I finally got a chance to check the timing. It's currently set at 10* (@ 850rpm, w/ vac adv disconnected)... Hmmmm, seems like it should be pinging like crazy on regular fuel! I guess this engine was modified when it was rebuilt... sure wish I had more info on what was done. I guess I'll have to just adjust it by ear.

 

Thanks, that is very interesting info... I didn't think there was 425 HC w/ a 4bbl available, but looks like there was.

 

If you mean a 425 HC with a 2-barrel carb, I thought the same thing until I looked more closely at the chart.
I also didn't realize the the Toro and Starfire engines were 10.5:1 like the 4-4-2.
I thought 10.25 was the highest CR in a 425.

 

I knew there was a 425 HC w/ 2bbl, that's what mine is (was). I didn't think there was a HC 4 bbl option, but looking back at the chart I see it now (prefix code R, no suffix code)

 

10.25:1 was the standard compression, all others were by request.
Olds brand identity was "Ultra High Compression."

As far as your timing, there are two possibilities:
Your timing mark is off (it does happen), or
Your engine has had different pistons and / or head gaskets installed.
Did you ever look at the visible part of the gaskets to see if they were thin shiny metal or thick dull fiber?

- Eric

 

Hard to tell for sure, but I'm guessing the thicker gasket's... lowering the compression ratio. Seems I've got a bit of Frankenmotor, lol... but, hey, I'm not building a race car.
That being said, I installed the Pertronix ignitor today (with the stock coil), replaced the cap & rotor, new NGK plugs (last week), adjusted the carb, set the base idle to 550rpm and the timing to 10* (I tried backing it down... not good), filled up with mid-grade (89) and went for a drive... it runs like a scalded dog! Much better throttle response, smoother idle, starts quicker... and NO pinging, not even accelerating up long grades. That's good enough for me... I'm closing the hood and moving on to other things (mostly interior projects). Thanks much for all the help & advise... I really appreciate it!

 

Sounds great!

Enjoying the way it runs is what counts!

- Eric

 

That Pertronix ignitor is really cool... easy install & really made a difference. I will be keeping my points & condenser in the trunk though... just in case, lol.

 

To illustrate a point I made earlier, and that has been made by others when difficult-to-explain timing questions have come up, see this post from this morning.

It would not be unreasonable, in light of your good-running engine with timing numbers that shouldn't be, to double check the position of your timing mark.

- Eric

 

Thanks for the info, I will verify the marks just to be sure. I think in my case, since were only talking about 2.5-5* difference in timing... and the fact that my engine runs great (no smoking, etc), that your earlier suggestion of thicker head gaskets or other engine modifications is more likely. The PO was a professional mechanic, and I'm thinking he may have purposely (or accidentally) set the engine up to run on lower octane fuel. He has since moved away and I have no way to contact him... but he gave me a folder of receipts. I found one from a local speed shop that did the machine work, it's hard for me make sense out of all the info listed, but I do see, among other things: 1 gasket set- Felpro (no part # though)... and resurface/milling .008. I'm probably letting my curiosity create a problem where there isn't one, lol. I'm gonna run 89 octane fuel and drive it!

 

The factory head gaskets seem to be about 0.014 to 0.016" (though the manual says they're 0.025"), while the Fel-Pros are about 0.047".
Subtracting 0.008" milling, you get a distance of about 0.039", which is about 0.025" greater than stock, which adds about 5cc of volume, which will reduce the CR by probably a bit less than a whole number (ie: 10:1 down to 9.2:1 or something - others with the combustion chamber volumes at their fingertips can correct me).
It seems that the original CRs were a bit less than advertised (with production tolerances, better to have a motor that runs well than one that pings all the time), so I'd bet that's a reasonable guestimate of your current CR, which would explain your good performance on 89 octane .

- Eric

 

Damn, your good!
Did I mention it'll do a wicked burn-out?! And that's what really matters!
Thanks again!

 

Why would they put the most HP in the Toro? Nice to know though I have access to that motor in my friends garage. We scrapped a 67 Toro and kept the motor.

 

Ummmmm... Marketing?

Top-of-the-Line car gets most powerful engine.

Just a theory...

- Eric