edelbrock dual feed fuel line

[tmracing62]

I decided to try 2 600 cfm Edelbrocks and immediately ran into a problem setting it up for the dual inlet fuel lines. How do you get the driver's side inlet plug out? It looks like it should be threaded and identical to the normal (passenger side) inlet. I talked to Edelbrock and the guy told me to drill it out with a 3/8" drill and tap it with a 5/8-16 thread. That just didn't sound right, but since it would not come out, I drilled it. And there's no 5/8"-16 tap so I think he was jerking me around. So feeling stupid, I set it aside so I don't wreck it more. Any suggestions?

 

[Ronnie Russell]

Michael, The Carter book says to drill the hole 3/8 and then tap the boss to 9/16-18 Dont knowwhy this would not work on Edelbrock.

 

[jim_ss409]

I thought I rememberd hearing that the newer Thunder series (AVS style) carbs were already set up for dual inlets, it looks like it in this picture. http://www.edelbrock.com/automotive_new/mc/carbs_acc/thunder.shtml But I think the regular Performer series (AFB style) have to be drilled and tapped. http://www.edelbrock.com/automotive_new/mc/carbs_acc/performer.shtml I'll bet the Edelbrock guy got the size wrong and the Carter book Ronnie mentioned is right. You could compare the threads on the inlet fitting suplied with the carb with an 9/16-18 die just to make sure you end up with the same threads on both sides. I think the dual inlets would be a worthwhile upgrade on a big engine like yours. It might not be absolutely nessisary but the piece of mind might make it worth the trouble.

 

[Fathead Racing]

Plug.

My 600 CFM Carter Competition Plus carb has what looks to be a knock out plug, no threads are evident. Just curious Mike, why did you chose the Edelbrock carbs? I decided to go with the Carter Comp series because the carb body was made from aluminum and the Edelbrocks were allegedly cast from pot metal! No perfomance gain as I know of, may just look better in 5 years.

 

[models916]

both made by weber

I believe both carter and edlebrock are cast of the same material. Carter (Fereral Mogul) is no longer produced. Edlebrock is tumble polished the carter was not. All AFB type carbs on the market today are made in Italy by Weber. Somebody correct me if they know better.

 

[jim_ss409]

I tried the fitting from a new Edelbrock into a 5/8" fine thread nut today just to see how close that was. It almost fits but the threads are wrong. It's close, it actually goes in a few threads but then starts to bind. I don't know how many threads there are per inch on a 5/8 NF nut but I think the carb fitting has a few less. 5/8" is about right though and as for the drill size it's gonna be alot bigger than 3/8".

 

[Ronnie Russell]

Jim, Seems like I remember these figures from my rookie fire dept days. 1971 , memory is terrible today as compared to then. 7 1/2 threads per in. for national standard thread------- 11 threads per in. for pipe thread. I am sure those carb. inlets are a different thread but I dont know what they are called. As far as the 3/8 drilled hole, it only needs to be the size of the fuel line. After all this is an extra fuel source filling a common reservoir. With a 2 4bbl intake and a large gph fuel pump , I cant see an engine emptying two carb. reservoirs in a 1/4 mile run with the stock one inlet per carb. By starting with full bowls and the pump is replenishing at the same time, I just cant see using that much gas. I have never had a fuel starvation problem with 2 4s on a stroker motor, but Michaels motor is probably making much more hp . Just my opinion.

 

[tmracing62]

My 800 cfm is already using the Edelbrock dual feed line setup for the Thunder AVS series and I wanted to use them for this so there wouldn't be a whole bunch to change. It is definitely a 5/8-16 thread banjo bolt. The plug hole is 0.578", perfect for a 5/8" fine tap. It is this diameter deep enough to seat the banjo bolt and the remainder of the plug was the solid part that needed to be drilled with the 3/8" hole. So I found a tap - it is considered a specialty tap - and will finish the setup as time permits in the next week or so. And to be fair, the Edelbrock guy was entirely correct.

I chose the Edelbrock for AFB sentimentality. It's not as tunable as the Holley, but I like the look and did not want to alter real AFBs. By alter, I mean installing air bleeds and other tricks I can't entirely take credit for. John at C&J Engineering in Whittier, CA did the initial mods. I will do the fine tuning. Even though they are 1405 600 cfm, they flow better now. There's enough air.

As for the finish, it looks like they were dipped in silver paint. Ugh. But I sandblasted a roached Edelbrock I got at the swap meet and if it's tumbled it may come out looking like the old AFB finish. Maybe someday I'll try it on these.

Dual lines are not necessary for Lamar's engine. It's been set up both ways and there's no difference. But it was as easy on the pre-tapped AVS as a single so I just did it.

And thanks for all the ideas and info.

 

[jim_ss409]

Oh yea, now I get it. The 3/8 hole is just for letting the fuel in and there's already a larger hole in the casting that just needs to be tapped. The next time I've got the top off of an Edelbrock, maybe Friday, I'll have a look at how the fuel gets from the right, inlet, side over to the left side. I've been wondering if the right side would get most of the fuel while the left side only got the leftovers. I'd expect that both sides should get fuel somewhat equally but I'm not sure. I've got one of these new Innovate wideband oxigen sensors and I've noticed that I get a lean spike right after shifting gears. It made me wonder whether the drivers side is getting enough fuel to refill the excelerator pump cavity under hard exceleration. There's no lean spike when leaving the line, only when shifting. Low fuel pressure might be the culprit in my case though because I've only got a stock style fuel pump. It's a high performance Carter unit but I put a guage on it and the pressure drops to about 2 1/2 psi under hard exeleration. I've read that as long as you stay over 2 psi you're okay but this still seems low to me. But aside from the spikes I've mentioned there doesn't seem to be any problem with it running out of gas before the end of the quarter so maybe an electric pump that would maintain a steady 5.5 psi would be enough, even a more powerfull engine like Michael's.

 

[tmracing62]

There's a tube running straight through so once it is filled, there's no reason one or the other side would get preference unless the needles and seats stayed open for a long time. Then it might divert the most to the passenger side, but even then under 4-5 psi it just couldn't divert that much because it has to make a 90 degree turn into a smaller opening. I guess that could happen with a huge engine at running WOT for a while. I think it's more to guarantee that both bowls are full for the momentary event that one bowl full couldn't keep up. Am I making sense? Maybe not. I agree with Ronnie though - in a quarter mile or in a fairly straight line it's not likely at all that it would require that much gas unless it's a monster engine.

2 psi is iffy at WOT. 4-5 psi is where it needs to be. What is it at idle? You might rebuild your mechanical pump or use an electric pump with a regulator.

 

[jim_ss409]

I guess I was typing while you were posting. I just thought I'd add that I'm going to try to get out to the track on Friday. I ordered a couple of K&N Stub Stacks. http://www.knfilters.com/Racing/stubstacks.htm If they get here on time I'm going to give them a try. I'll let you know if they help or not. From what I can tell some guys gained a bit while others went slower with them. I can't see why they should slow me down as long as I re-adjust the jetting to maintain the proper fuel-air ratio. Also if I get time I'm going to try and coble together a poor mans ram air setup. Kind of like this only uglier. http://www.ramairbox.com/

 

[jim_ss409]

It's a fairly new pump and It's got about 6 psi at an idle. I think I'm going to change over to an electric pump with a return line style regulator this winter though. And I understand your description of the fuel channel. As you said there really shouldn't be any problem. I hadn't really taken a look at it so it just had me wondering.