Need Carb suggestions for 406ci engine
Thread Starter
Instructor
Joined: Sep 2004
Posts: 184
Likes: 0
Need Carb suggestions for 406ci engine
Got a 406ci engine on the way from AR Racing. It uses Canfied heads, and is supposed to have almost 500hp/torque.
I talked with Mark at AR Racing and he recommended a 750 cfm Demon with vacuum secondary.
However, the guy who is putting the engine in recommended a 750 Demon with mechanical secondary.
Can you guys give me suggestions as to what carb I should run, either between these two or any other carb out there?
Also, I had an Edlebrock carb on an old mustang of mine. Whenever I would take a corner fast it would die. I believe it is because it was based on an old design and the fuel would splash around in there and the engine would starve. Do Demons and/or Hollys have this problem?
Thanks!
I talked with Mark at AR Racing and he recommended a 750 cfm Demon with vacuum secondary.
However, the guy who is putting the engine in recommended a 750 Demon with mechanical secondary.
Can you guys give me suggestions as to what carb I should run, either between these two or any other carb out there?
Also, I had an Edlebrock carb on an old mustang of mine. Whenever I would take a corner fast it would die. I believe it is because it was based on an old design and the fuel would splash around in there and the engine would starve. Do Demons and/or Hollys have this problem?
Thanks!
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Originally Posted by Homie
Got a 406ci engine on the way from AR Racing. It uses Canfied heads, and is supposed to have almost 500hp/torque.
I talked with Mark at AR Racing and he recommended a 750 cfm Demon with vacuum secondary.
However, the guy who is putting the engine in recommended a 750 Demon with mechanical secondary.
Can you guys give me suggestions as to what carb I should run, either between these two or any other carb out there?
Also, I had an Edlebrock carb on an old mustang of mine. Whenever I would take a corner fast it would die. I believe it is because it was based on an old design and the fuel would splash around in there and the engine would starve. Do Demons and/or Hollys have this problem?
Thanks!
I talked with Mark at AR Racing and he recommended a 750 cfm Demon with vacuum secondary.
However, the guy who is putting the engine in recommended a 750 Demon with mechanical secondary.
Can you guys give me suggestions as to what carb I should run, either between these two or any other carb out there?
Also, I had an Edlebrock carb on an old mustang of mine. Whenever I would take a corner fast it would die. I believe it is because it was based on an old design and the fuel would splash around in there and the engine would starve. Do Demons and/or Hollys have this problem?
Thanks!
800-850 HOLLEY.
Mechanical secondaries (manual or auto) for a car that goes to the track. Vacuum secondaries (manual or auto) for a car that spends all its time in the street.
Thread Starter
Instructor
Joined: Sep 2004
Posts: 184
Likes: 0
800-850? Wow.
I was looking at a speed demon at jegs, and saw it was rated for like 427ci or bigger engines. Their 750 was rated to cover engine sizes well over 406ci.
Why are all yall going the 800-850 route? If 750 will flow enough air to cover the engine needs, won't an 800/850 give a little worse throttle response?
Thanks again.
I was looking at a speed demon at jegs, and saw it was rated for like 427ci or bigger engines. Their 750 was rated to cover engine sizes well over 406ci.
Why are all yall going the 800-850 route? If 750 will flow enough air to cover the engine needs, won't an 800/850 give a little worse throttle response?
Thanks again.
Pro
Joined: Oct 2004
Posts: 510
Likes: 5
From: Pipe Creek TX
A 500 hp 406 doesn't lack low end torque or response. It will use about 730 - 780 cfm at peak power of around 6200 rpm.
Carbs are rated at 1.5 hg.
The vacum at 6200 rpm will be 1.5 -2.0 hg with a 750 carb. A 850 carb will have less restriction , giving 1.0 -1.5 hg resulting in a power increase of 25-35 HP on a 406 . Anytime you can decrease engine vacum at wide open throttle , you will increase power.
The mistake alot of people make is to over carb a base engine like a L-48 ;that the carb is not the restriction; the intake and heads are the problem.
Carbs are rated at 1.5 hg.
The vacum at 6200 rpm will be 1.5 -2.0 hg with a 750 carb. A 850 carb will have less restriction , giving 1.0 -1.5 hg resulting in a power increase of 25-35 HP on a 406 . Anytime you can decrease engine vacum at wide open throttle , you will increase power.
The mistake alot of people make is to over carb a base engine like a L-48 ;that the carb is not the restriction; the intake and heads are the problem.
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Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Originally Posted by Homie
800-850? Wow.
I was looking at a speed demon at jegs, and saw it was rated for like 427ci or bigger engines. Their 750 was rated to cover engine sizes well over 406ci.
Why are all yall going the 800-850 route? If 750 will flow enough air to cover the engine needs, won't an 800/850 give a little worse throttle response?
Thanks again.
I was looking at a speed demon at jegs, and saw it was rated for like 427ci or bigger engines. Their 750 was rated to cover engine sizes well over 406ci.
Why are all yall going the 800-850 route? If 750 will flow enough air to cover the engine needs, won't an 800/850 give a little worse throttle response?
Thanks again.
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
I would think a 750cfm would work well. Going to an 850 will more than likely add a few ponies to the top end. I don't think it would add more than 5hp but if you're looking for a little tad more hp and you have to buy a carb, then that's the way to go. I think the 750 will be a better choice if the thing is almost always going to be on the street.
AR may have tested different carbs and perhaps that is why they are recommending a 750 vacuum secondary carb.
AR may have tested different carbs and perhaps that is why they are recommending a 750 vacuum secondary carb.
Thread Starter
Instructor
Joined: Sep 2004
Posts: 184
Likes: 0
Shucks, seems we got a 750 versus 850 problem.
Have magazines ever run tests and compared the two on a 406 engine to conclude that you get more HP up top?
Oh yeah, why do some of you guys suggest Holly over Demon? Any problems with Demons?
Also, can anyone comment on whether Holly/Demon carbs will cause the car to stall in a tight turn do to fuel distribution problems like an Edlebrock carb will?
Thanks.
Have magazines ever run tests and compared the two on a 406 engine to conclude that you get more HP up top?
Oh yeah, why do some of you guys suggest Holly over Demon? Any problems with Demons?
Also, can anyone comment on whether Holly/Demon carbs will cause the car to stall in a tight turn do to fuel distribution problems like an Edlebrock carb will?
Thanks.
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Originally Posted by Homie
Shucks, seems we got a 750 versus 850 problem.
Have magazines ever run tests and compared the two on a 406 engine to conclude that you get more HP up top?
Oh yeah, why do some of you guys suggest Holly over Demon? Any problems with Demons?
Also, can anyone comment on whether Holly/Demon carbs will cause the car to stall in a tight turn do to fuel distribution problems like an Edlebrock carb will? Thanks.
Last edited by The Dude; Oct 5, 2004 at 05:56 PM.
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
I think that a 80528 Holley would be the best choice... That's only a 750 cfm carb but it should be enough to feed your 406.. I personally don't like vacuum secondaries carbs at all.. I initially ran a vacuum secondaries 750 Holley on the engine and had over 20 RWHP less with the vacuum secondaries carb compared to my 80528 that's currently on the engine... I've had mech. secondaries carbs on most of my C3's and never had any issues with streetability.. If you want performance - mech. secondaries are the way to go!
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I had a Holley 750 DP ( mechanical secondaries ) and a Victor Jr. single plane intake on my warmed over 355ci L48 and it ran great, so that's why I went with a 850 DP on the 406ci
Drifting
Joined: Nov 2002
Posts: 1,951
Likes: 1
From: Shore NJ
Originally Posted by Gordonm
A 750 Demon should be all that motor needs. The Demon carbs actually flow better than what they are rated for. So a 750 flows into the 800+ range. I would go with mech. secondaries
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Originally Posted by Homie
Some of you guys say vacuum secondaries is the way to go on the street.
Lemme ask yall this: Do stock quadrajets come with mechanical or vacuum secondaries?
Thanks.
Lemme ask yall this: Do stock quadrajets come with mechanical or vacuum secondaries?
Thanks.
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Originally Posted by Fevre
According to Lars they have mech sec with a check valve (or something to that affect but def mech sec).
Last edited by The Dude; Oct 6, 2004 at 01:30 PM.