Lazeum

Your carbs are not set up right if one is sticky... Most likely your throttle shaft is bent or twisted. If some plugs are black (too rich) and some are white (too lean), it means you haven't set them up right. You should adjust them with what they need to make the engine runs good instead of having all the same adjustment. If cylinders 5 & 6 are showing lean mixture, open up a little idle adjustment screw, if other cylinders are too rich, turn the idle screw of the following carbs down. Too rich could also be because of not proper timing, make sure it is also right at idle but once more, to fix properly your issue, you should fix carbs instead of adding stiffer spring than would make your issue worse in the long range. btw, on spark plug, you forgot in the reference the heat range, that's what matters the most. It should 5 or 6 to run good.

How do the pistons look like? If it was a spark plug debris, the pistons should have some markings also at the same spot. It makes sense to be detonation. It happened at quench area were the pressure is the greatest & the furthest from spark.

3 years ago, I wasn't satisfied with my setup (F54 / N42 & flat tops). I've looked at many options, I ended up sending an email to engine builders. We had some discussions about my expectations (street engine, torque at low rpm) & we've defined my new setup accordingly. It was not cheap but I'm sure to have a combo with parts that match each other. Cam, head, comp ratio, they all go together. I've done the bottom end locally, head was done & setup by Braap. The new combo is so much better than previous one, I've never looked back.

"tune - tune -tune" means => right AFR across the rpm band + proper ignition Good ignition is not cheap either. You can recurve a stock unit, get a MSD AL2 box with programable timing, Electromotive kit or Megajolt + many other options I've forgotten. That's 500-1000$ to be added to the list.

They call the cable "Lokar cable". Cable install on 4-barrel manifold - Arizona Zcar ....and this thread on Classiczcars

You might be right! I need to change my 32mm chokes with 34 in the future. So I'll experience it. The video now works, it seems the U shape is pinched without spring inside it. People who switched to cable came with very good feedback. The cam going with the cable allows for smoother action of idle compared to the very sensitive system with rod.

We cannot see your video. Youtube is telling us "it is private". When using bigger chokes, you decrease vacuum in carbs so you need bigger idle jets. If you haven't changed your idle jets with chokes, you need to do it. There's some slope on the linkage, especially at the U shape connection at rod tip (where the slotted hole is). You can reduce it with some springs inside the U shape. Extra slope could come from ball joints, make sure they are tight. If they aren't, change them. At the tip of the pedal, you have a pin also, one of them on clutch pedal was crushed. check it out. When I setup my linkage, I usually untighten every linkage arm from the main rod going to carbs, I get the carbs throttle closed & sync' before locking everything up. So I know everything is ok at idle. I adjust arms length to get Carbs 100% open at WOT afterwards. Some people are, as suggested, setting everything up by looking at progression holes for idle. Since I cannot do it (there're plugs instead of bolts on my carbs), I use the best lean idle method with a lot of success. I've got AFR at cruise at 14.0/15.0, good progression & smooth idle. My chokes are small (32mm) so it also helps.

I've noticed it as well when I was putting everything back together. Spacers on end links might be shortened to get back to normal to avoid too much side load on supports.

If you can record some pulls with your wideband you'll see more info than just looking at your gauge. You will be able to see what could be improved. When I fine tune my carbs, I'm not looking at my AFR anymore. It becomes feeling. This is only when I'm undecided between 2 jets. It seems too small venturi will create a rich mixture at high rpm due to lack of air since venturi are not able to keep up. Check it with your setup, you might be able to tell. Going from 36mm to 32mm is a huge step.

That's a brutal way of fixing things but it works

That's a good point. The car is lowered with Tokico springs, nothing crazy. However control arms are horinzontal or maybe a little bit higher on the wheel side by 1/8". It makes the problem worse indeed.

shims are done. No more clearance issue. I've made 2 shims per side, 3mm thick, each. I've also changed bolts with longer ones to fit new setup (M8 x 1.25 x 30mm, grade 8.8)

I have looked for identical issue with no luck. I'm well aware about sway bar mount failure but I'm questioning the root cause. Everybody is saying load from sway bar, I'm wondering if it isn't clearance issue against frame rail causing the loading condition leading to failure. I've made some spacers today, it should be good now. [edit]: I found one post (#65) from JMortensen talking about it but pictures are gone

While I was working on the Z, I've noticed yesterday a clearance issue with my front sway bar (1" diameter). At rest, the bar touches the frame rails which is not good. Is it standard on every 1" sway bar? Am I the only one experiencing this situation? It could be a reason why some people adviced to add some supports to beef up the supports? The bar is actually adding some stress and it could explain why some have experienced some failure... It is definitely not ok and I'm going to shim the supports to get some extra clearance to solve the issue. I'm wondering also if the end links are the correct ones for my setup, they might be for stock sway bar. They might be too long. Can someone would have to correct length of the insert between bushings? Issue could also be solved by cutting up the tube at the correct length. here's some pictures to show the situation with car at rest. At jounce, it would be even worse!

have you checked valve clearance? It seems I'd got the same exact issue except I found it when cam lobe & rockers were so worn that one rocker came out lose & get broken into pieces in my head. I had driven the car for 200 mi max before it happened after new head made by Braap was installed on my L28 short block. We've suspected oil starvation but after engine tear-down, I haven't noticed anything blocked. I've contacted Rebello who was the cam grinder, he said issue had nothing to do with cam or rocker, only lube issue. I've also checked part geometry. I was working in auto industry. I had access to state of the art equipment to measure anything as low as a tenth of micrometer. Everything was very straight. So a 5-why analysis allowed me to come up to the following conclusion: Lack of lube => heat => metal tempering => hardness down => wear => failure Since, I've rebuilt my engine; crankshaft needed regrind, piston clearance was bad, block had metal chips in every gallery, oil pump was shot. Head was sent back to Paul (see where I live!?), cam was changed with a brand new reground core, rockers were replaced with new ones, wipe pattern was fully checked, lube system was upgraded with spray bar. Have you also noticed any black spots on rockers? looking at my rockers, they were black on the tip which is a clear sign of a lot of heat generation. New engine has now 700 mi & it seems valve clearance is the culprit on my side. At failure time, I've noticed 0 clearance and I've experienced it also on my new engine. Since I was checking valve clearance every 50 mi (talk about being paranoid!) on new engine, I've taken care of it. Valve clearance is now almost stabilized but I'm still checking every 100-150 mi. So I believe the lack of lube being caused by no clearance (=permanent friction) had been the root cause for heat on my side. See my thread about it. no valve clearance => Lack of lube => heat => metal tempering => hardness getting down => wear => failure also, 0 valve clearance = no time for valves to cool down against seats => burnt valves => failure I've got tons of pictures in my archives, if you'd like to get some more, just shoot me an IM and I'll send you some if that could help.

Thanks! I'm also on Sidedraft central but it would be very interesting to get feedback from you & your L28.

This is what I'm running.

Not sure why you'd like to keep square exhaust port but I've asked the same question to Braap and we end up with the combo I've got in my Z: F54 / flat top & P79 that could be switched with P90 if you really want square ports. What has been done however was a street porting (ie. improving flow without making the port bigger), valve unshrouding, etc. Install a properly designed cam (Rebello street cam with tight lash) that match the rest of the engine with surrounding components such as springs & retainers, lash pads. head has been milled by 0.020" to bring compression around 9.5, towers had to be shimmed in the process, pistons have been milled also to make sure quench clearance was spot on. In the process we also revised oil system with bigger restrictor in block (ID = 3mm), turbo oil pump, internally oiled cam + spray bar.

Since last post, I've made some progress First, I've spent 2 full weekends scrapping old material with heat gun, then wire wheels. I've purchased a heavy duty mask to avoid swallowing fumes, particles & paint, I should have done it way earlier, it is a very good tool to get, much better than paper mask that are more or less useless. I ended up with 2 rusty shells. I took pictures of the bottom side only. Top is more difficult to scrap since shape is more complex + I had to clean every inlet/outlet. Parts were then sanded by an outside company. They come up very clean! Next step was to remove some material all around on bottom cover. It created a step to weld more easily both parts. ...following with welds all around, only by spots to avoid making holes. I've added supports as well to hold the tank for further operations & to hold fuel filter in car (not showed on pictures). Toughest area was below filler inlet since both shells are not flat against each others. There was also a hole with a cap on the corner of the tank. No idea why, so I've plugged it. If anybody knows what it is, I'll be curious to know. Tank was ground to remove any sharp edges or material excess. We have in France a company called Restom providing special products for classic cars. They have a resin (epoxy?) to protect tank against rust & gas. It is an alternative to POR15. Here's how the tank looks like inside after treatment (product looks like liquid honey - a pain to properly spread it inside!) There were many little holes on welds, resin covered them all up. Tank is now fully sealed. I've finally chosen not to add any extra baffles or features to prevent fuel starvation with high G's. Knowing how difficult it was to spread the resin, it was a good decision. I would have had to cover with resin the features BEFORE welding everything together with the risk to cook the resin or to block some paths. Last step was to spray some paint outside. I did it with a 2 components epoxy paint that do not require any primer. Properties once cured are advertised as tough as powder coating. here's how the final product looks like now. Resin needs 2 weeks at least to cure, paint needs 48hrs.

Being local surely helps! I would be part of the game if I was living next to Keith also. It's definitely rewarding to get good running carbs. You're basically on the other side of the planet, it does not help to play trials & error... :/

If Keith suceeds with immediate throttle response at 1200 as well as 5000rpm. Allow us to run the engine at WOT around 12.5 without breaking the bank (= not much more expensive than "official" parts) I'm going to be Keith customer soon. He seems to achieve quite good results so far.

Your car is making weird noises on the video Your idle & progression seems off, idle jet could help but the only way to tell would be to give it a try Leon, While I'm following on Sidedraft central discussion about gravity e-tube with a lot of interest, I've never had to complain about my carbs. They work flawlessly with immediate action. I'm running F11 tubes with no issue at all. People run for decades DCOE with great success so I'm a little bit biased. I don't doubt about Keith results but the improvement, as far as I'm concerned, would be marginal. I'd rather focus on ignition as we've done it both with Megajolt.

Ok, for timing. with your P90 quench head, some lower timing could help but only dyno time or trials on the street with something to measure performance would tell you if you're fine. Your problem isn't related to timing at high rpm anyway. If you have a AFR sensor, what does it say when you're driving the car on the streets? Does it bounce around? do you see anything suspect such as too high AFR? Your issue could be a too large choke but it could also be an idle jet not appropriate. It was with 40DCOE but a friend running xxf8 idle jet was running very poorly until we've switched to xxf9, which were providing much better mix during progression mode. With a wideband, you can see too high AFR when using little pedal throttle. In your case, I would try 50f9 instead of 55f8. Your emulsion tubes could also be a reason but I wouldn't mess with them; they cost a lot & F16 are known to be usually very fine for gasoline. For information, I'm running F11 tubes with success.

Before getting some conclusions about your carb setup regarding airflow based on simple test, I believe it could be worth it to check AFR & timing. If the carbs are well setup the way they are now, very small difference between main & air jet are a sign something is not right. I have the opposite issue: too small chokes. I do believe 36mm choke are however on the high side, especially on 45DCOE.

I've kept the 1st gen coil pack I had. I've put some rubber pads to install it on the fender. they raise the coil pack enough to install it flat wherever you'd like in addition to dampen vibrations. You can even install the coil pack on head cover above spark plugs if you'd like - make sure pads can handle heat from engine. For spark plug wires, you can reuse the stock edis wires; cut them to proper length and install new spark plug terminals, easy to source to make a custom install clean.