Which Carb. For 408?

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321Scamp

321Scamp

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I have been looking at different 408 builds and have seen a range of carbs that are used. I have seen 650-750 being used. My question is.. Which one is the best one. When i get to my build it will have the XE274 comp cam, 2.02 1.60 heads and should have in the area of 10 to 1 compression. I have a 600 cfm on my 318, but i think it will be too small for the 408.

Whats your opinions?
 
321Scamp said:
I have been looking at different 408 builds and have seen a range of carbs that are used. I have seen 650-750 being used. My question is.. Which one is the best one. When i get to my build it will have the XE274 comp cam, 2.02 1.60 heads and should have in the area of 10 to 1 compression. I have a 600 cfm on my 318, but i think it will be too small for the 408.

Whats your opinions?
Click to expand...

A 750DP Holley will work great. Best carb for the $$$!
Brian
 
Will this be an auto or manual? I thought DP's were only good for std transmisions??? Arent DP's too much for an auto? Maybe w/ a really loose converter and tall gears, but I'd go with a 770sa vac sec if it were me. I was on the fence of 670 and 770 too, so I just bought both. The 570 on my 318 was shot so I replaced it w/ the 670 and now have 770 for my 408 if when I try the 670 and it dont work. Not the cheapest rout but atleast I'll know which one I'll need.

I did notice a loss in throttle response and torque from the 570 to the 670 and didn't gain any top end on my teener. Then again its basically all stock other than a RV cam, performer intake and 2.5 dual manifold exhaust so its a lil restricted with the stock heads. either way you should be happy w/ a 750/770 and have a lil room to grow if need be in the future. Just my .0002 cents :)
 
mopar4x4stroker said:
Will this be an auto or manual? I thought DP's were only good for std transmisions??? Arent DP's too much for an auto? Maybe w/ a really loose converter and tall gears, but I'd go with a 770sa vac sec if it were me. I was on the fence of 670 and 770 too, so I just bought both. The 570 on my 318 was shot so I replaced it w/ the 670 and now have 770 for my 408 if when I try the 670 and it dont work. Not the cheapest rout but atleast I'll know which one I'll need.

I did notice a loss in throttle response and torque from the 570 to the 670 and didn't gain any top end on my teener. Then again its basically all stock other than a RV cam, performer intake and 2.5 dual manifold exhaust so its a lil restricted with the stock heads. either way you should be happy w/ a 750/770 and have a lil room to grow if need be in the future. Just my .0002 cents :)
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There,s a big diference between a 318 and a 408 HP wise.I run a 850dp on my 408,runs in the 10,s.
 
If your build is mild (and running basically stock factory heads I'm assuming it is) then the typical 750 or 800 Holley or Edelbrock/Carter would be fine. They will need to be tuned for your combo. But they'll work fine. Most strokers will benefit from a larger carb than normal sizing recommendations because the engine acts like a much larger engine than it really is in terms of the physics that makes a carb work. I use vacuum secondaries on street cars and my smallest starting point is a Holley Street Avenger 870.
 
Listen to the ones with experience, (that leaves me out) but, I just took my 750 DP Quick fuel off yesterday and replaced it with a Davinci 950cfm square, NO power valve,(flows over 1000cfm came off a 9 second 427) on my 422 10.5:1 CR and it cold started and idled like it was running for an hour. went out and (no sticky tires yet) got on it and had to let off the gas at about 50mph cuz the tires were still spinning and I didn't want to ditch it. I haven't done any tuning yet but just shows me that there are many options. I am guessing my gas mileage will suck but I didn't build the car for gas mileage, I built it for fun. anyway, for what it's worth. best of luck. Oh, I have a like new QF 750 for sale.
 
I would use a 750dp for a mild build (streeter) or a 950dp for something more race oriented…..of course I’m being totally hypocritical because I’m using a heavily worked over 750dp in my car (see sig below)…but only because I don’t have the coin for a 950 or 1050. One of these days I’ll spring for a better carb, just not anytime soon.:glasses8:
 
For the $, hard to beat the old holley 4779 - 750dp at $400.

The HP series carbs are better, but, also cost 250-400 more. It's like some other issues with headers, might one make 3-8 more hp, yes, is it worth the extra 200-500, not really IMO.
 
Cubic inch times max RPM divided by 3456. Mine was 416 times 7900 rpm divided by 3456 equals. 950.92592. Equates to 950 cfm. I'm using a 1000 cfm carb. A 408 times 7200 rpm divided by 3456 equals 850. Holleys web site has a carb calculator Same numbers used.
 
also one thing to take into concideration is Headers.
600-750 1 5/8" tubes
750-850 1 3/4" tubes
850-950 1 7/8" tubes
950up 2" tubes
You can't take in more than you can get rid of. RPM's play a cridical role in carb selection. a 440 at 6000 needs a 750. a A 340 at 7500 also needs a 750
 
i've run an 830 dp and it ran great on my 416 w2 headed motor. car ran mid 7.40's in the 1/8. went to a tunnel ram with two 660's and and ran 7.36's with a 3 mph gain. ran two 450's and ran 7.38's down 2mph. this a solid lifter cammed motor with 10.5:1 comp. it's not a radical engine and can be driven on the street . i'm also running a 4spd so it helps street driving. it all depends on what you want to do. the 750 dp and the carter/edelbrocks work well also. mine is a pure performance aspect. i don't care about fuel economy hence the tunnel ram. at the very least run a single plane manifold, an old holley strip dominator will do the trick, if you decide to run a dual plane you will not be happy with the performance. the motor will feel like a tractor, especially if you're running a stock style head ie x or j head. remember when you build a motor like a stroker smallblock you have to increase the breathing of that motor because when you're 408 is at 5000rpm it's like a 340 at 6800rpm. just a few things to think about hope this helps a bit
 
Thanks for all the input. It will be an auto trans with 3.55 SG. Going to be a street build that will be driven like a car should be. :burnout:
 
Man, I saw a few 750 quick fuel annular booster carbs with choke for like 450.
I wish I remembered where they were...would probably be awesome on your setup.

I went with a mighty demon 750 with annular boosters and a few other tweaks.
 
The 3310 with a secondary jet plate would be ok for that. For the most of your driving smaller's fine. It's when you race or wind it up that you're leaving power on the table and being honest with yourself you have to wonder how often you'll be doing that...lol.
 
What Moper said. While I agree with alot of suggestions here, no one actualy asked gears and type of driving to be done. Are you concerned with top end power if your only there once in awhile? Are you competeing for cash? Are you worried about what others say when you answer the question. (Screw them!)

The smaller carb will ofer crisp throttle response and great mid range torque. Leaveing a few poines on the table at top end for a streeter is not an issue. Or is it to you?
 
FWIW, I went with a Thermoquad on my 408. Excellent throttle response, 14+mpg on hwy @ 65-70 mph through a 4000 stalled 727 into a 3.73 dana. Best time is 12.09 @ 110 (7.696 @89 mph), about 0.15 better than my best time with the Holley 750 w/proform center, which got 8 mpg hwy, BTW. 73 Duster, ~3400 lbs without me.
 
Sounds like you already have plenty of good advice here but I can tell you from my own experience. I had been using that same XE274 cam in my 340/416 with stock X-heads, 4 speed and 3.91 gears. I experimented with a few different carbs and the Holley 750dp was just the best choice. It even worked fine when I had changed over to 3.23 gears for a trip out to Carlisle.
 
I have a very lightly used QF 750 Mech Sec I'll let go for $495 Shipped.
 

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rumblefish360 said:
What Moper said. While I agree with alot of suggestions here, no one actualy asked gears and type of driving to be done. Are you concerned with top end power if your only there once in awhile? Are you competeing for cash? Are you worried about what others say when you answer the question. (Screw them!)

The smaller carb will ofer crisp throttle response and great mid range torque. Leaveing a few poines on the table at top end for a streeter is not an issue. Or is it to you?
Click to expand...

Yea, it will just be my cruiser. When you say smaller, you mean the 750?
 
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