silent running

OK there are two different cambelt tensioner designs on the classic engine, the early pre-96 one with a long narrow cylinder secured by two smallish bolts, with an eccentric bearing on the end; the other being the later post-96 one which seems much simpler - a chunky cast arm with a big thick bolt bolt at one end and another thick bolt through a standard big bearing at the other end.

Which is stronger. I've heard stories of the newer design shearing off because it only has one bolt, but then the older two bolt design has also done the same, because each bolt is thinner, and I've seen the photos - not a pretty sight.

I'm asking because I've got both types sitting here and need to decide which to refit to my new engine build - the new design one is AFAIK only a couple of years old and actually looks new; the older design one seems to be OK but looks its age I suppose. What should I do?

jim litten

Do you have the different mounts for the them? It all comes down to luck tbh, I bought a pattern part for the later version and it failed, and I've also know that if you compress the earlier ones to quick they fail. If they're second hand and don't have the pin in them and compressed then I'd buy a new one as its not worth taking the risk, I gambled and lost.

ticky

I just recently fitted my phase 1 (sti4)heads & timing belt on my new engine last weekend. My short block is a phase 2 & came with the new style tensioner along with the extra small pulley. At first I tried fitting the belt with the new tensioner but could not get the timing marks perfect. I think it was down to my technique but then again I found having the timing marks out a tooth in a certain direction & then when you finally pull the pin the timing mark align perfect. Mind you phase 2 are fitted with thinner head gaskets & I was using thicker gasket hence why I think that may have contributed to the timing issue. That was one reason I went for the old style tensioner. However I did try fitting the belt without the smaller pulley but found the belt was slack & with the smaller pulley fitted the belt seemed to tight.
When I refitted the old style tensioner & new belt I managed to get the timing marks perfect. God knows how others manage to get the timing marks aligned first & when they release the pin still get them to stay where they are??
The other reason was the fact that I heard of the same stories of phase 2 tensioner failing.
The only good point about the phase 2 tensioner is that they are cheaper than the phase 1 new?

Ticky

silent running

Yes I've got the mounts for them. After seeing a pattern water pump and how it the impeller is totally different - and basically **** - I'll never use pattern parts. They are both second hand but not in the sense that I bought them off a scrappy or off ebay - in fact I personally removed them from two broken engines. The later tensioner was from my own MY98 WRX that had had it fitted new 1-2 years ago, and the earlier tensioner was from an early closed deck block of unknown history.

Both are sitting there uncompressed at the moment - do they need to be recompressed before fitting?

silent running

Ticky, that's the thing, I've heard stories of both kinds failing, the older style might have two mounting bolts but they're both half as thick as the later one. I suppose if one fails you won't have a catastrophic loss of tension, or at least less chance of it. I guess the best thing will be to wait til I'm ready to fit and see what works best. I am inclined to fit the newer one, purely because it's newer and I don't know how close to failure the older one is.

Any trick to getting them compressed back again so I can stick a pin through?

ticky

Yes they need to be compressed vertical & done slowly. I used a small allen key as a pin & a small vice or G clamp to compress the pins.

silent running

Excellent advice, I'll get straight on it. Does it do them any harm being left uncompressed for a while?

ticky

I thought I would add the vice I had gave a better grip but was small & not bolted down, hence turning it around so the tensioner/pin was mounted vertical. Just compress it very slow, take your time. If you find it has no tension/fight at all then throw it away. There is a guide of how much pressure it have but I had no way of measuring it. I see if I can find the specs.

ticky

I dont know but both of mine where compressed & pin held when removed.

silent running

Ah, well my vice is pretty heavy duty, but bench mounted so will compress horizontal. Maybe I'll use a G cramp instead.

jim litten

Horizontal isn't a problem, just compress it till you feel some resistance then stop, let it rest for a period, and then start again.

ticky

Just to add from the manual.

"Caution: Slight traces of oil at rods oil seal does not indicate a problem."

A bit odd I thought that would be a problem???

Continue:

" While holding the tensioner with both hands push the rod section against the floor or wall with a force of 147 to 490N (15 to 30kg, 33 to 110 lb) to ensure that the rod section does not move. If it moves replace the rod adjuster with a new one.

Measure the extension of the rod beyond the body, If it is not within specification replace with a new one.

Rod Extension: 15.4 to 16.4mm (0.606 - 0.646in)"

Thats what the manual states based on the old style tensioner.

Ticky

nez-wrx

if in doubt i no they are expensive but just replace with a new genuine one at least then you have the piece of mind that your rebuild engine is not gonna let go

silent running

Well this thread has already answered a whole load of questions, cheers! Still don't know if one design is actually stronger/more reliable than the other, but it's given me some more info to think about.