Fuel Problem??
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Joined: Dec 2008
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Fuel Problem?? Hi Guys I have an odd problem (a long saga too)
I have a car with a 4link rear th350 and a 427 lsx with world heads, twin 950qft carbs on a sheet metal ram. This engine made 832hp at 7400rpm (correctedc) on a friends SF901 his dyno always translates well to the track so we expected low 9's and high 140's
The car weighs 3200 with driver. Out of the box it ran 9.5 and 140 but after much tuning and trying over a number of meetings ran no better than 9.45 and 141.
I had borrowed a 6000rpm converter off a friend and most people seemed to think this was the issue, I sent the converter away to a reputable shop who claimed it was high slip rather than high stall and sold me a new one.. here is where it gets interesting.
First pass it seemed to launch real hard (harder than before) but layed over massively (friend asked if i had backed off) it ran a 9.9 at 139 (1.44 60' instead of 1.33) It felt just as though the ignition cut off, but when it continued it didnt backfire, cough or do anything wrong, just ran hard.
We first thought it was a fuel issue.. we extended the vents (which helped a little) tried running it richer and leaner, higher floats, lower floats, more fuel pressure less fuel pressure a different pump different filters, more bypass pressure, less etc this has been going on for about 8 meets and test and tunes. I am incredibly frustrated!!
The only other thing which helped a little was to try to launch at lower rpm and flash the converter, but it didnt cure the problem. last time out I changed diff ratio as it was crossing the line at max power and i wanted it to rev harder ( this also made it leave harder) which made the problem real bad again. I got hold of competetion floats and bowls and used jet extensions but this didnt help. Flow tested fuel system and totally dismantled and cleaned.
It has an msd7 and doesn't seem to be a spark issue, It only plays up under that initial hard acceleration, it runs to 9000in top gear in the burnout and runs strong all the rest of the track. Have tried making sure fuel tank is full tried it with and without foam. My only other thing to try is I have 2 dominators (and a different top plate for manifold) but this set up only made 790hp on dyno
Please help.. any ideas greatly appreciated, or any advice on where (or who) else to ask.
Also .. is there any way a converter could do this (not just be a harder launch problem)
I have a car with a 4link rear th350 and a 427 lsx with world heads, twin 950qft carbs on a sheet metal ram. This engine made 832hp at 7400rpm (correctedc) on a friends SF901 his dyno always translates well to the track so we expected low 9's and high 140's
The car weighs 3200 with driver. Out of the box it ran 9.5 and 140 but after much tuning and trying over a number of meetings ran no better than 9.45 and 141.
I had borrowed a 6000rpm converter off a friend and most people seemed to think this was the issue, I sent the converter away to a reputable shop who claimed it was high slip rather than high stall and sold me a new one.. here is where it gets interesting.
First pass it seemed to launch real hard (harder than before) but layed over massively (friend asked if i had backed off) it ran a 9.9 at 139 (1.44 60' instead of 1.33) It felt just as though the ignition cut off, but when it continued it didnt backfire, cough or do anything wrong, just ran hard.
We first thought it was a fuel issue.. we extended the vents (which helped a little) tried running it richer and leaner, higher floats, lower floats, more fuel pressure less fuel pressure a different pump different filters, more bypass pressure, less etc this has been going on for about 8 meets and test and tunes. I am incredibly frustrated!!
The only other thing which helped a little was to try to launch at lower rpm and flash the converter, but it didnt cure the problem. last time out I changed diff ratio as it was crossing the line at max power and i wanted it to rev harder ( this also made it leave harder) which made the problem real bad again. I got hold of competetion floats and bowls and used jet extensions but this didnt help. Flow tested fuel system and totally dismantled and cleaned.
It has an msd7 and doesn't seem to be a spark issue, It only plays up under that initial hard acceleration, it runs to 9000in top gear in the burnout and runs strong all the rest of the track. Have tried making sure fuel tank is full tried it with and without foam. My only other thing to try is I have 2 dominators (and a different top plate for manifold) but this set up only made 790hp on dyno
Please help.. any ideas greatly appreciated, or any advice on where (or who) else to ask.
Also .. is there any way a converter could do this (not just be a harder launch problem)
Have you logging capabilities?
If so, look at the fuel psi.
Look at rpm, and do the converter slip calculations.
9000 in the burnout will kill valve springs...
Have you looked into putting the fuel up ft, ALA P/S??
If so, look at the fuel psi.
Look at rpm, and do the converter slip calculations.
9000 in the burnout will kill valve springs...
Have you looked into putting the fuel up ft, ALA P/S??
Thread Starter
Registered User
Joined: Dec 2008
Posts: 2
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I am going to have to buy a logger, as I suspect fuel pressure too, but as it happens about half a second into a run i dont get a chance to watch the guage, once i am in second i have checked gauge and it seems ok.
Agree on the 9k with valve springs, usually only use about 7500 but it did flash to 9 last time out
Agree on the 9k with valve springs, usually only use about 7500 but it did flash to 9 last time out
