What differentiates K-Series engines from Honda's engine series of the 90's?
Of course, the chain-driven valve train.
After decades of building belt-driven engines, Honda's engineers decided to switch to a maintenance-free system to keep crank and camshafts synchronised.
Maintenance-free? At least, they claim that.
According to this, you can drive your car 300.000+ miles without worrying about the timing chain. Nice benefit compared to belt-driven cars, which need a new belt after every 60,000 - 105,000 miles.
I bought a K20A2 engine with 80,000 miles on the clock for my swap.
With that mileage in mind, I didn't worry about inspecting or even replacing the chain and auto-tensioner.
I loved driving my Civic after the K-Swap was done, but I was a bit disappointed about the power the engine built in VTEC.
There was like a rattling noise in the higher revs and the hyped VTEC-Kick was missing.
I read many posts of people, which complained about stretched timing chains. Could this be the problem?
After a few failed troubleshooting attempts like cleaning the VTEC solenoid, we pulled out the engine again and inspected the timing chain, guides and the auto-tensioner.
After we had removed the chain case cover, we were able to check if the timing was synchronised.
The engine needs to be rotated clockwise to TDC (Cylinder one is at top dead center).
Then, two marks on the camshaft gears which have to be in-line indicate if the timing is correct.
Here is the result of our 80,000 miles engine:
As you can see on the photo, there is a difference of about one link.
Although we found the cause of the bad performance in VTEC, I was very surprised that the engine ran so good in lower rpm's with this offset.
Stretched Timing Chains
The chance was high, that the chain was already stretched.
If the marks on the camshaft gears don't line up anymore, it's a clear indicator.
But I wanted to know exactly if this was the cause.
A few days later I received a little package from the United Kingdom with a brand new original chain and auto tensioner in it.
I compared the old with the new chain and this was the result:
The old chain (right side) was two millimeters longer.
You probably think "... so, who cares about two millimeters?" right now.
I thought the same. I was actually a bit disappointed about the result. I expected a significant difference.
One hour later the new chain and tensioner were installed.
While I was rotating the engine a few times, I really hoped that the timing is synchronized now.
This was the final result:
The marks on the crankshaft gears lined up perfectly!
The timing is perfect now. I wouldn't have expected that two additional millimeters have so much impact on the whole timing.
But it's true.
Now I can't wait to drive the car again! 🙂