peej410 Posted October 3, 2003 Share Posted October 3, 2003 hey guys, i know i havent posted in a while but I GOT MY Z RUNNING i work on it almost 6 hours a day now, for a while i was working full time and spending 8 hours a day on it. but it runs, and it goes straight at like 90 anyways, ive had the unfortunate trouble that most newbies have with the whole engine process.. first day i bent a valve. pulled the head off replaced propperly lapped the valve and installed a new head gasket. last i checked i have compression in all the cylinders, not much (120) cold but its uniform and the motor is bone stock. i bought a brand new edelbrock carb (was told they were plug and play for the most part) and at first it ran pretty well. Then when i bent the valve because it was running funny at idle i was trying to adjust the roughness out (didnt know the valve was bent) well ever since then it pretty much ran like crap. i have played with it quite a bit. i know im getting pretty much full spark, but with my vacuum advance im getting way too much advance at like 1500 rpm (41 degrees) , i have the vac advance connected to the correct port. i took off the top of the carb and adjusted the floats like is recommended in the carb manual. i need to adjust the idle mixture. my question is, when i give it throttle underload it bogs, one time it backfired through the carb, is it my ignition ? is it my carb ??? sorry if this is all jibberish my mind goes like a mile a minute when it comes to solving stuff like this and i get confused easily (the wonders of adult add) thanks -pete Quote Link to comment Share on other sites More sharing options...
Guest mikey_clark Posted October 7, 2003 Share Posted October 7, 2003 What size carb did you put on it? If the motor is bone stock, anything over 600cfm is going to bog because it's over carbed. Sounds like your timing is a litle far advanced for a bone stock engine. Quote Link to comment Share on other sites More sharing options...
Pyro Posted October 7, 2003 Share Posted October 7, 2003 Sounds like an accelerator pump problem. I had one of those carbs a few years ago and the seal in the accelerator pump would always go bad. I finally threw that carb in the trash (major piece of junk!). It is made of the wrong material anyways. Alum. carbs heat soak and boil the gas in the fuel bowls. You should buy a Holley 750 with vacuum secondarys (Holley 3310). Then install leaner jets in the primaries because Holleys always come jettted rich. A set of 68's or 69's should be about right. Jets are very easy to change in a old style Holley. Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 7, 2003 Author Share Posted October 7, 2003 hrm, i just bought this carb too, for my purposes over the winter and into next summer it should be alright, i disconnected my vacuum advance and took it for a rip last night and blew my driveshaft. needless to say its A LOT faster.... the drive shaft was a temp i tig welded together at work and im not suprised that the datsun universal joint broke. but itll be down for at least a day before ill be able to drive it again. i have a question though why if anything bigger than a 600 is too big for a stock motor would i put a holley 750 on it? Quote Link to comment Share on other sites More sharing options...
Pyro Posted October 7, 2003 Share Posted October 7, 2003 Chevy put 750 cfm carbs on most of their 4 barrel engines from 283 to 454 cid. Most quadrajet carbs are 750 cfms and some are even more. However, the carbs have vacuum secondaries. This allows the engine to only pull the secondaries open to the amount it needs. So, you might not use all 750 cfm's. When the secondaries start to open is tunable on a Holley by changing the vacuum spring. A lighter spring will allow the secondaries to open fast and fully, a heavy spring will require more rpms to open and will reduce the amount it opens. So, if you get a 750, it will give you room to grow. If you stay stock then use smaller jets and a heavier vacuum secondary spring. You can also change the size of the accelerator squirter and cam. springs, jets, and squirter are very easy to change and allows you to tune your carb to fit the car/engine combo. Holleys rock. They are easy to tune, parts are easy to find, and they last for years and years. Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 7, 2003 Author Share Posted October 7, 2003 alright, well just for referance, are the screws on the front of my carb (edelbrock) air bleeds or fuel ? and is screwing it in richening it or leaning it. Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 8, 2003 Share Posted October 8, 2003 Get a vacuum gauge, attach it to a good vacuum port. Turn in air, and fuel bleeds in all the way( one is air, one is fuel), then backout 2 turns each. This is your starting point. Start engine, and slowly turn either the fuel or air bleed ( one at a time) untill the vacuum gauge reads the highest. Then do the same with the other bleed. You may have to turn down your idle screw a little as your idle will climb. This is the easiest and best way to adjust your air/fuel bleeds. Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 8, 2003 Author Share Posted October 8, 2003 im thinking i may have a fuel flow problem, is it true that more than 5 psi can cause fuel to squeeze past the needle and seat? Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 8, 2003 Share Posted October 8, 2003 5 psi for a stock engine, up to 7 psi for hi perf. You may need a regulator. Moving to fuel forum. Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 8, 2003 Author Share Posted October 8, 2003 wow, i dont think i ever noticed a fuel forum, when did that happen ? Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 9, 2003 Author Share Posted October 9, 2003 ok well to get it to run close to proper it seems like i have to have the right hand screw all the way in and the left hand out two turns, this is when facing the carb from the front. am i still doing something wrong? Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 9, 2003 Share Posted October 9, 2003 ok well to get it to run close to proper it seems like i have to have the right hand screw all the way in and the left hand out two turns, this is when facing the carb from the front. am i still doing something wrong? One screw all the way in is a little weird, but if you got the highest vacuum that way and it's running alright, I guess you got it. Did the Idel speed go up when you adjusted the screws? Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 9, 2003 Author Share Posted October 9, 2003 yes it did go up when i adjusted them then i backed off a taste to get it back to 650 i also went around and adjusted all my valves took the top of the carb off and adjusted the floats aswell, now it idles really well but when i give it sudden full throttle under load it bogs then screams like all hell, i think that means its rich, im going to leave it for now, its not really fully street legal yet so im going to button up every system in the car before driving it much more. thanks soo much for your help i read through the edelbrock manual a dozen times looked online, your simplified version made the difference though. thanks again - pete Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 9, 2003 Share Posted October 9, 2003 , now it idles really well but when i give it sudden full throttle under load it bogs then screams like all hell, i think that means its rich, - pete Actually that means it is lean. You may need richer needles on the secondaries. Quote Link to comment Share on other sites More sharing options...
peej410 Posted October 10, 2003 Author Share Posted October 10, 2003 this is frustrating i wish i could afford all the highend nice stuff for my car, im using a cheapo regulator and an electric fuel pump i got when i had my 2.4l for all i know that could be the main problem. im going to go play with it some more thanks -pete Quote Link to comment Share on other sites More sharing options...
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