What is the mileage on the engine, have you adjusted the valves, what is the compression numbers? If the comp numbers aren't in the high 160's it might be pointless to add a cam and head w/oversized valves w/o rebuilding the engine.
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>>>*A very true statement here. We see a lot of folks bolt in a camshaft profile and expect to feel serious gains, when the fact is that without the foundation, nothing helps.
*I am bored this morning so here we go....
The first step is to test compression. If those numbers check out good and are uniform, then adding airflow can help.
Remember all that any camshaft and head combo can do is add potential, it simply increases available airflow volumes, this is all there is to it. I suppose I could claim a "secret" camshaft design, but I would be fibbing, there are no secrets. It's not a good idea to fib when the customer has your phone number... <img src="/forums/images/graemlins/lol.gif" alt="" />
Inside your engine there is a fire. Think of what happens to a fire when you open the draft? The influx of available air causes a sudden increase in flame, now add some fuel to the available air, that tells the story.
Performance gains are a balancing act. If the exhaust is too large, things slow down. To speed the flow back up, we run the engine at a faster pace. Cam designs with more lift/duration on the exhaust side are aimed at making power by spinning the engine faster.
More lift/duration on the intake side adds fuel/air volume potential, this only works if the engine can use it.
Otherwise, adding intake mods is a bit like trying to pour 6 gallons into a 5 gallon bucket. This is why slightly larger inlet valves work well, great big ones don't unless we force things a little, then they do..
Oversize tires reduce engine speed at all given MPH's, add in leverage from them being larger, and mass plus rolling resistance and we can see the probable results. Then increase airflow to that situation and the results can be less than we expect.
To compensate some with a cam design, the idea is to open the valves sooner and more, give things a head start. There are physical limitations of course, but this is why advancing a cam profile works within reason.
So when the situation is oversize tires, stock gears, and exhaust system a bit too large? We would in theory want to advance the intake lobe centerline, and leave the exhaust side alone.
We can do that a tiny bit but core blanks come in mostly precut, and air doesn't grind well. Sure we can have a special design made just for a specific situation, I can see the ad now "Only $2995.00, buy it now...$3000.00".
So to do this the intake valve ramp is quickened, which just means the valve opens at a faster rate and early. Of what I offer, the 261C is closest to that. There is very likely somewhere around 50 different camshaft part numbers doing something similar, I think my lobe shape runs quieter but then I am prejudiced...*LOL**.
The bottom line is when the tires are larger than stock, and you need a bit more power? Think gears, this is number one. Exhaust system is number two on the list of things to do, it seems the factory wanted the engine nice and quiet so they strangled it with a system that would work well on a Briggs and Stratton.
(You folks with the 3VZE? Go look at your stock system..Good grief!... <img src="/forums/images/graemlins/frown.gif" alt="" />...)
Then adding that camshaft design can put a real smile on your face....*EB
