Another Carb question for you gurus

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MoparLvr

MoparLvr

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Ever since my 340 was rebuilt I've questioned whether or not I made the right choice in carbs. Presently it has a 600 cfm Holley but I'm wondering if I should step it up and would I notice a lot of difference. I don't race it per say so not a lot of W.O.T. but I'd like to be able to utilize the engine's full potential on demand.(if you know what I mean). So here's what I have:
69 Dart
340 bored .030 over with KB 243 slugs
10:1 compression
stock 69 340 heads with some mild porting
XE274H cam
TTI headers 2.5 in exhaust
Eddy Airgap intake
A833 4 speed
3:55 suregrip
Any advice would be appreciated.

Thanks
Bill
 
Back when we were kids we use to put stock 440 carbs on stock 340's and you could feel the improvement just by the seat of your pants...
A 600 cfm Holley is a POOR choice for a stock 340 let alone a 340 with a cam and all your hardware. IMHO
 
Thanks for the reply Rob. I kind of got talked into it by the builder ( but my own fault as I should have researched it more). Do you have a recommendation based on my info?
 
My two cents...750 cfm Holley or Demon carb with mechanical secondary and choke if you need it. Or, 800 cfm Thermoquad if you want stock look.
 
Just even going with a 650dp 4777 over the 600 vs. would be a major improvement, if your staying conservative on gears, i'd run the 650dp, or a factory 440 TQ if you can find a good one, just remember though, the TQ can be tempramental but its a great performer once dialed in, I'm a holley guy, so i'll never recammend an eddy, especially when running an aftermarket cam, the 750dp will work, but with 3.55s it won't be the best choice IF you get it to hook up from a dead stop, the 650dp may seem small, but it rips *** pretty darn good & i think you'll be very happy with it.
 
Thanks guys!!! I considered an 800 TQ but with my manifold and the square bore to spread bore adapter I thought hood clearance would become an issue not to mention 71 TQ's are hard to find. I've read that 750 holley is too much for a street driven 340 and my low end would suffer and as I said most of my driving will probably be done in the low/medium range rpms. I guess I'm looking for the best of both worlds. I've got a few more ponies now than before the rebuild so it's difficult to compare but it seems like there should be more seat-of-the pants performance. As you know carbs aren't cheap so if I upgrade I want to do it right.
 
I know exactly what carb you should have...there are two and I happen to have customers that have either one and I'm sure I could borrow both carbs for a week or so.;) You could test drive them...plus I have the carb that's going on Vic's car that you could try also...
But first how much ign do you have ? type of plug wires..ignition box "if you run one"
the more voltage to the plug the more aggressive the fuel curve you can tune into your engine...
 
Rob R said:
I know exactly what carb you should have...there are two and I happen to have customers that have either one and I'm sure I could borrow both carbs for a week or so.;) You could test drive them...plus I have the carb that's going on Vic's car that you could try also...
But first how much ign do you have ? type of plug wires..ignition box "if you run one"
the more voltage to the plug the more aggressive the fuel curve you can tune into your engine...
Click to expand...

I've got mp orange plug wires 8mm (I think). FBO ignition box (close in specs to the mp chrome box). New Mp distributor. I'm afraid I'm not very well versed in fine tuning but I'm trying to learn. That sounds good Rob. What carbs did you have in mind???
 
Bill,

I have a few more comments/suggestions based on your recent responses to others and their suggestions (see below).

MoparLvr said:
I don't race it per say so not a lot of W.O.T. but I'd like to be able to utilize the engine's full potential on demand.(if you know what I mean).
Click to expand...
Your desire for "full potential on demand" is why I suggested a 750 with mechanical secondary. This won't be the best carb for mileage. You will need to regulate your "foot" to get good mileage.


MoparLvr said:
I've read that 750 holley is too much for a street driven 340 and my low end would suffer and as I said most of my driving will probably be done in the low/medium range rpms. I guess I'm looking for the best of both worlds.
Click to expand...
My Demon has 3:55 rear and a close ratio 4-speed with 26" tall tires. With proper jetting, I do not believe a 750 cfm is too "large". But again, your mileage will suffer. By the way my 408 has a 950 cfm Holley and it's a "street" car. But I'm not concerned about mileage or choke.


MoparLvr said:
I've got mp orange plug wires 8mm (I think). FBO ignition box (close in specs to the mp chrome box). New Mp distributor. I'm afraid I'm not very well versed in fine tuning but I'm trying to learn.
Click to expand...
I also run the FBO ignition box, so that’s more than adequate for your combo. Based on all the above I suggest you send your distributor and your complete set of specs (engine, gears, rear tire size, chassis and car weight) and your type of driving to Don Gould at FBO. Have Don re-curve your distributor and build you a Demon carb. Then you can tap into Don’s knowledge to fine tune your combo. In the long run this will save you money.
 
Put two Predators on it on a tunnel ram.
 
Demon 408 said:
Bill,

I have a few more comments/suggestions based on your recent responses to others and their suggestions (see below).

This is exactly why I posted, to get info from guys in the know who have experienced the same situation. So thank you, Demon ,for your comments/suggestions- you have opened my eyes to other possibilities. I do like Rob's suggestion about try before you buy.
Click to expand...
 
MoparLvr said:
I've got mp orange plug wires 8mm (I think). FBO ignition box (close in specs to the mp chrome box). New Mp distributor. I'm afraid I'm not very well versed in fine tuning but I'm trying to learn. That sounds good Rob. What carbs did you have in mind???
Click to expand...


My personal opinion is that you don't have enough ign...I know FBO is a great company and has good stuff but for what I was thinking for a curve it's always going to be fat...
a 750 with annular boosters will work but I'd do something with those wires...any 50 ohm set will bring down the resistance from the average 12000 ohms in your present wire set to 120...that alone will wake up your ign.
You will be fine with any 750...
 
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