6-71 blower and Edelbrock 1405 carbs

[GT63]

Well I gave up on the Crappy Demon carbs. I followed all of Barry Grant's recommendations and still couldn't it to run right. So I switched to Edelbrock 1405 carbs. I had to order the rods, jets, and needle and seats that Edelbrock recommends for blowers. While I'm waiting on that I went ahead and mounted up the 1405s. Engine started right up and idles smooth at 1000 RPM. It still wants to die when I hit the throttle quick and let it return to idle.

Hey RPM, I know you said you followed EB instructions for blowers, did you have to adjust the idle screws any?

Lee from KC, what did you do to your 1405s?

 

[RPM]

Yea you might have to back the idle screws out some, these things like it rich. I think Lee is running a progressive linkage on his, but I have both of mine working together all the time.

 

[Lee_in_KC]

I changed out the rods, jets, springs, float needle & seat and increased the stroke of the pump, all per Edel's recommendations. I also checked the float heights. They were both off quite a bit from the factory.

These carbs don't like any more than about 5# of fuel pressure, so check that carefully. A symptom of too much fuel pressure is the engine will stumble and may even die in a hard turn or stop. I had this problem when I had the fuel pressure at 6#, which was the recommendation in the Edel manual. Edel tech explained that in a hard corner or stop the fuel in the bowl is thrown to the side or front of the bowl, reducing its ability to hold the float up. With fuel pressure too high, it will force open the needle valve and flood the carb, causing the engine to stall.

I just checked my idle screws, and they are out about 1 turn, maybe 1-1/4. I have just a little blower surge at 800 rpm idle. I have the idle screws on the front carb completely closed, just to simplify tuning.

 

[Lee_in_KC]

Yes, I'm using Edel's progressive linkage.

 

[GT63]

Yea you might have to back the idle screws out some, these things like it rich. I think Lee is running a progressive linkage on his, but I have both of mine working together all the time.

Mine is also setup to run off both all the time. As soon as my jets and needles etc get here I 'll re-calibrate them and play with the idle.

 

[RPM]

Mine is also setup to run off both all the time. As soon as my jets and needles etc get here I 'll re-calibrate them and play with the idle.

Oh you have not changed the stuff in the carbs then. That could be a problem. Don't get into boost with those cabs that way cause it is very lean. It could detonate and that ain't purty when does that.

 

[Photoman]

Grant,

I talked to Randy about your tune the other day. This is the friend of mine that runs blowers on everything he has. Been using them for 20+ years on street cars and really knows how to make them run. His recommendations:

1. Set the idle screws for highest vacuum. Like Ron said, they like to idle rich.

2. Set the timing to 36 or so. No centrifugal or vacuum advance.

3. Bump the pulleys to at least 10% under. Running it 18% under makes idle and low rpm tuning difficult. Highly unlikely you'll see more than 5psi or so at 18% under with your combo. He ran a combo almost exactly like yours in a Vega (milder cam and AFB carbs) and it ran great at 10% over on the strip (6.teens in the 1/8th) or 1:1 around town.

4. NGK #7 plugs or Champion RC12YC if you want to run junk plugs that will burn away before hurting the engine.

I realize some of his advice is not the common recommendation, but he sure gets them running good and reliable.

 

[Lee_in_KC]

Yeah, what Ron said. You are running very lean with the stock parts. Gonna melt some pistons if you get on it!!

 

[Lee_in_KC]

In re-reading my big post above, I thought it might sound pretty complicated to change out all the bits and pieces of the carb... it's not. I did both carbs on my kitchen table in about 30 minutes (they were new out of the box, so I had no gas to deal with!). The only tools you need are a medium phillips and a medium flat blade screwdriver and some needle-nose pliers to adjust the tab on the float.

 

[Vegas T]

GT63,
Does the blower cause the car to run hotter than if it wasn't blown? I am trying to get mine to run cooler now without the blower. If I can achieve this, I would like to entertain installing a blower on mine....

 

[Photoman]

VT...you're on the right track getting your cooling system worked out before installing the blower. They will always add heat to the system. Not only are you making more power (more heat) but the friction of the system will add heat also.

 

[GT63]

GT63,
Does the blower cause the car to run hotter than if it wasn't blown? I am trying to get mine to run cooler now without the blower. If I can achieve this, I would like to entertain installing a blower on mine....

I haven't noticed it running hotter even with it idleing in the garage. I have a 180 degree thermostat in it and it jumps up to about 210 then comes back down to about 180. I 'm also running a Walker radiator and my electric fan comes on with the key.

 

[GT63]

Yeah, what Ron said. You are running very lean with the stock parts. Gonna melt some pistons if you get on it!!

I'm not gonna drive it till I get the parts swapped out. I did the same thing to the 800CFM Edelbrock carb I had on the Weiand 142 blower. It's not hard to do, just takes time.

 

[GT63]

Grant,

I talked to Randy about your tune the other day. This is the friend of mine that runs blowers on everything he has. Been using them for 20+ years on street cars and really knows how to make them run. His recommendations:

1. Set the idle screws for highest vacuum. Like Ron said, they like to idle rich.

2. Set the timing to 36 or so. No centrifugal or vacuum advance.

3. Bump the pulleys to at least 10% under. Running it 18% under makes idle and low rpm tuning difficult. Highly unlikely you'll see more than 5psi or so at 18% under with your combo. He ran a combo almost exactly like yours in a Vega (milder cam and AFB carbs) and it ran great at 10% over on the strip (6.teens in the 1/8th) or 1:1 around town.

4. NGK #7 plugs or Champion RC12YC if you want to run junk plugs that will burn away before hurting the engine.

I realize some of his advice is not the common recommendation, but he sure gets them running good and reliable.

I have about 36 degrees of timing in it now. It's at 18 initial and 18 all in at 2800. Thats as far as the MSD calibration kit will let you take it.

I have the new E3 plugs in it. They definitley burn everything in the cylinder.

My vacuum with the stock 1405s is at 18-19 Hg at the manifold and at the carbs. I haven't been able to get it any higher than that.

I have an 8mm pulley setup so I'll have to check out what I need to change it.

I did take the zoomies off, I was going deaf. Lol switched back to sprint headers and 20" side pipes.

 

[GT63]

Grant,

I talked to Randy about your tune the other day. This is the friend of mine that runs blowers on everything he has. Been using them for 20+ years on street cars and really knows how to make them run. His recommendations:

1. Set the idle screws for highest vacuum. Like Ron said, they like to idle rich.

2. Set the timing to 36 or so. No centrifugal or vacuum advance.

3. Bump the pulleys to at least 10% under. Running it 18% under makes idle and low rpm tuning difficult. Highly unlikely you'll see more than 5psi or so at 18% under with your combo. He ran a combo almost exactly like yours in a Vega (milder cam and AFB carbs) and it ran great at 10% over on the strip (6.teens in the 1/8th) or 1:1 around town.

4. NGK #7 plugs or Champion RC12YC if you want to run junk plugs that will burn away before hurting the engine.

I realize some of his advice is not the common recommendation, but he sure gets them running good and reliable.

Looks like I could change the top pulley from a 59 tooth 8mm to a 53 tooth 8mm and get 9.5 under driven. The bottom pulley is a 48 tooth 8mm.

 

[Photoman]

Looks like I could change the top pulley from a 59 tooth 8mm to a 53 tooth 8mm and get 9.5 under driven. The bottom pulley is a 48 tooth 8mm.

I think it's worth a try. Also worth a try is locking the timing at 36 or so. The centrifugal advance can drive you nuts hunting up and down at idle.

 

[Photoman]

Blowers work great on street cars. :lol:

Here's a pic of a good one. This car has the same setup as yours but with a smaller cam and smaller 6-71. Same heads, pistons, carbs, etc.

 

[RPM]

Blowers work great on street cars.

Here's a pic of a good one. This car has the same setup as yours but with a smaller cam and smaller 6-71. Same heads, pistons, carbs, etc.

Do you know what that car runs at the track?:lol:

 

[Photoman]

I think the best was a 6.14 in the 1/8th. He sold that one a few years back. Latest project was a '56 with 502 and 8-71. The customer drives it every day to work. :lol:

Edit to add: That Vega was a fuuuun street car!

 

[GT63]

Re: 6-71 blower and Edelbrock 1405 carbs, Finally got it tuned

Well I spent this morning changing out the needles and seats, jets, and metering rods on the 1405s, changed the top pulley from a 59 tooth 8mm to a 53 tooth 8mm, and readjusted the timing.

She started right up and idled at 950 RPM just as smooth as can be. I adjusted the idle up to 1000 and took it for a little spin. Wow is she a hand full now. Engine pulls strong. I hammered it once and listened for any detonation and didn't hear any. I think I'll drive it like it is for awhile until the blower gears get broke in, etc, At least now all I have to do is tweak on it.

Thank you to all that gave me suggestions. I do appreciate it. :ciao: