I have a 77 302 and it is running bad, it missfires and acts like my timing is off but I have it set perfect and still has the same problems... I have tried everything except to replace the dizzy (doing this as soon as I can) I hooked up the vacuum guage to it the other day and the needle was on normal but it bounced arround a bit ( moves side to side aprox a little smaller than 1/4") and when I rev it up it goes completly straight and into the red zone which says (late ignition timing) and befor I had the timing sey by ear and it said that the valve timing was off, I looked in my book and read that it says ( bounces arround except when in high rpms and the needle straightens out was a sign of my valve guides being worn... ? Are valve guides hard to replace? I have a valve spring compressor and all of the basic tools to disasemble the top of my engine.... I am puting a edelbrock cam in it very soon and was wondering if I should wait for the cam to get here and take everything apart and check it out and clean my heads and check everything ( also check compression ) because my spark plugs are doing some weird things also, I took them out the other day and the connector that clipson to the top of the plug busted off... and all of my plugs look weird they are clean in some spots and one is completly black its my #6 I think....? not totaly sure I would have to go check again.... but what does everyone think I should do and how much would this cost me as for gaskets and special tools? and mainly is it a hard project?

 

Before you tear everything apart do a compression test and post the results here. The bouncing vacuum gauge sounds like it could be bad valves. Without the compression test it's hard to guess.

 

ok ill do that, but I wanted to know anyways if it is hard to change all of the valves, seats and seals.. ? I am planing on upgradeing to edelbrock heads in the long run and wanted to upgrade my valves to somthing stronger... Also if I get a aftermarket cam, I know I have to get stiffer valve springs, but will I have to buy anything else to put in a new cam... keep in mind this cam is NOT going to be to radical.

 

If you're planning a cam swap you want to know the condition of the engine first. That's why I suggested the compression test. If it shows much variation you'll probably be in for a valve job. Also, you can't just put in new valves without doing some machine work to the heads and expect it to hold up. If you're doing a valve job then you might want to think about rings and bearings at the least. Too many times a valve job was done when the rest of the engine was tired and caused problems with blowby, etc.
Also, depending on the cam selection, the valve springs might not be stiffer than the stock springs. It would depend on what's recommended for the cam. This is a case of more is not necessarily better. Heavier springs can handle higher rpm's and more radical cam profiles but they also create more wear on the valve train. You want to match the springs to the cam.


It all starts with the compression test.

 

ok thanks ill do that first.

 

Your no. 6 being black is suspicous! Was the black a fluffy substance that would wipe off on your hand like a powder, or was it wet and oily? If it was dry (and the other 7 plugs were not like this) then that cylinder is not firing well, or at all, which would be the cause of your miss. Could be a bad plug, plug wire, dist cap or rotor, bad lobe if points or bad pole if pickup. I doubt it's a rich mixture or it would effect all the plugs.

If it's wet and oily, then that cylinder has bad rings or a bad intake guide (and the rest are following). Do as the others say and get a compression check (or better yet a leakdown test). It won't tell you if the guides are bad (unless the valves are leaking or burned), but it will detect bad rings. Both bad rings and bad guides can cause a tick at idle in the vacuum gauge. Bad guides alone, or a vacuum leak elsewhere will usually cause the gauge to move slowly back and forth about as much as you state, and the overall vacuum will be lower.

Bad guides result in pulling the heads and heading to a machine shop. Bad rings...full rebuild.

 

well that is a huge weight off my shoulders..... Its not wet and oily.... I know what a bad valve or rings are like.... I had a DOHC 2.3 H onda engine that had a bad valve.... expencive to machine the head.... and to take it off.... buy its a sooty black powder... i know the cylender is not always firing.... I can hear it pop every so often... I am replaceing the dizzy and geting all new plugs wires, cap and rotor. Also might replace my stock coil to aftermarket Ford Blaster II coil... but that would be after this is running fine.... I will keep you up to date on whats going on with it...