swa240z

I have suspected a small leak somewhere but I can never find it using carb cleaner. I replaced the seals on the throttle shafts last weekend, so I know those are good. I might try some starting fluid or something more flamable than carb cleaner to see if it does a better job finding small leaks.

40 type 2

Ok, so I just finished adjusting the throttle plates so that the center of the plate is centered in the first progression hole, basically closing off the first hole. Idle RPMs are now at 1800. This is the reason why I originally backed it off so that about 25% of the hole (the part of the hole closest to the filters) remained uncovered. At that setting, I could get idle RPMs at about 900. I can't really control it at all with the idle mix screws. I can bring the idle down to about 1500 at 1/4 turn out on the mix screws, but it idles terrible when I do that. Is there another adjustment that I'm missing? Other thoughts?

I just noticed that Samurai7one is running Mikuni's so that explains why he was recommending 23mm vs. the Weber 25mm. I ended up ordering some 130 mains and 55f9 idles. I hope to have them by Saturday. I'll recheck fuel levels and try to adjust the throttle plate relative to the first progression hole tonight. It is amazing how much time and money these carbs can burn up LOL. Thanks for the help so far!

I have a cheap digital caliper that might work. I'll give it a try tonight. I was under the impression that 25mm was the target fuel level? Are there different levels for different e-tubes?

Chickenman - great read on the 510 site. I'll try again to get the progression hole completely covered, but it seems like the last time I tried that, I struggled with idle RPMs. As little as I know about getting these webers tuned, I know even less about tweaking the distributor to get advance exactly when you need it. Regarding the vacuum advance, I find it interesting that there are those who think it is completely unnecessary to run vacuum advance with triples and those who think just the opposite. Long ago, I had a mechanic who used to work on race z's outfitted with triples recommend that my intake be drilled out so that it would have a balance tube running between all 6 intake runners. I kind of remember him saying that it would improve overall performance and make the idle more smooth or something like that. Anyway, I went with his recommendation and had the intake drilled out. I have a bolt threaded in the end to close it off, but could easily thread in a port to hook up the vacuum advance if needed. If vacuum advance was utilized, what specs would you recommend for static, centrifugal, vacuum and total timing for an L24? Just how much advance is too much? Also, at what RPM would you have it max out? T-Bone - In reading through this thread, I have noticed that others have had some success eliminating flat spots with a smaller or zero pump exhaust. Like you, I don't know if that is the right way to correct the issue. I'm not sure under what circumstances the fuel needs to flow back to the bowl via the pump exhausts. To me, it seems like larger pump jets would be better than a zero pump exhaust but again, I don't really understand the reasoning behind the pump exhaust. Samurai7one - I totally agree on the fuel levels. I'm trying to find a tool to simplify the measurement but I'm having some trouble sourcing one. Keith Franck developed a sight glass type that you insert into the well where the mains go, but I can't find it for sale anywhere on his webstore. Also, another forum member recommended one from OER/SK Racing that ships from Japan. Nothing seems to be available in the states. I really appreciate all of the feedback so far. It sounds like my next brass order needs to be: 130 mains and 55f9 or f8 idles and maybe some 0.0 exhaust valves. What is the difference between the f8 and f9 and how will it impact my setup? Thanks again! Steve

Hey Steve - I'm confident the leather seals aren't leaking since I replaced them this past weekend and have a nice layer of grease between them and the bearings. The old seals were questionable, but one was in very bad shape. If I have a leak, it is probably around one of those damn soft mount gaskets with the o-rings and plastic spacers - but I can't find it using carb cleaner. As far as the pump jets go, they were all definitely shooting out a good stream of fuel. I checked them before dumping the fuel out of the carbs. I think I'm going to order some bigger idle jets to see what effect they have. From a dead stop, the flat spot is very noticeable as soon as I hit the pedal. The flat spot becomes less noticeable the higher the RPMs are when I hit the gas (I don't know if that is indicative of anything though). Once I'm past the transition point, I don't really notice the flat spot. I wish I knew someone with a pile of extra jets so I could experiment. That would save a lot of time and a lot of money! Steve

Hey Steve - I was writing my last post while you posted yours. Regarding shimming the cam towers, I talked with Ron Iskenderian about this. He isn't a huge fan of shimming cam towers because it throws off the geometry of everything under the cam cover. With a new timing chain, tensioner and guides, he said there was enough room to take up the slack created by shaving the head. He was the one that suggested an adjustable cam gear to make up for the retarding of the cam due to the head shave. I bumped it to about the 2* advance mark on the cam gear to compensate. At one point, I had seen where someone posted in one of the z forums a formula for calculating the cam timing effect of shaving the head by a certain amount but I can't find it anywhere. Regarding the carbs, the flat spot is evident when revving all carbs with the car just sitting there, but not as evident as when under load on the road. I never thought about running this test with each carb but I can give it a try and report back. Regarding the idle screws, see my comments in the previous post. I agree that the "norm" is about 1.5 turns out but my engine runs terrible if I do that. I'm a little concerned about going with bigger idles but I think the engine needs it to help alleviate the lean spot that seems to be causing the flat spot. The idle screws are all relatively new and purchased from Pierce Manifolds a couple of years ago. Maybe they are ground at different angles than the seats? I replaced the throttle shaft seals this past weekend since I was suspecting some air leak around them. Five of the seals were in ok shape, but there was no grease left behind them. One of the seals was shot and I'm sure leaking air. That was the one cylinder that I was having trouble syncing. All cylinders are now sync'd and the engine idles much smoother, but not perfect. I still suspect a small air leak somewhere but I can't find it. Steve

Chickenman - I too was thinking that the idles might be too small causing things to go lean before the transition. I keep reading about where idle screws "should" be, but given mine are only 1/2 turn out with 50f9s, I'm guessing that they will be something less than a half turn out with 55s. Is that really a problem - assuming everything seems to run fine? The carbs are all sync'd and flowing the same at idle. To get idle RPMs around 1000 or a little less, the throttle plate is covering about 75% of the first progression hole. I don't know if that is good or bad, but that is what it takes to get the idle where it needs to be. Also, I was thinking about your recommendation of going with 130 or 135 mains to richen things up at higher RPMS. Will increasing both the idles and mains at the same time maintain the same basic lean shortfall at the time of transition? In other words, to close the gap, should the idles go up a couple sizes with maybe just one size jump in mains to help close the gap? Leon - I have just recently subscribed to Sidedraft Central to get more insight into what Keith Franck is doing in regards to the Weber DCOEs. He has a tremendous amount of knowledge. I'm just learning about how the webers work in regards to using the weber jetting. I'm also trying to learn more about his proprietary jetting and e-tubes and determine what combination might work well with my setup. My problem is that even though I am now a member of the group and receiving the daily email updates, I can't seem to get logged into the group to actually read what is already posted on the site. I hate the way Yahoo Groups works.

Ok, I guess it's time for me to join this excellent discussion to see if I can get some help with the issue I'm having with the Weber Type 2 triples on my L24. First some history on the engine and the original carb setup. The engine was originally rebuilt about 2 years ago and was mostly stock. With the setup below, the engine ran pretty well. No real noticeable issues. 125 mains F16 e-tubes 150 air correctors 50f9 idle 135 pump jets 50 pump exhaust 30mm chokes 4.5 aux venturis Idle screws at about 3/4 turns about 3.5 psi fuel pressure Pertronix ignition Ignition timing at 12* with 24* mech advance No vacuum advance 2.5" 6-2-1 header/exhaust ZX 5-speed with Subi 3.90 LS rear end After a couple hundred miles, I started hearing some odd disconcerting noises in the 2000 to the 2500 RPM range. Late last winter I tore the engine down and took it to a different (and more respectable) machine shop for inspection and rework. Come to find out that the last guy over honed the cylinders by about .011 using standard pistons. I guess I was hearing some piston slap. Anyway, the engine was rebuilt .5mm over. In the process, I added an L480 Isky cam, had the head ported and polished and the valves unshrouded. In addition, the head was milled about .035 to achieve a 10:1 compression ratio using a 1mm metal head gasket. I have also added a Kameari adjustable cam gear to assist with cam timing due to milling the head and the thinner head gasket. With the engine rebuilt and the carbs reinstalled, I noticed a fairly bad stumble when accelerating moderately hard off idle or low RPM. Since then I have been fiddling with various jets and e-tubes but the bog is still there BUT the engine now runs much stronger in general than it did before. The new engine has about 200 miles on it now. Here is the current setup: 125 mains F11 e-tubes 170 air correctors 50f9 idle 140 pump jets 50 pump exhaust 30mm chokes 4.5 aux venturis Idle screws at about 1/2 turn about 3.5 psi fuel pressure Fuel levels adjusted to 25mm (I think) based on Keith Franck's recommendations. Throttle shaft seals replaced ZX dizzy with ignition timing at about 20* with 17* mech advance No vacuum advance Kameari cam gear set at the 2* advanced mark (I assume that is 2* cam and 4* at the crank but not sure) 2.5" 6-2-1 header/exhaust ZX 5-speed with Subi 3.90 LS rear end The engine seems to run smoother with the F11 vs. the F16 e-tubes. Definitely more kick with the 140 pump jet upgrade. The higher initial ignition timing with the ZX dizzy seemed to help with overall performance as well BUT the bog is still there. I plan to purchase some sort of fuel level sight tool to confirm the fuel level in the bowl is correct. I have been using a strip of index card that was marked at 25mm and dipping it into the fuel well until it made contact with the fuel. AFRs are in the upper 11s to low 12s at idle. I have tried to get that a little leaner, but the engine idles worse if i lean it out any more. I have tried dropping the idle jets to 45f9s but the engine ran way too lean below 2500 RPM so I put the 50s back in. Cruising AFR's are in the 13 range. WOT AFR is in the 13s to about 14. When the engine bogs after hitting the throttle hard off idle or at low RPMs, the AFR's lean out in the 16s but once I get past the bog which lasts about 1 second or less, the car pulls hard and the AFRs get back to the 13s. I have contemplated some larger idle jets since the engine seems to be lacking fuel during the bog, but I'm not sure how that will play out given I'm only running about a 1/2 turn out on the idle mix screws with the 50f9s. I have not messed with the cam timing at this point, but it is currently set on the 2* advanced mark. If I can get this car to launch without issue, I'll be a very happy camper! Let me know if you have any ideas or if I need to provide any more info. Like I said earlier, I plan to buy a tool to better measure the fuel levels in the bowl just in case my current measurement method is giving me false readings. Any help would be greatly appreciated! Steve