This may be two problems, but the one is baffling me.

97 Toyota T100 3.4 V6 engine. Four camshafts, mechanical adjusters (shim and bucket).

Head gasket gave out on one side, replaced both. Not a fun job. Involves pulling all four camshafts, and getting the interconnected timing right on them. Put it all back together.

Go to start it, and whirs with that classic no/low compression spin. Damn!

Put a compression gauge on a cylinder, spin the engine, and get 80 psi. Damn damn damn.

Now this is where it gets weird.

Noticed when I cranked the engine the gauge only jumped once. There was no sign of pumping up. Retest compression, get 30 psi. Do it one more time, get...nothing. It's like the valves are pumping up and staying open, which on a mechanically adjusted engine I don't see how. Let it sit for a few minutes, and I can repeat this. Low compression in a single pulse, almost no compression, none. What the heck???

At this point, I'm figuring I screwed something up with the camshafts, in spite of my best efforts to keep them straight. They're even factory marked as I recall. But, I've got to check them, which means pulling the intake back off to get the valve covers off.

But this single pulse of compession, and then a lowering of compression to nothing, that baffles me.

MS sucks, I get so confused these days. I wouldn't be surprised if I really did install the camshafts on the wrong banks, in spite of my best efforts not too. Sad looking at my coding for the vacuum hoses. I'd try to write the same number on the hose end and fitting, but about half the time I wrote the next number. So connect hose two to fitting two, or three, or one. The physical debilitation is minor, but this mental degradation, arg!

Did you take the rags out that you used to block off the intake ports?

Well, I don't feel quite so bad now. Pulled the intake and got the valve covers off so I could admire things in there. Thecams are on the correct sides, and in the correct holes. So all is good that way.

But after looking at things, and then going back to look at the factory manual, I found it. There are multiple timing marks on the sprockets, and the manual gives three different contradictory ways to align them. 1 dot to 1 dot, or 2 dots to 2 dots, or 1 dot to 2 dots.

So, the good news is I can leave the belt and intake cams on, and just lift out and reposition the exhaust cams. And while I'll still use the various dots, I'll have to actually use my brain and see where things are in relationship to the lobe timing in order to pick which sets of dots to line up.

Maybe I'll be finished before Christmas.

Sorry I can not be of more help. There has to be someone that has done this and posted it on the web someplace.

Is the loss of compression for each test becuase the valves are now bent?

Rob R.

This is exactly why I play with rotaries.

It's a non-interference engine. Can't explain the way the compression was cycling down when tested (on a single cylinder though). That part still makes no sense to me.

1 @ TDC before you reset the cams?

Spinout007 wrote: #1 @ TDC before you reset the cams?

The crankshaft marker is right at TDC, and the intake cams and their markers are spot on.

But, I do intend to use some dowels down the spark plug holes, just to make sure, and to follow the firing order around the engine. I don't want to repeat this.

Yay! It started. Didn't run it but for a few seconds, since its not all together, but after some farting and sneezing, it ran.

Then it started to rain, so I stopped for the night.

Good thing the truck started. The miata just grenaded its power steering pump coming home tonight.

foxtrapper wrote: Yay! It started. Didn't run it but for a few seconds, since its not all together, but after some farting and sneezing, it ran. Then it started to rain, so I stopped for the night. Good thing the truck started. The miata just grenaded its power steering pump coming home tonight.

glad for your truck news... sad for your Miata news.......