434 cu in SBC installed a 950cfm Holley ultra XP carb at first obtained the highest vacuum reading of between 9" and 10". ( this after exposing some secondary transfer slot otherwise idle mixture screws had no effect at idle except when nearly closed idle improved primary was cranked up exposing too much transfer slot and found that Idle bypass fully closed gave the best idle ) installed a 4.5 power valve in this carb . Fuel bowls level set to 1/2 sight gage. everything runs ok (some unburnt fuel smell from exhaust) when I come back an hour or two and have to readjust all over again?
I got timing set at 34 degrees@ 3400 rpm as per engine makers specs.
Ok So I tried a new Holley HP Carb (950) CFM use same number power valve, bowls set to 1/2 I get occasional backfire through carb when blipping throttle, adjusted pump shot, only get 4" to 5" of vacuum with this carb and adjusting idle miture has no effect.rpms seem to rise after throttle opening and closing on second carb. I do notice that my vacuum pump is constantly on all the time though and it should turn off after engine start up and it senses engine vacuum? maybe got a vacuum leak im thinkin?
this is my Cam specs:
vid of engine running, seems good https://www.youtube.com/watch?v=yUnMTZMRZCU
then restart a few hours later runs like crap?
Part Type: Camshaft
Application: Chevrolet Small Block V8 305-350, '87-'98 (Carbureted)
Cam Style: Hydraulic Roller for OE Roller Applications
Basic RPM Range: 2600-6400 2800-6600
Manufacturers Description: Rough idle, needs good heads. Good upper mid-range. Needs 3500+ stall.
Intake Duration @ .050": 247
Exhaust Duration @ .050": 253
Advertised Intake Duration (@ .006"): 300
Advertised Exhaust Duration (@ .006"): 306
Intake Valve Lift with 1.60 Rocker Ratio: .603"
Exhaust Valve Lift with 1.60 Rocker Ratio: .619"
Lobe Separation Angle: 110 Degrees
Intake Centerline: 106 Degrees
Small Base Circle: No
Cam Gear Attachment: 3-Bolt (step-nose)
Valve Adjustment: Zero Lash Plus ½ Turn
Manufacturer: Howards Cams & Racing Components
Manufacturer's Part Number: 180345-10
Weight: 10.0 lbs.
Note: Oil with ZDDP or ZDDP Additive Required
Note: Stock (O.E) valve springs cannot be used.
Pulling my hair out on this one!
I got timing set at 34 degrees@ 3400 rpm as per engine makers specs.
Ok So I tried a new Holley HP Carb (950) CFM use same number power valve, bowls set to 1/2 I get occasional backfire through carb when blipping throttle, adjusted pump shot, only get 4" to 5" of vacuum with this carb and adjusting idle miture has no effect.rpms seem to rise after throttle opening and closing on second carb. I do notice that my vacuum pump is constantly on all the time though and it should turn off after engine start up and it senses engine vacuum? maybe got a vacuum leak im thinkin?
this is my Cam specs:
vid of engine running, seems good https://www.youtube.com/watch?v=yUnMTZMRZCU
then restart a few hours later runs like crap?
Part Type: Camshaft
Application: Chevrolet Small Block V8 305-350, '87-'98 (Carbureted)
Cam Style: Hydraulic Roller for OE Roller Applications
Basic RPM Range: 2600-6400 2800-6600
Manufacturers Description: Rough idle, needs good heads. Good upper mid-range. Needs 3500+ stall.
Intake Duration @ .050": 247
Exhaust Duration @ .050": 253
Advertised Intake Duration (@ .006"): 300
Advertised Exhaust Duration (@ .006"): 306
Intake Valve Lift with 1.60 Rocker Ratio: .603"
Exhaust Valve Lift with 1.60 Rocker Ratio: .619"
Lobe Separation Angle: 110 Degrees
Intake Centerline: 106 Degrees
Small Base Circle: No
Cam Gear Attachment: 3-Bolt (step-nose)
Valve Adjustment: Zero Lash Plus ½ Turn
Manufacturer: Howards Cams & Racing Components
Manufacturer's Part Number: 180345-10
Weight: 10.0 lbs.
Note: Oil with ZDDP or ZDDP Additive Required
Note: Stock (O.E) valve springs cannot be used.
Pulling my hair out on this one!