Controling detonation

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Aug 29, 2007 | 09:34 PM

BLKFE

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Controling detonation

While working as an automotive machinist I got the opportunity to build two identical engines. The only difference between them was I polished the combustion chambers on one of them. The other was left alone.
I could not beleive (nor could my boss) the difference it made. The one with polished chambers could run MUCH more timing with the same octaine gas. Or... much lower octane gas with the same timing. Can anyone verify my findings?
Both motors were 9.5:1 by calculation, not by guess.
Thanks, Brad

Aug 30, 2007 | 12:35 AM

eco

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From: The dark carnival

I am not a machinest and I have never heard of the polished VS unpollished cylinder thing.I would be curious to know what you ran the motors in/on and how they were set up. Were they in a vehicle or on a engine dyno?

Aug 30, 2007 | 08:46 AM

EPNCSU2006

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From: Concord, NC

If it eliminated some sharp edges, I can definitely believe it. Removing any possible hot spots will help tremendously.

Aug 30, 2007 | 08:52 AM

Conanski

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From: Ottawa, Ontario

I made a point of removing all the sharp edges and casting nodules(small bumps) in the combustion chambers of the E6 heads I have on my 5.8, I did quite a bit of work the unshrown the intake valves among other things. This motor will take 18deg advance without audible detonation....

Aug 30, 2007 | 09:50 AM

BLKFE

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They were identical .030 over 390 cid fords. Both installed in work trucks. Real world test. Even the distributors had idenical timing curves. I even switched carbs thinking one was running lean and it did not change a thing. I guess the reason I am bringing this up on this forum is I see alot of guy's doing head swaps and such and from my findings, spending a little time and very little money on the heads before reinstalling them can really pay off big time.
I am in the process of fixing my 1995 f-350 with a efi460 (Head gasket) and this is one of the changes I am going to make. My list for changes includes.
Polished chambers
Gasket match ports
Larger exhaust valves
Crane roller Fulcrums
headers with heat wrap
Dr Gas X-pipe
21/2 exhaust with flowmasters.
Delete EGR
EGR bypass resister
Adjustable fuel regulator
Hood scoop from 79 mustang pace car with custom made cold air intake.
Bump timing as much as possible.
180 degree thermostat
Goal is increased HP & Torque with a cooler running engine

Aug 30, 2007 | 11:03 AM

Conanski

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From: Ottawa, Ontario

Quote:

Originally Posted by BLKFE

I am in the process of fixing my 1995 f-350 with a efi460 (Head gasket) and this is one of the changes I am going to make. My list for changes includes.
Polished chambers
Gasket match ports
Larger exhaust valves
Crane roller Fulcrums
headers with heat wrap
Dr Gas X-pipe
21/2 exhaust with flowmasters.
Delete EGR
EGR bypass resister
Adjustable fuel regulator
Hood scoop from 79 mustang pace car with custom made cold air intake.
Bump timing as much as possible.
180 degree thermostat
Goal is increased HP & Torque with a cooler running engine

Gasket matching is an old technique that often does more harm than good. The key to good airflow is consistent port dimensions or smoothly increasing dimensions, do not do this unless you plan to fully port the whole length of each runner from valve seat to plenum.
On a 460 I hope you intend to put dual 2.5" exhaust..

Aug 30, 2007 | 02:22 PM

eco

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From: The dark carnival

Quote:

Originally Posted by BLKFE

I am in the process of fixing my 1995 f-350 with a efi460 (Head gasket) and this is one of the changes I am going to make. My list for changes includes....
headers with heat wrap
...
...
EGR bypass resister
...
Goal is increased HP & Torque with a cooler running engine

Are you talking about the Termo-Tech wrap? It works well, but it sure does not do much for the life span of the headers. I could grasp and squeez the headers on a 350 RWHP 12:1 Chrysler 340 with my bare hands while the motor was running.

And that EGR resistor is defintely a good thing to install if you want to shut down the EGR system....