I have a pontiac 400...fresh rebuild with 280 comp cam, running 850 quadrajet, points replaced with hall sensor
It wont start until initial timing is 24deg, vac adv not connected...
Checked harm balance, set to tdc manually mark falls on 0deg so that's still good-didnt slip
Question is: do I hook up the vac adv to manifold vac port AND retard timing a bit to compensate for vac advance being hooked up before I try to start again ?
First off I don't think they made an 850cfm quadrajet. Secondly, something is wrong if you can't start it without 24 BTDC timing. I suspect it's something else keeping it from starting. Hard to diagnose over the internet. Could be a lot of things.
I wouldn't hook up the vacuum that way until you figure out what's going on. Some low compression engines with big cams might like a lot of initial, to need 24 just to run still excessive.
So you've verified TDC, that's a good starting point
Please give us more details: -What's your compression ratio calculated out to with the rebuild? (You'd want at least 10:1 with that camshaft) -Was the camshaft installed using a degree wheel to verify proper intake centerline position? -What intake manifold are you running (dual plane, single plane)? -Does the distributor conversion require a 12 volts to the coil? And did you verify the distributor is getting that 12 volts both during crank AND during idle? (early cars had an inline resistor to limit voltage to the primary coil in order to not burn up the points. Some systems that eliminate points require a full 12 volts. HEI conversions also require this). -What spark plugs are you running, and what gap?
Try running a compression check. That should tell you if something is way off with either the compression or cam. Also, see if you're getting a strong spark and like I said, make sure the proper voltage input is reaching the coil. The spark plugs you'll want to gap to factory spec. (035" I believe) unless you have a higher voltage output coil, in which you could open that to .045".
With the cam ,using points it liked 18deg After replaced with breakerless se module it's now liking 24deg
Thinking it might have to do with dwell. ..
If you're saying that the only change to the setup (same compression, cam, etc.), then yes probably related to dwell or maybe it's getting a weak spark. What brand did you go with?
Mickey Saw what yours is doing on other thread, mine is a 400 pontiac Timing pretty much the same
Timed mine today, after installing timing tape, Initial 28 deg Total 52 deg
Starts right up, idles real lopy Does not like to idle under 800-850 If you try it will idle until you rev it up and it comes down and dies 950...very stable doesn't die coming down off revs
Might have to kick your idle up
Followed a thread today that said 280 cams need 900-1000 rpm to stabilize
I have a 4 speed man so don't have any load at a stop like you would
Have you guys verified at top dead center your timing marks on the balancer and timing cover were correct. I have personally had engines that the timing marks were 4 degrees off on the timing cover and or balancer. Also have you degreed the camshaft and made sure that was installed to the specifications on the cam card. A cam that is installed a tooth or two off will have the timing way off to the point of where you can have the engine actually idle. Like initial timing will either have to be at 30-40 degrees BTDC before you can even get the engine to run.
