To Dry Deck Or Not ?

[maguromic]

Can some one tell me the pros and cons of dry decking a motor (other than the time involved).  Like is it better for high RPM (7000-9000), and other aspects of doing it.

[ddahlgren]

It is more a matter of engine design and cylinder pressure. Some engines are poorly designed for racing use as they don't have many head bolts or they are not easy to upgrade to larger fasteners. They probably did not need any better than stock for the original application so the design is not really flawed from the start. Other engines are over built from the start so need no upgrade. So it depends might be the correct answer not knowing the application. It has nothing to do with rpm either and everything to do about BMEP.
Dave

[Dean Los Angeles]

Yep, absolutely true.

"dry deck" is where you plug the coolant passages to the head.

If the engine you are using won't take the pressure of a racing engine and runs the risk of lifting the head, dry decking will avoid coolant into the engine. If this is the case then that engine may be a poor choice for Bonneville.

Eliminating the coolant from the head makes the head hotter (Duh!) For anyone unfamiliar with the term BMEP it means Brake Mean Effective Pressure. "The average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output." If we try to compare a 1 liter engine to a 2 liter engine the only way to do that is through BMEP. How big is the explosion? If we calculate the average pressure that results from the ignition of the fuel mixture, BMEP results.

BMEP also tells us how the intake, exhaust, timing, etc is working.

In a perfect engine we would insulate everything. The internal combustion engine is a heat engine. The heat of expansion is what pushes the piston. We throw lots of heat away by cooling the engine. In a production car that's necessary to get longevity. In a race car it is only needed to avoid melting. Dry decking puts more heat into the engine and can produce more horsepower.

Run it until it melts, and then back off a little!

[JackD]

Perhaps if you said what kind of engine you propose to use the answer might be tailored better to your application.
 Instead if your first lesson being how to fly when all you want is to learn to drive.
A simple question can generate an overwhelming answer that is right in the detail and wrong for the level of the question.

SIT DOWN GUYS !

[Bob Drury]

Damn!  I am still trying to figure out how to index my spark plugs, and you guys get into engine theory...........

[RichFox]

When Larry Climbie was running his 455 Pontiac, he would blow the head gaskets every time he ran the car. There was a large hole to the water jacket very close to the cylinder bore that was where it would let go. It seemed clear to me that that hole needed to be plugged. As long as I was doing it I plugged all the water holes. Then I punched out solid copper gaskets without water holes. No more blown head gaskets. I ran water into and out of the heads and then into and out of the block. I don't do this on other engines that don't blow gaskets all the time.  RF

[maguromic]

Lots of good information.  The engine is a Ford "c" class motor.  Its cam less with my own heads.  It's a high reving motor and I was worried about loosing head gaskets.  The engine doesn?t come alive till your high up in the RPM.  That?s when other things go wrong.

Rich, I was thinking along your idea , and feeding the heads separately.  These are billet heads so I can make them without the water holes.

[maguromic]

WOW,

That's weired, the spell check mesed up the words. Oh well!!

[joea]

..........no worries happens to JackD all the time................

not sure if its from dry decking...............

[ddahlgren]

How many foot pounds/cubic inch ?? A small block ford with good studs is a pretty robust piece. RPM has nothing to do with the need to dry deck. It is all about ft/lbs... if under 2.0 per cubic inch you are wasting your time as long as you used a good block with thick decks. If this is an N/A engine it is even a bigger waste of time. A 302 with a fel-pro gasket can run the 24hrs of Daytona and win... at 720 hp and 8200 rpm
Dave

[maguromic]

Guys, thanks for all the good info.  The engine torque is close to 2.3 per cubic inch.   The block is a NASCAR unit and all the parts are good, it will run normally aspirated on fuel with some nitro.

[Tom Simon]

I have this "cylinder pressure" discussion with guys all of the time. Some of them insist they can get away with an 8mm head stud with 30psi of turbo boost without lifting the heads. Another guy claims about 22psi is all he can put to the cylinders. I contend it's not lbs of boost, it's cylinder pressure.

The more I think about it, it's not average or mean cylinder pressure, it's  peak pressure that lifts heads, isn't it?

[ddahlgren]

I would be certain it is the peak pressures that will lift the head. A nitrous engine is more likely to lift a gasket than a similar output turbo engine.. What i was looking for was a relative performance of the engine to start with.
It always gets down to the same thing.. start with the most appropriate car, bike or engine for what you need to do. What you have in the garage or a favorite is seldom what you need to accomplish your goals unless they are modest or you have already acknowledged that the new favorite is the one best suited for the task at hand due to correct engineering and not because it is a favorite. My favorite bikes and cars are the fastest ones.. The OEM builder is just a historical footnote attached at the end..
Dave

[RichFox]

Are you saying that my choice of a '55 Packard V8 engine to run in C/CGAlt could be a mistake?

[Dynoroom]

Dave, why were you up at 3:15 a.m. replying to this?  

Rich, not a mistake an adventure.....