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Item Posts    Sort Order

Timing/Vacuum Troubles

 
Shawns66Mustang
New User
Posts: 28
Joined: 01/08
Posted: 11/04/13 02:11 PM

I’m trying to figure out what’s going on with my timing and vacuum on  a 71 302 that I dropped into my 66 couple.  I’ve played with the timing between 6BTD and 12BTD to see if the car ran better but there was no noticeable change. This weekend I put a vacuum gauge on it and found that I’m only running 10in of vacuum, which I know is too low. I checked for vacuum leaks with both propane and starter fluid around the carb and manifold but didn’t find anything. So next I started retarting the time until I got the most vacuum which is 15in., but now my timing is at 49BTD which seems very odd but the car still running good. I’m hoping someone has an idea.
I installed the timing chain while the engine was on a stand so I’d be surprised if I was off a tooth. I’ve also verified TDC.
Engine Description
• Stock pistons
• Edelbrock RPM cam
• Edelbrock RPM dual plain manifold
• Edelbrock 500 cfm carb
• Headers
• MSD A6 ignition box w/distributor
• Edelbrock timing chain  

Post Reply
waynep712222
User
Posts: 223
Joined: 04/13
Posted: 11/04/13 09:50 PM

do you still have the cam card that came with the cam????

look at the card and see where the valves start to open..

the intake should start to open at xx degrees before TDC... usually somewhere between 6 and 22 before... refer to the cam card..

guess. what.. you might be able to see this with the passenger side valve cover off..

i have always wanted to try to see if i could use the spark from the cylinder that is 180 out.. to see if i set the actual spark timing at ZERO... and then i can use the adjustable advance to turn it and see when the rocker first starts to move.. with the engine idling and the valve cover off..  aiming the timing lite at the rockers arms of course..

how many keyways in the crank sprocket did it come with... 1.. 3.. 9...

any chance the power brake booster is leaking???

any chance of an incorrect calibration of the PCV..  engine at best lean idle.  looking at the RPMs with a digital TACH... pinch off the PCV hose..

if the PCV Valve is properly sized for your calibration . the engine should drop between 50 and 70 RPMS at lean best idle..

do you have an aftermarket damper with multiple marks slightly offset..

3Keycranksprocketalignment  

Post Reply
70bird
User
Posts: 86
Joined: 07/13
Posted: 11/04/13 11:01 PM

YOUR CHAIN IS NOT OFF A TOOTH OTHERWISE IT WOULD RUN LIKE CRAP.

YOUR TIMING IS NOT 49 DEGREES, YOUR TIMING MARKS ARE OFF FOR SOME REASON.

IF IT RUNS FINE WITH NO PINGING I WOULD JUST LEAVE IT.


YOU MUST HAVE DISTRIBUTOR VAC CONNECTED TO PORT ON PASSENGER SIDE OF CARB NOT THE FRONT OF CARB.  

Post Reply
Shawns66Mustang
New User
Posts: 28
Joined: 01/08
Posted: 11/06/13 08:27 AM

I’ve disconnected and capped all the lines to the carb and manifold to try and narrow down the vacuum problem.
I do have the cam card, see below. I know that my harmonic balancer timing marks must be off but I did retard it a lot so I’m wonder if it firing with one of the valves partly open?
INTAKE TIMING @ .050" LIFT: Opens: 5° ATDC
                               Closes: 29° ABDC
EXHAUST TIMING @ .050" LIFT: Opens: 44° BBDC
                               Closes: 10° BTDC  

Post Reply
70bird
User
Posts: 86
Joined: 07/13
Posted: 11/06/13 11:47 PM

that cam info means nothing.

you need the advertised duration also and/or the intake valve timing at .006 lift.

as i mentioned just run it since you said there is no problem with the timing adv to 49 deg at idle.
.  

Post Reply
waynep712222
User
Posts: 223
Joined: 04/13
Posted: 11/07/13 02:29 AM

i wonder at this point a FEW things..

did the harmonic damper slip the outer ring..

did the harmonic damper shear the keyway and spin on the crank snout.. this is going to lead to vibration on most ford engines..

is the timing light an advance type unit and the knob or adjusting buttons NOT set to ZERO...

please... recheck that the TDC is in the proper place by removing the first spark plug on the passenger side of the engine..  and what ever you use is cannot get smashed..  

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