predawson Posted April 10, 2005 Share Posted April 10, 2005 Hi chaps/chappesses, Having read a worrying post about bore wash I would like to try reducing fuel pressure going into the carbs. Do I screw in or screw out to reduce pressure (filter king)?? Getting a few pops and bangs on overrun and mixture adjustment can't cure it. Thanks. Quote Link to comment Share on other sites More sharing options...
itguy Posted April 10, 2005 Share Posted April 10, 2005 might not be down the the fuel pressure - the pops and bangs are usually down to the lack of ignition advance at 0% throttle (overrun). Without vac advance or a 3D (ecu controlled ignition) you probably won't be able to totally cure it. What is the pressure set to currently? Will. Quote Link to comment Share on other sites More sharing options...
hilux Posted April 10, 2005 Share Posted April 10, 2005 Getting a few pops and bangs on overrun and mixture adjustment can't cure it. WOOOOOAAAAAAAHHHHHH 1st ensure your exhaust isnt leaking at header to silencer, this will cause oxygen(air) to be sucked in and ignite with unburnt fuel Anyway whats wrong with pops and bangs, as long as its not all the time and mainly after lifting off from high revs I`d enjoy if I were you Quote Link to comment Share on other sites More sharing options...
stu999 Posted April 10, 2005 Share Posted April 10, 2005 But FYI, winding the adjuster out reduces pressure... Quote Link to comment Share on other sites More sharing options...
predawson Posted April 11, 2005 Author Share Posted April 11, 2005 Thanks for the advice guys. Firstly there is no putty at header to silencer junction so could well be sucking in air. Will def seal that up. IT guy, I have a luminition electronic ignition kit with an optical sensor in the dizzy. Timing is set to 14 degrees at 3000 rpm for a pinto with twin 45's fr33 cam. Does that sound about right? I know you are a recent expert on carbs so any information I can soak out of you is extremely welcome Prepare to be pestered with pm. stu999, thanks for actually answering the original question. Quote Link to comment Share on other sites More sharing options...
predawson Posted April 11, 2005 Author Share Posted April 11, 2005 might not be down the the fuel pressure - the pops and bangs are usually down to the lack of ignition advance at 0% throttle (overrun). Without vac advance or a 3D (ecu controlled ignition) you probably won't be able to totally cure it. What is the pressure set to currently? Will. No idea what pressure is set to. Factory default. Quote Link to comment Share on other sites More sharing options...
itguy Posted April 11, 2005 Share Posted April 11, 2005 I know you are a recent expert on carbs Wouldn't go that far!!! I've read a few book and had a few very enlightening coversations and now I'm an expert Well I would have said 14 degrees at 3000rpm is way too little advance to me for a pinto. I would have been looking for about 14 degrees static advance (ie on tickover). Are you sure that's correct? Bob Green will be able to suggest what 'full in' advance you should be aiming for as at 3000rpm the bob weights inside the dizzy should be well in action and advancing it nicely. Could be your issue, as high revs and not much advance makes for poping and banging.... Will. Quote Link to comment Share on other sites More sharing options...
predawson Posted April 11, 2005 Author Share Posted April 11, 2005 Winding the engine up to max rpm seems no probs. It responds really well and doesn't pop on the way down. The problem comes when I am pootling along (if that's a word ) and come off the gas at around 3500 rpm. As the engine slowly winds down it pops over and over, only quietly but would rather not have to listen to it, and more importantly, don't want it damaging the engine. IT guy, while I have your attention, you may be able to explain something else. Before being told that unscrewing the adjuster on the fuel flow regulator would reduce pressure I was ignorantly screwing it in (increasing pressure). The popping and banging got slightly better but there came a point where the engine would struggle to pick up. I assumed this was fuel starvation as I was reducing pressure but now I've found out I was actually increasing pressure I'm not sure what was causing the engine to hesitate. Could it be because I was flooding the floats on the carbs? Quote Link to comment Share on other sites More sharing options...
itguy Posted April 11, 2005 Share Posted April 11, 2005 more than likely flooding the float chambers. any signs of dripping petrol anywhere under the carbs? Seems funny that if you were flooding the float chambers then it helped cure the popping/banging etc... Still maintain the only way you will get rid of it is to fit a 3D ignition system, that way the ignition advance will be high enough to not allow the unburnt fuel down the exhaust at 0% throttle. Cured my xflow a treat - can't get it to pop/bang/spit if I tried... from any revs Quote Link to comment Share on other sites More sharing options...
Bob Green Posted April 11, 2005 Share Posted April 11, 2005 Bob Green will be able to suggest what 'full in' advance you should be aiming for as at 3000rpm the bob weights inside the dizzy should be well in action and advancing it nicely. My Pinto is set at 38 degrees at 3,800 rpm. From memory (and mine is crap!) the fuel pressure is set at 3 psi for 45's. As mentioned elsewhere on this thread, just be sure everything else such as inlet and exhaust joints are perfect. Quote Link to comment Share on other sites More sharing options...
Shovey Posted April 15, 2005 Share Posted April 15, 2005 On this subject - I have recently fitted a Malpassi fuel regulator but am kicking myself for not buying one with a pressure gauge. I dont suppose anyone knows what psi they come set at but can anyone give me an idea as to the sort of psi adjustment is made per 1/2 rotation for example? shovey Quote Link to comment Share on other sites More sharing options...
Blatman Posted April 15, 2005 Share Posted April 15, 2005 So buy the pressure gauge. I'm pretty sure the regulators all have a fitting for a pressure guage, so it's not like it wouldn't fit... OR, if there really isn't anywhere to put a gauge on the regulator, the othe way to test pressure is to just jam the gauge in to the end of a handy fuel line that you've removed from a carb... Either way, buy the gauge... Quote Link to comment Share on other sites More sharing options...
Shovey Posted April 23, 2005 Share Posted April 23, 2005 I've bought the pressure gauge from Burton now could you just remind me what the fuel pressure should aproximately be set at? Is it 3.5psi ?? Also is it measured when the engine is running or just when the ignition is on?? I have Weber 45's cheers Quote Link to comment Share on other sites More sharing options...
itguy Posted April 23, 2005 Share Posted April 23, 2005 I would have said 2 to 3psi... Quote Link to comment Share on other sites More sharing options...
predawson Posted April 23, 2005 Author Share Posted April 23, 2005 Update on progress! I set the pressure to 3.5 psi on recommendation from the engine builder (was at 2 psi). They said set the timing to 30-32 degrees at 4500 rpm so I will have to invest in a strobe with an electronic advance. Anyway, I sealed up the exhaust as recommended and set the timing to 14 degrees static. Popping and banging still there but significantly better. When I advanced the timing the idle went up by 300 rpm without touching the idle screw. Also the engine pulls a little harder which is ab fan. Thanks for your help all Quote Link to comment Share on other sites More sharing options...
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