Re: [Spits] 79 Spitfire with SU carbs
Hi Roger, I installed a Weber DGV, and the fuel pressure is a little over
2.5 lbs.
I ordered the weber after the CD150 went nuts after a rebuild. In
retrospect, the rebuild was fine, it was the new fuel pump I installed
shoving 5+ psi down it's throat that caused the problems.
Original Message Follows
From: Roger Elliott [EMAIL PROTECTED]
To: Paul Meyer [EMAIL PROTECTED], spitfires@autox.team.net
Subject: Re: [Spits] 79 Spitfire with SU carbs
Date: Fri, 29 Jun 2007 18:25:34 -0500
I have been chasing similar problems for quite a while. It never occurred
to me that the problem could be too high of fuel pressure.
What did you need to set the pressure at to make the car run correctly? I
stopped at Napa, they had one that could be adjusted 2 - 4 pounds and one
that could be adjusted 4-9 pounds.
Thanks,
Roger Elliott
Paul Meyer wrote:
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: spitfires@autox.team.net
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
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Re: [Spits] 79 Spitfire with SU carbs
The moment it starts stumbling, pull out the choke partway and see if it gets better. If so, it suggests that it is leaning out at high RPMs. Also, does it stumble instantly at high RPMs, or is it only after several seconds of full-throttle running, like when merging onto a freeway? That is the classic symptom of a clogged fuel filter , lines, etc. Doug Braun '72 Spit --- David Woerpel [EMAIL PROTECTED] wrote: So we rotated the distributor a bit and I got it up to 5200 before it stumbled. But once it started to stumble the 'stumble limit' (not a character from Harry Potter) became lower until we were around 4000 again. The pinch bolt is tight so that didn't slip and we drew an index line so we could check for that. ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
Roger, 2 - 2 1/2 lbs. is all SU's need. Get a regulator and a guage. Mount the guage on a T downstream of the regulator. The regulators with the numbers on them aren't all that accurate. I have to ask againShould this 79 1500 with SU's and a couple of thou skimmed from the head still be timed to 10* BTDC? Dave Burlington WI Roger Elliott wrote: I have been chasing similar problems for quite a while. It never occurred to me that the problem could be too high of fuel pressure. What did you need to set the pressure at to make the car run correctly? I stopped at Napa, they had one that could be adjusted 2 - 4 pounds and one that could be adjusted 4-9 pounds. Thanks, Roger Elliott Paul Meyer wrote: 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] ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
Jeff started me thinking, which is very dangerous. If an engine has been de-smogged, would the plug gap be different? Should we be treating this car like a non-U.S. 1500? Which data should we use from the following web-site? http://www.triumphspitfire.com/Tuning.html more questions; always more questions! Dave Burlington WI Jeff Scarbrough wrote: At 02:49 PM 6/30/2007, you wrote: The stumble or miss almost has me wondering about the ignition or dizzy advance. How does one check to see if the centrifugal or vacuum advance is working? But most important is what is causing the problem at higher rpms?? Have you replaced the plugs, checked the gap, and or the wires, cap, rotor, and coil? Cheers, Jeff ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
On 30 Jun 2007 at 22:25, David Woerpel wrote: If an engine has been de-smogged, would the plug gap be different? No. Nor would the point gap (i.e. dwell angle). My 1500 has been demogged and it has the 1976 head with 9.0:1 compression ratio, original carb. I've experimented with the timing to get it to accept modern gas, and no change (within reason) in the timing would make it behave the way you describe. I don't think your stumble is due to using North American tuning specs. You need to make sure your coil, points, condensor, and plugs (and wiring connections) are good. I've never experienced a bad coil but if I recall correctly it might cause a high-speed stumble. Another thing to consider is that your plugs might be getting fouled, which is why the rpms of stumble onset seemed to come back down after you got it raised. That could be the result of a bad mixture. Given the carb-swap I suspect that. But first try swapping coil with a known good one. -- Jim Muller [EMAIL PROTECTED] '80 Spitfire, '70 GT6+ -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.9.14/880 - Release Date: 6/29/2007 2:15 PM ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
I have been chasing similar problems for quite a while. It never
occurred to me that the problem could be too high of fuel pressure.
What did you need to set the pressure at to make the car run correctly?
I stopped at Napa, they had one that could be adjusted 2 - 4 pounds and
one that could be adjusted 4-9 pounds.
Thanks,
Roger Elliott
Paul Meyer wrote:
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: spitfires@autox.team.net
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
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[Spits] 79 Spitfire with SU carbs
I replaced my 80 Spitfire's original mechanical fuel pump last year due to it leaking from several parts of it's body onto the starter motor. I have been suspicious for some time that it was sending too much pressure to the carbs, especially at idle. Your problem sure sounds like an air leak to me. Did you replace the exhaust/inlet to head gasket? Mark From: David Woerpel [EMAIL PROTECTED] Subject: Re: [Spits] 79 Spitfire with SU carbs To: spitfires@autox.team.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1; format=flowed Thanks to all who have responded. We've ordered some parts and made some calls. Joe Curto told me that he's had a few TR's come in with after-market MECHANICAL pumps that are putting out too high a pressure. Anyone else run into that? We'll put the old pump back on or get a good regulator and gauge. The carbs are FZX 1258's which calls for a standard metering needle of ABT. Also, I hate to admit I didn't notice that there were no piston springs (I'm used to working on H1's for the Bugeye which have no springs but I should have caught that anyway...duh.) ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
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: spitfires@autox.team.net
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
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Re: [Spits] 79 Spitfire with SU carbs
I'd suggest checking that you have the right needle. Also you mentioned some modification to the motor - head skimming - relatively small changes to the stock set up can require non standard needles etc. The exhaust was swapped on my car and with the stock needles it would barely run. Also was the head work done at the same time as the carb install? There may be all kinds of factors in play if that is the case. Assuming that the head work is OK there can still be all kinds of unforeseen issues such as reversion issues etc. I think we need more information to really get to the bottom of you problem. Good luck! Neil Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=listsid=396545433 ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
Thanks to all who have responded. We've ordered some parts and made some calls. Joe Curto told me that he's had a few TR's come in with after-market MECHANICAL pumps that are putting out too high a pressure. Anyone else run into that? We'll put the old pump back on or get a good regulator and gauge. The carbs are FZX 1258's which calls for a standard metering needle of ABT. Also, I hate to admit I didn't notice that there were no piston springs (I'm used to working on H1's for the Bugeye which have no springs but I should have caught that anyway...duh.) Given the fact that the car is desmogged is the timing still 10* BTDC? Neil, I'm not sure what you mean by reversion issues? I shall find the answers to your questions. Again thanks for the help...we'll see what Thursday brings! Dave Neil Penberthy wrote: I'd suggest checking that you have the right needle. Also you mentioned some modification to the motor - head skimming - relatively small changes to the stock set up can require non standard needles etc. The exhaust was swapped on my car and with the stock needles it would barely run. Also was the head work done at the same time as the carb install? There may be all kinds of factors in play if that is the case. Assuming that the head work is OK there can still be all kinds of unforeseen issues such as reversion issues etc. I think we need more information to really get to the bottom of you problem. Good luck! Neil ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
[Spits] 79 Spitfire with SU carbs
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
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Re: [Spits] 79 Spitfire with SU carbs
I'll give you credit for having the courage to show up on a Triumphs list with an MGA! :-) On 26 Jun 2007 at 17:43, David Woerpel wrote: 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. The fact that it runs with the choke pulled back on suggests that it has a bad air leak. Does it blow black smoke with the choke pulled out? And how much choke too? Maybe those carbs had really worn throttle shafts? Boy, they'd have to really worn though. It ran better off choke momentarily but then fuel poured out both float bowl overflows. The momentary running well was obviously due to the excess gas. One possibility is that the float valves were and still are sticking. If the old pump couldn't keep the bowls full, then adding choke could help. Apparently the new pump forced more gas through the valves. Even so, a big air leak would still cause that behavior. Forcing enough gas through to spill out of the bowls through the jets would enrichen the mixture and compensate for the air leak. Getting it dialed in would be difficult because idle would greatly affected, I would think. Could the vacuum retard unit have a split diaphram? (Is it hooked up?) The coughing back through the carbs makes me suspect timing but when it runs it's pretty smooth. N, bad timing doesn't feel right. Just for kicks, what are the timing specs for a 79 1500? Static 10BTDC, dynamic at idle 2ATDC. Of course, the vacuum retard unit has to be hooked up for that dynamic spec to apply. It's always possible that something else broke, but coincidences don't happen in cop shows and detective mystery books. -- Jim Muller [EMAIL PROTECTED] '80 Spitfire, '70 GT6+ -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.9.8/869 - Release Date: 6/25/2007 5:32 PM ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
Re: [Spits] 79 Spitfire with SU carbs
On 26 Jun 2007 at 17:43, David Woerpel wrote: The carbs are set correctly. Your puzzle still puzzles me. How do you mean the carbs are set correctly? I assume that means you've gotten it to idle well and the problem is with actual running, not idling. An air leak would normally get less significant as you opened the throttle, so if it idles well that probably isn't the cause. However... A PO installed SUs on my GT6 but it had running problems. At part throttle it ran lean, and full throttle rich. I finally figured out that the piston springs were too soft, being for an MGB's 1800 4-cyl instead of the bigger-breathing 2000 6-cyl. Projecting this problem on to you (probably not valid, I realize), if the springs are too soft, the mixture gets too lean quickly as you open the throttle. You didn't say where these SUs came from, and it's hard to imagine they came from a shallower-breathing engine than the Spitfire, but it's possible. On the other hand, supposing one or more was broken or missing. You might not notice it at idle because you aren't measuring just how much the pistons rise with a bit of throttle, but under running conditions it could be significant. Have you checked them? You being an MGA guy you probably did, I imagine. -- Jim Muller [EMAIL PROTECTED] '80 Spitfire, '70 GT6+ -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.9.8/869 - Release Date: 6/25/2007 5:32 PM ___ Spitfires mailing list Spitfires@autox.team.net http://autox.team.net/mailman/listinfo/spitfires
