I think you are barking up the wrong tree. The crank keyway does not change. The timing marks move on the tab and balancer. The crank key should be pointing up at the drivers side deck at #1 (and #6) TDC. Only the tab on the timing chain cover and the damper are moved for the motorhome chassis applications.

They wil all look like this regardless of the application. Crank key pointing to drivers side block deck

 

If the timing line on the balancer moves, why then does there not seem to be different harmonic balancers listed for different 400 applications?

Some 400’s were used in cars, trucks and vans. I found only a common part # for all 400 balancer listings. Maybe that old listing info has just fallen a-stray.

I ordered a new Harmonic balancer for my 400. The timing mark on the balancer was in the exact same position as the mark on the original balancer in the van.

Either way I have timed my engine wrong based on where I thought the timing marks should be on an SBC engine. In a van application , that won’t work.

 

Not a lot of pointers listed for a motor home. Not a lot of dampers listed for a motor home either. Maybe you are on to something.

 

I don't think this is true. It's only possible to orient the cam and crank gears in single places (unless you're using an aftermarket crank gear with 3 possible settings). The cam dowel and crank key mean that it doesn't matter where the timing mark on the tab may end up, the dot on each gear has to be aligned with the other.

Maybe I'm unclear on what you're saying or I'm thinking about this wrong...

 

You may be right. I was thinking the timing gears may be out, despite having then lined up pin to pin. I am pretty sure my valves are incorrectly adjusted though.
I had the timing mark on the balancer pointed toward the 2 o'clock marker area when I set them. I am going old-school and will manually find TDC with a pin.
I'll mark it on my balancer and go from there. I'll readjust valves check for any possible bent push rods. If good fire it up again.

 

Where the Cam manufacturer locates its dowel pin AND where the timing set manufacturer of its Cam sprocket locates its dowel pin hole matters a great deal; where those're indexed matters most.

 

Exactly, but those are predetermined and not something that's adjustable in a standard timing chain installation.

 

You may be on to something.
But do NOT rely on the balancer to tell you where TRUE TDC is.

Do that with a piston stop.
Then make sure the timing chain is correct then.

Then figure out the balancer and timing tab location.
They can be anywhere, as long as they line up, at TRUE TDC.
Honestly we put that on the bottom on one race car, it was the best spot.

 

I will locate real TDC with a piston stop soon, reset valves and report back.

 

NO. Those are Not always in a sole, fixed relationship.
And that relationship has long-been selectable by choosing from among different sets and/or installing an offset bushing in that hole. Also; offset Crank Keys

No Ai here.

 

I inserted a piston stop. Turned crank over slowly and marked the balancer. Then rotated engine backwards until I touched the pin again. Marked the balancer. Measured the distance and found the center. Took out the pin, then I rounded-up a helper. While I turned over the engine by hand, we used a bent coat hanger in the spark plug hole of #1. Touching the top of piston #1. Watching piston movement. I also inspected the distributor rotor to insure we were at proper TDC #1. We found exact TDC. The brief flat spot where the piston changes direction. We noted that this was the exact same spot where the mark was cut into the harmonic balancer by the manufacturer. It was sitting at 0 degrees on the chrome bolt-on timing indicator at about 2 o’clock.

I removed my valve covers and set the valve clearances again as outlined in the factory shop manual. #1 at TDC, then setting certain exhaust and intake valves. Next the engine was turned 360 degrees. I then set certain other valves. Exactly as they instruct in the OEM Chevy shop manual.

2 things:
I cannot wrap my head around how the original 400 timing indicator marks are up at noon on the timing cover. Yet, static check, with piston is at TDC and the timing mark is at 0 degrees on the bolt-on timing indicator at 2 o’clock.

When timing my car by feel at idle, it purrs nicely, and smooth. Then inspecting timing marks, with timing light on #1 spark plug wire, it is recording way up at around 1 o’clock. Using the timing light when revving the engine, the timing mark advances as expected. Heads backwards to about the 12 o’clock ish position.

Adjusting my distributor several degrees in either direction while running, dictates when timing is close to being right. I can hear it smooth out. I can also confirm if I’m too far advanced or retarded when starting the engine. It pauses when cranking over. When timing is close, it cranks over easily. Quickly starting. (brand new battery just installed)

When timing is set to the point where the engine is happiest at idle, and starting, it feels just right. Yet under a load the engine pops a bit and bucks, pushing burnt gases out through the carb. I have confirmed all spark wires are in correct positions. Spark plugs are clean and new. I opened the timing gears up to confirm they are correctly aligned. Just re-set my valves, hydraulic lifters pre-load.

My next step may be to remove the MSD distributor. Take a look inside. I can stab-in a
Chevy original distributor. See what happens.

Image below was taken with engine running at idle. With MSD distributor. Timing line as seen is located before bolt-on chrome timing indicator, when spark plug #1 fires. I am pretty confident my bucking issues under load are related to timing. Somehow. Yet I can’t quite wrap my head around why.




Other notes, new Edelbrock 1906 AVS 650 cfm. New fuel pump installed. Making about 7-8 psi. Maybe I need to dial it down. Edelbrock manual does state max 6.5 psi. Maybe engine bucking under load is related to rich air fuel mixture due to fuel pump pressure forcing needle open? I’ll go get a fuel pressure regulator.

Thoughts, tips are appreciated in settling these issues. Thanks.

 

Update regarding bucking back thru the carb. I had adjacent spark plugb wires 3&4 mixed up. Despite checking them 2x. 3rd time was the charm.

Its peeling rubber now. Still scratching my head about the timing marks though. At this point I’m not caring much all of a sudden. Lol.

 

So all in all, it starts and runs well? That's a big step in the right direction!
Was your vac advance at the distributor disconnected and line plugged when you were getting 16°+ timing in the pic?

What you're referring to as bucking could be what's known as trailer-hitching. Do a google on this term: <timing and "trailer hitching" site:corvetteforum.com> and read about it on the C1/C2 and C3 forums.

 

As of 20 mins ago, after I typed out that message I scratched my head again. Its got to be something simple. I found my error in 2 adjacent spark plug wires.

It’s now starting excellent and roaring smoothly, as the tires roast.

 

It could be me, or the angle of the pic, or the fact that I am looking at my phone but. I held a straight edge up and the cam gear dot & crank dot look 1 tooth off...

 

Heres a better photo.

 

Sounds like you got it nailed now.
"Roasting Tires" LOL
16-18* timing advance at idle sounds correct, as long as you had the vac can hooked up.
Sounds like you nailed the piston stop tool and now have the new balancer and new timing tab lined up at the 2 o'clock position at TDC. Perfect for a C3.

Great job.