camaro_junkie

So I worked on my car a little today. I did a compression test. The results showed 140psi, 150psi, and 160psi on the first, second, and third strokes respectively, pretty much consistently across all cylinders. Although we had to test each cylinder a few times because sometimes the first stroke was 100-110psi, but we figured this could be due to the fact that the piston may have already been part way through the compression stroke on the first stroke. Any comments? Good/bad results?

I was also checking to make sure the timing mark was accurate. And I found something very funny. My timing is set at 12°BTDC. So I pulled the crank to 12° on the #1 cylinder compression stroke. And I used my old cap with a window in it to see where the rotor was (thanks to whoever gave me this idea, I can't remember who it was). And the rotor was halfway between #1 and #2 cylinder. So I moved the crank until the rotor was right at the #1 cylinder, it was like 20-25° advanced. Now this is really weird because the engine runs okay. Any ideas?

Last thing, this is a funny story. So I was about to set the timing (spec at 10°). I disconnected the by-pass plug and started the car. But it ran really rough. So I figured I must have messed up the timing loosening the distributor. I go around to adjust the distributor and shock myself really bad when I touch the distributor but... I HAD FORGOT TO PUT THE LEFT BANK WIRES BACK ON THE DISTRIBUTOR!

2_point8_boy

At least you found out why your car was running crappy.

KED85

Your results are perfect!
My 3.4 in the Firebird registered 175 + each cylinder for a 44K used motor.
Your distributor twist compensated for the slack in timing chain.
And I'll bet it's almost touching the firewall, right?
Replace T chain, remove distributor for rebuild, buy new tranny mount!
You'll be amazed how much life may still be left.
Watch out for valvesprings

camaro_junkie

Karl: is that 175 on the first stroke, or is there some minor build-up like mine. Do you really think my compression results look good?

Do you mean the rotor is pointing at the firewall?

As for the timing set, I have a brand spankin' new steel/cast iron Cloyes set to install. But I'm in my 4th year of university, so you can imagine it's hard to spend a day or two to install it.

edit: oh yeah the dist is brand new entirely... the body, gear, module, pick-up, all of it. And the rubber all needs replacing on my car.

nadster

Heheh, did that one once when I was working on another car and was listening to it idle funny, so I started pushing on the spark plug cable boot and ZAP! Apparently that one boot was the reason it was running funny. Was sparking off the block half the time at the boot crack. Which wasn't that noticable unless you bent the boot a little.

-Dan

nadster

Just out of curiousity, how often do timing chains wear like that? Also, any guesses on the average life span of the valve springs?

-Dan

KED85

Chain
From what's said, IT SEEMS like a life span of about 50,000 - 75,000 miles. After that, twisting distributor (toward firewall) restores "proper" timing
OR
The timing is done by "engine" sound (engine idle sounds much smoother)

Compression
My 3.4 in my Blazer showed 150 each cylinder and that is a 50,000 used 1995 Camaro mill.
The Firebird, same story.

I used a screw in (spark plug) compression gauge.
I rotated engine several times by starter & watched where numbers settled.
Does that answer help you?

Valvesprings
Dependant on your request for over 5,000 RPMs too often!!

nadster

Helps a lot. Thanks much.



-Dan

camaro_junkie

I also used a screw-in gauge. And yes you answered my question. I've learned that how the pressure builds up also indicates what sort of problem you have if any. For instance, if you get 90psi on the first stroke which slowly builds up to 160, then your rings are worn or something like that. In my case 140psi on the first stroke isn't too shabby. And the consistency is also comforting.

In terms of turning the distributor towards the firewall (retard)... I had that idea, but I only went 2° so that it was at spec. I didn't want to screw around too much at the end of the day. Although I think I noticed it did make the idle rougher, but like I said I didn't play around too much.

Anyways thanks for the help Karl, hopefully when I get a chance to put in that new timing chain I will find a very stretched chain with very worn gears and the new chain will make a load of difference.

KED85

When I first got my Firebird, it BARELY RAN or made it home.
Eventually I twisted distb toward firewall, idle smoothed out & the engine ran like "stink" (compared to....!).
Marks registered 20*!
It ran great.
Installed chain & yeah, that REALLY DOES compliment the engine.
Gians are
Power (much smoother pull)
Cooler engine
Better MPG
IF you need so, replace tensioner, too. A very WISE suggestion.
When ready to do chain swap, search out old threads.
It's ALONG day project, too.
Add new water pump at same time, as it's in our hands upon removal to access chain.

camaro_junkie

Couple more things. First of all, what's the tensioner.

I was thinking, like I said, the rotor was halfway between #1 and #2 cylinders when the crank was at 12° (where the engine is firing). So the rotor was ahead of the crank, but wouldn't a loose chain cause it to fall behind? And also, when I actually lined up the rotor with #1 in the dist, it was like a good 20° advanced meaning 30°BTDC. Doesn't that seem weird? My engine doesn't run that bad.

BTW was it you Karl, who gave me the idea of cutting a window in the old dist?

funstick

its entirely likely that the outer ring on the harmonic balancer has spun around with age indicating more or less timming. id bet though the the timing chain is in fact toast. so due the chain and replace the balancer with a NEW ONE. dont buy a reman as they have been noted for being extermly inaccurate.

anyways peace out;

camaro_junkie

Of course the balancer theory could be tested if you could accurately determine #1 TDC and see where the mark lies. But I will be doing the chain and gears, and I will most likely put a brand new water pump on as I've had bad experiences with reman crap in the past. I'll check out the balancer also of course.

KED85

Noi wasn't myself to put a window in a distb cap.
BUT they come standard in 90% of all Chevy Small Block caps (For adjusting points-oh that's right I'm stuck in 1967, 1968 & 1974 Small Block Chevy's!!). Yeah I still runpints & they work just perfect & last quite a very long time (have changed points under my Corvette car since like 2000 or 2001 & about 10,000 or less miles ago).
We MIGHT know of a NEW 2.8 balancer available. A guy put in a 3.4 & those items not compatible.

I'm not sure on "exact" numbers of degrees.
I have & usually tune my engines by ear & hills.
Using a light? I let teh smog guy do it & I've been right about where it should be.
Tensioner...
It's the triangle thing in MIDDLE of timing chain area.
IF ya using a cloyes chain, I HEAR it's unnecessary for reinstalling.
I use the cheap stuff & it works great ($30 dynagear chain).
Waterpump
IF it's quality rebuild, not a problem usually. YET NEW is right about same price. BUT change hoses & MAKE 100% SURE that lower hose is secure.
My lower hose fell off while driving & that killed my 2.8 (but that also lead to my installing a 3.4 see good things do occur from bad stuff!!).
One day I'll take pic of the 2.8 #1 piston & the hole size of Silver Dollar!

Easy way to tell balancer is "off".
Pull #1 plug (front passenger side)
Stick in finger in plug hole to feel peak compression, look at balancer see mark.
You have "changed" timing setting so it should be "Advanced" in numbers.
Your space between #1 & #2 is too tech for myself to offer secure answer.
I'll learn more by reading from another, also!

camaro_junkie

Just replaced lower hose due to scuffing from the steering components. We won't find out the results of my repairs for quite a while though. I'm busy with school.

KED85

Been there!
Right now, keep car band-aided.
Works well.
Oh
Use ANY GIRLS CARS YA CAN!
Just wash in return.
Car or girl, your choice:>

camaro_junkie

Karl, I was thinking about what you said, turning the distributor towards the firewall (retarding the timing) to correct for a loose timing chain. Now assuming this is true, the fact that my car runs way better when it's cold might make sense. If the EST doesn't kick in until the engine reaches operating temp (just guessing), and when it does, it advances the timing (again, just guessing), then of course this would make it worse if it's already too far "advanced" due to the slack in the chain. Did I make sense explaining this? Of course I'm really just taking a wild guess. But anything to narrow down the search on these engines. Right?

Denis.V

Camaro jun:

In order to read the true compression you needs 6 strokes, when the gauge don't move more (maximun gauge readings is the right compresion)

You'll hear RUU PUF! RUU PUF! RUU PUF! RUU PUF! RUU PUF! RUU PUF! = 6 PUF!, Then you see the compresion tester and you write: Cyl # 1: 160....etc. .... engine warm or cold.


Compresion = 130 or less= engine to rebuild process.

Denis V.

KED85

That's true on # of strokes to reach maximum compression. As mentioned. I read after gauge steadied at 150 - 175 - 200psi range on my used low milage 3.4's.

I consider rotating distb. toward firewall "advancing" timing.
Seriously, I (with worn 2.8) loosened distb, rotated toward firewall, heard engine smooth out in Idle, tightened down, took ride WAS MAJOR PLEASED!
Replaced chain soon after & chain was worn, yes, worn, history.
New chain, "correct" timing, old 2.8 had "umph" again (compared too...).

My Blazer, still "ran" & had 50 PSI after 211,500 miles.

Old high milage engines, ya wonder why no power?
COMPRESION EQUALS POWER!
Drive those older mills until it dies, get a 3.4 block source NOW!
I got your source FAST RS!!

camaro_junkie

Denis: 160psi was the maximum gauge reading across all cylinders, although on the first stroke they reached 140psi maximum. But the absolute maximum was 160psi.

I was told that my engine was rebuilt before I bought the car, but the whole thing is a little fishy. I replaced the clutch not long after I bought it, and there was nothing left on it. A decent rebuild would have included a new clutch. And there's other things too.

Karl: Looking at my distributor from the top, turning it in the clockwise direction retards it, and this is what I took to mean turning towards the firewall. Perhaps we're not understanding each other. Nevertheless, I'm going to play with the timing this weekend and do it by ear. Then test drive it. We'll see. I'll tell you where I've finally set it, and we'll see if it's a really bizarre number.

KED85

Looking at my distributor from the top, turning it in the clockwise direction retards it, and this is what I took to mean turning towards the firewall. Perhaps we're not understanding each other. Nevertheless, I'm going to play with the timing this weekend and do it by ear. Then test drive it. We'll see. I'll tell you where I've finally set it, and we'll see if it's a really bizarre number.

I hear ya...
ANY HELP FOR US!

By ear is easy.
Loosen, twist one way or other until engine "smoothes out/idle speed "increases".
Back off by "slight twist" from best sound of idle.
Then hit the road & find a slight incline.
You'll know if right very quick.
IF chain setting "jumps" at marks (while idling & using a light for checking), you need chain.
AND
Easy way, also.
Engine off, pop off distb cap, & twist crankshaft by socket (17mm or 19mm). Check rotor for quick or slow movement. Help?
How are plugs & the plug wires? Solid & fresh, & are they the proper called for plug of your engine.
My 1995 3.4 mill came with wrong plugs & that effected driving (I heard a ping & that was way!). I had 2.8 plugs in a 3.4 mill!

camaro_junkie

Ya, sounds good, I'll give it a try. As far as plugs, wires, and the rest of the ignition, it's all new, and I don't have any reason to suspect they're not right for the engine.

Thanks again.

Jason