Adding to stock engines

[Michael W.]

Re: Adding to stock engines

With all of the advanced driver aids in modern cars, you'd think they would add an audible that said something like "Hey dummy, turn off your engine now or prepare to buy a new one."

Experience shows that no amount of warnings of any type will dissuade someone who is determined to get home no matter what. Some modern cars have a last-chance device that rolls back engine power and cuts ignition to some cylinders in the case of an extreme over heat. Despite this, people continue to drive to destruction.

[Domenic T.]

Re: Adding to stock engines

Going along with what was said above about cleaning spark plugs ETC. When I was a mechanic at the dealership back in the days of the stock 300/327, the old folks that drove them easy brought them back with carbon knocks and dirty plugs. GM had a can of top end cleaner that would remove the carbon on the top of the pistons that hit the head.
It has been proven (and in effect) in aircraft engines that the higher the compression the lower TBO (time before overhaul) is. Also not known to many but, the higher altitude a engine is operated the longer it lasts because they only (non turbo charged) operate at about 60% power and the cylinders have less pressure. The more pressure behind the rings the harder the ring is forced against the cylinder.
All that said, I'm sure if you treat the engine with respect that you would not notice that it had a somewhat shorter life, if any.

[Eric E.]

Re: Adding to stock engines

As an added note on the filter issue. I experienced an extreme on the air flow vs filtration discussion. I worked with an engineer that came from a farming family and he told me that his dad felt that filters were too hard on the engine and straight air flow was better so he never used them. I thought that was a bit of a stretch until one day his dad showed up at the office and dropped of his sons truck after using it at the farm for harvest. After he left we walked out opened the hood and the air cleaner and there was no filter. Guess not all old habits are good ones!

Thanks Duke, have heard similar comments on their filters for motorcycles but couldn't put any testing as a reference.

[Duke W.]

Re: Adding to stock engines

It's amazing the myths that people believe. An air filter element should be sized to yield no more that a 6" H2O pressure drop across the element and many are less. In the "Tale of Two Camshafts" article, chassis dyno testing showed that removing the entire air cleaner reduced power across the entire rev range about one percent.

In the bike world it was popular to replace the OE air box and filter with individual K & N air filters on each carb. A buddy of mine who is a very talented machinist (but no engineer) did this to his '83 Honda CB1100F. I told him it was a mistake. The big OE filter allows each cylinder to aspirate from the entire filter where as the small individual filters only aspiraded one-quarter of the cycle time, so they were restrictive. He also reduced his F's weight by about 40 pounds, and Dick probably only weighed 140 dripping wet against my 190. So all up he had nearly a 100 pound weight advantage.

All I did to my F was increase the idle jet size and adjust the idle mixture to eliminate the off-idle lean surge that caused problems, like driveline jerk, in downhill turns. (This was a common problem on eighties vintage bikes due to emission regulations.) With that tweak, throttle control and response was perfect.

After all was said and done we did some roll-ons, and it was a dead heat! His weight advantage was offset by his engine's power loss.

Duke

[Domenic T.]

Re: Adding to stock engines

Duke,
Interesting that you said that about the filter not providing the correct air. I bought one of those small filters back in the 60's for my 500 single thumper, I think it was Cal Custom. It was for a 6 cylinder and about 4" in diameter. My bike only had a velocity stach so I decided to filter the air and adapted the custom auto filter to the bike. I installed it and went for a ride, the plug fouled in about 10 miles. I removed the new filter and changed the plug. when I started the bike it ran good till I put the filter on. I then noticed the tail pipe and smoke.
HOW could that have worked on a 235 chevy 6 cylinder?

Dom

[Duke W.]

Re: Adding to stock engines

Without looking at both configurations, I have no idea, but, especially on a single, there should be a large air box between the filter and velocity stack, with plenty of clearance above the velocity stack inlet to the top of the air box.

A 500cc single needs a filter/air box and carb/throttle body about the same flow/sizes as a 2-liter four-cylinder because the single is only aspirating one-quarter of the cycle time.

If you look at the air box/filter on a modern 2-liter class automotive engine, which are usually well designed for negligible restriction, it would be tough to fit on any bike.

Duke