turboteko

I just finished rebuilding my 3.0 83 SC motor and when I started it up there was a constant thrashing noise. I ran it for about a minute, shut it off and went into a lite depression. I decided there was a problem with the chain guides or something, I looked through all of my assymbly photos but didn't see anything odd. Pulled the motor back out and pulled the plugs and timing covers. I had noticed that when I turned the motor over by hand there was a slight, tightnes at each TDC spot but very slight. I finally figured that I had set my cam timing wrong, I had set the advance to .2mm [DC cams #15] instead of 2mm so I'm hoping the exhaust valves were just kissing the pistons and it will be quite now. It spins over very freely by hand now. Rookie mistake, hopefully, but I hope this might help some other new builder to be aware of the cam timing numbers better.

theiceman

Thanks Turbo

Please post a pic of your car and join the club .. also let us know what happens when you throw it back in and turn it over ....

Welcome to Rennlist

rusnak

fingers crossed for you. Welcome to RL.

Peter Zimmermann

Better do a leak down test before you spend valuable time installing the motor. If the valves were "kissing" the pistons they're probably bent.

turboteko

I decided to take the warning from Mr. Zimmerman and ran a leakdown test. My motor had only run for under 2 minutes but I know how that story can go. The good news was that all cyl. were from 3 -5% which I thought was OK for all new rings/bores, valves etc. I'll get it back together tonight and hopefully in the car tomorrow. Thank you all for the invitation, I have been lurking here for several years.

83 SC Cab
87 944
91 C2 Turbo

whalebird

Besides the cam timing, did you find anything "thrashing" about?

Ed Hughes

A couple of questions:

1. Did you get both cam sprockets on correctly? One has the dish toward the rear, one has it toward the front-meaning the sprockets are identical, and can be installed backwards.

2. Did you check alignment of the cam sprockets to the intermediate shaft?

3. What kind of tensioners do you have, and are they in good shape?

You mention constant thrashing. Improperly timed cams won't cause this, but either of the situations above, if wrong, could.

turboteko

I have updated hydraulic tensioners and I set the alignment for the gears, I believe very straight. I did recheck the gear offsets and that's all good, I've been building V8 motors regularly for 40 years, [I'm 61] and was suprised by the noise. I bought Waynes book and followed it carefully except that I got stupid on the valve timing. It's going back in the car tomorrow so I'll know soon. Thanks for all the tips and suggestions these things all help everybody.

rusnak

Did you prime the tensioners under oil and re-set the grenade pin?

turboteko

I wanted to post a quick update on my motor noise. I have pluged the motor back in the car, started it up and gone for a test ride. No crazy noises or rattling, I am at piece with the 911 world. I really think it was my valve timing but as another member mentioned, I needed to better check my new tensioners, I did soak them and pump them in oil but they felt about the same. I at least know everything is very right at this time and the motor pulls very good, though I'm still doing the break in running. I want to thank everyone for their help and insights.

rusnak

If the tensioner check valve fails, then you get a sound like you're holding a wooden shingle against a chain link fence at about 10mph. Wayne mentioned the noise in his book. I think the tensioners just needed oil pressure.

whalebird

Maybe it's a blessing - the tensioner needing pressure - that he found the timing issue.
How about some photos Turboteko. It's very respectful that your a paying member with 4 posts.
Ask lots of questions here, we will help if we can.
Good luck and have a great holiday weekend
Welcome to Rennlist.

rusnak

WB, that's a very good way to look at it.