the op said in 1st post he adjusted the valves, if a lope was completley gone I think even Ray Charles would notice the difference in the static position of the rockers
1981 Elco 305 - 2 cylinders not firing
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the op said in 1st post he adjusted the valves, if a lope was completley gone I think even Ray Charles would notice the difference in the static position of the rockers
count the threads above the adjustment nut. on a good cam, they should be within half a thread of each other.
In the late 70s to early 80s there was a bad batch of cams out of the factory. GM changed a lot of the really crappy ones cuz they didn't make warranty. I sold a million of those mothers at about 70-80k that was the second wave. Almost all of them I remember selling were for 305s. Get a travel indicator and measure the travel at the pushrod side of the rocker arm. Then you will know what your cam is doing. I'll bet it's flat on 1 lobe. It doesn't take much. .005 on the cam is .0075 valve lift. On a factory cam that little bit is already 2% of you total lift. It is also possible that the stud is pulling out of the head. Those are pressed in. Back in the day we used to pin them. My 334 started pulling studs with a mild Crower cam. Well below where it should have been pinned.
A travel indicator can be had from Amazon for next to nothing. You don't need a quality one. Get a mag base as well. You need both to degree a cam or set up a rear end. You could spring for a degree kit as well.
A travel indicator can be had from Amazon for next to nothing. You don't need a quality one. Get a mag base as well. You need both to degree a cam or set up a rear end. You could spring for a degree kit as well.
Ok when i did the compression test at first i really didn't know where to expect the air leak to come from so i watched a video from Eric The Car Guy and i also didn't know the piston had to be at TDC. So today i redid the test on both 1&7, each with its piston at TDC this time. And recorded a video of it. Air is escaping through the carb. What am i looking at now? Thanks fellas.
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intake valve or valves are not seated causing air to escape thru the intake. this is your popping back and low compression. one or more valves could be burnt, bent, held open by a bad lifter, valve stems sticking in the head, etc.
i would take the rocker arm off of those intake valves and retest, to see if anything changes.
oh, and add some zinc to the oil.
i would take the rocker arm off of those intake valves and retest, to see if anything changes.
oh, and add some zinc to the oil.
I'll see if i can bother my stepdad for his compressor again lol. But here's a video of the valves moving (if it helps to narrow anything down)
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My 86 305 is worn. I went to adjust the lash, and after one revolution it loosened back up. I’m pretty sure it’s the studs are pulling out. I have a reman with a flat tappet cam. I had the same issue years ago with a reman 305 in a Camaro. I’m just cruising mine as it is for now.
Ok so i did the test again, this time with the rocker arms removed and it is still shooting air out the carb. So i removed the intake and took a video of the valves through the ports. Hard to see but here it is...
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