Sorry, but you are confusing combustion efficiency with COST efficiency. The 307s died with Qjets because GM didn't want to pour any EFI development money into a low-production dead-end motor. At the time that GM was converting all it's SBCs to throttle body injection and TPI, the only applications for the 307 were the B-body wagons and the Fleetwood. By 1987, GM knew that the G-body cars were dead and they were already planning the 1991 whale-body wagons. With the 307 dead after 1990, and with the CCC Qjet (which looks an awful lot like "electronic controls for emission compliance"), GM was able to squeak by without pouring a dime into development.

As an aside, TBI was contemplated on the 307, as evidenced by this experimental intake, but apparently was not considered cost-effective.

 

The one I spoke of had 29* during pulls, then 32* and I never heard a knock or ping either, and I was standing right next to it. But the 14hp loss at 32* and subsequent pounding of the rod bearings told us it was detonating.
I addition, last year I did another iron headed 455, but this one was only 10.0:1. On 91 pump it would only take 32 or so, but also only made 413hp no matter what we did. Not exactly stellar numbers either way.
Conversely I did an Edelbrock headed 434 DX last year as well. With 10.2:1, a much shorter rod ratio and the aluminum heads it wanted all the timing I could throw at it. We stopped at 39 and it was making more power everywhere with every change.

I don't doubt your findings, but I'm of the opinion that the Olds combustion chamber is less than perfect, in a lot of ways.

 

Can you please explain it to me why some late seventies Cadilacs, with the 350 Olds engine, got fuel injection? Joe, you said they didn't have to invest a dime into designing a fuel injection set up for the 307, but they already did it for the 350. The 307 just had smaller runners.

 

I think your mixing detonation with having too much timing. There is a difference. Too much timing just ignites the fuel earlier and combustion expands enough before TDC that it hurts power. And yes it can eventually take the bearings out of it. You can have too much timing and hurt power without having detonation. The less timing needed to make peak torque the more efficient the chamber. The timing requirement after peak torque will be less as RPM increases.
Detonation is when the combustion front is split in two and it slams into itself and will make a noise like glass pop bottles rattling. Often happens when your on the lean side with lots of vacuum advance at cruise and put a slight load on the engine.
Then there is pre-detonation that is caused by a hot spot that lights of the mixture before the spark plug fires and that front collides with the front lit by the spark plug to also give that rattling bottle sound. Pre-detonation in a properly maintained engine is actually rather rare.

 

Correct, but i didnt mention we had galled wrist pins AND pounded out rod bearings I'd tend to stick with detonation.
Plus I never went below 29. In hindsight we could have already been on the edge at that point.

 

Really good article,
http://www.contactmagazine.com/Issue...ineBasics.html

"KEY DEFINITIONS
Detonation: Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug."

Heat and pressure? Does that not mean cylinder pressure? Which means compression ratio and cam?


"CAUSES
Detonation is influenced by chamber design (shape, size, geometry, plug location), compression ratio, engine timing, mixture temperature, cylinder pressure and fuel octane rating."


"Another thing you can do is increase the burn rate of the combustion chamber. That is why with modem engines you hear about fast burn chambers or quick burn chambers. The goal is the faster you can make the chamber burn, the more tolerant to detonation it is. It is a very simple phenomenon, the faster it burns, the quicker the burn is completed, the less time the end gas has to detonate. If it can't sit there and soak up heat and have the pressure act upon it, it can't detonate.


Again,
"The goal is the faster you can make the chamber burn, the more tolerant to detonation it is. It is a very simple phenomenon, the faster it burns, the quicker the burn is completed, the less time the end gas has to detonate".

Our Oldsmobiles are the definition of large, slow-burning chambers.

 

Our factory chambers are 83cc at the max. BBC (factory) chambers are usually 50% larger at approximately 120 give or take a few. Olds chambers are actually more the norm for volume being right there with most BBFs in the 70s cc range, Buick ran from 69 to 78cc.
Pontiacs had a little of everything for size with some at 60 and others at 119cc. Olds chambers are also a lot shallower because of the shallow valve angle which helps promote the flame across the area instead of spreading out in multiple directions. There's a lot to it but all in all the Olds chamber isn't that bad.

 

I agree, the Pontiac chamber is probably worse.
Smitty you know we share a brain on a lot of stuff but a couple of points.
A larger chamber would have more of a tendency to spread out in multiple directions. More distance from one side to the other, more chance of spreading unevenly. Hot spots and mixture variations will have more of an effect on the flame front moving across the chamber.
And again with all due respect, if the Olds chamber isn't that bad, then why hasn't anyone copied it? Or why did pretty much all head companies that make heads for Olds change it? Hmmmm....

Again, it's not the worst but it left a lot of room for improvement.
Jmo

 

For the time it was decent. I agree on more isn't always better. I swore 38 total felt better everywhere, till I took it to the track and it ran better at 36. Again 34 was slower. The only Olds I made noticeably ping was the exact condition Smitty mentioned, tons of timing and very lean, especially the secondary rods in the Qjet.

 

Well, Batten left it alone. Wensler left it alone on the Rocket Racing heads. Edelbrock added a second small quench area behind the spark plug which has been proven to be better removed. ProComp just didn't know any different and thought Edelbrock was onto something so they added in the second small guench behind the spark plug. Mondo/Knowlton and Bulldogs just extended the original quench so it eyebrowed the valves. Wise is the only one to do much that is actually a change as he made his with ad much a quench pad as possible all around the valves to make a kidney shape chamber and we've yet to see how that works out. So the majority of the changes have been very minor. And as I've already stated here and elsewhere that the second quench pad on the E'brock and probably the ProComp is best removed if your looking for more power.
Why hasn't someone copied it. I can't say. How many heads have such a shallow valve angle. And in today's world of 4 valve heads everything is more hemi or pent roof like to be able to get the valve in and came on top of them..

 

Correct, I guess we'll need to see how that pans out.
And until someone does a side by side on the old Edelbrock/Procomp vs the new Edelbrocks vs a revised Procomp as you mentioned it'll all be just conjecture.

 

I understand Cadillac didn't have a small engine available and the injected Olds motor was a bridging fix.


To address the OP;
Eric, you say you don't want a tarmac wrinkling torque monster, with that in mind perhaps going to a lot of trouble for a 3 angle valve job or getting more involved in modifying the engine isn't the road you want to go down.
Assuming the bottom end of the engine is sound I would focus on properly sealing valves and making sure you have equal combustion chambers with the same compression on both sides is where your focus should be.


Roger.