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Ive looked on the site (probably not in the right place) and couldnt find a chart of which 928's had interference engines. Could someone point me in the right direction or provide a quick answer?
Are you sure????
I was under the impression that all 16 valve cars were non-interference!
Altough I'm always carefull with timing belt and water pump, in that case I must double my attention!
Are you sure????
I was under the impression that all 16 valve cars were non-interference!
Altough I'm always carefull with timing belt and water pump, in that case I must double my attention!
Regards
Some have sworn that the Euro S2 is non-interference as broken belt incidents didn't result in valvetrain damage. Others, though, have reported bent valves. I would work under the assumption that they are interference for that reason. At the very least, the valves and pistons come very close. Maybe even close enough that carbon deposits may be the determining factor of whether valves touch or not.
One more thing, which timing belt tensioner is better to use?
1) The lever type
2) The graduated **** type.
Thanks again. getting ready to do the water pump, timing belt and tensioner (if anybody knows where to get a rebuild kit).
My understanding (and it certainly could be wrong) is that the 4.7L, 16 valve, high-compression M28/21 engine in the S2 (84-86 Euro) is an interference engine.
The earlier motor is not.
Edit to add: Your pic seems to show a 16 valve (spider intake). Should be a US 84 or earlier.
So, it seems the Euro 16 valve, 4.7, M28/11 and 12 are the last non-interference!
I suppose I'm a little more safe, but nothing beats a good maintenance with the recommended intervals!
That's one thing I don't want to find out in real life if my 83S is interference or non-interference!
Thanks for the answers!
WALTSTAR
Regarding the tensioners I'll let the experts tell you because there is no consense on the factory tensioner versus the Porkensioner!
IMHO - Porkensioner is the only way to go. Self contained, no bleeding needed and no re tension after 1500 miles (or what ever the recommended interval is)
So, it seems the Euro 16 valve, 4.7, M28/11 and 12 are the last non-interference!
I suppose I'm a little more safe, but nothing beats a good maintenance with the recommended intervals!
That's one thing I don't want to find out in real life if my 83S is interference or non-interference!
Thanks for the answers!
WALTSTAR
Regarding the tensioners I'll let the experts tell you because there is no consense on the factory tensioner versus the Porkensioner!
Regards
m28-11 is non interference. ( 80-83) the later 16 valve (84-85) has the very shallow valve reliefs (.175") and its interference.
all the US motors are crap shoot for the 83-84. very close. generally, the cam lift is low enough so it might not be an issue. when i put in the euro cams, it became interference. (1-2mm more cam lift) the 4.5s are non interference.
what are you worried or thinking about , in reference to whether its non or not?
stock tensioner works find.. i wouldnt mess with it
Originally Posted by Kiln_Red
I'd just rebuild the original if your car is a US spec.
put an 85 short block under it all... thats easy and gets you some big power and parts are cheap. all you need is new rings, rod bearings and put it together, and boom! you have a 5 liter!
Originally Posted by giddyupp
IMHO - Porkensioner is the only way to go. Self contained, no bleeding needed and no re tension after 1500 miles (or what ever the recommended interval is)
ive never messed with the stock stuff much... i check tension yearly and its always fine.
as far as tension testing.. the Porsche tool is best, but the spring lever kind is ok, but usually winds it a little tight. if you use the lightest setting on the spring tool, its usually pretty close. all bets off on the older 82 and earlier cars . (square teeth and different thickness belt throws off test settings)
Some have sworn that the Euro S2 is non-interference as broken belt incidents didn't result in valvetrain damage. Others, though, have reported bent valves. I would work under the assumption that they are interference for that reason. At the very least, the valves and pistons come very close. Maybe even close enough that carbon deposits may be the determining factor of whether valves touch or not.
a running engine NEVER NEVER NEVER has any problem with the pistons getting close to the valves. just look at the spec for the S4 cam settings. 2mm lift when the crank is 20 past TDC. go see how far a piston goes down when you have 20 degrees ATDC.....anything past that, and the piston is dropping much further. point is, max lift of the cam happens at half stroke, and thats well over an inch down the cylinder. max lift is never more than about 1/2" total!
so the main concern of non vs interference, is when the belt breaks or you are rotating things in the garage with the belt off the car.
Ok, now that its still not clear...
Who is and where is Roger? (keep in mind that I havent been on here with you guys long and am not as familiar with you all as you all are with each other).
What is a porkensioner?
Why would I rebuild a 60,000 mile engine that has been babied? If I was going to swap engines, I have a 406 dual quad, roller, gear driven, 4 bolt main small block that I would drop in rather than another Porsche engine (forgive me purists, but no vehicle of mine remains stock once I decide to start modifying it)
I was wondering if in the event of a belt failure, would my valves be struck by the pistons.
a running engine NEVER NEVER NEVER has any problem with the pistons getting close to the valves. just look at the spec for the S4 cam settings. 2mm lift when the crank is 20 past TDC. go see how far a piston goes down when you have 20 degrees ATDC.....anything past that, and the piston is dropping much further. point is, max lift of the cam happens at half stroke, and thats well over an inch down the cylinder. max lift is never more than about 1/2" total!
so the main concern of non vs interference, is when the belt breaks or you are rotating things in the garage with the belt off the car.
Of course I meant with the belt displaced. I understand with the valvetrain working as it should that pistons and valves don't make contact. In my experience, the '80-'83 Euro is non-interference (meaning when the bottom end continues rotations while the valvetrain does not). The good news that from '78-'95, they are all non-interference when the belt is equipped and the timing is correct.
05-28-2015, 12:22 PM
INTERFERENCE?
