Compression test

[BLACK Ttype]

Doing a compression test.
When I crank the motor the needle on the guage jumps to 90psi, is this enough?

 

[6SENSE]

1st off, is engine warmed up, all plugs out, and throttle blade open?
90 psi is pretty low. The major issue is that all the cylinders arent too far off from each other. I'll have to look it up but I think that they should be within 20% (?) of each other, but 90 does sound low. The last time I did mine they were all around 130ish. Which cylinder is that and what are the other readings?

 

[BLACK Ttype]

No that was pulling the plugs one at a time, throttle blade closed.

All cylinders were exactly on 90 accept the center one on the passenger side.( don't feel like thinking about cyl. # right now.)
It was at about 78-79

Put the last plug back in and started it up.
horrible tapping sound from the motor.
I think I F***ed up the cam.

I guess I need new cam and lifters now huh?

 

[6SENSE]

It helps to have all the plugs out, battery fully charged (or hook up a battery charger set to high/start), and the throttle blade propped open. All of this will help with getting the maximum readings. With out doing these things the engine wont be able to crank/rotate as quickly. Your relying on the starter to turn the engine so if spark plugs are left in, the compression of each cyl will retard the starter's movement. Same deal with the battery. It needs to be up to charge and remain so throughout the test. If the starter does not spin the engine fast enough, the cylinders will not fill up properly for the test. Opening the throttle blade/valve will help to bring in air to fill the cylinders. Also, let the engine crank four or more times until you get the highest reading for that cylinder. You dont have to do the test with the engine hot, but some prefer to because it better duplicates running conditions. It is possible to have good compression while the engine is cold, but have a leak when the engine is warm.
That percentage spec I mentioned before is actually 25%. So your minimum compression readings must be within 25% of the highest reading (= or > 75% of the highest). The absolute minimum reading should be 100psi, which is why I thought your 90psi didnt sound so good. I do know that hi-perf engines will sometimes have low readings due to their cams. Im not too sure that would apply to our vehicles though. Our cams arent nearly as wild as what Im thinking that statement applies to. Ive got the same cam as you and my lowest reading was 120-125 with the highest at 145. With my bad cam in the past the readings werent too far off (110L, 130H). Try the test as I stated above, and see if your readings go up.
How is the needle on your vac gauge moving, is it steady? Also, again, how did you break the cam in Did you follow the proper break-in instructions, and also use a generous amount of engine lube on the cam and lifters?

I would be surprised if your #s jump up drastically , you did mention something about blue smoke didnt you? Is this coming from the valve cover breather? Is there pressure coming out of this breather when the car is running?

 

[6SENSE]

Oops, Im sorry, I just saw your post in your other thread about the cam break-in . When I wiped my old Postons 202/202 a few years ago, it was my first crack at putting together a TR. I couldnt seem to keep the car running when I first started it up. It sat idling a couple times during break-in, which is not good , especially with our goofy oiling systems. Much more to deal with on these engines with sensors, etc., then just starting up a carbed small block chevy.

What Ive always done before start up (after changing cam or timing chain, etc.) is to crank the engine (with the ECM pwr lead unplugged) until I get oil pressure started on the gauge (having a battery charger hooked up may help too). If the engine has sat for a long period of time, you may need to use a drill driven pre oiling tool. If youve had the oil pump apart, definately pack with petroleum jelly.

 

[BLACK Ttype]

So what is the definite way to know if the cam has a wiped lobe?
I take it the vac and lower compression in one cylinder is a good indication.

 

[cool 84]

Probably a wiped cam. But something easy to try is pull the valve covers and inspect the rocker arms, pushrods, and rocker shafts. It only takes a couple minutes. You can also have someone turn the motor over without starting it and watch the motion of the valve train. If the cam is wiped or in the process of wiping you shouldn't be running the motor or you'll have much bigger problems than a wiped cam. Pull the oil filter and cut it open to see if there's metal in it.

90psi is barely enough for that cylinder to fire. Any lower and you'll probably have a dead hole.