I am looking into getting a new Holly 2 bbl carb for my F100 with a fresh built 390 with an RV cam and stock exhaust manifolds. Will a 500 cfm be too much? Or go with the 350 cfm? This will be a daily driver for the most part with mostly highway driving. Just looking for the best all around performance without going 4 bbl.

 

Unless you plan on driving over 3000 rpm a lot, that engine only requires about 300 CFM. The Holley 2300's at 350 CFM are a good choice.

 

Find a 2100 and save considerable money. Stamped inside the "clockface" on the driver's side of the carb will indicate the CFM rating:

0.98 = 190 CFM
1.01 = 240 CFM
1.02 = 245 CFM
1.08 = 287 CFM
1.14 = 300 CFM
1.21 = 351 CFM
1.23 = 356 CFM
1.33 = 424 CFM <!-- / message --><!-- sig -->

 

I just installed a rebuilt Autolite on my '69 F-100 with a 390......
I went with The C9TF-K which is a 1.23 venturi(356 CFM), and is correct for '69 360 and 390 engines

I am happy with it.....
just my 2 cents....

 

I have a rebuilt 2100 on there now but the performance could stand to be better, why i was thinkin about a 500 holly.

 

What HIO Silver is saying is that you can get a 2100 to match the Holly and save some money. Check out the stamping on your 2100 and see what CFM it is, it may be smaller than you need/want.

 

Simply installing a bigger CFM carb will not typically provide additional performance unless the the engine is designed as a system. Bigger is not always better and putting your money into a different carb is putting the cart in front of the horse.

Carbs need to be sized according to the displacement, volumetric efficiency, and typical RPM range that the engine will typically operate in.

d = Displacement in Cubic Inches.(d x 2) - 15% = CFM
EXAMPLE: d = 350 (350 X 2) = 700 (700 - 15%) = 595 CFM

The example above would be the optimum size but these trucks aren't operated at >5000 RPM on a regular basis. The torque curve of an RV cam is designed for maximum pulling and fuel economy on an otherwise thirsty engine. That's why the OEM carb size is tuned at lower RPMs where torque is king to get these heavy trucks moving.

Your best bet is to build a solid foundation before installing a bigger carb. I suggest first improving the exhaust with headers, mandrel bent tubing, and free flowing mufflers. This improvement and a proper tune can bump HP and torque by as much as 20 percent... a VERY noticeable improvement. Heck, this might be all you do to get the grunt out of the motor that you might be looking for. I think you'd be pleasantly surprised with a good exhaust system.

Ready for more? Second would be a 4bbl intake and carburetor combination. For a 390FE, the Performer RPM (PN 7105) or Performer (PN 2105) with a 600 or 650 cfm carb is a good choice. Third would be a cam but you've already got that covered.

 

I went and got the Holley 350 cfm carb today and all I can say is WOW!! What a difference it made. This new engine is runing the best it has ever since the rebuild. The 2100 carb from the parts store just wouldnt tune in where I thaught it should, just couldnt get it right, so I gave up and got the new Holley 2bbl and in my opinion it was well worth the price. I got Autozone to give me a refund on the carb and only had to ad about $40 bucks to get the Holley. Happy camper here! As far as the headers go, I did buy a used pair a few mo back and decided not to use them. I just prefer the simplicity of the stock logs even if they dont flow well. As of now I am happy with how it runs.

 

Well there ya go... it was a tuning issue rather than a CFM issue. Congrats Mr. Happy Camper!

Just a word on stock manifolds... if you ever have exhaust leak at the flange, make sure you take care of it right away and don't let it go for too long. The PO of my rig let it go waaaaay too long and the constant leak had eroded away the cast iron where the leak occured. Luckily I had a spare manifold but the passenger side manifold was a PITA to replace!!

 

You can lead a horse to water...

 

What? You not thirsty right now? The stamping on the 2100 was 1.23, is that 356 cfm? I know alot of people have problems with Holley but I have ran many 4 bbl's in the past and always had good luck with them and have had good luck with 2100's as well, but this one was not cutting it and I was not going to rebuild a rebuilt carb that has a warranty.

 

Good choice...can you post some pix of it on your truck?

 

 

Wow, that's sharp...what'd you pay for that pup at the parts store? Looks kinda like my old Holley 2300/7448 but not quite...mine is DOA so I'm waiting on an Autolite 2100 from California to transplant onto the 360 in my 69 F250. Are you gonna top it off with a full body chrome air cleaner, rather than the stock air cleaner?

 

I paid $321 at O'Reilly auto. I already have a chrome open filter that looks pretty good on there.