I replaced the n.o.m. in my 66 with a rebuilt 350 (blueprinted shortblock, World Products cast iron heads, Isky custom cam, Edelbrock Intake & 600 cfm Carb, 9.5:1 compression). Upon intial startup, it started quickly but ran very rough (missing and popping @2000 rpm). When I let off the gas for a second it died imediately, as if I had shut off the key. Then, it would not start again. Before I tore into it, I was wondering if anyone knew what the problem could be. It seems to be getting fuel ok, so I figured it must be a timing/spark issue. I also switched to a breakerless se ignition system when I changed engines. Also, the new cam is quite a bit bigger than the old one (0.490" lift and 226 degrees @ 0.050" lift), so I think the original vacuum can might not be sufficient. I can't remember the part number, but I decoded it once and know it came from a 390 hp 427. If necessary, what would be a good replacement? Thanks, Dan
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Re: 66 startup problems
Just a real quick guess: maybe the lifters not adjusted properly? Is the cam hydraulic? -
Addendum
Don't overlook the obvious. Check the plug wire routing and be sure nothing got crossed. Very easy to do.Comment
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Re: Addendum
I checked the plug wire routing once, but I will recheck it. The cam is hydraulic, and I adjusted 1 turn past 0 lash, following the procedure in the 66 chassis sevice manual. Thanks, DanComment
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Re: Addendum
One turn past zero lash is too tight, especially if you were off just a bit finding zero. Most knowledgable folks like to set at zero or perhaps a 1/4 turn tighter. I suspect you had some too tight and the popping was due to some of the valves not being closed. To start with, I would suggest going back and setting all valves to "0" lash, again using the proceedure in the service manual for #1 and #6 cylinders. If they are noisy after the engine is sorted out, you can adjust with the engine running so that they just barely don't tap.
To reliably find "0" lash, loosen the rocker nut and then tighten until up and down movement just stops. The directions in many manuals say to turn the pushrod until you feel resistance, but often this isn't a reliable indicator and the valves end up too tight. This may be what has happened in your case.Comment
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Re: 66 startup problems
Dan is your electronic ignition connected to full time 12 volts or do you have it connected like your original point ignition at the ballast resister? Another check is to verify that you are not a tooth off when you installed the distributor. Did you have to remove the gear from the shaft to install the electronic ignition? Back years ago a Mallory electronic ignition required this. The distributor gear could be 180 out. The demple mark on the gear should line up with the rotor point.Comment
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Re: 66 startup problems
A tooth off on the distributor wouldn't matter, so long as the distributor can be turned to the proper spot to achieve the desired timing. Depending on intake manifold, ignition shielding and tach drive, many Corvettes have to have this indexed just right for everything to clear. Others with low rise manifolds and "passenger car" configuration distributors may not make any difference.
If you have a high rise manifold, ignition shielding brackets, and a vacuum can, all this has to be right or the distributor won't have sufficient adjustment available to allow proper timing without the vacuum can hitting something.Comment
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Re: Addendum
"Check the plug wire routing to be sure nothing gets crossed"
Am I reading too much into this? As long as the plugs are on the right towers is it possible to still have it wrong? It seems to me some wires have to cross each other to get to the grommets in the shields? Can a spark be induced into another plug wire??
RandyComment
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Re: Addendum
It is theoretically possible to get cross fire from an ajacent plug wire. Check your firing order, in this case 1-8-4-3-6-5-7-2 and see if any ajacent cylinders fire, in this case being 5 and 7. Pay careful attention to the routing of these wires being sure that they do not run parallel for any distance. The rest of the firing order is scattered around the engine.
I am not sure that this is of any consequence today with the modern plug wires we have, but is very cheap insurance to keep them separated. Maybe Duke or Clem would want to add comments on this issueDick WhittingtonComment
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