Hello, I was wondering if a holley 850 HP would be too much carb for a 70's 460 with a full performance exhaust with headers and a weiand stealth intake. I have access to a 650 double pumper if the 850 is too much what are your guys opinions? Also I am using a 3.73 rear gear.

 

For street I would say yes a 750 CFM would be better but "I" think the 650 CFM would be too small even for street.
Then again the 850 CFM would be OK if the 460 is a drag motor.
Maybe someone that runs 460's may say the 650 would be a great carb for the street?
Dave ----

 

The Holley 850 HP is a double pumper without choke. That is not a good carb for street use.
A carb anywhere around 750 to 870 cfm is fine for a 460 with performance upgrades - but you want a carb with vacuum Secondaries. A Double Pumper is never a good idea on a street use build.


A choke is not required (especially if you live in a hot climate) but it does make startup and warm up easier.

 

I agree, avoid the double pumpers, especially on a heavy truck. Unless you want to "nurse" the throttle each time you want to open the throttle up. Double pumpers are best on lightweight vehicles. Like was said, get a vacuum secondary carb. The size is not as critical then, it will "size itself" to what the engine can take with the vacuum secondaries.

 

Thanks for the reply guys, I only have access to a 650 DP or the holley HP 850 or else I would consider a non double pumper. My current carb is a edelbrock 1406 600 cfm with vacuum secondaries and it falls on its face above 3000 rpm.

 

What cam are you running? Have you changed to a straight up timing set? What heads and any port work?

My 460 has ported E6TE heads (basicanlly D3VE), straight up double roller, Weiand Stealth, long tubes, Comp 262/270 (34-235-4), and a Holley 750 double pumper. I'm very pleased with how it performs. It's a torque monster at any RPM. Truck weighs 6000 lbs and is on 35" tires, no issues with driveability with the double pumper. I'd wager those in this thread saying to avoid a double pumper have never driven one either in a similar vehicle or at all.

I had a 650 4160 vacuum secondary on this 460 originally and while throttle response was very crisp down low it required a lot of throttle to get going and felt like it should make more power overall. Once I swapped to the 750 CFM 4150 double pumper it had more power all around though maybe a little less crisp off idle. Still, by no means does it feel mushy or unresponsive down low. Yes, if you mash it to the floor at 900 RPM in 4th gear putzing around town it'll accelerate more slowly than if you roll into it. That's normal and to be expected when you lug the engine, though this torquey engine doesn't really "lug" per se. It's worth noting this truck has a manual trans, so there's no revving up against the converter.

If your engine is a stock smog era 460 as it sounds like it is from your description the 650 would be fine and may be the better choice. If you plan to get more power from it eventually the 850 may be the more prudent choice. I have an 850 double pumper on a stock-ish marine 454, probably only putting out 350-360 HP. I think the holeshot would be nicer with a 750, and with the 850 the last bit of throttle makes no difference in performance, you just hear the tone of the engine change. Because marine parts are $$$ I ended up going with the 850 since a 750 marine double pumper is more expensive for some reason. How a low output marine 454 compares to a smog era 460 I'm not certain, but I'd guess the 454 makes a bit more power.

 

Its got a stock cam as far as I know and the crappy stock d2veaa heads which I plan on getting a set of dove heads. I'm not sure about the timing set is there a way to tell? The engine is a d1ve block. Also my truck weighs a little under 5000lbs with 33 inch tires. I also have a weiand stealth I would be putting on with the new carb.

 

I see no use for an 850 on a street driven vehicle....much less a double pumper. Do you plan on driving at 5-6000 rpm about 90% of the time? Id work toward your 460 having some healthy torque at lower Rpms...short duration and overlap, good manifold vacuum, vacuum secondaries....proper jetting...I must have missed it what rear end ratio do you have?

 

This is true I have never owned one.

 

I think the engine falling on it;s face after 3000 RPM is more a function of the heads and cam than anything else. the D2VE heads were the worst 385 heads made in terms of performance.

 

A DP carb can be used on the street in a stick car/truck, autos work better with vacuum carbs.


Being both carbs (650/850) are DP I would go with the 650 as said the throttle will be more crisp down low were the motor will be most of the time on the street.


I had that same issue, crisp, off the line with a 650 HP & 750 HP on a 360 cid drag motor. The 650 felt more crisp off the line but both had the same ET and being lazy I left the 750 HP carb on.
Dave ----

 

It really comes down to tuning. A DP needs more setup/tuning to the "specific vehicle" to get it right. A VS is more forgiving since the secondaries open based on engine load rather than throttle position.
If your good with carbs, a DP is fine - but I would recommend a VS carb first over a DP for street use for a guy with average mechanical/carb knowledge.


Regarding low end performance only, I think to compare a 650 to 850 you need to be comparing the primary throttle blade sizes and jetting.

 

You also have to look at the air bleeds, booster type, etc. between the 2 not just the primary throttle blade sizes and jetting.
Could also have 4 corner idle mix adjusting.


If both HP carbs are the newer type he might be able to adjust the bleeds to dial it in better but I still think he would be better off with the 650
Dave ----

 

I am not changing my mind. A double pumper was not designed for street use on a heavy vehicle. Yes you can run it, but it's not going to be a very friendly setup, being very aggravating to drive. It will be one of those "drive it like you stole it" setups, keeping it revved up to avoid the large bog when all 4 barrels open at once.

 

I don't think I would run a DP in a heavy vehicle either but I don't see a "large bog when all 4 barrels open at once" then it is not set up right.
Beside a carb is not just idle & wide open you know?
If you are slamming the carb open and getting a bog I don't think you are driving right.
Dave ----