By the way puting a comp tester on a Big Block with headers in a C-3 is a BIZITCH!!!!!

Here are the results:

#1 145psi
#2 140psi
#3 145psi
#4 150psi
#5 145psi
#6 146psi
#7 145psi
#8 144psi

Glad to see there are almost no major problems. My plugs where HEAVILY oil fouled and carboned. I have gotten advice from a mechanic to change my valve seals IMMEDIATELY. So what kind of valve seals should I go with?????

Any comments and suggestions much appreciated.

 

Looks like they are all within the limit. You do have me a little worried as mine were 230 psi :eek:

 

Out of curiousity.... what got you to do the compression test? The oiled plugs? Valve seals are a pretty inexpensive item, so no reason not to go after high performance aftermarket applications. I haven't checked into it in quite awhile but Manley, Crane & K-Motion all make good stuff for valve trains that you can't go wrong with.

 

I was always curious what kind of condition my engine is in, I have no idea what kind of life its had before I got it.... Lately I have had a mis at 3000 rpm and the plugs were the last thing to get changed in the ignition system. While I had them out I wanted to give it the test. I think I can now safely say my rings, cam, valves, etc. will be OK for now. I have known my seals were bad for a while, smoking a little and oil consumption. Now I know that its also trashing my plugs.

 

Small blocks (BUT NOT BIG BLOCKS) are known for pulling oil through the valve guides. The reason the plugs foul is the location of the plugs. BB plug location is different, so plugs usually do not foul from valve guide seals. You can install umbrella type aftermarket valve guide seals with the heads in place, however... they can be used ONLY if the boss is machined for them. Some heads are..Some are not. You can have them machined but of course the heads need to be removed. Again this is a small block issue.
What also seems strange to me aside from the fact that you have a big block is that all of your plugs fouled!! Usually only one or two do this. Sometimes a coulpe will be fouled and a few more will be carboned up but .... not all of the plugs. At least I have not seen that from valve guide seals. I would check for pugged PVC system and clean out the oil return holes in the heads. Also.. if your engine has a lot of blow-by and uses lots of oil, the rings can be not seated (stuck in the groove) or worn, in which case oil will be pushed up into the cylinder. This excess of oil will actually raise the compression,much as if you were squiring oil ino the cylinder to check for ring wear. If your engine is not using a LOT of oil then the that is probably not the case.


[


[Modified by silvervetteman, 6:03 AM 2/4/2003]


[Modified by silvervetteman, 6:04 AM 2/4/2003]

 

I think I heard somewhere that the cylinders should be within 10% of each other. If this is true, looks like you're in good shape.

I have the same problem. I changed my plugs last week for the first time and they all had black crusty stuff on the ends and the threads were soaked with oil. It doesn't use much oil and the only time it smokes is when it's first fired up after a long (1 month or more) layup. I bleve there's a seal job looming!!

 

Your numbers look good. You really can't compare the number from one engine to another. There are too many variables which come into play (cranking speed, cam, etc). Those numbers are real consistant.

I believe you want to stay away from teflon seals and either go with rubber or viton seals.

I also like this for removing the valve springs:

 

Your right Silv, my mistake, I can't really say that all the plugs were all fouled because she still ran decent until 3000rpm or under load, then would mis horably. They defininetly were all carboned. PCV system seems ok. Oil passages are really clean. But, I am getting oil blowing out of the fill hole. Any more advice??

Wouldn't it be safe to say that ring blow by is not an issue in my case??


[Modified by 71,454,4spd, 3:36 PM 2/4/2003]

 

consistant numbers are great!!!

 

Oil from the fill hole is not normal. The Pcv valve should eliminate that unless it is plugged or restricted. Crankcase pressure is created by blow-by and controlled by the pcv within limits. If you have aftermarket valve covers then maybe the breather hole is not open which would not allow the crankcase to vent properly. PCV pulls vapors (and oil mist) through one valve cover and the opposite cover must breathe.

 

This might be my next step. tonight as I left the house to go to a local show after about three miles the BB started running on what sounded like 7 cyl..
plugs are only about 2000 miles old but I have had carb problems so that could be it. :confused:

 

EXTREMELY rich mixture will foul plugs.

 

Not to worry. Mine was a little higher than that. 406 with 12 to 1 CR. I had a Comp Cam 244@ .050 I used Rhoads lifters for a nice 500rpm street idle and low end but doing so raised the cylinder pressure at low rpm and made it hard to start when hot. Comp Cams ground a special cam for me with more overlap to bleed off the cly pressure and everything worked out fine.

1976 406 TH400 3000 stall switchpitch 4.11 12.14 on radials

 

Joey, I would go with GM valve stem seals, Kieth @ Ray Chev in Abberville can help. Call me if you need his number, he is a great parts dude and a vette owner too. His BB 76 ran 10.47 on NOS!!! Really fast. Anyway oil control on BB's is a problum but according to your info I would guess that the valve guides are the real problum! Keep in touch. Thad

 

Hey Thad, Thanks a bunch for your info. You know what kind of heads I have, (I remember you spotted them with your evil eye) ;) any idea which seals I need? What about this I have heard that aftermarket seals my be better (last longer) than the GM stuff?

 

Please help me understand, if I had a problem with rings wouldn't the compression test have revealed a problem?

Should I replace the valve seals?

 

The compression test won't necessarilly reveal a ring problem if all of the rings are in similar condition. Specs call for 160 psi on your engine but the variables involved in testing could account for your numbers being less even if your rings were ok. Assuming that there were no variables in your test (cranking speed, cylinder wall oiling, etc.), I would suspect worn rings. Oiled plugs and noticible blowby are also clues. Worn (but not "shot") rings can cause there to be more oil mist being sent through the PCV system to coat your plugs without oil consumption being enough to be obvious or showing as a problem in the PCV system.

The next time you suspect a problem, pull the plugs first, not last. As wear items with a limited life, the plugs are often the problem. What plugs are you ruinning? A plug that's too cold is likely to mimic other problems. While wires, cap, rotor, and other parts of the ignition system degrade over time and use, the plugs function in a MUCH harsher environment. The long plug replacement intervals that are typical of our other, EFI, computer controlled cars don't apply. Even the factory recommendations for early Vettes are too long except for stock daily drivers. Weekend drivers, modified cars, and those that spend a lot of time being warmed up or idleing while being fiddled with, would probably benefit from an plug change every few thousand miles.

 

Thanks a bunch Vetterodder and everyone else for your advice, its been a great help. I am running the recommended plug for my motor, AC Delco R????? I forget the number. The last time I replaced the plugs was about 2 years ago(2000 miles ago). But like you said, under its unique conditions that may be to be expected, which I really don't have a problem with......