I just got done installing my GM846 cam but now I'm not able to adjust the valves according to the factory manual. I know the timing marks were lined up dot to dot so it shouldn't be a timing problem. According to the manual, after I adjusted the #1 cylinder, I should've been able to adjust the rockers on a few of the other cylinders. On the #7 cylinder, I should've been able to adjust the intake valve, I wasn't able to do that because it appeared that both valves were still open. What gives? Others that were supposed to be closed were still slightly or completely open.

 

IMHO, you shouldn't try to adjust all valves with two turns of the crank. -Not on such a large camshaft.

I would personally loosen all the adjusting nuts, and try it again with TDC for each cylinder (-8 positions of the crank). This would ensure that you're not riding the base of a cam lobe.


[EDIT] ...and Dot-to-Dot is TDC for cylinder #6. 12-and-12 is #1 TDC. That may be part of your problem...

 

Go to 1/4 with the feel on the push rod method.When you get them loose,tighten them down a little at a time while rotating the pushrod.You will feel a slight drag when turning--this is zero-- go 1/4 past and lock it down.Now you have to get ALL valves on the cam heel.Pull all plugs,follow ithe firing order,put your finger in each cyl in the firing order and turn it over with a ratchet on the balancer bolt and when it goes WOOOSH--it will start small with the wooosh and get more sound as the piston comes closer to the top, adjust that cyl's valves.
Follow the firing order 18436572 starting from TDC#1.

 

I agree with the above suggestion to adjust the valves one at a time. Here's a link to Shoebox's how to:

http://shbox.com/1/4th_gen_tech2.html#adjust_valves

 

This really is strange to me because the cam I'm replacing is only slightly smaller than this one. In fact, the cam had the same exact duration, but less lift. I'd been able to follow the book method when adjusting those valves. I didn't think the overlap would've been that much more but I guess that's possible.

 

According to Chiltons, dot to dot is TDC for cylinder #1.

 

Dave,


I guess Chiltons is wrong then -- at least, misconceiving.

At dot-to-dot, the #1 piston is at the top of it's travel along with cylinder #6, but only cylinder #6 is on the compression stroke. "Top Dead Center," in this case, is referring to the compression stroke only -- not the exhaust stroke. Your manual should note this. The crank doesn't care what the cam is doing...


If you were following Chiltons, then I would have to assume you were adjusting the 'right valves' at the wrong crank position -- which is why some valves were still open, when they should have been closed. Just an assumption.


But what do I know, right? You dont have to take my word for it -- someone else will confirm this...

 

Alex is right. You are most likely 180 degrees off on the cam. You can either adjust the other 8 valves now, or turn the crank over once to put the #1 piston on TDC compression. Many people(myself included) have installed the distributor 180 degrees off in a Gen1 small block, because after installing the cam with the gears dot to dot, you need to rotate the crank once so the cam gear dot is at the top. It's a small but very important step that is often overlooked. Good luck.

 

When you do the #1 and #6 method, all you have to do to tell which one you are at, is to look at all the rockers or pushrods to see what position they are in. Compare that to the list of valves you can or cannot adjust at either TDC position. You should then be able to easily tell whether 1 or 6 is at TDC.

BTW Alex is correct and your Chilton's is not.

 

I appreciate the replies guys. Sorry, I'm not questioning what you're saying, I was just a little confused as to why I wasn't able to adjust the rockers the way I had before. Is there any way the cam could've been installed 180 degrees off, and if so, is there an easy way to determine this without pulling the timing cover? Thanks again for the help.

 

If you are referring to the timing set, then No, I dont believe there's any feasible way to install a cam 180-degrees off.

All that will do is put you at a different point in the firing order. Instead of being at #1 TDC, you'll be at #6 TDC. Or, instead of being dot-to-dot, you'll be 12:00 and 12:00. Remember, the crank rotates twice for every single revolution of the camshaft.

 

Thanks Alex.

 

It's not likely that it would be 180° off. If lined up dot to dot or both dots straight up-either would work and be correct. Cam indexing issues are usually like a cam tooth off one way or the other.

As I said before, bring the hub arrow up to 12 o'clock and look at the position of the pushrods or rockers (if they are tightened). Compare what you see to the list of valves you can adjust at either 1 or 6 TDC. Though they will be in various stages of lift, it should be obvious whether you are at 1 or 6 TDC.

IOW, if you see one of the pushrods way up, you know it is up on the lobe of the cam. That valve should correspond to one in your list that you should not be adjusting (you should be adjusting the group of the pushrods that are down). Compare a few more and you will see what I mean. The ones you see up, will all be in one list for 1 or 6 TDC. LOL, the more I try to explain, the worse it seems to get!

 

The only problem is, the hub isn't on the crankshaft yet. I've already identified TDC on #1 with both valves being closed. One of my concerns was that I should've been able to adjust one of the valves on the #7 cylinder but it appears that both are still open.

 

Then maybe you should use the individual method 3 that was in the link to my site that was posted early in the thread.