Even a 600 is a bit big for a 327 but if that is smallest option you
have use it. With a 750 it would run poorly most of the time. Based
on 90% efficency in induction (if you are lucky) you only need about
520 CFM at 6000 RPM with a bored 327. Smaller carbs give better low
RPM responce and torque. A carb is one thing where bigger is not
I was thinking to put smaller jets in the 600 VS carb I have. I agree , it
wastes gas to run that big.. If I could get a decent 550 carb, I would be
happy but up here in shitholeville , not many hi performance stores.. I
order from summit in the U.S
WHat are you planning for you peak RPM (I am guess that cam should
peak HP between 5000 and 5500 depending on intake). It you have no
plans of taking past 6000 regularly I see not problem with a 500 CFM
one on that engine. The reason you want to stay smaller is because you
have a higher average velocity in venturi and better mixing and
metering of gas which improves throttle responce and mid range torque.
With a carb in a big heavy vehicle is it better to error a bit small
than a bit big. BTW a 500CFM 4bbl is rated at 500 CFM at 1.5 inches of
mecury in pressure drop across carb (about .75 PSI) so it can flow
well beyond 500CFM with just a bit more drop.
oops.. forgot to add that the cam was 2500rpm-6500 and the intake is a
performer RPM, headers,2.02 1.60 valves screw ins aluminum,stall was suppose
to be 3000 on the th350 but feels like a 2500 .. bought it used so I was
ging bhy what he said.. thanx again... I'l use the 600 (as I just had it
rebuilt tonight) and if it gives me any issues with flooding etc.. I'l buy
the 500 edelbrock.. Thanx for all the advice..
The reason it is stalling at about 2500 RPM is because the engine is
not making enough torque to hit rated stall due engine build/cam.
Knowing this I think I would suggest that you install a 3500 RPM stall
or try advaning cam about 4 degrees as that will increase lower RPM
responce. They make offset keys or a degree wheel. (retarding cam
increases top end a bit) Smaller 500CFM carb would help too. BTW,
6500 is no big deal for a 327 but I would consider a RPM limiter set
as 6500 or a bit less to keep it from overreving with that cam into
Big Al Your forgetting they also had crossram with two 4295 600 cfm
holleys... 1200 cfm, a little over kill. But along with what snoman is
saying most cars are over carbureted. 600 is about perfect for a 302 or 327.
When younger and dumber I ran 850 dbl pumpers on everything. From my 165 hp
factory 350 to my 600 + hp 454... same carb just rejetted. it ran like shit
on the 350. With factory heads you'll never flow that much cfm, butterflies
will be open but not that much air going thru.
Also on the stall, it takes torque to stall a converter. On a stock engine a
3,500 will only stall 2,500- 2,800 give it more power you can bring it up to
the 3,500. Worked on a race car that had vacuum advance that had a 3,500
stall, wouldn't stall past about 1,800 put a timing light on and set total
advance to 38 with no vacuum advance and it stalled to 3,200 (engine didn't
have enough power to stall to 3,500)
What application are you using the 327 in ?
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