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My son's 1968 Chevy

He has one but it requires a hydraulic clutch. we would have to figure out how to fab up the MC on the firewall for it. when he bought the truck the guy gave him a 5 speed trans and custom cross member that he was going to put in it, but never got that far.

I have read about something from a late 80's S10 would work also which is a T5 where his mechanical clutch linkage would work with it. but those are very hard to find now.
 
I wonder where or who would be able to find out about the TC in that TH400 if it will work with this 250 engine? idk about the low stall but iirc the RPM range is about the same between our beloved diesels and this engine. idle is about 500-600 and top end RPM is 5000 before it claims the dame "comeapart"

I wonder if there is a database somewhere that lists the stall specs for them, I don't think a th400 came factory behind a 250 at all in GM's lineups. I know the th350's did but those didn't come behind a 6.2 diesel!
 
Got the valve cover sealed up using the right stuff. I had a left over can from when I did the valve covers on the 93 but it has dried up in the spout! I was able to easily remove the silicone plug from the spout of the cheese wiz can but couldn't get anything out. ended up poking the bear on that one. shoved a small pointed screw driver in and it all... I mean it all came out LOL. I ended up finger painting a layer of it on the gasket, then had a massive glob of sealant on a piece of card board left over HAHA



I made some changes to the fueling on the ECM and we took it out for a cruise. all seems well other than when you goose the throttle from a dead idle. if you go from idle to wot it will pop and back fire out of the throttle body. I haven't figured that one out yet. played with the timing some thinking that was it, but otherwise putting it under a load going down the road it pulls good. even accelerates in 3rd gear well when you shift too early. before it wouldn't do that at all.
 
Next is loading the parts cannon for a new fuel sending unit for the tank so we can get the tank back in the truck instead of running the 6 gallon boat tank LOL
 
dbrannon79 said:
I made some changes to the fueling on the ECM and we took it out for a cruise. all seems well other than when you goose the throttle from a dead idle. if you go from idle to wot it will pop and back fire out of the throttle body. I haven't figured that one out yet. played with the timing some thinking that was it, but otherwise putting it under a load going down the road it pulls good. even accelerates in 3rd gear well when you shift too early. before it wouldn't do that at all.
Click to expand...
Timing first, then Be sure distributor cap and rotor show no signs of carbon. Blackish looking soot.
Check plug wires with multimeter.
Then try enrichening the fuel just a little.
 
For anyone that has dabbled with OBD1 and 2 and tuner pro for custom tunes here is the current spark advance timing table map and graph for this 250 engine. If someone sees something out of the norm for the spark advance for this engine let me know.

I basically plotted it with the theory behind how a regular vacuum advance HEI distributor would work or at least I tried to picture it in that sense basing the initial base setting (where you set the distributor at) which is 9 degrees for cranking and initial startup and trying to plot a table out on how the timing advance would increase with RPM and vacuum.

This is what I came up with. iirc max advance is set to 36 degrees.

1777943970586.png
1777944009026.png
 
There are variations in the ECM for things like coolant temps and if the knock sensor picks up knocks it retards the timing a bit, but for building a timing table for the ECM is not easy. it's way over my head!

O2 still seems to function and read fine. I see the voltages on the live data rise and fall like it's supposed to. the readout on the laptop shows the air fuel ratio is staying in the 14's. there is no black or blue smoke like there was prior to it having three dead cylinders.

when I had the manifold off I could see the end of the O2 sensor in the pipe and it was clean, no carbon build up and didn't looked torched.
 
The ECM is also no longer reporting any spark knock from the knock sensor other than at crank time. I believe it's hearing the starter. it was explained to me that the knock sensor is basically a microphone mounted to the side of the block and listens for knocking. driving around today it didn't pick up anything other than when you crank it up. the engine is running so smooth it's like a well oiled sewing machine! placing a cup of water on the valve cover and it will stay put, not vibrating off of the valve cover.
 
I also failed to mention that when you rev the engine then let off, during the deceleration you can faintly hear a bu-bu-bump like it's lightly popping from the exhaust on decel. I am sure that also has to do with timing, but does not stumble at all though. other than doing a foot stomp from idle to wot it will back fire through the intake.
 
Could that backfire also be a lack of fuel for sudden acceleration like on a carb when the accelerator pump isn't giving enough fuel?
 
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