top 10 engine myths debunked...

[kc8oye]

10 Engine Wives‘ Tales - Debunked

by Don Terrill ©2003

1.) Grinding a crank under makes it weaker – Cranks always break in the same place, the radius – it’s the weakest part of the crank. The larger the radius, the stronger the crank. When a crank is ground there’s actually an opportunity to increase the radius and thus increase the strength of the crank. It’s all in the hands of the person doing the grinding – choose him or her wisely.

 

2.) Fuel Injection always makes more power – Fuel injection does a great job when throttle position changes often. For types of racing where the throttle is wide open most of the time (i.e. drag racing), a carburetor is a formidable opponent – especially when matched against throttle body injection.

 

3.) Too much spring pressure is hard on valves – What’s hard on valves is the speed at which they contact the valve seat at closing. What dictates how hard the valve hits the seat? It’s supposed to be the camshaft closing ramp, but when spring pressure is too low the valve does not follow it’s intended path and instead slams into the seat and actually bounces. So, actually more spring pressure helps the valve by forcing it to more closely follow the cam shape.

 

4.) Rod bolts break because they’re bad – Rod bolts are falsely accused of engine failure more often than any other part in the engine. 99% of the time a rod bolt breaks it’s not the bolt's fault, it’s the engine builder's fault – more directly the one who torqued the rod bolts. Not surprisingly, I’ve had a hard time getting people to agree – it’s a lot easier to say and believe that “It’s not my fault.” Rod bolts work by stretching, usually around .006”. They’re almost always less (say .004) when torqued with just a torque wrench. A stretch gauge is the only way to go.

 

5.) A 10qt oil pan needs 10 qts – Your engine needs only enough oil so the oil pump pick-up never gets uncovered, not an ounce more. I think you’d be surprised how little an engine can run on – I’ve raced with three before and heard rumors of racers successfully using even less. If pan manufacturers would stop “rating” their pans this way, the confusion would eventually end. Most wet-sump engines are perfectly safe at five quarts.

 

6.) Head gaskets can’t be reused – Motivated by the cost of current racing head gaskets, I started reusing them. The shorter the engine run time, the better your chances of success. Buy one set of gaskets, use them when honing with torque plates, reuse them for mock up, reuse them for assembly and reuse them after tech teardown. The biggest risk is a water leak – if that portion of the gasket looks good, go for it.

 

7.) Glowing headers mean the engine is lean – This wives’ tale is starting to lose steam, but still believed more often than not. Headers glow red for only one reason, there’s fuel burning inside. The two main reasons are a rich mixture and late ignition timing - which doesn’t give the fuel enough time to burn inside the combustion chamber. Test it for yourself, let your engine idle and crank the ignition timing back to the point where it barely runs, then get out the marshmallows.

 

8.) Bigger cam and ports = more max power – I know that most people now understand that bigger is not always better, but there’s still a great many people who think that bigger always means more peak power. Well, this isn’t true either, too big a cam or ports can lead to reduced cylinder filling, which in turn leads to LESS max power. Remember, everything in moderation.

 

9.) Setting ignition timing by ear works – There are still some old-schoolers left that believe this one, and you can’t tell them otherwise. Someone setting ignition timing by ear will always end up setting the timing too high – at idle it sounds great at 60 BTDC, at 7000 RPM (under load) I’m sure it’s down right scary.

 

10.) Flick ashes in the oil pan for good luck – Now this is a real wives’ tale. Believe it or not, people actually do this – I’ve seen it. If your engine builder thinks he needs some good luck, maybe you need a new engine builder.

 

Think I’m out to lunch? Fine, write your own article

Original Source

[Andy's Auto]

Hey man, I have been flicking my ashes in my engines for over twenty years. Not saying it does anything but add good JuJu to the build/

 

Andy

[kc8oye]

andy: heh yeah.. I've never heard that one until now, but it doesn't surprise me there are a lot of superstitious people in the world. Me, I did my best to keep everything out of the oil pan except oil

a little surface rust for good measure maybe

 

[BuffaloBillPatri]

Great Info!

[Slaman]

Very good info. I agree that fuel injection does not always make the most power, but I do beleive it is a preferred method for alot of race engines in that it ensures equal fuel to each cylinder. This is of course limited to multi-port injection and not throttle body injection. the TBI injection would be subject to the same short comings as a carbed engine, lean cylinders up front and rich in the rear upon launch... just a thought and my opinion...

 

Steve

[Andy's Auto]

When I was 16 years old in 1988 I left high school to persue a career in late nights and busted nuckles. My shop teacher told me in two years carburators would be a thing of the past. The he handed me the keys to his 1973 Monte Carlo 454 Landau and said fuel injection could never compete with a properly functioning carb.

 

I miss Mr Jonas. He got me out of Pontiacs and into the world of the Big Block Chevy.

 

Ondy

[kc8oye]

slaman: I would think ease of tuning would apply to racecars too.. why spend 15 minutes tearing a carb down to change jets when you can make a couple of mouseclicks and send the changes to the car?

port fuel injection also allows for far better intake runner design, because the designers don't have to worry about things like fuel pooling, because there is no fuel in the runners.