88 van 350 tbi problems

At this point, being that the bearings have been eliminated, I'd be leaning towards it being the wrist pin.

There is something you could try. I'm not going to guarantee this will tell you anything or not, but what is there to lose except some more of your time and labor (easy for ME to say, right? lol).

Take all the plugs out except the bad cylinder's plug.

Rotate the engine around until you start to feel compression come up on the bad cylinder (plug still in).

At that point, with a breaker bar/socket on the crank bolt, see if quickly bringing the piston up against the pressure will let you hear the noise.

If you can- and you are sure the bearings are good- that's the wrist pin.

Do this with the engine warmed up real good.

EDIT- There's NO WAY that #3 and #4 plug wires are swapped at the cap, right? Even if you're you checked, just to be absolutely sure, please check again.



Firing order is:
1-8-4-3-6-5-7-2


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A head gasket leaking between two cylinders can cause this exact issue. Do a compression test, and look fo 2 cylinders side by side to be low. Makes a bad "spark knock" type sound, and no amount of timing adjustment will cure it. BTDT.

Ok thanks I will try are copression tester wouldnt work right so I will check it thanks But when I retard the timing it seems to go away or is that maybe bgecause were not producing aenough power to here the knock?

It will seem to go away, but it is just because the thing is firing so late that you basically can't hear it. The compression test is the diffinitive test for the head gasket in this case. Is will either confirm, or rule out the gasket as the source of the issue.

Thanks man for you help Ill check it and let you know thanks again