Little help with initial, mechanical, and total timing on my rebuilt 360

[Johnny Dart]

And also we know his garbage won’t run for **** at 0-4 degrees.

But it will last longer. Lol

 

[TT5.9mag]

But it will last longer. Lol

The exhaust valves and seats won’t.

 

[Mattax]

I did find out why the MA is so high. The stop plate is stamped R17, so that is 17* at the distributor meaning 34* at the crank at least that is my understanding. Not much room for initial if one only wants 34-36* total.

We pretty much already knew that.

There is at least 30 degrees in the governer.

Now knowing its a 17 tells us either there was signicant slew by 3000 rpm (timing lost in the electronic switching) or 24* at 800 was not the initial.
Initial was more likely around 20 at 500 rpm

Establishing the best initial timing still will need to be done iteratively, especially with an automatic transmision. But having timing that is stable at idle rpms will make it easier.

The right way to do this (tune in a mystery engine) is put enough spring tension on the weight so timing at idle rpms is stable. Follow the links I posted or follow FBO's guidance. Don't try to do both. I can't and won't help with Don's stuff. He's got his method and you got his kit, then go with it.

. I would need to put the initial at around 4* to get a safe all in of 34* This engine/cam combination wants 22* initial, that I know. So now I have to dial back the MA to around 12-14* to get somewhere around 34-36*.

Bingo! This is how people came to conclude that using manifold vacuum is better. Using a smogger distributor, set the timing close to factory and then using manifold vacuum to get a decent initial. Maybe not ideal but its an easy work around. The problem with your distributor's advance is that its a straight line, not a curve. It will ping at part throttle when used with vac advance.

What you recommended is even more initial than the 68 340 had and it was clearly a performance engine. What was it like 8 initial?

That's a BS arguement and you know it. 1968 was a smog year across the board. There never was a non-CAP/CAS version of the 340 production ignition. A stock 340 or 360 is going to be happier at 12* BTD than at TDC, and given a rich enough idle mix should run at 650 rpm even shifted into drive. Even with the stockish mystery cam somewhere it should end up somewhere between 12- 18 BTDC. How low it will idle, I don't know.

 

[RustyRatRod]

We pretty much already knew that.

Now knowing its a 17 tells us either there was signicant slew by 3000 rpm (timing lost in the electronic switching) or 24* at 800 was not the initial.
Initial was more likely around 20 at 500 rpm
View attachment 1716544123


The right way to do this (tune in a mystery engine) is put enough spring tension on the weight so timing at idle rpms is stable. Follow the links I posted or follow FBO's guidance. Don't try to do both. I can't and won't help with Don's stuff. He's got his method and you got his kit, then go with it.



Bingo! This is how people came to conclude that using manifold vacuum is better. Using a smogger distributor, set the timing close to factory and then using manifold vacuum to get a decent initial. Maybe not ideal but its an easy work around. The problem with your distributor's advance is that its a straight line, not a curve. It will ping at part throttle when used with vac advance.

That's a BS arguement and you know it. 1968 was a smog year across the board. There never was a non-CAP/CAS version of the 340 production ignition. A stock 340 or 360 is going to be happier at 12* BTD than at TDC, and given a rich enough idle mix should run at 650 rpm even shifted into drive. Even with the stockish mystery cam somewhere it should end up somewhere between 12- 18 BTDC. How low it will idle, I don't know.

I wasn't arguing. I was giving a comparison. Wanna scrap about it? lol

 

[Builderguy]

Put the new distributor in. Marked the base to line it up with the one I took out. What did this one do? It now runs 15* initial and 34* all in at 3800 RPM.
I may map the curve but I will test drive it for a bit to see what it does. If it performs well, I will leave it, and move on to the speedo cable that needs replacing. Checked the heat soak startup and fires right off. PERFECT I did add some 2500 degree heat boots for the left side spark plugs. Not a fan of the look but wire protection is the goal.

Thank you for all who gave their time and knowledge on this. Much appreciated!

Now, if I can just find a buyer at the show tomorrow, now that would be better than PERFECT. That would move right to OUTSTANDING!

 

[crackedback]

Very nice.

 

[Oldiron440]

There’s some great advice here and it sounds like the op is getting it. Being off only five degrees on your timing will kill your torque and horsepower. But once you’ve got everything set I believe you’ll be surprised how much deference it will make.

The only thing I can add is that if you’re using a stock damper you should verify TopDeadCenter, TDC on number 1 cylinder because the outer ring on the stock style damper will rotate with time because the rubber drys out shrinks and the ring gets loose. Nex thing your timing doesn’t make sense and you have a damper going through your hood.