Does quench affect power?

[panic]

Paraphrasing Bill Jenkins on quench in the SBC (1973?): any tighter than needed to control knock increases pumping loss.

[Elroy]

Paraphrasing Bill Jenkins on quench in the SBC (1973?): any tighter than needed to control knock increases pumping loss.

Wonder how he arrived at that theory? Can't remember if he stated that in his book or not. Makes sense, but quantifying it would be very difficult I would think. Could easily get blurred in with compression ratio and pumping loss.

[Dan Timberlake]

US OEM tricks/designs to reduce emissions in the early days were often aimed at reducing unburned hydrocarbons.

Wide open piston to head clearance and even beveled piston domes supposedly reduced nooks and crannies available for hydrocarbons to hide in and avoid burning.

https://cdn11.bigcommerce.com/s-jvsxk4z ... 04.jpg?c=2

Made sense.

[hoffman900]

Paraphrasing Bill Jenkins on quench in the SBC (1973?): any tighter than needed to control knock increases pumping loss.

Wonder how he arrived at that theory? Can't remember if he stated that in his book or not. Makes sense, but quantifying it would be very difficult I would think. Could easily get blurred in with compression ratio and pumping loss.

Bill’s theory is analogous to lifting a sheet of glass off a flat surface and they stick together. They’re called Van Der Waals forces.

In my opinion, combustion measurement and technology has moved to point where I don’t think that is a consideration and because the gains there far outweigh any losses from that. It would be very hard to quantify as well.

[F-BIRD'88]

You guys are #reading about and repeating about the benefits of quench. but are not testing to see if. when and where this benefit is realized..

I had a 350 sbc.. 10.30:1 cr with (shaved down) old open chamber 882 heads. Right on the edge WOT and roll on knock.
Swapped to vortecs. different thicker gasket, cr was now 10.02:1 cr. .Bigger quench , but lower cr by .30 cr.
Engine could not be made to knock no matter what.
Quench was .033". VS .055". But CR was .30 lower.
Same carb cam etc same car. same gas
Engine wanted Same WOT timing.
No difference in timing. yet loss of effective quench.

The combo with less quench and slightly lower cr made A lOT more power and tiorue. (vortec heads). Again best WOT spark advance and carb jetting did not change.
More than 1 carb was tested on each.
On removal the 882's were inspected for a fault etc. No faults found. In good very re-usable condition.

[Chris_Hamilton]

You guys are #reading about and repeating about the benefits of quench. but are not testing to see if. when and where this benefit is realized..

I had a 350 sbc.. 10.30:1 cr with (shaved down) old open chamber 882 heads. Right on the edge WOT and roll on knock.
Swapped to vortecs. different thicker gasket, cr was now 10.02:1 cr. .Bigger quench , but lower cr by .30 cr.
Engine could not be made to knock no matter what.
Quench was .033". VS .055". But CR was .30 lower.
Same carb cam etc same car. same gas
Engine wanted Same WOT timing.
No difference in timing. yet loss of effective quench.

That's not really apples to apples though is it? Different head gasket but also different head. Wouldn't you think the difference in knock was more attributable to the better vortec heads?

[skinny z]

Paraphrasing Bill Jenkins on quench in the SBC (1973?): any tighter than needed to control knock increases pumping loss.

The prospect of improved knock control, to me, has as much impact as any of the other attributes. Especially if I were to go a more street orientated route.
But as Jenkins states, any more than what's needed is a waste.
.034" or .047"?

[hoffman900]

Paraphrasing Bill Jenkins on quench in the SBC (1973?): any tighter than needed to control knock increases pumping loss.

The prospect of improved knock control, to me, has as much impact as any of the other attributes. Especially if I were to go a more street orientated route.
But as Jenkins states, any more than what's needed is a waste.
.034" or .047"?

If a bit of carbon at the end of a NASCAR weekend is enough to cause p-h clearance, then in their application, and with their ability to measure and R&D, to me, less distance is better if you know how to use it.

[F-BIRD'88]

You guys are #reading about and repeating about the benefits of quench. but are not testing to see if. when and where this benefit is realized..

I had a 350 sbc.. 10.30:1 cr with (shaved down) old open chamber 882 heads. Right on the edge WOT and roll on knock.
Swapped to vortecs. different thicker gasket, cr was now 10.02:1 cr. .Bigger quench , but lower cr by .30 cr.
Engine could not be made to knock no matter what.
Quench was .033". VS .055". But CR was .30 lower.
Same carb cam etc same car. same gas
Engine wanted Same WOT timing.
No difference in timing. yet loss of effective quench.

That's not really apples to apples though is it? Different head gasket but also different head. Wouldn't you think the difference in knock was more attributable to the better vortec heads?

But should not the miracirle of effective quench clearance even the odds?
The conclusion is NO..
Getting the CR back just under the auto ignition threshold with the slightly lower cr and the better plug position played a BIGGER factor. than the loss of effective quench.
The 882 head with tight quench and 10.30:1 was able to be tuned in needed a slightly cooler spark plug non projected tip and 94 octane gas..
The vortec head ran on any gas (87 was not tested) standard plugs. Could not be forced into knock even with
excessive WOT timing. not knock sensitive at all.

Both heads wanted the SAME WOT timing for best perf
36° btdc. Yet the tight quench engine was very sensitive to the fuel used and spark advance. 94 octane good ,93. iffy results very on the edge. 91 and 92 octane NOT ENOUGH.

The engine without effective quench was not fuel nor spark sensitive AT ALL. YET no effective quench.

The "prospect of" better "knock control" with tight effective quench. WAS NOT realized.

[skinny z]

The "prospect of" better "knock control" with tight effective quench. WAS NOT realized.

With all due respect, that test sample is very small (although I'm sure you have others) but the overwhelming bulk of evidence points to tight quench and detonation resistance.
Apples to apples that is.
But again, where to draw the line? You've obviously crossed it a one point.

[F-BIRD'88]

Where is this bulk of evidence of testing?

Do not confuse bulk of repeating stuff on the internetas being evidence . with bulk of real testing. evidence.



You have the ability to juggle the quench clearance on yiur upcomming build. Test and post your results.
What I am saying is don't believe everything you read as gospel.

Yes I have other examples.

I have never found a difference in best power WOT spark timing on any of my different engines over the years ..
Reguardless of different net measured quench clearance. No effect on timing or combustion efficientcy
All the sbc's wanted the same WOT timing.. All the BBC's wanted the same WOT timing for best perf...

On this 350. one other difference was intake manifold
Eddy performer VS Eddy Performer RPM (vortec).

This is also the same short block I did most all of my ported 305 head testing on.
(everybody kept buying those off me. ha ha)
Used to tell people any any dissatisfaction at all with these heads. just bring them back. I will buy them back.
Not one return... I would have liked to get one of those sets back after someon elses testing them out.
Proof is in the pudding. (Other people getting good results with them vS just me.)

[skinny z]

Where is this bulk of evidence of testing?

Do not confuse bulk of repeating stuff on the internet. with bulk of real testing.



You have the ability to juggle the quench clearance on yiur upcomming build. Test and post your results.
What I am saying is don't believe everything you read as gospel.

Yes I have other examples.

It's not a question of repeating internet blather. It's more about researching the results from respected sources. Are there too many too ignore.
That's said, this build I hope will be one and done. I don't have it in me to indulge in the sport the way I used too. I'd like to nail it the first time.
Some of you guys tire me out with your constant building and rebuilding.
Maybe when I retire...

[rgalajda]

Well that explains the rattling, no power, retarded timing of the 70's. vortec vs 882

[F-BIRD'88]

Well that explains the rattling, no power, retarded timing of the 70's. vortec vs 882

Political / lawyer spin.. The timing was the same.
I tested 492'S and a few 305 heads in various forms on this same engine.. The 882's made the expected power these are known for. Other than that ran good.
Just were more sensitive to the gas in the tank and the spark plug choice.
Yes the vortecs are way better.

No difference in WOT best power spark timing on any all these. The only tests that required less WOT spark advance was the 12.65:1 cr version with 51cc shaved 305 heads.. 27° on pump gas to avoid knock. 36° on 110 race gas.. No surprise there. Yes very tight effective quench on this one too.. .033". That one sure liked the race gas.. Ran very good (for a while)

[rgalajda]

My comment was "no pun intended " if that's the correct word.