I thought I would share this helpful hint since my search around this topic came up with zilch, and it ended up costing me $200 and a day's worth of work for nothing. Please ignore me if this is common knowlege, and I'm just an idiot.

You should never check the compression before starting your car if there is any chance of carbon deposits on the piston. It can cause your valves to leak. Any fuel that sits on the piston can cause the carbon to flake off. Then, when you do a compression test, the piston can actually throw these hard carbon flakes up into the valves during the overlap. The valve seat pressure will smash these carbon flakes into hard deposits in between the valve and seat. In my case, this caused all 16 valves to stay open by 2-3mils (verified by rechecking valve lash), which resulted in a 90-95% leak on all 16 valves (ok, one was only 75%).

I know some of you are thinking...why would I do that? I did it because I broke a timing belt after 2K miles on a rebuilt motor, and found that I bent two valves with a compression check . Once I had the head fixed and reinstalled it, I figured I would check the machine shop's work with a compression check before firing her up. I thought, this is how I found it was bad, so it should be a good way to make sure it is now good. I know that it would affect the compression some since it is cold, but I figured that I shouldn't have to fire it up since the rings were already seated. Well, I was painfully wrong. The leakdown test I did after the fact would have been a much better method.

I hope this helps some other poor soul that made the same mistake I did. I debated all night whether or not I should remove the head, and searched for someone else that ran into the same issues. My first thought was headgasket (leakdown test shot that down), then I thought the valves were just too far out of adjustment for some reason (why would it change by turning over the moter a few times), and then I even considered the carbon issue...but all 16 valves...no way...way. It may have cleared up if I just fired her up, but I thought the risk was too high. What if the machine shop accidentally bent all of my valves, or the valve guides? Starting it up would have been a mistake then.

Oh, by the way, Power Enterprise timing belts suck! I reused the timing belt after my rebuild since I only had 14K miles on it, and it ended up shearing the teeth off in 16K miles. Sure, maybe they make the strongest "belt" in the world, but I could pull most of the teeth off with my fingers. The belt was exposed, working against Toda B cams and Toda valve springs, and on a hard driven ~200whp B18C, so I figured that it would only last <60K miles...but 16K!!! I put a Toda timing belt on there now. They advertise the belt AND teeth to be 2-4X stronger than stock, and they told me on the phone that they have been running one on their race car for >50K miles now, exposed, with the same setup. After all, it was made for this setup. However, they did mention that running it exposed always poses a risk.


Modified by 2xtrme at 4:09 PM 10/17/2005

 

I see hundreds of people that run exposed belts, and always ask myself "why?"!!! IMO that is the dumbest thing to do! Many of my friends and customers want to do the same thing because everyone else is doing it cause it "looks cool"! However it is not smart at all!! Toda says in the instructions not to expose it to the elements, and to NEVER get any oil or solvents on the belt. Well it is almost impossible to do if you leave your covers off! Look in Honda Tuning and on Honda tech and you will see all kinds of people with dirty oil stained Toda timing belts! The timing belt is the most important part to keeping a motor running right, and from saving you thousands$$. Why not protect it?!?!?

 

Yeah, I know, but the look is only part of the reason that I leave it exposed. The primary reason that I leave it exposed it is the same reason that Toda does it on their race car (which has over 50K miles on the belt), which is that it is way easier to dyno tune, or tune at the track. Also, I've been running exposed belts for years, and this is the first time that I had any problems. Usually, I can run the belts for over 60K miles (including OEM belts). Maybe I spilled something on this one during the rebuild, maybe the spun rod bearing had something to do with it, or maybe I just got a bogus belt. All timing belts are made by the same manufacturer (even OEM), but I believe that Toda specs them the best which is why I paid the extra $. This time, I will cover it while doing any engine work or cleaning, and I will inspect the teeth more often (another reason to leave it exposed).