383 engine low vacuum

[Ferd]

I’m having two issues with my 1969 roadrunner that may be related. I purchased the car last September. The engine was totally rebuilt by a professional. What I am experiencing is the engine always takes roughly five seconds of cranking to fire whether cold or hot. When driving if you shift into second gear with a light foot on the gas, the engine will lightly sneeze up the carburetor. I have set the timing using a mark at 36 degrees and power timed the engine to that setting at 3000 rpm with the vacuum advance plugged. I jetted the Edelbrock 650 carb to the old 1969 factory specs. It has a factory distributor with a Petronix conversion. The voltage to the distributor and coil are great. A vacuum gauge reading at 750rpm idle is only 5 inches. However, the idle is steady and once started the engine never stalls. The plugs look great with a light tan. I thought maybe a vacuum leak, but all intake gaskets are fresh and intake bolts are tight. I replaced the vacuum advance, and the vacuum hoses are good. I pulled a valve cover and tried a crude measurement of valve lift from the top of a valve retainer to a head surface and discovered only .300 lift . So I’m puzzled. There is absolutely no lifter or valve train noise. I’m debating on pulling the intake and lifter cover for a visual inspection of the camshaft and lifters, but I have a feeling based on the lack of valve train noise I’ll find nothing. Your constructive feedback is appreciated!

 

[STXCUDA]

What is your base timing at? What port on the edelbrock did you get that vacuum measurement from? Edelbrocks only have manifold vacuum at the front center 3/8 pcv port and the 3/16 port on the front driver's side. You may also consider buying a new vacuum gauge, yours may be defective. Based on everything else sounds like it's a healthy engine just need to figure what tune it wants.

 

[Ferd]

What is your base timing at? What port on the edelbrock did you get that vacuum measurement from? Edelbrocks only have manifold vacuum at the front center 3/8 pcv port and the 3/16 port on the front driver's side. You may also consider buying a new vacuum gauge, yours may be defective. Based on everything else sounds like it's a healthy engine just need to figure what tune it wants.

I went out and looked at my vacuum advance hose. It was hooked up to the incorrect “timed vacuum “ port. I changed over to the drivers side full time vacuum port. The car started up immediately. Thank you for your excellent advice. I then hooked up my vacuum gauge (which works fine) and determined 6 inches of vacuum at 750 rpm idle. Putting a timing light on with the vacuum advance plugged, the advance at 750rpm idle is roughly 15 degrees btdc. When I increase the throttle to 3,000 rpm the total advance of 36 degrees btdc is reached. I believe there is an aftermarket camshaft in the engine causing the low vacuum at idle. I have replaced the metering rod springs to the lightest ones from a kit (blue springs). Car is running strong. Will spin the tires on a firm second gear shift. Thanks again!