|12-12-2008 06:37 AM|
if u do the math, most engines from the factory r maybe around 80% volumetric efficiency. a cam, some head work, and an aftermarket intake on a mild build will still only maybe get u to 90% efficiency.
if u like the carb, jet it down., jets r cheap. otherwise, start looking for a carb around 600 cfm... that ought to get u in the ballpark. gl
|12-11-2008 10:19 PM|
|12-11-2008 10:17 PM|
|lg1969||It sounds to me the air bleeder on the top of the carb could be blocked. changing jets is not the problem. The gasket on the main body and metering block may not be aligned.|
|12-11-2008 09:59 PM|
|12-11-2008 09:56 PM|
Many years ago I had a Holley 3 barrel, wow does that age me or what, that thing never ran right. I rebuilt and replaced major parts on it and never solved the problems, the venturi body and throttle section finally ended up in the recycle barrel. The metering plates and float bowls went on to live in other Holley's.
|12-11-2008 05:22 PM|
|Silver00V6||read above my vac with the advance plugged up is 30 degrees. Both primay and secondary butterlfies are closed. the only idle screw that will kill the motor when going lean is the passenger side the driver side will do nothing but will go rich if you turn it out. I have tried the wire thing in the idle feed restrictors and it is still rich smelling. Float level and everything else is correct. I have had this rich idle problem since the day this carb was taken out of the box. I bought it brand new threw summit 2 years ago|
|12-11-2008 05:18 PM|
plug the vacuum advance into a manifold source. let it idle at 30 or 35 degrees.
then turn down the idle screw to lower the rpms to 950. (More timing will raise the rpms)
try readjusting the mixture screws for best idle. they should be working now with all that timing and more closed throttle blades.
check the vacuum. should be making more than 12 inhg. I would think that cam should pull 14 or 15 inhg.
try a new power valve. a size 5 would be better
make sure the float level is set right.
blow out the idl air bleeds with compressed air.
|12-11-2008 04:32 PM|
|Silver00V6||thorttle blades on botht he primary and secondary are closed. Thats was thought to be the problem last time when i found out the timing was messed up. i am seriously getting tired of this carb. the 80508 is just a 3310 vac secondary with an electric choke. 4160 style carb. The passenger side idle screw works like it should but the driver side does not. The driver side will not kill the car when turning it in to lean it out, but if you richen it it works fine.|
|12-11-2008 03:48 PM|
Where I was headed, is that engines pulling a lot of cam often cause the tuner to tip in too much throttle opening to get a decent idle. Your cam and lifter combination certainly qualify as one of those where if you're not careful you could tip the throttle plates open enough to where the transition slots are exposed to the manifold side of the throttle plates. In that case the transition slots will start feeding fuel making for a rich idle mixture that can't be controlled with the idle screws.
If this is the case, then looking down the primary throttle bore the plate will overlay the transition slot from some to all of it. The solution is to give the engine another source of idle air such that satisfactory idle can be achieved with the throttle blades closed to where all of the transition slot is above them.
Some Holley's have 4 corner idle circuits with a simple adjustment for throttle blade position on the secondaries. Other Holley's have a screw stop adjustment on the secondary accessible from underneath the carb. This can be used to crack the secondaries enough to get more idle air into the engine, allowing the primary plates to be repositioned properly. The last option is to drill a couple small .060 inch holes in each primary blade as an additional source of idle air, which again lets you adjust the primary throttle plates to a position under the transfer slots.
If this is the problem, then these type changes should put you back in control of the idle mixture.
You need to keep in mind that 1.6 rockers make the cam look bigger to the engine. While not adding duration, they increase the rate of change in lift relative to duration. The engine will react to that as if there was more overlap, the LSA was tighter, and closing intake valve as well as the exhaust was later, while opening events seem earlier. So you're alreading using a pretty aggressive cam, that with the 1.6 rockers will easily get you into idle adjustment problems.
|12-11-2008 02:02 PM|
·Torque: 400+ ft/lbs
·Compression ratio: 9.5:1
·Dyno-tested: Yes, includes balancer and 14" flexplate
·Dyno sheet: Included with engine's output
·Vacuum produced: 12hg @ 800RPM
·Recommended fuel: 92 octane
·Max recommended RPM- 6000
·Block: Seasoned 4-bolt iron
·Crankshaft: Nodular iron
·Connecting rods: Powdered metal
·Camshaft- Hydraulic roller
·Duration @ .050" (int/exh): 218deg/228deg
·Rocker arms: Stamped steel 1.6:1 ratio
·Cylinder heads: Ported Vortec
·Valves: Stainless steel 2.02 int/1.60 exh
·Valve springs: Heavy duty
·Bore x Stroke: 4.030" x 3.48"
·Intake manifold: Dual-plane aluminum
·Oil pan, timing cover, valve covers included
·Engine fasteners: High tensile strength
·Warranty: 12 mth/12,000 mi
|12-11-2008 01:50 PM|
|12-11-2008 12:31 PM|
Holley Running Rich
Ok well got my 80508s Holley Vac Secondary going good. It was a timing issue cuasing the heistation and some other problems. I have the base timing set at 20 degrees with the vac advance unplugged. its 30 with the advance plugged up. and timing with the advance unplugged is all in at 38 degrees at 3000 rpm. The hesitation is gone but at idle its rich. I have rebuilt the carb as my last thread. It has 70 jets on the primary and a 21 plate on the seconday. The power valve is a 6.5. I can not figure out any way to get this thing not to run rich at idle. its fine everywhere else but idle. I did notice that when I turn in the idle screws that only the right one will kill the motor when turned all the way in. The left on does not kill or even effect the idle in any way when turned in. Any help is appriciated. Im tired of smelling like gas and having burning eyes with the car at idle and im stumped. I have the tuning dvd and 2 Holley books but none really tell about a rich idle and what to do.