DatEz Posted November 6, 2015 Report Share Posted November 6, 2015 Hey you guys, so I don't come on here often, and I don't know much. I have been thinking about changing my set up on my 521 L16, from a 32/36 weber to dual SU Carbs. The only problem I have, is that I have found it pretty difficult to find a working pair of SU carbs for a decent price, EXCEPT for SU carbs off a Z engine. I have searched many sources online and no clear answer, my brother says no, my friend who has the z su carbs says yes. My question is this- Do Z SU carbs fit onto an L16 manifold if I only use two of them? I can't find the specs or the sizes of the SU carbs or manifolds for both cars, so I'm completely lost. 1 Quote Link to comment
Stoffregen Motorsports Posted November 6, 2015 Report Share Posted November 6, 2015 I can't remember for sure, but I think the L4 SU's are smaller bore than the L6 SU's. Just in case you weren't sure, the DGV will actually make more power than a pair of SU's. DGV's flow more air through the common plenum, the DGV has an accelerator pump making cold starts and throttle response better and tuning a DGV is far simpler than SU's. Quote Link to comment
Dolomite Posted November 6, 2015 Report Share Posted November 6, 2015 Z su are 4 bolt and 4cyl su have 2 bolts to the manifold. You should be able to find a set of flat top 38mm SUs for pretty cheap, not many people want them for some odd reason. Just de-smog them and they operate identically to the more expensive round tops. One bonus is SUs are constant velocity, set and forget for the most part. On a recent fun run at high altitude, my car ran perfect while others running other carbs had loss of power and drivability issues. 1 Quote Link to comment
fisch Posted November 6, 2015 Report Share Posted November 6, 2015 I have (46mm?) Z carbs on my 4-door. To make them fit, epoxie coated marine plywood spacers were made and blended from 46 to 38mm. And I think just two of the 4 holes were used to mount on a 510 manifold. see in my links bleow the Chapman 510. I didn't put the system in the car, but it works fantastic. That said I have a cammed LZ22 (L-series head and z22 block.) under the hood. So it is a little bigger and thirstier than a stock l16. Quote Link to comment
datzenmike Posted November 6, 2015 Report Share Posted November 6, 2015 The Z car SUs are a bit big is all. Even full throttle you won't be using all of them. and the jetting won't be right. If Z car, avoid the flattop SUs, get the dome ones.. Know the difference between the Z car and the 4 cylinder SU flattops they are not the same. Sealik (on here) has Z car SUs on one of his vehicles. Quote Link to comment
fisch Posted November 6, 2015 Report Share Posted November 6, 2015 Additionally, the guy who built my car had to do a lot of custom profiling of the needles to get it to run as good as it does. Quote Link to comment
banzai510(hainz) Posted November 6, 2015 Report Share Posted November 6, 2015 dude if you dont know much keep the DGV. Save you from proplems later 4 Quote Link to comment
Stoffregen Motorsports Posted November 6, 2015 Report Share Posted November 6, 2015 Additionally, the guy who built my car had to do a bit of custom profiling of the needles to get it to run as good as it does. dude if you dont know much keep the DGV. Save you from proplems later Exactly. SU's are not one size fits all, No carburetor is. So there must be some tuning and that doesn't mean just turning the adjuster on the well jet, it means filing needles, adjusting needle height, selecting oil viscosity and setting oil level, etc. If you want easy tuning, stick with the DGV. For that matter, have you ever done any tuning to your DGV? If not, don't change horses midstream. Spend some time and learn how. 1 Quote Link to comment
DatEz Posted November 6, 2015 Author Report Share Posted November 6, 2015 So if I buy the adapters for the Z SU's, then they will fit on the L16's SU manifold. Is that correct? I just put a brand new 32/36 Weber DGEV, but I thought the SU would get more power since it came with the SSS, no? Also, I heard the SU's are more reliable. What is the difference in power if I go to a single sidedraft instead then? I want more power with out doing an engine swap. I figured upgrading the carb would get me there the quickest way. I have my friend who is a mechanic who can adjust my carbs for me, so I am not too worried if I don't adjust them perfectly myself. Quote Link to comment
fisch Posted November 6, 2015 Report Share Posted November 6, 2015 I didn't know they made adapters for Z SUs on a 510? You need a 510 SU manifold, and then you need to hand make spacers to go from the 46mm Z carbs to the 38 510 manifold. But in the end I would guess you are only going to get so much out of an L16. Drop in an L18 or L20b or make a hybrid LZ22 is probably about as easy (Lz22 is more complicated.) And as cheap in some cases. As dialing in the l16 with carbs to where you will notice a big difference. I have no experience with a single DCOE side draft, but in researching, I thought I read they can be tricky to dial in. Maybe find one that is dialed already! Maybe look for a cam for your L16 if you are keeping with it and going twin carbs? Quote Link to comment
banzai510(hainz) Posted November 6, 2015 Report Share Posted November 6, 2015 Well if you wrote ealier what you wanted I wouls have said 38/38 DGEV carb as its bigger and a same install as a 32/36. However you do L16 ans if a 210 head ita getting a little on the big side for the carb. I never liked a 1 sidedraft set up. SUs are fine if all together complete and off a running car you just ran and heard it.(otherwise I lay money you get soembody elses junk. Most SUs are pushing 50years old now. They worn out!!!!!!!!!! This is a BIG NO NO, ( I have my friend who is a mechanic.) Unless hes old school type I wouldnt trust the outcome of this But I think you made up your mind already so if the carbs run like shit You have your mechanic and dont need Ratsun Quote Link to comment
datzenmike Posted November 6, 2015 Report Share Posted November 6, 2015 Hey you guys, so I don't come on here often, and I don't know much. I have been thinking about changing my set up on my 521 L16, from a 32/36 weber to dual SU Carbs. The only problem I have, is that I have found it pretty difficult to find a working pair of SU carbs for a decent price, EXCEPT for SU carbs off a Z engine. I have searched many sources online and no clear answer, my brother says no, my friend who has the z su carbs says yes. My question is this- Do Z SU carbs fit onto an L16 manifold if I only use two of them? I can't find the specs or the sizes of the SU carbs or manifolds for both cars, so I'm completely lost. There are only 2 SU carbs on the Z engine. The 4 bolt mount 46mm Z car SUs will bolt right onto the 2 bolt mount 38mm SU intake. The difference is a 1/10" narrowing at the intake. You could just file away or port the L16 intake to smooth out the transition. Again.... these carbs are too big for an L16. The L16SSS gets it's power by also having flattop pistons (compression 9.29) and also a 219 closed chamber head with 1.5" intake ports and 1.65" intake valves, 1.38" exhaust valves. In addition an SSS cam was used. SUs alone won't give you near as much. Keep the 32/36 and find an L20B cam... it's almost exactly the same as the L16SSS cam. Quote Link to comment
banzai510(hainz) Posted November 6, 2015 Report Share Posted November 6, 2015 Keep the 32/36 and find an L20B cam... it's almost exactly the same as the L16SSS cam. EZer to find just a whole L20b and install Quote Link to comment
wayno Posted November 7, 2015 Report Share Posted November 7, 2015 The absolute best upgrade I ever made to my 521 was going from a L16 to an L20b, there is no substitute for displacement, period!!! The L20b will bolt right in except you will need to use your L16 oilpan. The second best upgrade I ever made was going from a stock carb to Dual SUs, but I bought my SUs from Nissan, they had a clearance sale back in the mid 90s, I am still using them to this day. The third best upgrade I ever made to my 521 was building and installing a LZ23(more displacement), it turned my 521 into a torque monster, I broke my speedo needle off breaking in the engine, and I got the best gas mileage I had ever gotten in my life(hiway/same SUs) even going that fast(70/80mph). I would spend the money on a L20b, and then on Dual SUs, keep your L16/weber you have right now and start saving your money for the best bolt in upgrade you can make, an L20b. :) 1 Quote Link to comment
datzenmike Posted November 7, 2015 Report Share Posted November 7, 2015 Wayno is right. Larger displacement never goes out of tune. It's there working for you all the time and it makes more power and torque at lower speeds where you feel it sooner... and feeling torque push you back in the seat is where it's at. The L20B makes about 15-20 more HP than an L16 and it does not need a cam, flattop pistons or addition of carbs to do it. But with them added it makes even more power! Quote Link to comment
Jester Posted August 29, 2016 Report Share Posted August 29, 2016 Just in case you weren't sure, the DGV will actually make more power than a pair of SU's. Yep, that's why so many racecars run DGV's. :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :rofl: :poop: :poop: :poop: :poop: :poop: :poop: If you want a set of SU's to work properly, you need to size them to what you have. If your not running a bigger cam or ported heads, you really don't need the 46mm Z car SU's. The ones that came on the L16 and L18 were 38mm. The tuna can tops were actually from the L18's and they work just as good. ATF is best for oiling the piston. Reaching through the throat of the carb, lift the piston all the way up. Now fill just the center portion, release piston and replace cap. How hard is that? What else you got? If you seriously want a set of SU's that will make an improvement on your car, call Bruce @ Z Therapy. Quote Link to comment
datzenmike Posted August 29, 2016 Report Share Posted August 29, 2016 They look nicer too. Quote Link to comment
red13 Posted August 30, 2016 Report Share Posted August 30, 2016 Depending on your head you would need to get the intake ported to match the SU intake. I did that on my 210 head. Also if u are looking i might know if a set shoot me a msg Quote Link to comment
datzenmike Posted August 30, 2016 Report Share Posted August 30, 2016 Almost certainly the SUs were used with a 219 closed chamber head and flattop pistons on the L16SSS engine in the Bluebird Coupe. This would raise the compression to almost 9.3. (9.5 is what was advertised... but...) and 100 PS (98.6 BHP) '71 saw the introduction of the L18SSS engine (along with the continued L16SSS) and it's 115 PS (113.4 BHP) With a 219 head this would be a 9.0 compression engine. Quote Link to comment
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