[Hotrodjohn71]

Hey fellas
I have a fairly fresh, bone stock 326 (1965) with what i believe to be the stock D-port heads. All stock and Rochester 2-jet carb.

Currently i have about 39-40° total timing (19 init + 20 mechanical from an HEI distributor (the only non-stock part on the engine).

It always starts up great, hot or cold. No labor to the starter. And there is no pinging weather it be going 70mph down the road, mashing the throttle or going up a long steep hill. (I buy the highest octane gas at the pump). It really runs like a bat outta he\\, and seems to like that timing.

Im asking about this issue because ive been reading in other threads that dammage has been found on main bearings from too much total advance where no pinging was heard. It was said that clear signs of detonation damage were found on the rod bearings.

I do not want to be doing damage to my bearings.
Thoughts?

[steve25]

You need to be more detailed.

Do you have 39 to 40 degrees in just mechanical advance, or is this amount seen with your distributors vacuum advance plugged in?

Your 1965 heads are of the closed chamber type and as such they do not burn all that clean.

The left over fuel that they do not burn means more advance can be used to get the flame front to light off faster in the chamber.

Here’s a typical timing chart for a motor of your era to use as a starting point ball park setting.

If you do not have a working vacuum advance can to hook up you need to get that added part throttle timing to work.

Just note that these days you may find that your only able to run 8 to 12 degrees of added timing from the vacuum advance without getting part throttle pinging taking place.

If that’s the case then you will need to install a aftermarket adjustable vacuum advance can.

I would not fret over my bearings taking a beating because that happens from hard throttle application knock, but even ping has been known to break rings and crack factory cast pistons, especially high mileage ones.

Also keep in mind the condition of your motor, as nothing cuts into the octane rating of a given fuel faster then excess oil getting into the cylinders.

If your 326 has never had its valvetrain apart at least to replace the valve stem O-ring seals then doing such is now decades over due!

[Hotrodjohn71]

My timing light is an old Sears dial-back. And with eyesight these days, that total timing looks like 39-40° total. But for practical purposes. Its probably 39°.

Thats 19° initial, and 20° mechanical (39° total) with vacuum disconnected. I got my total from revving the motor until it would advance no further.

I get no knock or ping (at least that i can detect), but im not sure its necessarily a good setting.

Thank you for that info about the closed chamber heads. The engine had full machine work restoration 2 years ago and i assembled it and installed it so rings and valve train are all essentially new. Amazingly, its still standard bore.

[steve25]

19 initial is very high!
If you have never yourself replaced the timing chain & gears in this motor then I would preform this test .

Remove all the plugs, removed and back away thd dizzy cap so you can see the rotor and then grab the balancer and rock it back & forth 2 inches.

If the movement of the rotor lags behind that of the balancer by more then 1/2” then it’s time to replace the chain and gears, as your cam timing is then very retarded which is why your getting away with that 19 degrees.

PS
From what I have found about your motor in stock form initial timing should be 6 degrees, so your a wild 13 degrees above that If your timing light is correct.

[turbo69bird]

I’d say pull the plugs and see what they show . If it looks like it’s fat still it’s not likely detonating . That pinging can be hard to hear that’s for sure, a really rich mixture is harder to burn so that’s why it keeps detonation at bay. I’ve run that much timing before on NA engines (usually smaller CID stockers) and been fine but I had a pretty fat set up on the tune Every engine is different. The recomended setting for timing is a starting point.

My dad always set his final timing on his mustang by ear, he’d get it set w the light then he’d take the light off and find where it was happy. That car won a lot of street races w a 351 w and a 600cfm 2 bbl.

[67drake]

Myself, I would put a piston stop in to verify my true TDC. Your timing mark may be off. No Pontiac I’ve ever owned would want that much initial timing.
On the other hand, I believe in giving the engine what it wants. If it’s running great as it sits, leave it be. If you want to solve the mystery of why that much timing is needed, verify TDC and take it from there.

[Cliff R]

19 degrees Initial timing is high for any of these engines if they have much compression in them. Total timing a bit high, but I've had a few over the years that were fine in that area.

Timing at light engine load is pretty low, hence the advice to use Vacuum Advance above.

I'd also mention that unless the engine has higher compression running high octane fuel which burns slower has no benefits whatsoever and requires more timing as well..........

[nUcLeArEnVoY]

19 is way too high for your motor, yes. That depends a lot on the compression. For instance, the factory initial timing setting for my 1979 400 is 18 BTDC, and is the setting I use. My engine is super low compression, though, and with the advent of EGR cooling the combustion temps, they were able to get away with these high timed motors in the late 70's to make up for the lack of compression, so that they weren't totally gutless and anemic. You'll see a lot of the "performance" engines from the late 70's have very high initial timing, lazy mechanical advance curves that had to reach 4000+ RPM to even get 15 or so degrees out of them, and vacuum advance cans threw in a ton of vac advance (as high as 25 degrees). Timing was how they achieved driveability out of such low compression, choked out motors.

As for total timing, if you're going to use vacuum advance you're almost guaranteed to end up pinging. Most 60's motors were higher compression, so right now if you're not using vacuum advance that is probably all that's saving you from pinging.

Total timing WITH vacuum advance, though, can produce some really high numbers (as high as 52 degrees BTDC, sometimes) which is perfectly normal since this timing is typically achieved during very light engine loads where the mixture is very lean (cruising).

[steve25]

Sorry I missed the part about the full rebuild.
If you have not done a cranking compression test then I would do such, just to know what you have and for your own records, because the new time chain and gears you used may be marked wrong ( this has been seen before) and if your cam is in retarded then that would explain how your getting away with all that timing.

[Hotrodjohn71]

I verified my harmonic balancer timing mark (TDC) when i assembled the engine by using a dial indicator on #1 piston and verified it to the timing nub on my 8 bolt timing cover. My balancer has 2 lines. One for TDC, and one for 6°

I do have a vac advance canister on my HEI. It is set for 20° advance and has full pull (Manifold vacuum) at 15" of vacuum. The engine pulls about 20" at idle so its all in at idle.

That 39° advance at idle (in Drive, 600 rpm) seems too high, but thats right where it runs smoothest.

Thank you for the info about the possibility of a mismarked timing chain. That would have never occured to me, albeit it is new.

[77 TRASHCAN]

Doing a compression test (as mentioned by someone above) is a good idea. It will give you an idea of the dynamics of your new engine.

Having a new (clean) engine can possibly contribute to your timing possibly being accurate.

By clean I mean no carbon build up in combustion chambers or piston tops.
Removing all the sharp edges in the combustion chamber and piston top can contribute to the lack of pinging, that you thankfully have.

[Joe-Touring]

The 326 I run has about that much timing in it. 18 initial, ~38 mech, 10 vac. But my engine is a 0.040” over rebuild with #143 heads, so comp ratio is prolly in the mid to high 8s. I’d say it runs strong

[Cliff R]

Using an HEI is a game changer with these things. They tend to have a shorter mechanical advance curve and add a lot more vacuum advance

If I were setting up your HEI for the little 326 I would increase the mechanical advance curve to 11-12 degrees (22-24 at the crank), and reduce how much timing the VA is adding to 10-12 degrees.

This will allow the initial timing to be retarded some and add some timing at light engine load. Nothing will change for al total timing under load, assuming it likes, wants and needs around 39 degrees.

If it run fine at heavy/full throttle with less total timing you could simply retard the initial timing a bit, and modify the VA to add 10-12 degrees and try that first.

VA is your friend with these things and for a basically "stock" engine there is no reason not to be using it........

[Hotrodjohn71]

Thank you all. Very helpful information.