302 engine issues.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Now that I finally got the carburetor on my 302 dialed in and the engine running pretty good, i want to fix a valve tap. I have had a valve tap pretty much since buying the truck two years ago. My neighbor tried to address it buy putting shims under the tiny cap that is under the rocker on cylinder #2. I'm guessing the shims have been obliterated because the tap is as bad as ever. I'm thinking about pulling the valve covers and checking all the rockers for excess looseness and going to try and replace parts that are worn. I don't want to buy new or refurbished heads at this time. So do you think I could get away with just replacing worn parts?
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
If it's got lash caps, it's also got rail rockers, these were known to chew up the valve stems too. You can also remove the rocker nut and install a thick washer under it to gain some adjustment on the positive stop studs.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Indeed it has the lash caps, and your right it has the rail rockers which were not supposed to in production prior to 1978 says the machinist at Napa and my truck is a 1976 So if he is correct my truck had a engine replacement or at the very least the heads were replaced with 1978 or later production heads. Any how I went to Napa and the machinist said my #2 rocker has excessive wear and is likely the reason for my tap at #2. I ordered two new rocker arms with two new pedestals that the rocker sits on top of. Hopefully the tap goes away. I will let you all know next week.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
This whole situation has me scratching my head, I don't know what I have any more, or what's right and what's wrong?
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
If that's a 76 truck, the heads have been replaced. Look at the date codes in the rocker valley, next to the valve cover rail.
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Elder User
Joined: Jun 2015
Posts: 664
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From: York Pa.
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Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
C8AM is a Mexican block. It's got the thicker Hi-Po style main caps. It's no different otherwise than any other 68-79 302 block. Should also have two "knorbs" in the front walls (one on each bank) for a Mexican accessory application. Look and see if there's a data plate or tag on the block above the oil pan towards the front. If it was a reman engine, it would have a data plate/tag. If not then someone rebuilt it on their own, if rebuilt at all. The heads certainly aren't original to your truck. It's a good candidate for a stroker engine, provided it hasn't been bored .060 already.
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Elder User
Joined: Jun 2015
Posts: 664
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From: York Pa.
I don't need to find tdc to tighten cylinder 1, rotate 1/4 turn to tighten next cylinder in the firing order, etc,etc,etc.? Just simply tighten all rockers to 25ft/lbs, no rotating? Gotcha, thanks.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
No, just torque em all down.
Lead Driver
Joined: Sep 2003
Posts: 7,016
Likes: 208
From: SoCal
You check the lash of each cylinder using the old procedure of turning the crank until the valves are closed. Then turn the bolts down until they take up all the gaps between the rockers, pushrods, and lifters. Then you should be able to turn the bolts about 3/4 turn to torque them down. That should push the rods about .030" into the lifter plungers. If the rods push in much more than that, you can install a shim under the pedestal. I did that recently with a newly rebuilt set of heads, and they've been running very quietly after warm up, with only a slight tick right after start up. Of course, mine are rollers, so they did not need that initial 2000 rpm for 20 minute break-in.