This is going to be long, and I come here because you'll seem to have the most experience with TBI engines, so here goes:

First, I'm working on a 69 C-10 that I swapped in a TBI 350 from a 90 C1500. The donor truck had a 700R4 behind it and I'm using a sm-465 (granny low 4 speed manual). I have a JTR VSS hooked up to the ECM. I'm using the stock ECM, stock harness. I tried not to change anything in the swap. I am running the 69 exhaust manifolds and have the 02 sensor in the exhaust as close to the manifold as I can. I'm going for mpg over HP here.

So, I get the engine in, seems to run fine. I didn't have the VSS hooked up for awhile and was getting relatively bad gas mileage (11.5-13). I was getting 13.5mpg with my carbed 350. I drove it this way for about 2 months.

I made one trip (300 miles) and got the poor gas mileage. So I finally get my VSS hooked up thinking that should help. I get some gas and I head out of town (same 300 mile trip) and I get about 30 miles outside of town (doing 75 on the turnpike) and its starts to ping and knock. So I get to the next gas station and get some octane booster thinking maybe the gas I got was just low on octane for some reason. No change. I kept going with it pinging and knocking (cause I was running late for a meeting and didn't have much choice). So I make it the rest of the 90 miles to my meeting.

After the meeting I do a little internet research and it sounds like an EGR issue. I'm thinking, great, that should be easy. So I get a new EGR from Orieily's. No change. So I get a new EGR solenoid from autozone ~1 mile from orielys. No change.

I filled up with gas, get a can of injector cleaner and do some additional testing with a multimeter and don't find anything. So I say F it and drive home 150 miles with it knocking and pinging (would do this mainly going up hills, but also sometimes on relatively flat ground doing 60-65).

So I posted a question on my truck board (67-72chevytrucks.com FYI) and got some advice that the Oriely EGRs are known to have issues. So I replaced the EGR valve with a new Delphi EGR valve. I also replaced the knock sensor and thermostat (put in a 195 deg unit). No change.

I pulled the spark plugs. A few of them were black on part of them, otherwise they had a light brown color to them. Nothing really looked that abnormal so I cleaned them up and put them back in. Test drive: No change

I have a OBD1 cable and winALDL and can post the results if needed.

Then I did some more checking and removed the hose from the EGR solenoid to the EGR valve and found a hole worn/melted on the underside of it. I thought this was the key. Being that it was 9:30 at night I just used a piece of hose I had laying around to make a temp. hose and headed out for another test drive, hoping I'd finally found the "smoking gun". Well I didn't get very far. Just down the block the truck just died and I couldn't get it started again.

I ended up changing the coil and ignition module to get it going again. Test drive: No change

So I tested the fuel pressure and it was 9 psi at idle and would drop to ~7 when I blipped the throttle. Made the regulator adjustable and that didn't really raise the fuel pressure, so I got a new fuel pump and now my fuel pressure is about 15 psi. Test drive: No change.

Things kept leading me back to something with the EGR valve, so I got a new one of those. Test drive: NO change

I checked a few things and went for another test drive. Things start to get dim and it barely makes it home. Dead alternotor. So I get a new alternator and its charging now, but still have the pinging/knocking.

So in summary:
Starts and idles fine
Drives relatively fine except for the loud knocking/pinging
No SES lights

New parts:
Alternator
EGR valve
EGR solenoid valve
coil
ignition module
knock sensor
O2 sensor (before the problem started)
cap
rotor
fuel pump

Rebuilt the TBI unit and cleaned it up
"adjustable" regulator set to 15psi now (instead of 9 when problem started)


Any suggestions before I drive it off a cliff?

Here is my thread and the more detailed info of what I've gone through: http://67-72chevytrucks.com/vboard/s...d.php?t=503351

 

Did you check the ignition timing?
Make sure the egr opens up when you rev it. You can put a vacuum gauge on it to see if its getting vacuum.

 

Base Timing is set to 0 with ECT (or whatever the timing plug is called) unplugged.

When its setting just idling, I can rev it up and feel the EGR opening opening (by feeling the underside of the EGR)

 

Since you have replaced bunch of parts without any effect I would dig a bit deeper. Get a timing light - allow engine to warm. Disconnect EST connector and verify that your base timing is between 0 deg to 2deg advanced. While engine is idling (EST is open, around 500 RPM) point timing light onto the dampener - the strobe light should rock steady as there should be no variation in timing. Any type of jumping or a miss would indicate reluctor coil or a rotor magnet problem. If inside of your distributor is very rusty that's another sign that you may have reluctor coil problem. If a magnet has fallen off from the ring this would cause persistent miss. Get a spare dizzy from JY!

Another common problem with high millage SBC's is a timing chain stretch! Here is couple of photos that demonstrate this:

Pushing out


Pushing in


God only know how many miles this engine had before I got it (it also had a spun rod bearing). Stretched timing chains cause unsteady timing or can even jump gear!

//RF

 

The timing chain was one of my dad's thoughts to check. To check without having to remove the timing cover I was going to pull the valve covers and put a dial indicator on a pushrod and turn the crank back and forth to see if I can get it to move without movement on the pushrod (I'll do this while the valve is opening/closing cause I know there are times when the valve is either open or close and is not moving).

I'm also going to put a borescope in the spark plug holes and down the intake to see if I can see any damage.

 

So tonight I pulled the spark plugs and popped off the valve covers. I put a dial indicator on one of the valves and turned the crank until the valve was opening. Then I turned the crank the other way. I was able to turn the crank very little until the valve started closing. Didn't seem excessive at all.

Then I pulled the distributor. I took off the rotor and and the pickup coil and everything looked very corroded. When I would spin the distributor it was not spinning freely (some internal friction and kinda hung in one spot) I decided I'd just get a new distributor. While I'm changing things I'm also going to get new spark plug wires. I've been meaning to get new plug wires for a long time, just haven't gotten to it.

 

having kinda the same problem. Did the new distributor fix the issue?

 

New distributor did not fix the issue.

Last night I was doing some reading about the issue and ran across what the Electronic spark control module does (I don't know if the F-bodies had one of these) Anyways it works in conjunction with the knock sensor to control the timing when knock is sensed. I though for sure this was it. Got a new one......no change

In my reading, I also ran across a guy who was having nearly the exact same symptoms as what I am having. The only difference was he was having some occasional popping from the exhaust on deceleration. Anyways, it turned out to be a blown head gasket.

So I checked my compression (after a new ESC)
#1: 130
#3: 20
#5: 20
#7: 150

Yep....blown head gasket Its not having any of the typical symptoms of a blown head gasket like over heating or bubbles in the coolant (and I hope no water in the oil....the oil looked normal on the distributor when I pulled it and in the valve covers). Hopefully the heads aren't warped, but since it didn't overheat, it eases my concerns a little.

 

Ouch!

Yeap, the infamous 3-5 blown head gasket. If and when you do the tear down check the exhaust valve seat 3 -5) for cracks.

//RF