Discussion
Hi there,
I have a 4.2 V8 in my 110 CSW, Which since March I have completely rebuilt the engine and since then I have been having elecrical problems with the efi. So far I have replaced the stepper motor, air flow meter, dizzy cap, rotor arm, electronic ignition module, coil, leads, plugs 4 times. All of the parts have been placed with high spec ones at a considerable cost but i am still having problems. I have also had the dizzy tested on a bench by a specialist and he says it is fine. I have run checks on the ecu with a multimeter and a test sheet and all the readings are well within the correct tollereneces. So as you may by now have appreciated I am pulling out hair.
So my plan now is to take off all the efi system and use it as a door stop and put on a Holley 600. My question is has anyone done this. I used to run a Weber 500 on an old 3.5 of mine and I loved it but it was very thirsty. I can only imagine that the 600 will be more so. I just don't want to go to all the trouble of swapping the thing over and be disappointed with performance.
Any views would be greatly appreciated.
Chris
I have a 4.2 V8 in my 110 CSW, Which since March I have completely rebuilt the engine and since then I have been having elecrical problems with the efi. So far I have replaced the stepper motor, air flow meter, dizzy cap, rotor arm, electronic ignition module, coil, leads, plugs 4 times. All of the parts have been placed with high spec ones at a considerable cost but i am still having problems. I have also had the dizzy tested on a bench by a specialist and he says it is fine. I have run checks on the ecu with a multimeter and a test sheet and all the readings are well within the correct tollereneces. So as you may by now have appreciated I am pulling out hair.
So my plan now is to take off all the efi system and use it as a door stop and put on a Holley 600. My question is has anyone done this. I used to run a Weber 500 on an old 3.5 of mine and I loved it but it was very thirsty. I can only imagine that the 600 will be more so. I just don't want to go to all the trouble of swapping the thing over and be disappointed with performance.
Any views would be greatly appreciated.
Chris
Chris,
I'm actually considering going the other way. I have a 90 with a 3.9 competition engine which is running on a 4 barrel Weber. It's quick but I'm getting about 10mpg. It's also quite problematic to set up and keep it running right.
In cold weather it tends to spit and splutter after about 3 miles from start. It's like carb icing but the gurus at RPi reckon that's not the case and suggested using their amplifier system. I did and it's improved a bit but still does it.
I think someone posted on here 1 time that unless you have a real big block V8, 6,7 or 8 litre the Weber/Holley route is wasted. Better to use well set up SU's in his view. Food for thought I guess.
I'm actually considering going the other way. I have a 90 with a 3.9 competition engine which is running on a 4 barrel Weber. It's quick but I'm getting about 10mpg. It's also quite problematic to set up and keep it running right.
In cold weather it tends to spit and splutter after about 3 miles from start. It's like carb icing but the gurus at RPi reckon that's not the case and suggested using their amplifier system. I did and it's improved a bit but still does it.
I think someone posted on here 1 time that unless you have a real big block V8, 6,7 or 8 litre the Weber/Holley route is wasted. Better to use well set up SU's in his view. Food for thought I guess.
Chris,
A 600 Holley is much too big for a 4.2 motor. Fitting a carb that big will result in low gas velocity, poor mixing/antomisation. Do the maths - capacity in C.Inch, divided by two, divide by 12 cubed, times rpm, times Volumetric efficiency (0.85) - gives carb requirement in CFM.
A Edelbrock/Carter/Weber 500 is also too big for the smaller RV8s IMO.
I run a 465 Holley on my 4.6 and it makes 275RWHP (in a Cobra replica). Your 4.2, even highly tuned, should be OK on a 390 and easily on a 465 Holley. Higher gas velocities on part throttle might even give you some economy (but not much!).
However, it is probably worthwhile in a last bid to get your Efi working properly. Drivability and fuel economy will both be much better on FI and I wouldn't really expect to see any big power gains from a swop to a 4 barrel.
Russ
>> Edited by russell_ram on Tuesday 9th August 14:54
A 600 Holley is much too big for a 4.2 motor. Fitting a carb that big will result in low gas velocity, poor mixing/antomisation. Do the maths - capacity in C.Inch, divided by two, divide by 12 cubed, times rpm, times Volumetric efficiency (0.85) - gives carb requirement in CFM.
A Edelbrock/Carter/Weber 500 is also too big for the smaller RV8s IMO.
I run a 465 Holley on my 4.6 and it makes 275RWHP (in a Cobra replica). Your 4.2, even highly tuned, should be OK on a 390 and easily on a 465 Holley. Higher gas velocities on part throttle might even give you some economy (but not much!).
However, it is probably worthwhile in a last bid to get your Efi working properly. Drivability and fuel economy will both be much better on FI and I wouldn't really expect to see any big power gains from a swop to a 4 barrel.
Russ
>> Edited by russell_ram on Tuesday 9th August 14:54
This thread was answered in the engines forum, but just to add; the weber 500 unlike the holley has smaller primaries, so its like two carbs in one. . the secondaries only open up on full-bore and then your fuel consumption goes down the pan!. Using a lambda sensor I rejetted the primaries down a stage or two as from the factory they are set for rich and richer still. (covering themselves i suspect)
The 600 is too big for a 4.6, I had a weber 500 on a 3.9 at it worked better than the SU's, BUT SU's are better for off-roading/bumpy surfaces.
Heres a carb sizer program, even at 100% ve and 5500rpm your'e only pulling 446cfm.
www.4secondsflat.com/Carb_CFM_Calculator.html
To put it into prospective, i'm running a 600cfm on my 5.7L twin turbo lump pushing over 400 bhp.
>> Edited by eliot on Friday 12th August 21:52
The 600 is too big for a 4.6, I had a weber 500 on a 3.9 at it worked better than the SU's, BUT SU's are better for off-roading/bumpy surfaces.
Heres a carb sizer program, even at 100% ve and 5500rpm your'e only pulling 446cfm.
www.4secondsflat.com/Carb_CFM_Calculator.html
To put it into prospective, i'm running a 600cfm on my 5.7L twin turbo lump pushing over 400 bhp.
>> Edited by eliot on Friday 12th August 21:52
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