Distributor Cap carboned new engine

[elorenzof]

SBC - 327 - newly built engine... No major upgrades. Cylinder heads already installed and valves adjusted at an engine build shop here in Phx. Initial Start and Timing set to about 13 degrees before top dead center. looking great so far! But, during the 15 min initial break in, the pass side was getting way too hot and melting the 90degree spark plug boots. So we shut it off immediately after about 10 mins when we noticed it. Water pump temp stayed at 190. But we could feel the heat on the pass side and the exhaust manifold was starting to get red

Next morning, replaced wire boots, and went to start engine and noticed there was a slight ticking sound coming from the pass side cyl head. So we figured the valves werent adjusted properly upon build, and yes they were too tight on the pass side. So, we pulled valve covers, adjusted all on pass and driver side to be safe. Only the pass side was too tight. So we are thinking this is the reason why the pass side cylinder head got so hot?

Next startup, now the timing light is showing the balancer timing mark WAAAY below the timing marker on the timing cover. Runs like dookey and bogging down when we try to accelerate it thru the linkage on the new edelbrock AVS carb. (we have the vacuum advance line going to the Right side on the front of the carb, and the left port is plugged off. So we figured we needed to adjust the distributor timing, and we can only go so far obviously turning it counter clockwise. Even though it was perfect last night when we were doing the initial startup. Decieded to pull the cap, and there is Burned into the contacts carbon pretty bad. New HEI dist from Autozone not reman.

Does anyone have any ideas on how to get this properly running? Possible bad distributor at this point? We are stumped. (sorry we arent engine builders) what is happening?

Lorenzo

[RustyPile]

Glowing exhaust manifolds shows all the signs of late timing.. First thing I'd suspect is the outer ring on the harmonic balancer has slipped.. Probably already slipped when the timing was initially set.

Is the balancer a new one? There are two different balancers with each having a different timing groove location. And also two timing tab locations.. One has the tab located at about the 12 o'clock position on the cover.. The other has the tab down around the 5 o'clock position. The balancer has to match the tab location.

[elorenzof]

Yes sir, the engine is 100% rebuilt 327 from an engine rebuild shop here in phoenix. The harmonic balancer is also new. We do have the old HB and it is the same size in diameter. We We did was put on the intake manifold, dist, carb, etc and dropped her in and hooked everything up to get her running

[Lee H]

Remove the drivers side valve cover and find top dead center on cylinder #1. Lots of YouTube videos on this method. Then check the balancer and timing tab to see how they line up. Also see if the distributor rotor is in the correct position.

[kwmech]

Possible lean condition in the carb

[RichardJ]

>>the pass side was getting way too hot and melting the 90degree spark plug boots. .................. But we could feel the heat on the pass side and the exhaust manifold was starting to get red<<................ >>why the pass side cylinder head got so hot?<<


Any ignition or carb issue will/should affect both banks.
I've never experienced it, but wouldn't a clogged exhaust on the pass side cause these problems.

[geezer#99]

You said, Initial start and timing set to 13 degrees.
Does that mean you started it and let it idle for enough time until you set timing?

Or you set timing on first start of 1500 rpm.

If you let it idle long enough to set timing, you might have started to flatten the cam.

[kwmech]

Originally Posted by RichardJ

>>

I've never experienced it, but wouldn't a clogged exhaust on the pass side cause these problems.

I had the same thought with an issue I went through in the mid 70s when I helped a friend put headers on his van. Then we took it to the exhaust shop to finish the pipes and mufflers. When finished we drove it about 2 miles down the road and smelled something really weird and stopped to look under. What we saw was 2 red hot headers. Took it back to the shop slowly and the guy said he inadvertently put the mufflers on backwards. Huh? he swapped them end for end and the problem went away. I didn't know that was possible then or even now that it would make a difference

[Ironangel]

Distributor cap was carboned up because the timing was retarded. Need more info like, how did you know the initial timing was set at 13 degrees BTDC? Never break a motor in at anything less than 2000 rpm and the timing light should be reading anywhere from 20 to 30 degrees BTDC @ 2000 rpm for at least 20 minutes. One whole bank of valves being set tight is a big red flag to me, did you call the shop and make them aware, maybe ask what their procedure was? Go through and reset all the valves, then set #1 piston at top dead center. Your timing marks should line up at 0 degrees and the rotor should be pointing at #1 on the cap. Now fire up the motor with the timing light ready, and keep the rpm at 2000 while you adjust the timing. Give it 35 degrees at
2500 to 3000 rpm and run it at 2000 rpm for 20 minutes with occasional blips up to 2500. Breaking in a new motor with an out of the box carburetor is never a good idea. Hopefully you've used a good break in oil and that cam survived. Change the oil after break in and cut that oil filter open and check them for fleck...

[HO455]

First you need to verify the outer ring on the balancer has not shifted or is loose. That would account for your wild timing movement. If the balancer checks out then you need to check the mechanical timing of the engine.

Is the piston at TDC when the balancer is lined up at TDC?

Is the rotor pointing at the correct post (#1) in the distributor cap when the timing mark is at what you set it at? It is possible you may have sheared a key in the timing chain (Worst case scenario). Or maybe a key didn't get installed. Did the engine ever backfire?

Having bad rotor phasing can cause excessive arcing under the cap. Look up some videos on rotor phasing if your not familiar with the concept.

I would not run the engine until these things are verified.

Take nothing for granted until you check it. This includes brand new parts.