3.2 question
 

I have a new to me Carerra with stock 3.2 and about 100K miles on it. It burns no oil, has no leaks, no smoke and runs OK. Starts right up idles a bit lumpy and runs to redline ok when the radio is on :-)

I have owned old 911's and rebuild two engines. Still not expert by any means.

Car seems slow. Did a valve adjustment and most were tight. Also did cap, rotor, wires and plugs. Now it runs a bit better and have been feeding it some Textron to clean off deposits.

Between 4k rpm's and 6k rpm's there is a knock on the right side. I suspect it might be a stretched timing chain. I theorize the stretched chains is also throwing the valve timing off a bit...thus the slow car. All 6 plugs have identical wear and seem to be getting the right mixture.

Since everything else in the engine seems healthy, can the timing chains be changed with the engine in the car? Or, am I looking down the wrong path.

The chain can be cut and new chain attached and cycled through the engine. My fear is the chain comes off the sprocket in the engine.....then case has to be split to repair. Also, don't want to have to time the cams (PITA) so hoping new chains will bring it back to spec.

Let me know your thoughts.

Thanks

Chris

Chris,
I think you are looking down the wrong path.

I suggest you first do a leakdown test and a dyno run (with AFR reading) to get a better idea of its current condition. I think the info from these two tests will give you a better understand of what you are dealing with and the likely solutions.

The "knock" between 4k to 6k is a worry but can't imagine its related to the cam chains or tensioners. If it was you would be hearing this at a much lower rpm as well. Are you sure its actually a knock?

Well... if it's actually a knock... then the rod bolts could be stretched and throwing the piston too far. The only reason I say this is because it would be odd for an engine to knock on one side.

As for the timing chain being an issue... if it WAS an issue, it would impact all the cylinders.. not just a few (or one side).

Have you pulled out your DME to see if you have a custom chip? Or perhaps get a chip from Wong and see if that fixes things.

If you want to look at what's going on in your engine, then as was previously mentioned, get a leak-down/compression check.
Could be you just need to readjust your valves again too.

These engines are so easy to pull, I can't imagine it would be worth your effort to mess with timing chains in the car. If you replace the chains you will have to re-time anyway, and I can't imagine how painful that would be in the car.

a knock noise can be several things, not many of them are super great. Does it make the noise if you rev the engine in neutral, or just under load? If it will make the noise in neutral you should get a mechanic's stethoscope and an assistant and figure out exactly where the noise is coming from.

Check continuity on the WOT switch which appears to be a TPS.

If it isn't working, it'll be running lean under WOT costing you some ponies.

its a knock or a bad rattle. Always at WOT between 4=6,k allways on the passenger side. Will check to see if it happens when not under load.

If the chains are badly stretched, that would have to significantly effect valve timing right? Chains would be the loosest then too right (at max torque & HP)?

Guess I can take the timing cover off and have a look.

I hate taking the car to the shop. Logistically it's a PITA

So not a best or common practice to change the chains except during a rebuild?

Thanks,
Chris

hi cm...why don`t you just start with basics?? Replace the fuel filter...how old it is ..? there is always a date on it so have a look ..

Ivan

Hey Ivan, I have replaced everything else tune up wise so fuel filter is next. It looks new and the fuel lines were all recently replaced. Will order one today just to know its not old.


Thanks,

Chris

Hi...Once you remove it have a look on the date and year on it..hopefully it is Mahle..
Ivan