OK, my friend have strange problem. He have ´73 Eldorado (http://usaraud.ee/?id=5_5_20_86), totally restored but...5 & 8 cylinders doesnt work.
Compression is OK in all cylinders (10 atm), distributor, wires, coil, carburator, fuel pump and filter spark plugs are new, no cloggings in intake...
If he tried to drive without wires in 5 and 8, engine was little worse, than with wires. So something works in those cylinders.
Is it possible, that carburetor isnt properly adjusted?
Any other ideas?
We really need help, as we dont know, what to try next... :crybaby:

Perhaps the intake manifold gasket has slipped or been sucked into the intake port on those two cylinders?
Have you checked for vacuum leaks, or oil in the clylinder?
Happened to me once before.
Maybe the #5 and #8 ignition wires are crossed?

Perhaps the intake manifold gasket has slipped or been sucked into the intake port on those two cylinders?
Have you checked for vacuum leaks, or oil in the clylinder?
Happened to me once before.
Maybe the #5 and #8 ignition wires are crossed?
No vacuum leaks.
No oil in cylinders.
No crossed wires - wiring order is OK.
He also tried to adjust distributor gear (few teeth forward or backward) - nothing.
He already uninstalled intake manifold today - no gasket problems eather.
He also plans take heads off - for inspection.

Have you checked for correct valve lift on those cylinders?
I assume a new cam and lifters were installed?
Mike

Yes, cam and lifters are new. But he doesnt checked valve lift - compression is OK, then valves must be OK too?

Well, if the valve opens any it will most likely yield a good static compression reading, but it won't run correctly in normal, power producing mode.

Any more help out there guys?

OK, my friend have strange problem. He have ´73 Eldorado (http://usaraud.ee/?id=5_5_20_86), totally restored but...5 & 8 cylinders doesnt work.
Compression is OK in all cylinders (10 atm), distributor, wires, coil, carburator, fuel pump and filter spark plugs are new, no cloggings in intake...
If he tried to drive without wires in 5 and 8, engine was little worse, than with wires. So something works in those cylinders.
Is it possible, that carburetor isnt properly adjusted?
Any other ideas?
We really need help, as we dont know, what to try next... :crybaby:
If you know for a fact you are getting spark from both the #5 and #8 plug wires then Check the E.G.R. valve and see if it is stuck open a small amount from carbon build-up also check its gasket for a leak.
I don’t remember if the E.G.R. valve on a 500ci was installed close to if not over the #5 intake runner. I don’t remember the location of the vacuum brake booster connection as to being at the base of the carburetor or at the rear half of the intake manifold but this hose should also be checked for leaks. There should be a common cause as to both cylinders problem and I would guess the #5-#8 intake runners are probably receiving their fuel-air mixture along with added air or exhaust gas causing a lean condition thus a misfire in those cylinders.

EGR is disabled (and closed with plate) and brake vacuum is also checked - no leaks.
Owner tries to replace lifters with working cylinder ones - maybe this helps something...

EGR is disabled (and closed with plate) and brake vacuum is also checked - no leaks.
Owner tries to replace lifters with working cylinder ones - maybe this helps something...
Remove the E.G.R blocking plate and view the underside to see if you can detect a leak (discolored area) cross its surface from the area that would be covering the exhaust gas port to the intake port. I have blocked the E.G.R. passages myself in the past and have had the gasket burn through. Have all the sparkplugs been removed and checked for gap setting, color and or fuel fouling especially #5 and #8? If none of these suggestions are helping I guess you will need to submit a more complete history of the engine before the problem started.
BTW detail the methods used in checking the cylinder compression (all sparkplugs removed and the throttle held wide open), vacuum (with a vacuum gauge at idle), ignition point gap or dwell angle (dwell meter), ignition timing, sparkplug wires, sparkplugs, sparkplug gap settings and carburetor adjustment. How many of the parts are new and did the owner or someone else install them?
The more accurate and detailed your submitted information the greater chance for an accurate diagnosis.

Haymaker - he already removed intake manifold and will remove heads too for inspection, i´ll let you know, what he find
Thanks for all you guys!
To be continued....