350 or 500 cfm

2Blew2B

Well-known member
anyone running 500 cfm Holley.

I am at my ends trying to tune the 07448 350 CFM Holley I have and want to start fresh. I want to see if i can run a 500 cfm

steve
 
The 350 is generally considered a better sized carb for all but the most modified engines.
Search posts by wsa111 for info regarding tuning the 500, as he did it up pretty well with a wideband O2 tuner.
 
Howdy Steve:

What's got you at the end in tuning the 350 Holley? I tried to get a 500 working on my 250 without much success. wsa111 did some major internal revisions to get idle circuit and air bleed systems to work better. He was in touch with the Holley tech guys and used an aftermarket metering block with screw in air bleeds and power valve channel restrictions. Without a A/F meter reader it's tough. The top end was definitely better, but low end was sluggish and cruise mileage sucked. With my 3:1 rear gear and OD I could barely pull 7 lbs of vacuum.

Next I switched to an Autolite 2100 in a 1.33 size which is rated at 424 cfm, but has annular discharge venturi boosters for a better vacuum signal. I'm still tuning on it, but am not satisfied so far. Great top end, but still not as crisp at lower rpm. I've got a 1.23 2100 on the work bench for next. It is rated at 356 cfm. So far the 1.08 was the best all-around carb, but gave up just a little on the top end.

Don't overlook the Autolite 2100s. I haven't come across a Holley 350 yet so I'm no specific help there.

Adios, David
 
I'm running the 500 Holley on my setup but I have a modified engine with 10.5 to 1 compression and 3.55 gears out back...see my signature for other mods. Throttle response is great and it runs lower et's at the track then when I had the 350 Holley on it. If you are running a fairly stock engine then the 500 would not be the best choice. What are your tuning issues with the 350 Holley and is it direct mounted or are you running an adaptor?
 
I run the 500 cfm Holley on my 200 cid engine since I do not drive the car on the street.

The 200 engine is built up a bit and the Holley is a direct mount on to the log head
 
All,

Got the 500 bolted down and what a difference. No more sputtering, no more lag on takeoff or lag while shifting through the gear and the hesitation is gone. The power is unbelievable. The only problem I still have got goes back to another post I have out there, it is still hard to start. I repainted my timing marks and spun her around until they were almost lined up with TDC and pulled the disto cap and sure enough it was at the contact point for #1. (See timing post) but please continue the discussion on 350 vs. 500. Oh yea, I pulled the Holley right out the box, I made no adjustments except for the idle screw. I'm sold on the 500.

Steve
 
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