AkumaNoZeta Posted January 24, 2011 Share Posted January 24, 2011 My 260Z came with an L28 with the N42 head already in it. It had bad SUs on it so I put the Arizona Z Car manifold with a Holley 390 on it. Then the ignition wasn't firing so I converted it to use the E12-80 distributor. After I had it running for a while I found that it had a bad headgasket so I bought the Fel-Pro complete gasket set and went ahead and did every gasket, I've heard that the Fel-Pro is thinner than OEM so that's why I mention that. Still running the stock exhaust system from manifold to dual mufflers. Since it never ran with the stock components I have nothing to judge it against so I was wondering if anyone had any idea how much better it should perform from a stock engine. When people ask me how much power it has I usually say "I'm probably lucky if I have 120hp." Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted January 24, 2011 Share Posted January 24, 2011 In stock new form they were 170hp or so, and I can only speculate that a holley 390 would be a significant improvement on the SU's because they were mostly used for fuel economy. That said, if it's seriously worn out or running like crap then who knows. Sheer numbers aren't important anyway and can be very misleading. If you're really pressed for a number but don't want to spend the money on a dyno run you can always do a 1/4 mile and put the time into an hp calculator to get an idea (purely theoretical). Quote Link to comment Share on other sites More sharing options...
AkumaNoZeta Posted January 25, 2011 Author Share Posted January 25, 2011 I don't really care about numbers. I don't even really trust numbers and dynos aren't consistent in there readings so I would only use one as a tuning aid. I just wanted to know if even with all those parts that it will drive a LOT better than all stock or if it wouldn't even be an noticable change. I really wish I could have drove it before so I can have a before and after comparison, and then be able to judge if making my L28 look like a Jeep engine was worth it or not. Quote Link to comment Share on other sites More sharing options...
ozzzzz Posted January 25, 2011 Share Posted January 25, 2011 In stock new form they were 170hp or so, and I can only speculate that a holley 390 would be a significant improvement on the SU's because they were mostly used for fuel economy. That said, if it's seriously worn out or running like crap then who knows. Sheer numbers aren't important anyway and can be very misleading. If you're really pressed for a number but don't want to spend the money on a dyno run you can always do a 1/4 mile and put the time into an hp calculator to get an idea (purely theoretical). The SUs are capable in stock form of flowing enough fuel and air for these motors at 100% VE. Last time I checked N/A motors are not capable of 100% volumetric efficiency(this includes N/A race motors). Properly tuned they work just fine.The holley is not an improvement. The question is what do you want from your car that is not providing you at this time? Quote Link to comment Share on other sites More sharing options...
Leon Posted January 25, 2011 Share Posted January 25, 2011 The SUs are capable in stock form of flowing enough fuel and air for these motors at 100% VE. Last time I checked N/A motors are not capable of 100% volumetric efficiency(this includes N/A race motors). Properly tuned they work just fine.The holley is not an improvement. The question is what do you want from your car that is not providing you at this time? NA engines are perfectly capable of obtaining 100% VE through resonance tuning. Quote Link to comment Share on other sites More sharing options...
AkumaNoZeta Posted January 25, 2011 Author Share Posted January 25, 2011 I'm not planning on keeping the L28 but it is a great runner, like I said I'm just wondering if all the stuff I added keeps the car "feeling" the same as it would stock or if the change in parts increases it. I've never got to ride in a stock S30 so I don't know how they perform and therefore I don't know if the parts keep close to stock performance or if it improves it, I doubt it lowers it. And to answer "The question is what do you want from your car that is not providing you at this time?" I love the car and I love how it just keeps on getting better and better so I think in more of the terms of what I can provide her with. I'm sure the SUs are good carbs, but when I got the car they were bad so I figured since it's my first carbed car I would be better off learning from the easier Holley than rebuilding the SUs and trying to learn from those. Of course though, I want Webers now. Quote Link to comment Share on other sites More sharing options...
Snailed Posted January 25, 2011 Share Posted January 25, 2011 The SUs are capable in stock form of flowing enough fuel and air for these motors at 100% VE. Last time I checked N/A motors are not capable of 100% volumetric efficiency(this includes N/A race motors). There are a bunch of factory car engines from Honda and others that break 100% VE. It's pretty well standard to be over 100% VE for NA race engines. Some of them breaking 125%. It's interesting stuff to read about if you have the interest. Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted January 25, 2011 Share Posted January 25, 2011 In stock new form they were 170hp or so, and I can only speculate that a holley 390 would be a significant improvement on the SU's because they were mostly used for fuel economy. That said, if it's seriously worn out or running like crap then who knows. Sheer numbers aren't important anyway and can be very misleading. If you're really pressed for a number but don't want to spend the money on a dyno run you can always do a 1/4 mile and put the time into an hp calculator to get an idea (purely theoretical). I would just like to say that 170hp stock in new form is not correct, I say this because it was the SAE rating and the horsepower stock was closer to 130-150hp. If the car runs the way you like it and it pulls the way you like it then your good. I am not sure if there has been a lot of documentation about the improvement of the 4 barrel manifold etc, over properly tuned SU's etc. and I believe there is a older thread arguing both sides. Either way with some work both could be great improvements over stock just depends on what you like and are more experienced with. Next time someone asks you how the 4 barrel is over stock take them for a ride so they can tell and let you know the difference. Quote Link to comment Share on other sites More sharing options...
ozzzzz Posted January 25, 2011 Share Posted January 25, 2011 There are a bunch of factory car engines from Honda and others that break 100% VE. It's pretty well standard to be over 100% VE for NA race engines. Some of them breaking 125%. It's interesting stuff to read about if you have the interest. I was meaning Nissan L28 ,26, 24 single overhead cam motors are not capable of. Sorry for the confusion. F1 motors have exceeded 130%. My point being SUs are not just for economy. They are matched to the motors. The holley isn't really any better. Quote Link to comment Share on other sites More sharing options...
Leon Posted January 25, 2011 Share Posted January 25, 2011 I was meaning Nissan L28 ,26, 24 single overhead cam motors are not capable of. Sorry for the confusion. F1 motors have exceeded 130%. My point being SUs are not just for economy. They are matched to the motors. The holley isn't really any better. Not to get more off-topic, but you said N/A engines not N/A L-series engines. Still, an N/A L-series is perfectly capable of exceeding 100% VE. Why wouldn't it be? Back to the other topic, the SUs are just fine for the engine in relatively stock form. I agree that the Holley is not any improvement at all, and I would think it would actually detract from performance in terms of mixture distribution when compared to dual carbs. The variation in runner length is greater than the SUs which leads to more uneven AFR across the cylinders. Onto the original topic, what does it matter how your engine compares to stock? If it performs to your liking, then enjoy it. Quote Link to comment Share on other sites More sharing options...
30 ounce Posted January 25, 2011 Share Posted January 25, 2011 (edited) Assuming the OP had the square top SU's, which were used to reduce emmissions, then the Holly probably performs better. Square tops were a PITA to get to perform properly. Round top SU's on the other hand can be made to perform amazingly well. I have Rebello modified SU's on my 3.0L that I put on until I could afford tripples but they perform so well that I'm reluctant to change. I can floor it at 1500 rpm's and it goes like a fuel injected car; no bog, hesitation or miss. I know that tripples will get me a few more ponies on the top end but at what cost in drivability? Everyone keeps saying SU's were used for better mileage...REALLY? The original 240 was a pretty good sports car and if I remember correctly Datsun didn't put SU's on their economy cars. I really want tripples but after my expierence with SU's I'm impressed at how simple the design is and how well they work. Edited January 25, 2011 by 30 ounce Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted January 25, 2011 Share Posted January 25, 2011 The SUs are capable in stock form of flowing enough fuel and air for these motors at 100% VE. Last time I checked N/A motors are not capable of 100% volumetric efficiency(this includes N/A race motors). Properly tuned they work just fine.The holley is not an improvement. No point in arguing that one, you completely contradicted yourself there... Besides you guys are misguidedly exchanging VE with power. I never said a single holley would be more efficient than two SU's, in fact I basically said the opposite ("used for fuel economy"). However, it's fairly common knowledge that the achilles' heel of SU carbs is throttle response. I would just like to say that 170hp stock in new form is not correct, I say this because it was the SAE rating and the horsepower stock was closer to 130-150hp. If the car runs the way you like it and it pulls the way you like it then your good. Are you saying that the SAE rating is altogether incorrect or that the 170 is a gross rating as opposed to net? I'm not even sure what's on topic anymore. I thought the question was about simple numbers... "any idea how much better it should perform from a stock engine. When people ask me how much power it has I usually say 'I'm probably lucky if I have 120hp.'" But if you don't care about numbers then all that's left is to drive the thing and feel how much power it has. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted January 25, 2011 Share Posted January 25, 2011 Everyone keeps saying SU's were used for better mileage...REALLY? The original 240 was a pretty good sports car and if I remember correctly Datsun didn't put SU's on their economy cars. I really want tripples but after my expierence with SU's I'm impressed at how simple the design is and how well they work. I'm not saying Datsun put in SU carbs specifically to make the z an economy car. I'm sure there were a variety of reasons, some of which you probably already answered ("how simple the design is and how well they work"). But it is that simplicity that makes them fairly economical. If they were inefficient I doubt they would be around at all, that is to say I'm sure those engineers didn't decide to go with SU's because they thought it was the most powerful option... Quote Link to comment Share on other sites More sharing options...
30 ounce Posted January 25, 2011 Share Posted January 25, 2011 (edited) However, it's fairly common knowledge that the achilles' heel of SU carbs is throttle response. Yes, I've heard that too. Des Hammills book (How to power tune SU's) addresses this. Many poeple use oil that is way too thick for the dampers in an attempt to richen the mixture on acceleration. The damper should be able to respond immediatley to throttle input (lightwieght oil(3 in 1) or ATF or none) and the mixture adjusted with the needle size. Mine responds immediately! No power valve needed. That being said, SU's are a compromise just as webers or possibly the Holly. Edited January 25, 2011 by 30 ounce Quote Link to comment Share on other sites More sharing options...
bradyzq Posted January 25, 2011 Share Posted January 25, 2011 My 260Z came with an L28 with the N42 head already in it. It had bad SUs on it so I put the Arizona Z Car manifold with a Holley 390 on it. Then the ignition wasn't firing so I converted it to use the E12-80 distributor. After I had it running for a while I found that it had a bad headgasket so I bought the Fel-Pro complete gasket set and went ahead and did every gasket, I've heard that the Fel-Pro is thinner than OEM so that's why I mention that. Still running the stock exhaust system from manifold to dual mufflers. Since it never ran with the stock components I have nothing to judge it against so I was wondering if anyone had any idea how much better it should perform from a stock engine. When people ask me how much power it has I usually say "I'm probably lucky if I have 120hp." This thread is getting a bit noisy, so I'll refer back to the OP. What are trying to compare to? A stock 75-76 280Z motor with EFI (170HP SAE gross)? Or a stock 260Z motor with flat top carbs (139HP SAE gross)? I ask this because your starting point didn't exist from the factory. I don't see how a well-tuned Holley 390 could perform better than a stock EFI setup that is running correctly. So, assuming all is set up correctly, I will guess that your engine is producing pretty much stock 280Z power, approximately 170HP SAE gross. Which would be more or less equivalent to 130ish HP SAE net. Which should be somewhere around just over 100HP at the wheels, give or take a few ponies. So, to answer your question, your guess of 120 HP is probably not far off, if you're talking about SAE net HP. And, you should have about the same power as a stock N42-engined 280Z. Quote Link to comment Share on other sites More sharing options...
dhartig Posted January 25, 2011 Share Posted January 25, 2011 I have driven SU's and the Holley 390. I thought both were about the same performance if properly tuned. Here is the old thread. http://forums.hybridz.org/index.php/topic/27905-4-barrel-intake-the-facts/ Quote Link to comment Share on other sites More sharing options...
AkumaNoZeta Posted January 26, 2011 Author Share Posted January 26, 2011 I was thinking that the 280ZX distributor and thinner head gasket would make more of a difference than the Holley, I don't see why you guys keep on focusing on that. I wish I could have SUs, but 30 Ounce was correct that the ones I had were square-tops and I found that switching to the Holley would be easier as in first learning how to mess with carbs. If I came across a set of round-tops with manifolds and factory air cleaner I would put them on just for the fact that my car won't look like it has a Jeep engine anymore, but I'm not looking for them because like I said, I'm planning to swap out engines in the future. Right now I'm focusing on the chassis and other little things. I think what I was really trying so say is that the car seems pretty quick for being a old sports car. When I got it I thought it would be quite a bit slower than my Mustang but now I think that it's actually faster and that suprises me. Hopefully the friend I gave the Mustang to will fix it so I can see how it does compared to it running side-by-side. Quote Link to comment Share on other sites More sharing options...
260ruztmachine Posted January 26, 2011 Share Posted January 26, 2011 (edited) I was thinking that the 280ZX distributor and thinner head gasket would make more of a difference than the Holley, I don't see why you guys keep on focusing on that. I wish I could have SUs, but 30 Ounce was correct that the ones I had were square-tops and I found that switching to the Holley would be easier as in first learning how to mess with carbs. If I came across a set of round-tops with manifolds and factory air cleaner I would put them on just for the fact that my car won't look like it has a Jeep engine anymore, but I'm not looking for them because like I said, I'm planning to swap out engines in the future. Right now I'm focusing on the chassis and other little things. I think what I was really trying so say is that the car seems pretty quick for being a old sports car. When I got it I thought it would be quite a bit slower than my Mustang but now I think that it's actually faster and that suprises me. Hopefully the friend I gave the Mustang to will fix it so I can see how it does compared to it running side-by-side. What mustang did you have? what engine? I "raced" a mach 1 on a red light last week from what I can tell, my car needs a lot of work (Sucky SU's) I lost! Good job man, I have a 260 also, but i'm running a 240 points distributor and SU's from a 240. I agree with you that a single Holley is better if you're barely learning to mess with carbs, as I am also barely learning to mess with carbs and I just bought a used AZ Z car manifold for a really good deal last night. If you're worried about the HP on a 37 year old car don't get your hopes up, if it drives how you want it then that's perfect. You on the other hand have a semi modded engine that most likely performs better than a stock engine, it all depends on the condition of the thing itself. What engine swap are you planning on doing? If you wanna get rid of the Holley any time soon IM me and I'd be happy to buy it off of you. Edited January 26, 2011 by 260ruztmachine Quote Link to comment Share on other sites More sharing options...
AkumaNoZeta Posted January 27, 2011 Author Share Posted January 27, 2011 I'll PM you about the carbs. The Mustang I had was a 1990 LX with the normal 302. Judging from RPM at 60mph in 5th gear and tire diameter, we suspect that it has 4.11 gear in it. The engine is stock but we removed every accessory off of it, people tell me that it has a set of pulleys on it but I've never seen a 302 without pullies so I can't tell. There's been some gearheads tell me that they believe the engine was bored to a 306 because they can't believe that a stock 302 runs that good, and there's evidence that the engine was either rehauled or replaced sometime in the past. I've gone through tons of ideas for engine swaps, as evident if you've been watching my posts over the years, but I finally got myself dead-set on getting a non-VVTi 2JZ-GE and running it N/A with triple Webers while also leaving room for the idea of pushing some boost through the Webers in the future. I doubt I'd go turbo because I'm obsessed with my idea of having a cover made for the cam-covers to simulate the look of an OS Giken valve cover with touches of a S20 valve cover (they're pretty similar anyways) and making a air cleaner box that looks like a factory Z432 one. Quote Link to comment Share on other sites More sharing options...
260ruztmachine Posted January 29, 2011 Share Posted January 29, 2011 (edited) I've gone through tons of ideas for engine swaps, as evident if you've been watching my posts over the years, but I finally got myself dead-set on getting a non-VVTi 2JZ-GE and running it N/A with triple Webers while also leaving room for the idea of pushing some boost through the Webers in the future. I doubt I'd go turbo because I'm obsessed with my idea of having a cover made for the cam-covers to simulate the look of an OS Giken valve cover with touches of a S20 valve cover (they're pretty similar anyways) and making a air cleaner box that looks like a factory Z432 one. OS Giken is the tunner company that made that dual cam head isn't it? The handful of heads they made retail for 10 or 20k some crazy figure around that. I read somewhere that with that head you can get around 300hp NA Edited January 29, 2011 by 260ruztmachine Quote Link to comment Share on other sites More sharing options...
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