I am trying to set the timing in a modified 427/390hp. In order to make it run my initial timing needs to be set really high, like 30 deg. The carb is running rich and I am not reading very much vacuum.

Engine has comp thumpr cam, 10.2CR, ported factory heads. 650 holley (Qjet replacement)

 

Are you saying that the base timing, at idle with the vacuum advance disconnected is 30*? Something has to be wrong with how you're measuring or with the balancer marks. I can't picture the engine having that much timing and not kicking back on the starter when you try to crank it. Have you checked actual TDC against the mark on the balancer?

 

I just checked TDC against the balancer, its right there.

I have the vacuum line to the distributor unhooked and the timing light hooked up to number 1 wire. 30* on the balancer lines up with the 0 mark on the pointer.

It will run, but it doesn't really idle and just runs like crap

 

Something sounds really screwy. Have you changed out the pointer or the balancer? How did you check TDC against the balancer? Did you remove the #1 plug and bringing #1 to the top of its compression stroke and see if it lines up to zero on the balancer. Maybe the outer balancer ring has slipped?

What are you calling #1 cylinder?

 

that was how I checked TDC against the balancer. Since they lined up fine I didn't really see a need to change out either part.

 

Have you double checked your plug wire routing and firing order? #1 is driver's side front.

 

What RPM is it running while idling?

Is the mechanical advance sticking?

Does your timing light have a advance dial? If so what is it set to?

Re-check TDC, remove valve cover to comfirm both intake & exhaust valves are closed at TDC.

Dave

 

Are the marks on the timing gears aligned correctly?

 

Was the cam advanced? What ignition do you have? If it's an MSD your timing light may not be compatible.

 

That's what I would check.

 

My experience is, with way too much advance and the engine runs poorly, there is a vacuum leak.

 

That's what I was thinking. IIRC the factory 390 intake has that hot slot in the front that uses the stainless baffle plate to block it. If you don't use the baffle and leave that slot open it will create a huge vacuum leak.

Best solution is to block the holes with plugs.

 

I didn't have the slot blocked off. I do now but its still not running well

 

Probably a dumb question, but did you replace the gasket too ? It most likely burned through it. How's the vacuum now ?

 

If your base timing (vacuum advance disconnected and plugged) is really 30* BTDC, it wouldn't start at all. Verify TDC and alignment of the index mark on the balancer with the "0" mark on the timing tab with a piston stop (not a screwdriver), and go from there. At #1 TDC on the compression stroke, both valves for #1 cylinder will be closed. What kind of timing light are you using?

 

I don't have piston stops, nor do I know where to get any. I have just a regular plane jane timing light. The motor was converted to HEI but I can't see how that would cause a problem.

 

I can.

If you installed the dist. and wiring as per GM manuals, the #1 plug wire is one tower different than a points dist. If you are unaware of that and connected your timing light at the dist end.- there's your error in indication.

 

I has a timing gear break some teeth and slip a few teeth on a BB once about 32 years ago.

Car ran like crap until I fixed it.

Doug

 

...and I am going to throw this out cause it was my problem. Even tho the dist. drive gear was installed correctly I still had to turn it 180* to get the car to run and adjust time.

 

How were the hydraulic lifters adjusted?
Give a readout of your idle vacuum and corresponding RPM.
With 30 initial, the engine should idle like a champ...........if the starter has enough juice to spin the motor. Of course, that is temporary, and you want your static timing somewhere between 10 - 15.

If the lifters are incorrectly adjusted, they will pump up and hold the valves open for too long, making the engine "think" that it uses a big, high duration cam. Part and parcel with high durations, goes high overlap. High overlap does not allow an engine to develop a lot of vacuum at idle. Low vacuum at idle does not enable very efficient fuel atomization, and, consequently, fouled plugs and smelly, dirty idle. The 650 Holley with its inefficient straight leg boosters is not helping. You made a mistake using the 650, and you should have used a 750 which has MUCH more efficient downleg boosters.

Hydraulics can be adjusted with the engine running, loosening each adjuster nut until its rocker arm clacks. Then tighten the nut until the clacking stops, and then tighten an additional 3/4 turn. This last step is eliminated when adjusting for zero lash, whose purpose is to eliminate lifter pump-up at high RPM's.

Can adjust with engine off and warm by loosening each adjuster then tighten just to the point that you can spin its corresponding pushrod between your thumb and index finger. Each lobe must be on the base circle when doing it this way.