340 w/ 650 double pumper ?

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Charlie's Dart

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I've always heard a 69 340 with a 650 double pumper performs very well. I've had a thermoquad that when it's tuned right it really moves when I get into the secondaries, but the car mostly sits all year then that thermoquad starts acting up. I've now got a Holley 600 on it now & seams to start real easy & run pretty well but was wondering about the double pumper . I've got the LD340 intake & a 68 Formula s cam & 3:91 gears , stock 10.5 pistons . Any thoughts ??
 
600 is a tad small - get a 650dp speed demon and let it rip. Best carb for a relatively stock 340 on the market.
 
It's a real gas hog, but I couldn't be happier with mine. :headbang:
 
hell I ran a 450 vac sec. on my 60 over 360 and it ran like a raped ape. Would have been better if I had had a 600 on it but still great. 13.94 @ 104 in 1/4. If you do the math on it you only need about 550 cfm if you turn it 5500. So a 600 would still be a little more than you would need by the #'s.
 
Though my example is not a mopar, my experience is that most people over carburet on the street. I am using a 600dp on my Datsun 280ZX. It has a 355 chevy with 9:1 comp. Vortec heads, 510/305 cam, and a modified Performer intake with a 1" spacer. If it is set up correctly, it should work well on a 340 on the street.
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i agree with dustpan my 340 curently has a 800cfm edelbrock and it runs harder at high rpm but its not as responsive as my old 650 dubbelpumper was.. i have also tried a 1050cfm dominator with a adapterspacer and that was even better at high rpm but a real pig runing lowrpm and just cruising...
 
If you have the $ Holley hp carbs are the best. Has no choke but the mettering blocks idle circuits are better so you really do not miss the choke. It comes in DP and vacuum types. I have a 750 DP on my 318 with 3.91 gears and a low gear set up on my 904 trans so first is close to 4.56 gears. Now even then when I had the MSD 6 box I needed to slowly-like 1 good full second-put my foot on the gas all the way down or sometimes it bog a little. I switch to a MSD 7 and now I can just punch it from a dead stop and it justs takes right off if the wheel don't spin. Helps to have a full tank of gas and stay of the blacktop. Some roads are much better than others.

I sometimes-mostly before I got my MSD 7-wish I got a vacuum 750 HP but only at slow speeds in the wrong gear its too big. If you can just buy the carb. I go with a vacuum one or maybe a 650 but you need to be able to burn all that gas the carb will force in it. Wish I would have know sooner how much better a racing spark box would help. Guess thats why they say DP only for racing. You need all the racing stuff, headers, intake and a good strong spark.
 
I have a 360 that I have had a Holley 600, Demon 725 and Holley 750 (all are vacuum secondaries). When I built the engine I had the 600 on the shelf so I put it on. The car ran great but everyone was telling me that I was leaving a lot of power on the table with the 600.

I hemmed and hawed for quite awhile between purchasing a Holley Street Avenger 670 and a BG Road Demon 725. I kind of liked the look of the Demon and enough people told me it would be a good choice I went for it. I fiddled with this carb all summer and could never get it to run well between 1200 and 1800 rpm. Once past 2000 rpm it ran a bunch harder than the 600. Since I use the Cuda as a daily driver in the nice weather and 90% of my driving is in the 1200-2000 rpm range I put the 600 back on.

I even called BG about my troubles and I was told the carb was to big for my application and I should have purchased the 650 Speed Demon vac secondary, never did get any real help to sort out the carb. I compared all the specs (BG does give you all the vital specs on there web page) and it seemed I could convert the 725 to a 650 with only a change of the main body and some jets. Couldn't get anyone at BG to tell me how to order a main body. If anyone knows where I can order a main body let me know I would like to make it a 650.

Couple of weeks ago I sold a 383 long block and took a Holley 750 vac sec (#3310-2) as part of the deal. I was comparing the 750 to the 725 and noticed the 750 had smaller butterflies than the Demon 725 so I threw a quick kit at it, verified the jets were all stock sizes and put it on the car to see how it would run. Made a couple of runs down the street and backed the secondary spring down from the black to the plain and called it good. The car runs just as hard on the top end as it did with the Demon and I am not giving up any driveability or throttle reponse in the 1200-1800 rpm range compared to the 600. Haven't checked fuel mileage or mixture yet but at this point I think I have found the carb I am going to stick with.

FWIW, the car has run a best of 13.7 sec @ 102 mph with a 2.2 sec 60' with the 600. The top end increase with the 750 is very noticable in the seat of the pants so I hope to see something on the order of 13.4s the next time I run it.
 
I hear that Summit Racing is no longer selling Demon carbs anymore--too many bad ones. I think your Demon might be one of those bad units and Demon tech is just saying oh its too big. Not too say a 600 Demon won't give you better miliage--It might--but it still should not act up like that at those rpms. Heck Holley even sells DP carbs where both throttle plates open at the same time same amount.
 
I've got a tuned 750 DP on my built 360... bags power everywhere, starts easy, only gets about 7 mpg! Great to drive but you couldn't use it every day (but we try :) )

My 340 has a Holley 670 Street Avenger. Awesome carb. I tried tuning it on the dyno and couldn't find a thing wrong. Go up one main size, I'd lose 5hp. Go down one main size, same thing, lost 5 hp. Super carb right outta the box. I wouldn't say it's THE carb for a 340 but I've got another car that's a toy... the 340 doesn't have to be right at the top of it's game, I enjoy the drivability instead.

Sean
 
Charlie Double pumper carbs are best for manual tranny cars. You can get them to work on auto tanny cars, but it is harder to dial in. The 650 IMO would be better, but not really worth the money spent.

If the car is not makeing use of a stock air cleaner, I would think about a different route. Try a K&N stub stack and extreme top ontop of as much filter hight you can get under the hood and keep the 600.
Betwen the stub stack helping out in add cfm flow through the carb, the extreme top also allows air to go straight down the carb.
 
Well a friend has 2- 650 dp carbs that he said need a little work but either one is free & I do have a K&N on top already . Another friend sold me a 10.5" convertor out of his 383 he said had a little stall for $20.00 I just need to install it . I wonder if its going to have enough stall ?
 
The more power you have, the more the converter stalls.
Is your engine making more power (Torque) than a 383?
Go and try that 650. Take care on the tune at idle and light throttle.
 
dodge freak said:
I hear that Summit Racing is no longer selling Demon carbs anymore--too many bad ones. I think your Demon might be one of those bad units and Demon tech is just saying oh its too big. Not too say a 600 Demon won't give you better miliage--It might--but it still should not act up like that at those rpms. Heck Holley even sells DP carbs where both throttle plates open at the same time same amount.
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Summit racing is not seeling Demon carbs anymore because Summit Racing couldn't sell them for what they wanted to. For instance Summit was trying to tell Demon WHAT THEY WERE GOING TO SELL THEM FOR......that is BS. While I am no fan of Demon carbs I think that Demon has a right to say what they want their list price to be. Summit also was upset that BG wouldn't give them better pricing than the other distrbutors on the market. Summit no longer carries the entire Barry Grant line not just Demon carbs.

As for the carb suggestion.....I'd run a Holley 750 vac secondary carb...i love mine. I am not a fan of the K&N stub stacks.....every time I have seen them tested on a dyno they cost power.....you'd be better off with a carb main body that has the choke tower removed and is contoured.
 
I am not a fan of the K&N stub stacks.....every time I have seen them tested on a dyno they cost power
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Really! Did the have a good overthe carb clearance? They do require abit of room. I removed the choke plate to get mine to work on the Carter 750.
 
The two times I have seen the dyno numbers were on Edelbrock carbs though....but I haven't heard anything good about the Holley ones either.
 
Well that is not what I seen on the dodgecharger site, and it was from major engine builders. They said in the last 1-2 years Demon could not keep up with demand and they were making and shipping the carbs. without checking them. IDK which is true but summit racing sells $1000 holleys what are the same price on Jegs and others so I am not sure on that price deal. I do know I am staying with holley-heck holley has been making carbs. since 1905
 
I don't know about Demon's QC control...it might be crap. I personally don't like their carbs either and it's probably true about them shipping junk carbs to keep up with demand....but I know for a fact the reason Summit doesn't carry the BG line anymore is because of the pricing issues. I have friends that work there and I used to go to the store every now and then. BG basically wouldn't let Summit bully them into a price break and Summit quit carring the line. Summit wanted to buy cheaper than everyone else and make more of a profit which I really don't have a problem with but I respect BG for standing their ground and saying that everyone of their suppliers is going to get the same price.....keeps the little guy in business too. Summit Racing should watch their mouth anyway cause their Customer Service has a lot to be desired. I for one won't buy **** from them and they are 45 min away from me......I'll drive the 1 1/2 hours to Jeg's anyday.
 
Oh I agree summit service is bad. They do returns great, even refund me more than it cost me to ship the stuff back. I got a set of spark plug wires-MSD super-and I check them all with a ohm meter, 1 wire was like 220 ohms and 2 others the same lenth were like 165 so I bitched. They sent me another set and gave me $10 for me to send the 1 set back, it only cost me $7 so I was happy ! But they are sssooo dumb, don't go asking anything, they either do not know or they tell you the wrong info. I was agruing for a few mins, when the guy told me the MSD 7al is race only and will burn up on the street. Told him I even ok it with MSD tech guys, he kept saying no no get the 6 box. I told him at the end " fine I go somewhere else" he put me on hold for 2 mins and said well the boss said yeah it work fine. It has too for 18 months now. There has been other things too, glad I am not young sometimes.
 
I have a mildly built 360 and just replaced my edelbrock 750 with a 650 Holley DP. The holley is outstanding. I do have a 4spd though.
 
No, but again, a $spd would be easier to use a DP with.
 
I have had good luck with small carbs on a 340. I ran a 650 double pumper and a Eddy 600. Bolth had great throttle responce and derivable. This was on a low compression 340 with a LD340 intake and a set of headers. My new 340 is a little wilder and is running a 830cfm Proform carb
 
Just came across my old thread , still not sure if I should run the DP, any more thoughts ? That old Thermoquad sure ran well !
 
I run a 11:1 340 with an isky 510 solid, M1 single plane, 727, 3.91's and a 3200 stall with an 850 dp. on the street and it works fine for me. The vac sec carbs tend to be better for the automatics and better for street driving. I did have a 3310 (750 vac sec) on it at one point with a 484/284 cam and 323's with stock converter, same M1 and it worked ok except when it was hot (100 plus) outside. Tended to flood easier, once I installed a heat shield it took care of that problem. Would start fine and everything but gas mileage was down compared to a smaller carb. Didn't lose much (maybe 1 or 2 mpg) going with the solid cam, converter, gears and the 850. Really up to you but I wouldn't go higher than a 750 on a pretty much stock 340. And no Double pumpers if your worried about flooding some times and lower mileage. 650 if it's all stock.
 
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