Author Topic: 305 Not Running Correctly. Unable to find problem.  (Read 55 times)

Offline StarrLion

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305 Not Running Correctly. Unable to find problem.
« on: September 14, 2021, 09:31:05 PM »
Hello everyone.  I am new here.  But I did search on here before I was approved to try and solve my problem.

85 3/4 ton utility bed 700R4 2 w/d Chevy. 

I have a 85 305 engine that started missing out under load.  And at certain cruising speeds.  I am at a lose to figure out why.  What I thought was going to be a simple fix has turned into any but.  I have owned the truck for 21 years now.  I have never had any problems with the engine till now.  Unknown miles.  And known history before I bought.  But it was still in stock configuration when I got it.

When the truck hits second gear it will act like it is cold.  Not warmed up yet.  Carburetor on this one.  It acts like fuel starvation.  You get up to speed and back off the throttle and then give it just a we bit to stay there.  It will spit and spatter and backfire sometimes.  Throttle down more it is fine.  It also does not do it all the time. 

What I have done.  Which has not solved this problem at all.

New fuel filter.  Then carb rebuild.  Then another carb.
New cap, rotor and modular Twice!  To make sure.  Dist. is 6 years old.  HEI Vac Advance. 
New plugs and wires.
New fuel pump.  Which the old one tested fine.  Flushed lines out also.
I can not find any vacuum leaks.  At idle it is 16.5 to 17.  Higher RPM 19 to 20.  Needle steady.
Does it with or with out vacuum advance hooked up.  Though not as bad with it not hooked up.
I could find nothing lose or wrong with the Distributor.  Tested advance at idle with a vacuum and it worked as should.
Plugs were correct color when removed.  Good shape really. 
Checking timing.  Checked advance with light.  All was fine.  I was more interested in seeing a unstable pattern then what it was set at.  I do not remember the number. But it was not way off or way advanced which could cause this also.

I have owned it for 21 years.  I have never put a timing chain on it.  That is my next thing to check.  If the timing chain is at the point it is causing retard timing in the engine.  I have noticed that since this has started.  There is no spark knock anymore.  This engine has always be really bad with knock.  Even with 93 Gas and the stat at 180 deg.  Not hearing the knock anymore has me at that, or this distributor is going bad.

Any idea or what I should test next would be grateful