Several years ago I swapped carbs on my '78. Similar fuel problems resulted, which were eventually identified as being caused by the new carb requiring less fuel pressure. Idle was ok, but as soon as I increased rpm or fiddled with the choke, it would roughen or stall. I too replaced the fuel pump, but that only made things worse.
I put in a cheap, in-line fuel pressure regulator, and got some improvement, but the cheap regulator caused flow problems in high rev conditions. Ultimately, I put in a higher quality fuel pressure regulator, and that solved it. Paul F. Meyer Home Phone: 781-551-8574 Cell Phone: 781-801-3170 e-mail: [EMAIL PROTECTED] ----Original Message Follows---- From: David Woerpel <[EMAIL PROTECTED]> To: [email protected] Subject: [Spits] 79 Spitfire with SU carbs Date: Tue, 26 Jun 2007 17:43:27 -0500 Hello, I am helping a friend with a 1979 Spitfire 1500. He's removed the Zenith and installed 2 S.U. HS4's. I'm one of the masochistic types that likes working on SU's and have no problem with the H4's on my MGA or H1's on the Bugeye Sprite but this problem has us stumped. The car has been desmogged, the head lightly shaved (I don't know how much) and the rest is stock as far as we know. It was running happily and he decided that he wanted SU's. The carbs are set correctly. We started with the jet adjusting nut at 12 flats down (yes, they are centered). The float levels are at 3/16", oil in the dashpot (1/2" above tube). The car starts and runs on choke and the pistons rise equally but when the choke is gradually reduced after, 3-5 min., it starts to stall. Add choke; it runs. Push off the choke and it wants to die. When we tried hand manipulating the throttle it occasionally coughs back through the carbs and dies. The owner had ordered a new mechanical fuel pump which we installed. It ran better off choke momentarily but then fuel poured out both float bowl overflows. I know the mechanical pump isn't putting out too much pressure so I'm suspecting the float needle and seat. New rubber tipped ones are on order. The coughing back through the carbs makes me suspect timing but when it runs it's pretty smooth. Just for kicks, what are the timing specs for a 79 1500? He has no manual and mine are for my above cars. Any suggestions would be very helpful. Thanks in advance. Dave 59 :{) 59 MGA 1500 05 MCS Burlington WI _______________________________________________ Spitfires mailing list [email protected] http://autox.team.net/mailman/listinfo/spitfires _________________________________________________________________ PC Magazines 2007 editors choice for best Web mailaward-winning Windows Live Hotmail. http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_pcmag_0507 _______________________________________________ Spitfires mailing list [email protected] http://autox.team.net/mailman/listinfo/spitfires
