Mopar Muscle Association UK

db wrote:Would my fuel system cope with the extra thirst of an 850dp?

No probs, Mick with the 440 Dart was running a 950 through 3/8" lines at 10.2's!!!!, I believe you have a good BG pump?...that should be ok.

My set up was a Holley blue pump with 1/2" lines up to the reg and then normal 3/8" rubber fuel lines to the carb.

As I said earlier, you''ll have more power/torque with the carb in the skies and a very crisp instant throttle response once set up right so you won't need to nail it half as much to do what you want...more air does require more fuel technically but its how you use what you have that counts and if its 99% street, you'll be on a winner db.....might cost you a bit more in rear tyres though!!!

I did actually try a smaller carb as everyone kept telling me an 850 was too big....it was naff and went slower.

Les

Of course wanting one and getting one are two different things... I've just scanned ebay, ebay.com, r'n's, eurodragster and the ain't one single 850dp for sale!

Doesn't totally have to be an 850....800DP is ok, just that if your gonna spend ££'s you might as well go for it...maybe even a used 950?...don't know how that would run as didn't have them back in my day but if I know SB's it would be fine with proper jetting/sorting.

I did have a 1050VS 3bbl Holley on mine for a short while, never seen another since.......was ok on the street, took it down to the Smoke City Wheelrs pub one night and they all thought I was off my head!!....it was crap on the launch but pulled well top end.

No rush though, one will turn up....at least you know the set up that should wake your car up nicely.

Les

870 is a cracking carb too!
Potentially less risk of bore wash too

What now? What's bore wash?

There's an 800 on eurod. for £80, but I've just been offered a loan of an 850

just one thing though and it goes without saying......Do Not try it until you got your total timing sorted to no more than 36 deg total.


les

db wrote:What now? What's bore wash?

Dumping in more fuel than you can burn, the bore wash relates to the excess fuel washing away oil from rings . . . Over fuelling can be just as detrimental as too lean. Think dominator on you lawnmower


If really excessive, it can go past rings & I to the sump, diluting the oil. Don't be concerned, for this to happen, you need Bananarama! loads of too much fuel

Stick with the 750.

A carb only flows the air and fuel the engine demands of it. Except for the pump shot.

Your engine will demand a certain volume of air. It will take that amount of air no matter what size carb you have. The air will just flow faster through a smaller carb and slower through a bigger one.

If the carb is on the small side the engine will respond better on the throttle. The fuel metering on the carb will work much better as the jets etc get a very strong signal. Mixture will be better and the fuel in that mixture will remain in suspension as the air velocity is higher.

The down side of too small a carb is at very high rpm. Athough a small carb will flow enough air at lower rpms, it does not have time to flow enough air at high rpms. Air has a certain mass and therefore inertia. It takes time to accelerate/deccellerate it.

A big carb will cope with high rpm very well. But at lower rpms you will have a poor signal to the fuel circuits. Also fuel will drop out of suspension and run down the sides of the intake runners. Making cyinder to cylinder variations in fuel mixture. Also fuel does not burn as well as it starts to drop out of suspension and form larger droplets in the air. Usually with a big carb you have to run it richer too to get around it's poor low rpm performance. You CAN make them work on a street car but not as well as a smaller carb.

The 750 carb a good all round size for a 340. Stick with it.

I ran a 750 DP with a 4 speed and it was sound as a pound.......

Paul

If you have 50 deg total timing I wouldn`t run it until you take some out as it is likely to go bang.

The absolute max I have ever run was 42 ... AND THAT WAS WAY TOO MUCH.

The best results I ever had on pump gas, alli heads, similar CR to you was


750 DOUBLE PUMPER - STOCK OUT THE BOX.
76 / 76 JETS.
34 DEG TIMING ALL IN.


Every set up will be different but that worked for me.

have you thought about a 600 vac sec that will tune real nice on your idle and good throttle responce,
also a 650 double pump will work real nice with your spec

Jon Connolly wrote:Paul

If you have 50 deg total timing I wouldn`t run it until you take some out as it is likely to go bang.

Wow, I must of missed that or my brain mis scanned info & disregarded 50 Degrees.

or a 1050 dommie will be sweet at the track for top end charge but you will have to keep revving it to clear its throat before lauch,

another alternative would be a nice six pak set up great for cruise and a blast on full throttle