mcmlxxxv Posted July 12, 2012 Report Share Posted July 12, 2012 will they be good for that on a L20?? most of the setup I see on ther run webers or mikuni twin carbs... since im pretty noob on carburated engines I want to know if im better sell the SU for some weber or whatever twin 45mm sidedraft carb.. I also want to know if mikunis and weber share the same mounting flange . thx guys :) Quote Link to comment
metalmonkey47 Posted July 12, 2012 Report Share Posted July 12, 2012 SU's are great, and IIRC is what BRE ran on the 510's back in the day on the L18's. And yes, Mikuni and Weber DCOE side drafts have the same mounting flange. Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 thx for the info :) , I'll try them ! then if I need more I'll switch for something else Quote Link to comment
Silky_Johnson Posted July 12, 2012 Report Share Posted July 12, 2012 SU's are great, and IIRC is what BRE ran on the 510's back in the day on the L18's. And yes, Mikuni and Weber DCOE side drafts have the same mounting flange. It is my understanding that the BRE cars ran Mikunis. And I believe John Morton's car, #46, ran an L16. Mike Downs' car, #35, ran the L18. 6:40 in this video shows the Mikunis. http://www.youtube.com/watch?v=U5XAP4pCRps Quote Link to comment
banzai510(hainz) Posted July 12, 2012 Report Share Posted July 12, 2012 How about keep the SUs you got if they work and bolt them to a L20 If you dont have them and want to go racing then Mikunis I suggest. Be leary of alot of Junk out there. Best to get a whole set up with linkage more or less a bolt on with cable set up if possible Quote Link to comment
ggzilla Posted July 12, 2012 Report Share Posted July 12, 2012 SUs work fine for racing. What kind of racing you plan on doing? The advantage of twin 2-bbls is one-barrel-per-cylinder. So it can get a ram effect. Also why four 45mm throttles don't overpower the engine compared to two 46mm throttles. Both flow a similar amount of air, because each 45 is only working 1/4 the time, while each 46 is working 1/2 the time. Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 the cars is a week-end racer ... so it's not even a real race car . the only thing I lose with the SU is the ram effect ?? can I put stacks on SU carbs ? I heard that they are much easier to tune also Quote Link to comment
ggzilla Posted July 12, 2012 Report Share Posted July 12, 2012 Then you don't need to change carbs. The stock Hitachi or even a weber 32/36 can be used for racing. The ram effect is substantial, not just a little. And stacks won't give it to you. It needs ITB (one-barrel-per cylinder) to get this. So twin weber/dellorto/mikuni can do it, but twin SU cannot. But this effect depends highly on the manifold, the cam, the exhaust, and the RPM ranges. SUs are not easier to tune, the stock carburetor is. In many ways Weber/Mikuni/Dellorto are easier. But maybe what you heard is they are easier to set/adjust. Which some say is true, others say not. Or maybe you heard that they "stay in tune" longer. Which some say is true, others say not. Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 I see.. It's more like a personal opinion lol anyway I dont have any stock carbs , just the set of SU i had with the ''car'' . I need to rebuild the engine anyway , , I 'll be able to tell you what else is in it .. For now I know it has a modified camshaft and titanium retainers , peanut shaped combustion chamber and gasket match porting (I have 2 head like that...)I know that the car had webers before, but the last owner sold them before I buy the car .... Quote Link to comment
Sealik Posted July 12, 2012 Report Share Posted July 12, 2012 Yeah.....lots of theories out there on stacks/horns.....all relative to the engine/app.... etc...I guess.....who knows.. :) http://www.zcarz.us/...Carburation.htm "Velocity stacks decrease the turbulence of the air ingested by the carbs...and presumable improve the atomization at the venturi...air filters should still be fitted...to prevent sucking in random debris (with decreased turbulence)! Stacks really only make a measurable improvement in the upper RPM range and wide open throttle (WOT), at low revs, so it seems to me that they follow the "silicon breast-implant theory" explanation of their existence (don't do much, but look great)." DQ article....might have to create an account to view. https://docs.google....mQ1ODFjZWFlMDkx SUs are easy to tune/setup as long as you have the appropriate needles....and the throttle shafts are not leaking I decided to install some horns on my 46s....cut out from a 240Z air cleaner.......what the who... :D Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 nice ! I'll have a good reading on this one :) Quote Link to comment
ggzilla Posted July 12, 2012 Report Share Posted July 12, 2012 1. Dyno tests prove velocity stacks make more power. Even the Datsun twin-Hitachi setups used them (horns inside the air cleaner). They especially make more power in the upper RPM ranges, just like your special camshaft. 2. But this is not the same as the ITB ram effect. Which makes even more power. 3. Make sure your Twin Hitachis are 46mm and not the common 38s, which are too small for a high RPM 2-liter. Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 i'll measure them tonight Quote Link to comment
Boaty Posted July 12, 2012 Report Share Posted July 12, 2012 FWIW, a stock hitachi might be fine in a straight stretch. Don't plan on using the engine on a hard left hand corner, though. :P PS I see no reason why SU's wouldn't work on the track... I mean, if you're going to dedicate the vehicle as track only, then obviously go with track-oriented stuff like a set of Mikuni's. But, if you plan on driving the car around town too, I'd stick with the SU's... I got 30mpg a few times on Grants Pass to Portland trips (270 miles or so depending, freeway driving) doing 65-75mph. I've never heard of anybody getting that with Mikuni's or Webers. But SU's are very capable, as long as they are in good shape. :) Quote Link to comment
Sealik Posted July 12, 2012 Report Share Posted July 12, 2012 i'll measure them tonight Most likely 38s........any pics of motor? Quote Link to comment
mcmlxxxv Posted July 12, 2012 Author Report Share Posted July 12, 2012 i'll take some too :) the carbs are in my living room tho ... Quote Link to comment
Boaty Posted July 12, 2012 Report Share Posted July 12, 2012 FWIW I ran 38 SU's on my L20B with mild cam. Would pull hard all the way to 5K, rarely took it over that but never ran out of breath that I could tell. Quote Link to comment
Silky_Johnson Posted July 12, 2012 Report Share Posted July 12, 2012 He's no where near Quebec, but I hear that Steve Epperly likes to race SUs. http://www.ztherapy.com/ 1 Quote Link to comment
john510 Posted July 12, 2012 Report Share Posted July 12, 2012 I just switched from 38 mm su to mikuni 44's.Ive got more top end,it keeps pulling up to 6000 rpms.What i lost was low rpm torque and smooth power at the lower rpms.With the su's it had great torque and smooth accelaration from idle to about 5000 rpms then it runs out of breath.The su's are much more drivable and i feel that if i was running on an autocross track the su's would be faster.I guess you just have to figure out what feels better to drive and go with it.Both sets of carbs were run on the same L-20b. Quote Link to comment
ggzilla Posted July 12, 2012 Report Share Posted July 12, 2012 Mikuni 44 doesn't tell us much. A 44 can have small or large venturis or something in between. If you use a small venturi it would have great low-RPM response and maybe still give better power at 6k than SUs. Or maybe not, the SU-type carburetor is a great carburetor. twin sidedraft can return close to the same fuel economy as stock, but almost everybody fits bigger cams, exhaust, etc and there goes the mileage I like to race the stock downdraft, so that doesn't mean much. You would expect Steve to race SU-type Hitachis as his business is servicing them. And a guy who sells Webers would probably race Webers. Any of them can be raced. Quote Link to comment
Boaty Posted July 12, 2012 Report Share Posted July 12, 2012 The triple-SU L/6 kits are mighty fancy. And mighty pricey. But, Z-Therapy does them the right way. I haven't talked with him for a couple years aside from the usual Canby hello's. But when I was doing the whole 38mm SU thing, I learned a lot talking to them. The way it was always explained to me, was that an SU is going to do 90% of what a Mikuni is going to do, only you're able to achieve great mileage and much better drivability, plus no jetting! But every car and engine is different, so YMMV. I think SU's are pretty, too - people that've neve seen them are all googly when they are all polished out. =D Mine back when I had the time and patience to actually polish stuff out and keep it nice... can't wait to do this to the KA. Quote Link to comment
mcmlxxxv Posted July 13, 2012 Author Report Share Posted July 13, 2012 this make me want to polish mine :P those are awsome ! but they look a bit different , mine are round on the top Quote Link to comment
ggzilla Posted July 13, 2012 Report Share Posted July 13, 2012 The round ones are pre-1973. 240Z are dome-top, 260Z are flat-top. Quote Link to comment
mcmlxxxv Posted July 16, 2012 Author Report Share Posted July 16, 2012 still no pics of the motor, but I took a closer look to the heads I have : there is 1xa87 ,1x210 , and I haven't found the last one number ... but it look like the A87 except for the chamber wich is not peanut shaped it has a flat section too but ''straight'' no ''peanut curve''... pistons are flat top, and I still need to check if there is something done to the rod/crank.... Quote Link to comment
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