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Wingsforwheels

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5 hours ago, 7000rpm said:

Sounds like you are onto something with water in the fuel. Matches the symptoms too.

Maybe try cranking it over with the fuel line pointed into a clear glass jar, and see what it looks like

Mmm I cranked a couple of litres of fuel into a bucket this morning and it looks fine... I'm wondering whether it may in fact be electrical. I'm not too sure what role the condensor and coil could play in all of this, but I might look at changing them both so I can at least rule them out.

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Pop the top off the carb & clean the jets and passages in the first throat. Just in case something was loosened up in your first clean and block a drilling afterwards.

It will idle on the idle jet & drive away to 1500-2000rpm still using the idle jet before it hands over fully to the main jet in the primary side of the carb. When you boot it the secondary comes in and it all works again until you back off and rely on the primary..  Does the accelerator pump push raw fuel down the carb when you open the throttle??

The condensor & coil could do it, either could break down under load, but it would be strange if they recovered at high throttle.

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Thanks a lot Altezza. I've done as you've said and cleaned out the passages twice since I cleaned the jets out--although the bowl and jets looked pretty good to start. 

The fact that it bogs down exclusively in the range of the primary jet was what made me suspect a fuel issue, but the pump is working fine, float and needle and seat fine, and yes you can see fuel shooting down the throats when the throttle is opened. 

There is a pretty substantial "sucking" sound when it bogs down, which sounds like the engine groping for more fuel? 

I know the jetting of the carb was on the lean side having been set up for a bog stock 4k--is it possible that as the piston rings seated and the motor started pulling more fuel, the lean condition got worse and worse? Seems extreme to say the least, but I'm clutching at anything in the hope my new motor is not buggered haha! 

Ideally I'd be able to borrow a compression gauge of someone and check that just to rule that out too. 

Edited by Wingsforwheels
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It could be asking for more fuel, now it's run in. My FJ20 was asking for 10-15% more fuel after about 500km. 

Condensers and points are cheap, it could be worth replacing them for a start. What dizzy is it? 5ks usually came with leccy dizzys was the dizzy from a 4k too?

 

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1 hour ago, kickn5k said:

It could be asking for more fuel, now it's run in. My FJ20 was asking for 10-15% more fuel after about 500km. 

Condensers and points are cheap, it could be worth replacing them for a start. What dizzy is it? 5ks usually came with leccy dizzys was the dizzy from a 4k too?

 

The change came on so quickly I think something else must be happening, even if it is compounding the lean condition... 

It's the dizzy off of the 4k, bosch points dizzy. I'll track down the part numbers and get a condenser, coil and points in at the local parts shop ASAP, and update from there!

 

But I would've thought from what I have read that Altezza is right that the condensor could cause the bogging, but would be all or nothing--it wouldn't recover again at higher revs. Is there some way to test a condensor? Either in the car on a bench?

Edited by Wingsforwheels
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You can buy capacitor testers, but condensors are so cheap its not worth it.

What happens if you pump the throttle up and down, often, but a little each time while its bogged down? That should have the accelerator pump push fuel in.

Quote

There is a pretty substantial "sucking" sound when it bogs down,

I imagine that is induction sound from having the throttle well open but no exhaust power roar to mask it.

Does it bog down with no load in the garage when you open the throttle? Does it just rev cleanly up the range then? Empty revs take no fuel and don't load the electrics either, so its not much of a test.

On the road, what happens if you load it up with some left-foot braking while the accelerator is down??  You can try that at different rev ranges and see if the flatspot is constant. Also, is it smooth or jerky?

I'd expect a lean issue to be a smooth loss of power, but an electrical issue to be a series of jerky missfires.

Edited by altezzaclub
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6 hours ago, altezzaclub said:

What happens if you pump the throttle up and down, often, but a little each time while its bogged down? That should have the accelerator pump push fuel in.

If I do this fuel is shot out of the jets up the top and it revs just fine--it seems like the issue is that when I open the throttle enough that the primary opens, as soon as the fuel from the accelerator pump is consumed, it starts gasping and will stall if the throttle is open. 

Together with the fact that the problem hasn't changed after I replaced the condenser and points this morning, has me firmly in the fueling issue camp. 

I have taken the carb off to give it a thorough clean, even though I put a kit through it about 4 months ago. The main jets are not blocked, and neither are the emulsifier/air corrector bits. The primary venturi is so completely stuck that I can't lift it up, so I will keep trying to remove it and then can clear out the passages.

 

Cheers 

Edited by Wingsforwheels
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Problem solved! 

After taking the carb off for a cleaning, I couldn't get the primary Auxiliary venturi off! Turns out the brass insert in the venturi had slid half a cm toward the float bowl, and rotated such that the opening was facing sideways instead of down toward the throttle valve. This was all but completely blocking fuel to the primary throat. 

I've attached some pictures of the before and after look at the venturi for the sake of explanation. The brass tube felt quite loose in its hole, so I shimmed it with a piece of beer can and tapped it back in with a pen, with the little fuel windows facing down. 

IMG_20180409_230635.jpg

IMG_20180409_230715.jpg

IMG_20180409_230733.jpg

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No, it certainly wasn't on my list of possible issues... But an easy fix!

3 minutes ago, altezzaclub said:

Back to running like a rocket?

Sure is! It's noticeably lean at the start of the primary opening, but even before I rejet it, this 5k is so much quicker than the 4! 

 

Thanks for all the help. 

Edited by Wingsforwheels
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12 hours ago, davew7 said:

How did you fix the discharge tube from rotating?   

I cut a tiny bit of a beer can and wrapped it around the float side of the tube, and tapped the tube and aluminium shim into the hole with a pen and a few gentle whacks with my palm. 

Eventually I might look at replacing it, but for now it's wobble-free. And it seems like weber spares don't come cheap! 

Edited by Wingsforwheels
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  • 3 months later...

Uni holidays have started, and I've had some progress (kind of)

The downdraft kept developing more and more issues, until I decided to spend a little more and scrap the 32/32.

I picked up a set of Dellorto DHLA40Fs on a redline manifold, have rebuilt them and fiddled with the linkages to get that perfect. Now to the bolting up... 

But I just cannot figure out how anyone can get these manifold bolts in! The outer/upper bolts near cylinders 1 and 4 are in such tight space with the curve of the intake runners that I can't even get  a spanner on to the 14mm bolts. I've tried with studs and nuts, but this didn't help much.

The ones underneath are more annoying but I think with the starter out they should be accessible from under the car. 

Someone suggested hex head bolts and a long ball end Alan key socket fitting, so I guess that might be my next try. 

Has anyone had success fitting these manifolds with regular bolts or studs and some tool configuration I haven't thought of? 

 

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Is this the manifold??

https://www.ebay.com/itm/12-3062-Redline-Manifold-Toyota-Corolla-Corona-twin-DCOE-Weber-3K-4K-5K-/331217079754

It looks pretty straightforward, which means it probably doesn't fit a K motor!  Are you fitting the manifold with the carbs on it already??

Pop up a few photos, it shouldn't be too bad. I've never had to take the starter out. The usual problem is a height difference between intake and exhaust manifolds which leads to air leaks, or weld too close to the bolts so the washers have no room to sit flat.

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Ah- is it lacking space here??  This is a Redline single side-draught manifold, but I expect it has the same shape. It looks like you have to put the nuts on with the manifold held off the head 5mm or so, then tighten them up.  Option B is some work with a grinder I suppose.

redline manifold.jpg

Edited by altezzaclub
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