Edelbrock 1404 or Holly 390
Hi,
MGB GT V8 SD1 Engine Engine fully rebuild with new parts, piston rings, new oil pump, Piper 285 cam, new followers and suitable valve springs, new Vitesse clutch, Peter Burgess Stage 2 heads Offenhauser inlet manifold, Mallory Dual point distribitor, Jan speed exhaust system with one rear silencer and Edelbrock 1404 Carb. The reason why I am changed from Holly 390 to Edelbrock was the period when the primary change to the secondary’s was the power during acceleration shortly stopping for a short time and that give a bad feeling when you drive the MG, I try to change a lot of things on the Holly and it slightly improved but not to my satisfaction to be honest! I have now changed to the Edelbrock and the idle is much better and the car drives much smoother in town. The bad point is that I have the feeling that the car was much quicker acceleration when you give her a hard time at traffic lights with the Holly and I have also now a misfiring at high rev (6000 rpm) what I never had with the Holly. Can someone give me an advice what can I do the make the carb in acceleration better and what can cause the misfiring at high rpm. I have checked the timing and I have 8° before. For me it looks like the car get not enough fuel at the top range of power and also during acceleration but this is only my guess! I hope that i get few tips what can I do? Thanks a lot! Volker |
Re: Edelbrock 1404 or Holly 390
Hi Carl,
I use a Fact Red Top with a pressure regulator and I use 5.5 psi fuel pressure, with the Holly I used 4 psi feuel pressure. Cheers, Volker |
Simon Austin Simon Austin Surrey, British Columbia (107 posts) Registered: 10/23/2007 01:44AM Main British Car: 1977 MGB V8 / 1970 MGB GT V8 project Rover 3.5 / Rover 3.5 |
Re: Edelbrock 1404 or Holly 390
Are you using the Edelbrock straight out of the box? I installed mine (on a 3.5) and found it way too rich. Since then, I've changed the jets/needles over to the following:
primaries: .080" (#1421 part number) secondaries: .086" (#1423) needles: .062" x .052" (#1441) I have to deal with annual emissions testing so I had to get the carb as lean as possible yet still run properly. RPI Engineering in the UK suggested the part numbers above for the primaries and needles (they don't touch the secondaries). Here's a link to a discussion on another forum about re-jetting the Edelbrock that you may find helpful: [www2.mgcars.org.uk] |
Re: Edelbrock 1404 or Holly 390
Hi Simon,
Yes I used the Edelbrock straight out of the box! I have no problem with emission test in Germany because I have a red no plate for classic cars and those cars don't need the emission test at the moment. I will try your suggestion with the different parts. Do you thi nk when the car is to rich then you get a miss fireing at high rpm? I thought always is a miss fireing a weak mixture? Thanks for your help so far, Volker |
MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: Edelbrock 1404 or Holly 390
Yeah, that's why I asked about the fuel pump. My stock MGB fuel pump couldn't keep up. You weren't running quite enough pressure on the Holley. I believe they recommend 5-7 psi. I always set my 750 double pumper on my Camaro right at 7 psi. Your 5.5 psi on the Edelbrock is right on the money.
For seat of the pants flooring the gas pedal, well, there's reason why Holley (or Holley clone) is the dominant choice in drag racing. A phenolic spacer between the carb & intake seems to be more important on the Edelbrock/Carter than on a Holley. Most of us Buick/ Rover V8 guys rejetting the Edelbrock/Carter carb leave the secondaries alone. I would double check the ignition system for that miss. |
Simon Austin Simon Austin Surrey, British Columbia (107 posts) Registered: 10/23/2007 01:44AM Main British Car: 1977 MGB V8 / 1970 MGB GT V8 project Rover 3.5 / Rover 3.5 |
Re: Edelbrock 1404 or Holly 390
[www.edelbrock.com]
According it the Edelbrock Manual (page 23 in the above link), too lean, low fuel pressure, air leaks, ignition issues, choke adjustment can all cause misses or surges. If you can get the car onto a dynomometer (rolling road), this is the best way to check things out. I've done this with my car and this helped me get it tuned properly. I'm running an electronic SU pump and haven't noticed any issues with this. For my ignition, I'm using a Buick distributor, Pertronix ignition and an MSD ignitor. The MSD was suggested by the dyno technician to help clean up emissions. Arguments either way as to whether these units are that effective on a street car. |
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Re: Edelbrock 1404 or Holly 390
Hi Simon, Hi Carl,
The ignition is ok because I have nothing changed on the carb! I changed after the first missfireing the distribitor to a new Mallory dual point one and a Mallory coil with new leads and the missfirering was still there and it looks for me that the varb is the reason for that! I am not sure about the fact that the Holly got 390cfm and the Edelbrock 500 cfm because for the Buick 215 is the 390 cfm the right volume, it mid be that the Edelbrock get to much airlow in the engine and not enough fuel with him under full power? Any were I will try a few things with different seting when I get in the next few days the tuning kit here in Germany. If some elese have a good suggestion please let me know! Cheers and than ks, Volker |
Re: Edelbrock 1404 or Holly 390
Had a similar high RPM mis and it was the voltage to the coil with the ignition in the run position. The voltage was being dropped through a resistive wire left over from the original MG electrical system. Bypassed the resistive and I eliminated the mis.
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castlesid Kevin Jackson Sidcup UK (361 posts) Registered: 11/18/2007 10:38AM Main British Car: 1975 MGB GT Rover V8 4.35L |
Re: Edelbrock 1404 or Holly 390
Just a thought, if you are using standard hydraulic lifters, they start to pump up at approx 5800RPM or earlier if you have too much lifter preload, and it would be easy to think that this was a missfire. Also if you are running standard rockers and shafts 6000RPM is the safe limit, as the unsupported ends of the rocker shafts are prone to snap at higher RPM. End supports are available to cure this problem.
Kevin |
Re: Edelbrock 1404 or Holly 390
Hi Kevin,
I am sorry for the late reply but I am just now in Bangkok after a week in Taiwan and I had not much time to read all my mails! Any were I am not sure if this is the problem because with the Holly was the misfireing not there! It would be nice when you can send me some information about the "End Supports" I have never heard about these thing! I have the new hydraulic lifters from RPI and they are suitable for the Piper 285 cam and this cam is a cam for high rev's and they also supplied the new suitable valave springs for the high rpm. I am looking forward to see you information about the end supports, Cheers and best regards from Bangkok, Volker |
Re: Edelbrock 1404 or Holly 390
I think these are the "End Supports" he is talking about. A company called J.E. Developments calls them “Rocker Posts” and sells them on their website, [www.rover-v8.com].
Others may sell them as well. They are discussed in the book “How to Power Tune Rover V8 Engines For Road & Track” by Des Hammill. |