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What CFM Carburater would I need for a four barrel conversion on an L-24 1972 240 Z or would I be better off going with dual Weber Carbs setup?
 

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> What CFM Carburater would I need for a four
> barrel conversion on an L-24 1972 240 Z or
> would I be better off going with dual Weber
> Carbs setup?

I will sell you my 390 4-barrel Holly. It's on my 73 240 now and I am struggling with the same dilema. The car just doesn't run right with a 4-barrel. I think I may settle on a Weber 6-pack until someone talks me out of that.
 

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Re: Four Barrel Conversion for an L-24

> What CFM Carburater would I need for a four
> barrel conversion on an L-24 1972 240 Z or
> would I be better off going with dual Weber
> Carbs setup?

First, what are you trying to accomplish? There are many people on the 240 list and the big list who claim that the SU's will deliver enough for any L-24. I have heard that the long runners on the 4 barrel setup (cylinders 1 & 6) run lean while the short runners (3 & 4) run rich (or do I have it backwards?).

Are you tired of trying to adjust the SUs? Are they worn out? Dual Webers have their own problems. I never liked them on my car. The SUs run a lot better.
 

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> What CFM Carburater would I need for a four
> barrel conversion on an L-24 1972 240 Z or
> would I be better off going with dual Weber
> Carbs setup?

As much as I love my 240Z and the setup I have with my 390cfm Holley, I would suggest getting a set of High Performance SU's. Finding a jetting setup that doesn't run to rich or lean is a pain in the you know what. It also has a tendency to overthrottle if you stand on it(which my foot likes to do).
 

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> As much as I love my 240Z and the setup I
> have with my 390cfm Holley, I would suggest
> getting a set of High Performance SU's.
> Finding a jetting setup that doesn't run to
> rich or lean is a pain in the you know what.
> It also has a tendency to overthrottle if
> you stand on it(which my foot likes to do).
ive had no problem what so ever with my 390
holley. but id recommend taking it in to a carb shop and have the jetting done proffesionlly.
if the shop is any good they can make this setup work extremely well. ive also got NOS which is a fun upgrade to the 390cfm
 

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107,695 Posts
> As much as I love my 240Z and the setup I
> have with my 390cfm Holley, I would suggest
> getting a set of High Performance SU's.
> Finding a jetting setup that doesn't run to
> rich or lean is a pain in the you know what.
> It also has a tendency to overthrottle if
> you stand on it(which my foot likes to do).

Go with the dual webbers. The 4bbl manifolds arn't designed worth a damm. I have ran 1, seen 2 others and 2 out of 3 had carb fires from backfires. The one piece manifold offered by motorsport is the worst by far, it doesn't offer balanced even flow to each cyl. 1,6 run lean, 2,5 run great and 3,4 run rich and nothing you do will fix this. I saw a little better result when someone welded a waterjacket to it but it has too much surface area under the carb and it puddles gas massively and are prone to backfire's and when combined watch out. The manifold that mates to the stock SU manifold is better but still it's throttle responce has a lot to be desired. The best carb I've seen work is the Carter (sorry holly fans) but it just flat out works better on the Z's. I've ran them both and got good results with a fairly built engine and a 500cfm Carter. And it doesn't have a damm power valve to blow out when the engine backfires. There is a fix for the holly's though at www.jeg.com for around $7.95 kit, (they also have some BG carbs that are very nice). I prefer the weber dual 2bbl setup myself, great performance, easy to setup, great gas mileage potental with performance which you just won't get with a 4bbl conversion cuz they arn't built well to begin with. Also if you get the urge to add more carb you can always add 2 holly 2300 carbs (500cfm ea.). BG also sells a race 2300 that's polished, tuned in every aspect along with a 546.25 price ea..
But steer clear of the 4bbl setup, if you want that much power go with tripple weber/mikuni or for overall power and driveability, get the dual webers. I use a .460 lift/270 duration cam with header 2.25 exaust, dual webers and it's one fast car with great gas mileage when doing normal driving. I recomend this cam spec and exaust size also, you go much bigger on the exaust and you loose low end power. I also recomend the Nissan Motorsport's race header, expensive but it's the best you'll find anywhere for the Z. I replaced it from that garbage Motorsport auto's 6-2 header and the difference was noticeable. That one isn't tuned but it's still ok if your on a budget, anything is better than stock. Sorry about the long post.... Good luck with what ever you pick.
 
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