hron13 Posted January 10, 2010 Share Posted January 10, 2010 As the title says im wondering about the induction side of things, i want to do a 4 barrel set up for simplicity. In terms of a carb for that 4 barrel set up how many cfm do you think it should pull? On top of that what should i do about a fuel pump, stock mechanical or an electric? if electric how many gph? Just asking for some help for the new guy. Quote Link to comment Share on other sites More sharing options...
kolonelklink87 Posted January 11, 2010 Share Posted January 11, 2010 As the title says im wondering about the induction side of things, i want to do a 4 barrel set up for simplicity. In terms of a carb for that 4 barrel set up how many cfm do you think it should pull? On top of that what should i do about a fuel pump, stock mechanical or an electric? if electric how many gph? Just asking for some help for the new guy. in order to answer those questons i think people might need a few more details - where did you source a 3.1L? they dont exactly just float around -what are your goals in terms of HP, how much do you want and where do you want to make it -What type of running do you expect from the car? (race/street?) -what is your budget? Cheers, -pete Quote Link to comment Share on other sites More sharing options...
hron13 Posted January 11, 2010 Author Share Posted January 11, 2010 Ok, so sourced it from a guy that lives locally and works on Datsuns, he builds motors. so its an l28 block with an n42 head that has been ported and polished, it currently has the stock cam and valve train but i plan to change that as soon as i can afford it. -this will mostly be a street motor, with some drag and auto cross thrown at it now and then. -I need to have money in my pocket so I can fix my floors and do some suspension work, so a mild but powerful build that doesn't break the bank would be great, that's why I'm asking about the 4 barrel intake. Just so you guys know, i do plan on getting an alluminum radiator, with twin electric fans, and full exhaust (custom 2.5 inch) with a 6-2-1 header. so im not afraid to spend, I just don't need some crazy power, just want torque. Quote Link to comment Share on other sites More sharing options...
roger280zx Posted January 11, 2010 Share Posted January 11, 2010 Search around. There are several folks here running the 4 barrels. If you are that strapped for cash though, throw some su's on it and spend some time withe ZTherapy's tunning video. There is a whole lot in those little su's. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted January 11, 2010 Share Posted January 11, 2010 Stock cam on a L31? that's going to be an interesting feeling . TBH, I'd say skip straight to EFI, but that's really up to you. I think most carb retailers have online calculators for engine size and carb sizing. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted January 11, 2010 Share Posted January 11, 2010 I've run Holleys on my l28 for years. The L series engines seem to be quite capable running a number of differently sized carbs. I produced the most power on the dyno with a 600 cfm square bore unit with annular discharge booster venturis fitted. I had good results from a vac sec 650 cfm spreadbore carb too. Those little primaries were great for low rpm throttle response. Hec, I even ran a Nascar #80507 390 cfm square bore "double pumper" at one point. The type of intake manifold you have will also affect the way the engine performs and the way you have to tune up your carb! The Arizona is much more of a torque manifold, especially if the divider is left in place. The Clifford is the power maker but response at low rpms can be a bit soggy, especially with the bigger 600 cfm unit. I'm currently running with a highly modified #4548 450 cfm square bore vac sec on the Arizona ATM. For me and my application, this is the best setup. What works for you will be a matter of choice. For most of the people out there running Holley's, an "outa the box" #8007 seems to be the popular choice along with an Arizona intake manifold. Carter electric, 4-6 psi with 5/16 fuel line with return should do it nicely. Quote Link to comment Share on other sites More sharing options...
hron13 Posted January 12, 2010 Author Share Posted January 12, 2010 Thanks guys for all the help, you are actually helping a lot, I had no idea the SU's could be capable of feeding the monster. The stock cam isn't staying in there for long (ie before it gets installed in the car its getting at least a 290 with .480 lift) but thanks for the concern, I am sure the stock cam would just choke any power the extra displacement would add. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 12, 2010 Share Posted January 12, 2010 Those silly looking SUs are two of the best little machines ever designed for feeding fuel into an engine. They open up to 2" in diameter, and that is twin 50mm throttles. To make them flow enough fuel at the right mix for the bigger engine, all it needs is a replacement of the needles and you are good to go. for an interim solution, the SUs are certainly not off the table. If you know four barrels, then stick with what you know, but there is far more know how regarding the SUs on a Z engine as there is four barrel on a Z engine. I am no SU tuning guru; for specifics, you will have to turn elsewhere.. but I had to step up in defense of my favorite toilet bowl apparatus Quote Link to comment Share on other sites More sharing options...
kolonelklink87 Posted January 12, 2010 Share Posted January 12, 2010 Those silly looking SUs are two of the best little machines ever designed for feeding fuel into an engine. *cough* efi. Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted January 12, 2010 Share Posted January 12, 2010 SU's were in a magazine article for worst 10 car parts ever lol. I will try to look for it. Quote Link to comment Share on other sites More sharing options...
WEBEZEEed Posted January 12, 2010 Share Posted January 12, 2010 I love my SU's, they have a lot of potential that can be realized thru some modifications that don't cost any $ just your time. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 12, 2010 Share Posted January 12, 2010 SU's were in a magazine article for worst 10 car parts ever lol. I will try to look for it. And alot of car magazine editors and writers have ever lifted a wrench in their lives. In fact, most of the ones I have read know more aboutworking on cars than anyone I know. *sarcasm*off* EFI is great, but only as great as the programming that goes into it. It is alos MUCH more finicky than any well built SUs, requiring clear grounds, good wiring, and far far far more components. I am on the EFI side of the fence here, guys, but I am simply saying that Skinners' Union carburetors are masterstroke of automotive engineering: maximum intake velocity and torque response right off idle, but maximum bore sizing and air flow at full throttle. Consistent and complete fuel atomization guaranteed at any RPM or throttle positioning, and only three moving parts per carburetor. (Throttle plate, needle assembly, float.) EFI has many electronic components that can fail, mechanical wire connections that can corrode.. and if you are talking non-stock EFI, the programming instantly becomes a question mark. Fully Tuned, the EFI machine will win hands down (and as I said, it is the choice I would call my "preferred" induction myself) but the SUs are top-notch machines. What magazine was that in? I need to avoid it in the future. SUs are right up there with NACA ducts and an electric starter motor on my list. Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted January 12, 2010 Share Posted January 12, 2010 I can't remember 240hoke had the magazine at his house. Quote Link to comment Share on other sites More sharing options...
johnc Posted January 12, 2010 Share Posted January 12, 2010 SU's were in a magazine article for worst 10 car parts ever lol. Most likely Hot Rod. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 13, 2010 Share Posted January 13, 2010 Most likely Hot Rod. Packing Material Magazine!!! Quote Link to comment Share on other sites More sharing options...
hron13 Posted January 16, 2010 Author Share Posted January 16, 2010 Ok thanks guys, i bought a 390 carb and the arizona Z car intake, need to save up to do the fuel system. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted January 16, 2010 Share Posted January 16, 2010 Ok thanks guys, i bought a 390 carb and the arizona Z car intake, need to save up to do the fuel system. I can just hear it....."OMG, you bought a what?" Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 16, 2010 Share Posted January 16, 2010 I can just hear it....."OMG, you bought a what?" Certainly Not!! My old man has run three different four barrels on his 240 shadetree racecar (390, 650 DP and a 750 IIRC?) but I have my preferences. I just like to make it clear that the stock option is not an immediate junker. A four-barrel is a TOTAL mystery to me; side draft carbs I can grok better. anyone who knows 4 barrels because it is what they grew up with, more power to em. (but yah, you were right on a different level) Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted January 21, 2010 Share Posted January 21, 2010 I know there has been a lot of debate in the past regarding the use of a 4-barrel carb on the L6. Let us know what you think of it once you have it installed. I personally have the SU's on my 3.1, and I have a set of webbers and manifold in a box that I dont think I will ever install. For street driving, the SU's should be capable of feeding the 3.1L and still being very drivable without a whole lot of complexity. Hope to hear your feedback after you get the AZC manifold/carb installed. Quote Link to comment Share on other sites More sharing options...
hron13 Posted January 22, 2010 Author Share Posted January 22, 2010 k will do buddy, just got to give me some time, the car is currently in shambles, and i need to do a whole lot of work before it will be drivable but look for a new thread all about the car in the future. Quote Link to comment Share on other sites More sharing options...
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