Engine guys please help!

[joed]

OK I'm hoping for some help from you engine guys. I have a fresh motor, basically stock with Comp 206/206 roller. Has maybe 10-20 hours driving around with some WOT's so rings should be seated and all broken in. stock shortblock, champion irons.


Running rough, compression 120-130 psi with minimal change (max delta +3 psi wet). Shouldn't it be 150 to 160 psi range on a fresh stock motor? Leak down is less than 1% on the odd cylinders were all I tested since all identical. 60# injectors, Old TE-60 turbo (for now) Alky control, wideband, power logger, Eric's TT chips.... standard stuff. Compression and leak down on cold engine


I've swapped injectors (had a spare set), replaced fuel pump (was 20 years old anyway), fuel pressure doesn't seem to drop off / leak some where, smoke tested intake and exhaust side all with no changes. What the heck is going on?
note - i'm not sure how up to date my sig is right now.

 

[Mr.Spool]

What compression is the motor?
120 is way low to me.
But usually I look for the variance between cylinders.

 

[Mr.Spool]

Do a cold and hot compression test. then look at the variance

 

[hensleyt]

Not a engine guy, but you no longer have OE cam and cam timing has effect on cylinder pressure. your leak down test is good and all cylinders are the same. Might double check your valve adjustment, but I really don't think low pressure is your problem. I would check plugs and wires. injectors wiring and MAS and cam sensor adjustment and condition

 

[Mr.Spool]

Running rough, compression 120-130 psi with minimal change (max delta +3 psi wet). Shouldn't it be 150 to 160 psi range on a fresh stock motor? Leak down is less than 1% on the odd cylinders were all I tested since all identical. 60# injectors, Old TE-60 turbo (for now) Alky control, wideband, power logger, Eric's TT chips.... standard stuff. Compression and leak down on cold engine

I hope you did all the cylinders

 

[Chuck Leeper]

What was the procedure used to do the compression test?
Cam degreed in?
Pushrod length checked?
I'd try another compression gauge. +/-3 psi is race engine territory for variation. Being yours is in that range, I'd look at a different gauge as a backup test.
As for the rough running:
What do you see on the data stream?
What do the plugs look like?
Stock ignition?

 

[joed]

Thanks for all the great input. Let me back up a minute. This motor ran great back in 21, with all these same parts, idled great, clean plugs, crisp starts, great power (side note, we degreed the cam when we put it together this first time with help of a seasoned guy)....but I somehow must have left some junk in there when I put it together the first time so it didn't run more than 100 miles and wiped the bearings. Just had motor repaired by good local shop this time (who says you can't teach on old dog?)fully disassembled, turned crank .010", replaced bearings and put back together. I am unsure if shop aligned timing set marks, or restored cam to original (degreed) location but they did not degree it again since it was running great. after second rebuild I drove around a little last year but running poorly at idle, smoking a little, fouling plugs which I discounted as break in issues. I was chasing some "transitional knock" last summer when I started driving with second build. Was running 15 psi boost (mostly) and my AFR was 10's trying to figure out the part throttle knock I was getting. By process of elimination the consensus was "false knock", so I moved on to how it's running. So all the parts have been verified....it actually drives ok but smells very rich, idles rough etc. and it seems power is down...

I've adjusted valves 3x per Johnson Lifters instruction exactly. Motor is stock compression and the 206/206 roller is supposed to be very mild, maybe the mildest roller...since it's a street car.
Compression test was pull plugs, remove intake tube from throttle body, install gage, crank with pedal to floor and record dry data. Squirt oil into cylinders via test hose, rerun test and record.
Data was:
1 120 dry 123 wet
2 124 dry 125 wet
3 120 dry 120 wet
4 124 dry 124 wet
5 128 dry 130 wet
6 128 dry 131 wet
The minimal change to wet numbers makes sense to me now that I've run the leakdown and it's so tight. I ran driver side with rocker removed and rockers on using a socket on crank got same results both times, maybe 1 psi leakage at 80 psi source pressure.
I'm running almost new Russ Merrit wires but will swap them not just to test. I've swapped and tested my stock coils using caspers tester and have never found either of them not firing at idle either using a test light. All injectors from both sets are stethoscope-verified firing via brand new racetronix harness, and verified and cleaned each individually using my injector tester. I'm running Turbo Tweak Z06 MAF with translator.
I have another compression tester now and will rerun that test, then reassemble with spare set of wires and get back.
Could the cam be off slightly and opening a valve too early or late? What other reason could there be for tight leakdown and low compression given the situation....? it's giving me headaches.
Thanks guys!

 

[joed]

another compression tester (also cheap but new)
1 140
2 144
3 137
4 144
5 149
6 146
I guess it's considered wet since the oil is in there from the other day. So they are up about 20 psi from last result.
If there is something I can grab from PowerLogger, let me know I'll try to get before we leave for NATS....car isn't going though.

 

[TIMINATOR]

Just because both valves are closed during compression testing doesn't mean that they are not pumping up when the oil pump is turning. Did you install a high volume/pressure oil pump when it was reassembled?
How much actual lifter preload do you have?
TIMINATOR

 

[Chuck Leeper]

and my AFR was 10's

I f those are the plugs run at 10:1, that will explain the fouling.
Looks like gas fouling, but pics don't allow for any reading.

 

[joed]

Oil pump is just stock…. earl brown front cover.
I will check my notes on preload soon as I get home…per Jim at Johnson.
I can take better pics of plugs, was running more fuel due to “knock” but will go back to chip default and start over with that. Plugs always seem wet with fuel whenever I pull them.
Thanks guys.

 

[Mr.Spool]

That afr at 10.1 at 15 psi will foul plugs and perhaps wash down cylinders,sput and spudder as well.

 

[Mr.Spool]

another compression tester (also cheap but new)
1 140
2 144
3 137
4 144
5 149
6 146
I guess it's considered wet since the oil is in there from the other day. So they are up about 20 psi from last result.
If there is something I can grab from PowerLogger, let me know I'll try to get before we leave for NATS....car isn't going though.

Is this hot or cold?

 

[Mr.Spool]

Knock can be octane related and or volume related

 

[Mr.Spool]

Plugs look wet from foul
but do the pic it's hard to see if oil is on there as well.
They dont look good

 

[Chuck Leeper]

Plugs always seem wet with fuel whenever I pull them.

I'd consider pulling the ft cover and checking the cam timing.
Verify the cam sensor position first.
There's no reason the plugs should be wet.

 

[Reggie West]

You're compression looks good and consistent across all cylinders.

Those plugs are fouled out, what is causing that?

Start with the basics on your fuel system, check filters, check pressure at the regulator. Check your MAF settings as well and see where it's set at because something is throwing a ton of fuel into the cylinders.

 

[joed]

Is this hot or cold?

cold

 

[joed]

You're compression looks good and consistent across all cylinders.

Those plugs are fouled out, what is causing that?

Start with the basics on your fuel system, check filters, check pressure at the regulator. Check your MAF settings as well and see where it's set at because something is throwing a ton of fuel into the cylinders.

Thanks Reggie, Covered those basics for sure last season. Maybe I need a fresh set and reset chip, turn alky back down and drive it a little more to get a better pic of plug situation for this troubleshooting...

 

[joed]

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