ottoauto Posted May 4, 2008 Share Posted May 4, 2008 Oh, there is actually no backfireing. runs really well. there was a small vacuum leak before but it's now running REALLY well. the only problem is that the fuel isn't burning up terribly well or clean. and there is some blue smoke, i probably really just need to take my head and have it rebuilt soon. but then im going to want to put bigger valves and a cam in.... and that costs more than i have. i'll start saving...... Quote Link to comment Share on other sites More sharing options...
brokebolt Posted May 6, 2008 Share Posted May 6, 2008 I...put an electric fuel pump on, plated the mechanical pump, put my 4 barrel, and threw a glass pack on... I am willing to bet that the electric fuel pump is overpressuring the needle and seats in the fuel bowl thus over flowing the fuel bowls. It's backfiring. It did the same thing with the su's. This is why the problem is the same on both sets of inducitons. Do a search here on solutions to this problem, fuel pressure or carb inlet pressure. I have responded to several posts so I know they exist. During testing mode, get a good quality fuel pressure guage and test the pressure first to confrim the potential problem and I bet your pushing greater than the required 5 P.S.I. Be advised that even with such a low pressure that with old or used needle and seats you can over flow the fuel bowls. Quote Link to comment Share on other sites More sharing options...
Clifton Posted May 6, 2008 Share Posted May 6, 2008 Apparently it's not backfiring now? Either way, if it had too much fuel it wouldn't be backfiring except on decel. It would just chug if it was way to rich everywhere else. If it's out the intake it's lean if it's fuel related. I am willing to bet that the electric fuel pump is overpressuring the needle and seats in the fuel bowl thus over flowing the fuel bowls. This is why the problem is the same on both sets of inducitons. Do a search here on solutions to this problem, fuel pressure or carb inlet pressure. I have responded to several posts so I know they exist. During testing mode, get a good quality fuel pressure guage and test the pressure first to confrim the potential problem and I bet your pushing greater than the required 5 P.S.I. Be advised that even with such a low pressure that with old or used needle and seats you can over flow the fuel bowls. Quote Link to comment Share on other sites More sharing options...
brokebolt Posted May 7, 2008 Share Posted May 7, 2008 Apparently it's not backfiring now? Either way, if it had too much fuel it wouldn't be backfiring except on decel. It would just chug if it was way to rich everywhere else. If it's out the intake it's lean if it's fuel related. Mine didn't backfire when it was rich but did puke out blue smoke...and lots of it. No backfire on deceleration and none of acceleration, from either out the intake or exhaust manifold. Also had a motor where the timing chain jump a link due to worn/broken chain tensioner. Same issue but raw fuel that would burn the eyes, like a top fuel drag car warming up in the pits, just not as bad. A backfire can be produced by for many reasons both out the intake and exhaust manifolds. You would really need to determine the condition when it exist and work from there. Yes bad ignition can also produce a backfire condition. But like he stated it isn't doing it now, so... My main tip was check the easy stuff to confirm it is where it should be. Guage should cost about 20 bucks and a great addition to any tool box. ...and there is some blue smoke... They smoke when they are lean and they smoke when they are rich. Quote Link to comment Share on other sites More sharing options...
donbyrd Posted August 19, 2008 Share Posted August 19, 2008 Even though this tread started quite a while ago, it still is valid for some Z's that the time has come make some changes (like I have to). I put my Z on the road after a complete rebuild in 1988, ran great, looked good, etc., but now the old "SU's" don't work like they used to. I have in the past, had an MGA with them, and like the ones on the Z, were a royal pain to sync. I have rebuilt them, swaped out to a different pair, and STILL had problems (the front one always seemed to run richer). So now I'm installing a new 390 Holley with a "Bob Sharp Racing" intake. I guess as I get older, I don't have the time nor the patience to play with these any longer. The motor is a stock 240, the only mod is an Allison electronic ignition module (also installed in '88). Quote Link to comment Share on other sites More sharing options...
Guest agentc73 Posted August 22, 2008 Share Posted August 22, 2008 You are correct sir. BUT, and this is surely the science part you were looking for, MY 4 barrel 240Z had it's way with another 240Z on the freeway, and THAT Z was running them funny sideways triple dueces A Thousand Bucks says that guy doesn't know how to work on them himself. Or hadn't in way too long. Quote Link to comment Share on other sites More sharing options...
travie319 Posted February 17, 2010 Share Posted February 17, 2010 I just ordered a Arizona manifold and have a dyno available. I will try to get some numbers on. It should take a week or so to get this sucker on. I haven't chose a carb yet.... Quote Link to comment Share on other sites More sharing options...
Bob_H Posted February 18, 2010 Share Posted February 18, 2010 I just ordered a Arizona manifold and have a dyno available. I will try to get some numbers on. It should take a week or so to get this sucker on. I haven't chose a carb yet.... But do you have numbers from before the swap? Please get good numbers BEFORE you swap so there is something to compare and contrast. I'd be interested in what the old setup was - were the carbs in good shape, etc... I did the flow testing for Scott Bruning back in 99-2000 when he was trying to get the SCCA approval for just the roller bearing SU's,(no thinned shafts). They laughed at us and said - fat chance, its modified from stock, doesn't matter if there is no flow advantage. I wish I still had that paper I submitted.... I can't find it to save my life. Oh, to the much earlier,(4 years earlier), questions about the rims on my car here: http://www.reocities.com/row4navy/rb26swap/72Datsun.html which is already massively modified and changed here: http://forums.hybridz.org/showthread.php?t=115751 The rims are CCW Classics - available in all sizes and offsets. -Bob Quote Link to comment Share on other sites More sharing options...
travie319 Posted February 19, 2010 Share Posted February 19, 2010 But do you have numbers from before the swap? Please get good numbers BEFORE you swap so there is something to compare and contrast. I'd be interested in what the old setup was - were the carbs in good shape, etc... I did the flow testing for Scott Bruning back in 99-2000 when he was trying to get the SCCA approval for just the roller bearing SU's,(no thinned shafts). They laughed at us and said - fat chance, its modified from stock, doesn't matter if there is no flow advantage. I wish I still had that paper I submitted.... I can't find it to save my life. Oh, to the much earlier,(4 years earlier), questions about the rims on my car here: http://www.reocities.com/row4navy/rb26swap/72Datsun.html which is already massively modified and changed here: http://forums.hybridz.org/showthread.php?t=115751 The rims are CCW Classics - available in all sizes and offsets. -Bob I will get some before and after numbers...BTW this car is a Stock 77" F/I L28 with minor bolt ons (Header/Magnaflow muffler/CAI/MSD Ignition/Aluminum flywheel/w CF DF clutch.) Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 19, 2010 Administrators Share Posted February 19, 2010 Took my desk top machine down a local computer store today to see what it'll take for it to run AutoCAD 2010, met the owner, very nice gentleman, happens to own a very nice clean burnt orange 240-Z that he daily drives, N/A L-28, 4 bbl carb, an aftermarket cam, headers, etc, (we didn't get too specific about the car or mods or even pop the hood, but I am anxious to see more, this car is VERY nice!), told me made he ran a 14.0x second pass at the drag strip! In my book that is pretty impressive for an N/A daily driven S-30, with a 4bbl carb. Maybe he'll sign up and share more with us. Quote Link to comment Share on other sites More sharing options...
travie319 Posted February 19, 2010 Share Posted February 19, 2010 Well I just received my intake today...Looks good and overall it's a nice piece... The only visual issues are that the intake needs to be cleaned out properly because of aluminum shavings inside. The carb mounting holes have also been drilled through into the runners. (Some may consider this to be a flow issue, but come on; I don't expect that to come into place on any N/A application.) These aren't really issues as I have installed many aftermarket parts that have been a nightmare in all aspects. As I mentioned above "it's a real nice piece." Quote Link to comment Share on other sites More sharing options...
WEBEZEEed Posted February 20, 2010 Share Posted February 20, 2010 Finished product out the door......with all those metal shavings! tacky in my book.I mean how hard would it have been to blow some compressed air thru there? I know I'm nit picking but that is just too simple to do before it is sent out. It wouldn't fly where I work. Quote Link to comment Share on other sites More sharing options...
thrustnut Posted February 20, 2010 Share Posted February 20, 2010 I bought the Arizona Z intake about a year ago, as stated nice piece. I had no problems with shavings, but I treated it to a solvent bath before install anyway. My car runs good, I like the simplicity of the carb over the old fuel injection. Nothing to break, and tuning easy and fun. Don't know what kind of HP I make, but its a fun dependable ride, and I like the look on peoples faces when I pop the hood. The only problem I had, and I'm not sure if it was an intake problem as much as a crappy header is that on install my intake would not sit flush on the head (a problem I found after trying to start for the first time...WOW) so make sure you don't have any clearance problems before you bolt it all together. All in all, nice part, easy install, fun ride..not for those looking for the crazy 300+ HP numbers, but I like it. Small edit: I'm sure you can build a 300+ HP N/A 4 BBL 2.8, but I would think that most of us out there interested in this part are not turbo'd or SC'd, we buy it for simplicity and just to be a little different. Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted February 20, 2010 Share Posted February 20, 2010 I have a Clifford Intake and a Two barrel Holley Race Carb on my car, its no where close to being on the road yet (hopefully this summer). But I do have a header on the car and there is not a lot of clearance between the intake and the header and its pretty hard to access the lower studs and bolts. Maybe I just have bigger hands, but still its nice and the two barrel is nice for me and what I will be using my car for but maybe eventually I will get it Dynoed. I can't wait to see the results for the AZ z car intake though, should be interesting. Quote Link to comment Share on other sites More sharing options...
roye@hrewheels.com Posted February 20, 2010 Share Posted February 20, 2010 I had the same problem, 150$ pace setter header gets in the way, I had to remove a bunch of material from the bottom of the manifold and put a well placed dent in the header to get it to fit. RE Quote Link to comment Share on other sites More sharing options...
thrustnut Posted February 20, 2010 Share Posted February 20, 2010 Chances are in my case its a shady header. I just beat the CRAP out of the header, planing on somthing nicer in the future. I didn't want to mess with the thickness of the walls on the intake, not sure how much was there. It would suck to go to far! Quote Link to comment Share on other sites More sharing options...
AZJoe Posted February 21, 2010 Share Posted February 21, 2010 Dyno Results I took my Holley 390 280Z to the Dyno last week. I rebuilt the engine about 4 years ago but never had the time to get to the dyno - life got in the way. A quick summary of my Z: 1977 280Z 274/274 Cam, performance springs Flat top pistons, ~10:1 compression Arizona Z cars 4bbl intake and 6-1 headers 2.5 inch exhaust, straight through muffler Holley 390, 47 main jets, 7.5" power valve, metering plate secondaries, short white spring on the secondaries Running 100LL Summary of the dyno run: way too rich at WOT. I'm running about 10.5:1 A/F. Even with that I'm pushing 155HP/162ft-lbs at the wheels. I'm happy. I've got a metering block on order for the secondaries. The plate is equivalent to 53 jets, we believe that putting in 47 or 49 jets in the secondary will bring up the A/F ratio and give me even more power. Once I get the carb reconfigured I'll be going back to the dyno. The 4bbl setup works VERY well! Here's the run: Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 21, 2010 Administrators Share Posted February 21, 2010 Talked to Roger again, this time got to look at his car. Nothing exotic here, just a very clean 240-Z with lots of attention to detail in all the right places. A true Datsun guy to the core, no big dollar parts, but will eat most cars with the big dollars parts thrown at them. Clifford intake, Holley carb, (change over to different one, I hope to be able to help him with the adaptor in the newer future), head shaved to to ragged edge thinness, cam, (we didn't discuss the specs), rest of the car is very well thought out, brakes, interior etc. I have made it known in the past that I am not a proponent of the 4bbl used on an inline 6, (Great for a V engine), I am now starting to eat those negatives words I have posted in the past. I still prefer the straighter shot of the side draft design, but am seeing the down draft 4bbl as viable option for a high performance L-6. Quote Link to comment Share on other sites More sharing options...
sticky280zx Posted February 22, 2010 Share Posted February 22, 2010 Also for me ( i have a l28 flat top, cammed, custom intake (for carb to sit on) with the original SU 3-1 manifolds on the car. But i think for me the 4brl is a great option for someone wanting to run a good amount of power out of these cars without stroking or turbo. Ie it only cost me $250 to put together a 125 wet plate setup on the car, and that bumps any decent 150-175hp that the car would run on just the motor/carb set up to damn near if not over the 300 mark. Obviously this is only used in straight lines and you dont have all that power all over the place and all the time BUT if your looking for 1/4 times it is definately a nicer, cheaper, safer, easier option to do with a 4brl plate than to do a dry shot or a direct port on an efi system. But let it be known, that always and forever my heart will be a fan of tripples on an L series. Quote Link to comment Share on other sites More sharing options...
Dtsnlvrs Posted February 22, 2010 Share Posted February 22, 2010 But let it be known, that always and forever my heart will be a fan of tripples on an L series. Be still my heart Quote Link to comment Share on other sites More sharing options...
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