Cody's '76 Sierra

It’s an OMU. Obsolete and Mostly Useless.


I average about an even 14:1 cruising at part throttle, and anytime I give it throttle it goes rich for a moment.

I bought the adjustable main jets but honestly I don’t think I’ll need them right now. Might need them for the Mazda. I really like these little Holley 94s they’re so simple.


Okay so initial timing I have set for 12 degrees Advanced without the vacuum advance on.

With vacuum attached(manifold source) it idles at 30 degrees of advance. As vacuum backs off that should let off the timing. I think total timing shouldn’t be more than 35 degrees if I remember correctly.

Edit: I guess part throttle is always a lot of advance and it tapers off after mid throttle?

I also realized I had advanced this distributor by a ton. I am surprised this engine wasn’t knocking.

Edit 2: Oh I forgot to mention my kickdown switch came in the mail. This particular TH400 is the very old style that doesn’t use a TV Cable or any of that crap. Just a vacuum modulator and an electronic solenoid Kickdown for wide open throttle hard pulls. Wonder if I can make another switch that goes to my lever throttle that acts in parallel, or if I should just leave well enough alone and keep my passing gear on gasoline only. I can always hand shift while on woodgas, my side detent shifter has the full range 1-2-3.


Wood gas is on a different scale, that gage is set for gasoline. Some gages you can change the scale to LP or NG. I just use the lamda scale when I set up the automixers. Also placement of the sensor is it reading both banks? It seems to run pretty good actually for the reading you are getting, so that makes me want to think you have a dead hole or a weak sparkem plug.


It’s coming off both banks, at the very end of the Y pipe.

These spark plugs were put in along with new wires when I got the truck, but they could be fouled to hell right now. Since I dialed back the timing its running a lot better at about 13.5:1 AFR with a little up and down fluctuation. I should probably try to tune the carb again tomorrow and cut off all air bleed at the woodgas throttle. With the way it is now, when woodgas is introduced I’d be running even richer and would have to lean out the woodgas mix until I cut off gasoline. Not a good idea. I have a feeling I can get it to idle all on it’s own with the woodgas throttle fully shut and tune off the needle valves again.

I read somewhere that the Driver’s side bank always reads leaner than Passenger, and the pipe coming from the Driver’s side is shorter. Maybe that’s influencing the reading?

I should check my compression soon.


Yeah make sure you dont have a sticky valve. But those old small blocks always ran pretty rich with the four barrels unless someone got in there there and jetted the carb. But I go by how it runs if its running good roll with it. I dont know seems like if they are comining together the mix between banks should average out. But thats just me thinking.


I personally don’t think I have a dead cylinder, I don’t have any gallop when starting up. I did notice one of my rockers was slightly cocked when I was changing my cover gaskets, but it was still contacting the valve and pushrod. I’ve been running 20% MMO and 10w40 in the block since I started driving it. It’s definitely been progressively running better. No ticking or other strange noises.

I wonder if this has an aftermarket cam in it.
Also I should mention I’m still running a PCV valve and EGR. I don’t have a Cat or any other emissions stuff on the engine.


uh oh, crooked rocker = bend push rod. I would investigate that cylinder first take a look at the plug and see if looks like its burning ok.


That could also be your detination issue maybe not. But always fix the obvouse.


I don’t have a detonation issue. It’s just when I started to run on the lean side I would start to hear the telltale little pops that indicate Lean condition in the exhaust note and also the cadence would be off when getting closer to stoichiometry. The pops could be exhaust leaks, though.


Okay so I could have sworn one of these rockers looked a touch crooked last time, but they’re all fairly straight.

This is the Passenger side head.


Yeah I chased a valve for a long time only to find out it was a tiny exhaust manifold leak.

Vavles look good. But yeah if you ever see a crooked valve need to investigate that push rod.


When I was under the truck I hated how I got lazy and didn’t try to run the tubing over the crossmember. So I yanked everything off. My 20 degree elbows don’t reach high enough so I ordered some extra short 45 degree elbows that should be steep enough to get me over the crossmember. If all else fails I’m breaking out the flex exhaust or at least a flex elbow. I need to get the exhaust running out the back and away from my eardrums.


If those 45s don’t work, I’ve got a freaking ton of 2" conduit that fits my 2.25" exhaust and I just bought a Bauer 14" chop saw that I need to test out.


The 45 elbows worked great to make a dogleg, and I ordered a Walker SoundFX muffler and hyper cheap perforated core resonator to tame the drone. I feel bad having to do hard pulls to get up to speed. All the rest of the tube I’m using my 2" conduit.

I’ll likely just terminate the exhaust under the bed with a turn down tip. I don’t feel like trying to reuse my old tailpipe. We’ll see what mood I’m in when I get the muffler and resonator hooked up.

Here’s what the guts of a SoundFX muffler look like.


Have a new problem. My kickdown solenoid switch doesn’t come near to touching the gas pedal anymore.

I may install a button or something on my shift lever for kickdown. Or maybe somewhere I can hit with a foot. It would be nice to have a passing gear though.


That is what I did Cody. I was too lazy to snake the tail pipe to the back where it was originally.

If I would do it again I think I would place the turndown in a different place instead of under the gasifier. It may be adding extra heat to the lower drum.


Doing a little investigating on my engine. Found out I have 333882 heads which means they’re 76cc. About to check the pistons and see if they’re dished or flat tops. Likely dished.

Honestly this means if I get any other set of heads that are a lower cc then I can bump compression. Kinda good news.

Update: I do have dished pistons. No wonder it can take so much advance I’ve probably only got like 8:1 or 7.5:1 compression.

I’m basically planning for power mods I can do without having to pull the engine out. If I can make something like an Edelbrock Performer 64cc head work nice with my stock cam and intake then I’ll consider that a success.


Oh yeah here’s what I’ve been procrastinating on doing since I got the truck.

Last picture is me just laying the floor pans in for test fitting.

I don’t even know where to begin.


A lesser man would have run away in horror Cody. Also no one said transmission tunnels had to be round. Easier to fab square. :smiling_face_with_three_hearts: