After over three years of procrastination, I finally got around to putting my RS engine back together after the typical head gasket failure. The last engine I rebuilt was my 1963 Lotus Cortina several decades ago, so I was a little rusty on the procedure! Amazingly it had not rusted away due to liberal periodic oiling. The heads were shaved and valves lapped and installed. I even smoothed out the intake and exhaust ports for that extra 5 bhp. The heads were installed with the new style metal gaskets and the valve lash was adjusted. They were all wrong because I switched heads by mistake. All the meticulous labeling I did three years ago had long gone. Luckily the heads are identical (Google told me so!). Then I realized this is an interference engine and I wondered if I had caused a problem during the valve lash adjustment because the timing belt was not yet fitted. So I figured some kind of compression check would let me know if the valves were bent. I installed the timing belt and checked compression by manually rotating the crankshaft. All four cylinders reached about 60 psi., even at that low cranking speed, which gave me confidence that the valves were still sealing properly. Does anyone have any experience of this or have any comments about whether this is a reasonable check for bent valves?
I had a few laps during the lunch break at Waterford Hills last weekend. Perhaps I went faster than I should have (it is a cruise only run) but the engine felt strong and the handling was tight. There is an engine rattle which was not there before. It is only on no to light load and only between 1 and 2000 rpm. I did not strip the short block so nothing I could have done wrong there! I am suspicious of the new timing belt tensioner. The old one seemed fine until I squeezed it in a vice. I learned later you are not supposed to do that with the tensioner horizontal. So I put in a new Beck Arnley part. Anyone have any experience with bad tensioner? Also the fuel gauge was stuck on empty with the low level light on. I filled her up but only managed to get 2 gallons in! I looked high and low for a connector I might have forgotten and tried to check float resistance. Eventually I found a mouse had taken up residence above the fuel tank and chewed through the wires of one of the floats. The picture is taken after the mouse bed was vacuumed out! I bet that wire tasted good.
On my WRX it sounded like a rod knock between 1-2000rpms and it was timing belt tensioner. The piston would not go out further than half way and it would bottom out against the block. I ended up with an used OEM one from Scott to test and it is still in my car running nice and quiet. Always compress them very slowly. I used a c-clamp and tightened a half or quarter turn at a time, waiting 30 seconds each turn. Otherwise it is easy to blow the seals. 02 WRX 91 Talon Tsi (sold)
Thanks Mike, that is reassuring. How did you come to that conclusion? Did you just take off the front cover on a hunch or did you have more reliable info on the cause of the rattle? I put in a brand new Beck Arnley tensioner which came compressed with the pin in place. I installed it and pulled the pin with the belt on and that's it. Must have been a bad part! In response to Jen, who thinks the 2.5 SOHC engine is non-inteference, here is an extract from Wikipedia, the bible of facts!: "The SOHC EJ Subaru boxer engines were non-interference engines through 1996, run by a single timing belt driving both cams (both sides of the engine) and the water pump. Because they are non-interference engines, if the timing belt fails, the engine of the models up to 1996 will not be destroyed. The oil pump is driven directly from the crank shaft and the waterpump by the timing belt. All DOHC and 1997-up SOHC EJ engines are interference engines, if the timing belt fails the engine will likely be destroyed or the valves & piston will be heavily damaged." 2012 Secretary
I am rebuilding my spare RS engine. I bought it for a song knowing it ran, but had a bad knock. Turns out the rod bearings (known as the "big end" bearings where I come from) are shot but the shells have not spun so the rods are OK. Anyone recommend a reliable machine shop to grind the crank? If I hear nothing I will go back to Auto Parts Machine in Ann Arbor who skimmed the heads. What about whether the cost to fix this engine including new oil pump, water pump, bearings, rings, etc, is worth it compared to the cost of a good used engine?
Can you be sure of the quality and reliability of a "good" used engine? At least you know what has gone into the engine that you build yourself.
If you use good quality replacement parts and assemble it properly - you can expect it to function as well as a new engine. Can you say the same thing about a used engine? Maybe. Maybe not.
I'm sure you'll find the cost of rings, bearings, pumps, gaskets and machine work will come in at or below the cost of a used engine. All you need to do is put it all back together. Unless the assembly process is too intimidating, you are likely to be better off doing it yourself. Somehow, I don't think this is beyond your capabilities.
Just be sure to document every step so you can show it on youTube...
[ Edited Tue Oct 16, 2012 - 09:06AM ] Scott Team Harco Motorsports Win on Sunday, Sleep on Monday