need Some help. I have a stock 305 tbi with headman shorty headers. Removed air pump and egr systems. Egr is blocked. I do have the stock ecm still. Cylinders 4 and 6 header tubes get extremely hot. About 200+ degrees hotter than the rest. Car runs smooth with no signs or misfire. Plugs look like they were never fired. Checked and I have spark. Out of ideas. Please, any advice would be great. Smart comments would no help thanks

 

How about cylinders 1 and 7? 1, 4, 6, and 7 are all fed from the same plane of the intake manifold. In the old days, that'd be a sign that one of the idle mixture screws wasn't adjusted properly; or one main jet was partially-clogged. In your case, maybe one injector is partially-plugged.

A vacuum leak into one plane of the manifold could do that, too. Is there a vacuum port shared by the #4 and #6 intake runners?

White, "new-looking" plug porcelain is a sign of lean combustion. OTOH, it takes thousands of miles to color plugs with unleaded fuel, so lack of color may mean nothing. What do the other plugs look like?

Cranking compression test results?
Power-balance test results?

Have you connected a scan tool to look at the data stream?

Why would you remove the EGR and air pump? No benefit from that. Removing the EGR is especially problematical as it requires re-tuning the fuel and spark curve or you'll have detonation that the knock sensor picks up and retards the timing--less power, lower fuel economy.

 

Hey thank you for the reply. As far as removing the egr and air pump. No Rhyme or reason for it. Not regretting it as of yet,but I do I feel it might be my underlining problem.

As far as everything else you covered,

I will have to do a compression test.

Plugs 2 and 8 which are on that bank are kind of black, they look like they are actually doing work. (I will remove all of them tomorrow and post pictures).

I did not know 2,4,6,7 were run off the same injector. I will look into that tomorrow as well.

As far as power balance... please explain that test.

And I definitely do not have a scan tool to check data. I do on the other hand intend to have the ecm reprogrammed, as long as I can get a grasp on this situation. Thank you again for the help.

 

I corrected my post; should be 1, 4, 6, 7. Look at how the manifold is shaped. The upper plane feeds two end cylinders on one bank, two center cylinders on the other bank. The lower plane does the same thing for the other cylinders--but it's harder to see.

Connect a tach; or vacuum gauge to manifold vacuum. Run engine to normal operating temperature. Grab a test light, connect the clip to a good engine ground. Put some dielectric grease on the pointy probe end.

Engine running, slide the pointy probe BETWEEN the plug wire and the distributor boot. DON'T puncture the insulation, just use the point to separate the wire from the boot. When the probe goes far enough up the boot, the spark will jump through the test light instead of the spark plug. (the light does not flash) This kills the one cylinder you're testing. Note how much the RPM or the vacuum drops. Pull the test light out of the plug boot--no harm done to the plug wire. Do the next wire. Again, note the RPM or vacuum drop. Every cylinder should have approximately the same amount of RPM or vacuum drop. Any cylinder with less is "weak". Any cylinder that doesn't drop at all is dead. If you go around the cap, doing the wires in order, and every other one is weak, you have a problem with that plane of the intake manifold; which could be a vacuum leak or weak injector.

Buy or borrow a scan tool BEFORE you reprogram anything. Find out what's really going on in that engine.