctly so this happens.

Changing squirters doesn't change the amount of fuel pumped in, it changes the duration of the shot. A lot of people go swapping them and make the problem worse because the shot doesn't go for long enough. Having said that, you might need to go up to 28s or 31s to dump it in quicker initially. Anyway, check the secondary pump cam and make sure that it's adjusted to achieve full stroke and pumps straight away. I assume that they're both pink?



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Thanks for the advice.

I have the transfer slots adjusted as you have said.

The front/primary squirter is instant, you breath on the throttle and it starts to activate.

The carb is set up standard for the secondaries to start to open once the primaries are at 60% (I’ll double check this) you can change this with different linkages, such as 50/50 or 1/1. I do have a 31 size pump squirter here, I’ll put that in the secondary and try it.

The throttle blades have a dimple in them to show where to drill if required, this would be a last resort, however a lot of people seem to do this on the quickfuel dp carbs from what I have been reading to get the idle mixture right.

My neighbour complained of the smell yesterday and her washing smelt bad.


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Thanks for the advice.

I have the transfer slots adjusted as you have said.

The front/primary squirter is instant, you breath on the throttle and it starts to activate.

The carb is set up standard for the secondaries to start to open once the primaries are at 60% (I’ll double check this) you can change this with different linkages, such as 50/50 or 1/1. I do have a 31 size pump squirter here, I’ll put that in the secondary and try it.

The throttle blades have a dimple in them to show where to drill if required, this would be a last resort, however a lot of people seem to do this on the quickfuel dp carbs from what I have been reading to get the idle mixture right.

My neighbour complained of the smell yesterday and her washing smelt bad.


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Sounds like you've got most of what I suggested covered already. You're onto it then.

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Sounds like you've got most of what I suggested covered already. You're onto it then.

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Now that I have the AFR gauge, I feel like I will want to have the ratio perfect haha.

Tomorrow I’ll change the rear pump cam to the 2nd hole and see if that helps the transition, then I’ll try the 31 size squirter. I’ll do one thing at a time to gauge progress.


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also note that cold engines run richer, so anything you are chasing needs to be on a warm engine
and if you have low vacuum due to big cam your idle mixture may not be possible to read or.tune with an O2 sensor accurately enough
 

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also note that cold engines run richer, so anything you are chasing needs to be on a warm engine
and if you have low vacuum due to big cam your idle mixture may not be possible to read or.tune with an O2 sensor accurately enough
 


It has 13-14 in vacuum using my vacuum gauge, that’s what I ended up with at about 900rpm. All done on a warmed up motor after a gentle drive.

The hyd roller cam isn’t huge, it has about 290 total duration and .515 lift.






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Afternoon all, thought I’d update this thread as I haven’t been coming into the forum much over the last year.

Facebook was taking up to much of my time and today I decided to turn it off for a while.

So updates with the XD:

Fitted Caltracs to the back last year, great investment, there is no diff wind up and the drive shaft stopped touching the trans tunnel over big bumps and aggressive acceleration.

I ended up fitting an AFR gauge (as above) and that is a great tool, managed to dial in a great tune in the carb. Recently upgraded to a QFT 650 Brawler DP, nice piece of gear and very adjustable. Made a couple of jet changes and got nearly perfect AFRs on cruise and WOT. I’m sure EFI would be better but this thing is on song.

Recently had some issues with the single rail and got some great advice to try, changed the gear oil for some 30 weight engine oil which assisted in the gear changes a lot but still not 100%. The box developed a leak at the front seal after the oil change.

I always wanted a stronger box so that I could really lean on it but keep it manual, so a rebuilt top loader is on its way including a Hurst shifter and RHD kit.

Over the next few weeks I will update this thread as I fit the new box.

75e16244d484143b591a89b34774a419.jpg
370424b12111bb4873bfa8f818d4e071.jpg


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That is a trick looking carby. Sounds like they're a good bit of kit to tune as well. There is still life in the old house brick after all!

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That is a trick looking carby. Sounds like they're a good bit of kit to tune as well. There is still life in the old house brick after all!

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Out of the box it ran pretty good apart from being on the slightly rich side, if I didn’t have the afr gauge I probably would have left it, there was no hesitation or stumble.


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7 hours ago, NZXD said:

Fitted Caltracs to the back last year, great investment, there is no diff wind up and the drive shaft stopped touching the trans tunnel over big bumps and aggressive acceleration

 

that's something that probably would have helped My cars, 

 

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Out of the box it ran pretty good apart from being on the slightly rich side, if I didn’t have the afr gauge I probably would have left it, there was no hesitation or stumble.


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Bolting on a brand new carby and having to jet down only slightly is epic winning

I would choose these over a Holley any day, seems like they're more refined in their tune, as opposed to a Holley HP which is slightly better than 4 fuel hoses roughly aimed at your engine. Then there's the Avengers, (vac sec) which by many accounts are a bit lean and stumbly.

How was the WOT tune when you leaned it off? Holley pumpers need lots of work to jet down at cruise and still be rich enough under load.

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Bolting on a brand new carby and having to jet down only slightly is epic winning

I would choose these over a Holley any day, seems like they're more refined in their tune, as opposed to a Holley HP which is slightly better than 4 fuel hoses roughly aimed at your engine. Then there's the Avengers, (vac sec) which by many accounts are a bit lean and stumbly.

How was the WOT tune when you leaned it off? Holley pumpers need lots of work to jet down at cruise and still be rich enough under load.

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With the jets I went from 76 at the back down to 74, and 68 to 66 at the front.

Cruise is 14:0 - 14:2
WOT is 12:5 - 12:7

Idle is a little rich at 13:5 - 14

Little fat n happy.



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