28buick

I am considering the use of 0.060 copper head gaskets to achieve my target compression ration for my engine rebuild. Are copper gaskets ok for street use? Are there any galvanic corrosion problems between copper and cast iron or copper and aluminum. Will I have alignment issues with my intake manifold by useing a 0.060 gasket instead of the normal 0.035.

gkull

I only use copper. but your going about getting the right compression the wrong way. With proper quench of @ .040 you can run more compression without pinging on low octane.

With iron heads high 9:1 is no problem and with aluminum 10.5+ is no problem.

28buick

Can you explain to me why quench height has such an impact on preignition.

gkull

QUENCH, the distance between the cylinder head and the pistons flat area in the combustion chamber read the links below, its worth the effort.

I run mine as near to .040 as possible. Right now I have 11.2 compression and use 91 octane. I also drive and race 1000's of miles a year without a problem.

Run less than about .035 thousands and at high rpm levels the pistons might hit the cylinder heads, run more than about .044 thousands the QUENCH effect of forceing the fuel air mix to the center of the cylinder from the cylinders edge area looses both speed and effectiveness, remember the quench area must be so tight that virtually all the fuel/air mix is forced into the center area and none is allowed to burn untill its squirted into the burn area increaseing turbulance and burn efficiency
in theory the much better quench, combined with the shorter more compact area the flame front needs to cover and the far higher turbulance combine to allow more of the pressure to build AFTER the crank passes TDC on the end of compression and begining of the power stroke

its mostly an advantage in that you get a more even burn in the cylinder and less chance of detonation.
look, it takes approximately 40 thousands of a second for the flame from the ignition to cross a 4.25" bore,at low rpms and still takes about 15 milliseconds at high RPM due to the much faster movement of the compressed fuel air mix in the cylinders, lets look at what that means
if the chevy plug is located 4/5ths of the way to one side thats a time of about 32 thousands for the pressure to build as the flame travels 3.4" in the chevy but in a compact combustion chamber it could only take the cylinder flame front less than 10-20 thousands of a second to travel acrossed the combustion chamber for a complete burn at low rpms, this of course speeds up as the swirl and turbulance increase with increased engine RPMs but the ratios stay similar. this results in more useable energy WORKING on the piston AFTER IT PASSES TOP DEAD CENTER ON THE POWER STROKE. BUT MODERN WEDGE combustion chambers use increased QUENCH to speed the flame front and lower the burn time combined with a smaller combustion chambers look at this chart http://www.iskycams.com/ART/techinfo/ncrank1.pdf

keep in mind that the cylinder pressure starts, builds to a peak and drops off all before the piston moves more than about 1/2 inch away from TDC and that if your wasteing 10-20 degrees of rotation compressing the burning mix in a slow to ignite combustion chamber your wasteing engine power
http://naca.larc.nasa.gov/reports/1939/naca-tm-914/
http://www.me.gatech.edu/energy/ICEn...nProcesses.pdf
http://www.combustion-net.com/librar...gine-cycle.pdf
http://www.nedians.8m.com/Comp_IC.html
http://mb-soft.com/public2/engine.html

http://hpp.primediaautomotive.com/ar...hpp_fire.shtml


things to read
http://racehelp.com/article_racing-10.html
http://chevyhiperformance.com/techarticles/94138/

gkull

I was also going to say that coated copper head gaskets aren't cheap. My last FlatOuts were $124 delivered to my door for .021 gaskets. My block has been shaved to only true up the deck and my pistons are now .020 down in the holes. I considered going with .015 gaskets except that I have very short piston skirts

ZD75blue

Thanks for the reading material gkull!

I'm in the process of putting one back together... and decided that using the stock heads (75 bucks...) instead of upgrading to vortecs (900+) would let me put some more cash into the suspension instead of just the engine. So... I've been trying to read up on all this stuff, but I'm probably going to have to get the heads shaved even with the flat tops to get the best quench... :cheers:

wacked

That is good reading :hurray: Thanks for the links:)

Desertdawg

:iagree: :thumbs: