Ok, I am planning to put a 2004R in my 67 Skylark 340-4. The motor is stock (for now), and I'm looking at the TV Made EZ from Bow Tie Overdrives. Since I need to take the carb off I am considering a replacement. It's a Carter carb and I would like the swap to be fairly easy. I know Buicks like Big carbs and am wondering which route to go Edelbrock or QJet? And what size is recommended for a 340? I know Edelbrock just released a newer Performer series carb and they have larger cfm's too. Any suggestions? BTW, in the future the 340 will be rebuilt and hopped up a little but nothing radical as it will be more of a cruiser. Thanks!
Well, being the Carter is a square bore carb, I suppose the Edelbrock would be your best bet. Go with the new 800(EPS 800). Your stock carb should be an AFB or AVS, the Edelbrock will probably be the best match. Just my .02
I have an Edelbrock Performer 600 on my 340. It operates great. But, all the linkages have to re-worked. Even the stock air cleaner won't fit. So, expect to do some fabricating if you buy one. 800 cfm seems like a lot of carb for a 340. Check with some more opinions before getting one over 600. What is a TV made EZ? I have a 200-4R, but am not familiar with that product. Back Again - checked their website. Looks like a good kit. Just be sure to read and follow the instructions carefully.
Guys, thanks for the replies! So I guess now the question is what size Edelbrock should I be looking at for my 340? 600 cfm or 800 cfm? Like I said, the motor is stock except for a Pertronix Ignitor and Coil. When rebuilt, it will get a few upgrades but for now it runs fine. So, what's the general consensus for carb size on a 340, 600 or 800 cfm? o No: Thanks!
Well the 350 runs just fine with a 750 Q-jet. That ought to tell you something. I would suggest you look into the newly released Edelbrock AVS. They are just like the AFB's, only they have an adjustable airvalve(much like a Q-jet), instead of the counterweighted airvalve(AFB). I wouldn't worry about overcarbing any Buick. The airvalve type carbs effectively size the carb to engine airflow demand. The Edelbrock 800 AVS w/electric choke is part#1813. 650 CFM is 1806
The recommendations that I got when switching my 300 from a 2 bbl to a 4 bbl was to use a 500 AFB, which is what came on the motor originally...I would think that for the extra 40 ci that you have over the 300, that the 600 cfm carb would work just fine for a stock motor...Now if you did a lot of head porting and bigger cam and such, then I would probably go with a 750, but otherwise the 600 would work fine, IMO...
There was a "definitive" posting on one of these boards about two years ago by a poster called "JIMMIEB", who laid out the technical argument why a 300 could not benefit from a carb over 500 cfm unless it had been radically modified. This JIMMIEB stated he had a great deal of experience with 300's and especially 340's, mostly in Jeep vehicles. None of the subsequent posters to that thread argued with his points. I have also heard of people using 750 and 800 cfm carbs on 350's, but that is a different engine with aftermarket performance items that are not available for 340's. For ignition, I have a complete MSD ignition system (6A, distributor, coil,cap,wires) and highly recommend it.
JimmieB has been around quite a while and posted frequenly on the Buick Perfomance web site. Not long ago, I was taken to task for suggesting that a 800cfm carb was wasted on a street tuned 350. When you can't make your point, you move on. Within a fairly constrained limit, there is only so much air that you can move through a normally aspirated auto engine. If you think of the engine as a compressor, maybe it'll make more sense. There's only so much volume available from the moving pistons. This volume is constrained by how fast the engine turns and to a lesser extent by how little parasitic loss the air mass experiences (head porting/polishing ring a bell?) A carb that's significantly larger than the engine can use may actually hurt performance because the larger than needed capacity will reduce induction velocity (the same mass of air moving through a small opening will move faster than the same mass through a larger opening-- ) , reduce atomization of the fuel and reduce the amount of fuel/air entering the combustion chamber because of the lower velocity... eg, bogging or flat spots. These mismatches are often 'corrected' by running a rich mixture, which in turn decreases fuel mileage. Here's a calculator that works well: http://www.corvetteactioncenter.com/tech/tools/carb.html Here's the formula: Engine size (cid) x max. rpm/3456 =cfm @100% VE (volume efficiency) Example: 350 cid x 6,000 rpm = 210,000/3456 = 608 This site discussed the background of the above formula in very clear terms: http://www.secoperformance.com/Tech_Corner_May2.htm Cheers, John
In the case of a Q-jet, or any other air-valve secondary carb, the carb will effectively size itself to the engine. It will only flow what the engine demands. Most of the time you are running on the primaries(most of us anyway:laugh: ), and no one worries about overcarbing on just the primaries. The secondary air valves will only open enough to flow the necessary air, when you stomp it. Remember, they put a Q-jet on some V-6's. The 800 Q-jet is better suited to a BB because of the idle capacity, but if you have a wild enough 350 with a big cam they can work well. I would rather have a bigger air valve carb to allow for future improvements. Just my .02
