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Join Date: Jul 2004
Location: Minneapolis
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Someone asked what base gasket I was using and if it was the same as the one that the shop had installed. I in fact had the shop buy all my parts for me so I assume they are the same. I did this because I was relying on them for some help and I figured it would be a nice gesture to buy some stuff from them.

Also there is a lot of discussion about wheter this method will work well or not. It seemed to work well enough to tell me I had a problem. When I can only turn a screw in a half a turn and it should be two turns that would tell me there is a problem. It seems to be repeatable and the tolerances seem to be pretty close from cylinder to cylinder. The reason why the #4 side exhaust was so much different from the #1 side is that they did the cam timing slightly different on that side. He said "they run better that way" but I don't know where that knowledge comes from.

The shop now has the motor and they are going to try to fix things by re-timing the engine. Since there were tolerance issues on both the intake and the exhaust sides I fail to see how things are going to get fixed by chaging the timing. (See chart on page 172) You can only make one side better but at the expense of the other side. Tomorrow the owner is going to check it all out personally and he is also going to check and see how much was taken off the heads the first time and how much, if any, was taken off this time. He said they sometimes take a little off when you have your valves done just to clean up the mounting surface.

I will find out more by Monday.

Wayne, I was interested in your opinion.... If it was your motor would you accept any less clearance than 1.5mm and 2mm? If so, how much? What if they can't fly cut enough off? I think they are going to be close but may not have enough room. How about fly cutting and a thicker gasket?

Thanks for all your help.
TK
Old 07-16-2004, 08:57 PM
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You know, I also heard that if you take something like a 255/40-17 and mount it on the right side of the cars wheels, and then take a 225/50-17 and mount that on the left, that the car runs better that way also. I mean, you may have to play with the steering wheel alot, and it may go around left turns differently than it goes aorund right turns, but for every day driving it just is better. I also heard that if you build the motor with 10.5:1 pistons on the left bank, and then use 7.5:1 on the right and run a turbocharger on that side also, you get the glorious blend of having both a naturally asprirated motor, along with the benefits of a turbo all wrapped up in one. (I'm joking)

Go ask the engine builder what he thinks about that, after all, he seems to think that timing that cams differently from one side of the motor to the next is a good idea. Seriously, if he told you that, take your motor somewhere else. It doesnt sound like they have too much confidence in what they are doing. If they are setting up your cams, why cant they get them the same, you can adjust each cam independent of the other, and get them dead on with a dial indicator. And..... if they are setting up your cams, the smart thing to do would be to check piston to valve. Why are they only doing half the job, and questionably at that? Be careful.
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Old 07-17-2004, 11:29 AM
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Originally posted by garibaldi
Seriously, if he told you that, take your motor somewhere else. It doesnt sound like they have too much confidence in what they are doing. If they are setting up your cams, why cant they get them the same, you can adjust each cam independent of the other, and get them dead on with a dial indicator. And..... if they are setting up your cams, the smart thing to do would be to check piston to valve. Why are they only doing half the job, and questionably at that? Be careful.
I have known of many 'reputable' shops that have done half assed work.

To suggest running different cam timing on one side of the motor as compared to the other sounds pretty bad to me.

I think the solution to your problem will be getting thicker base gaskets on the tight side.

Not just for the sake of the piston-valve clearance but also the compression ratio.

If your numbers are correct you are almost a millimeter short which equals almost a whole compression point.
Old 07-17-2004, 02:17 PM
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Everything shoudl be the same, the base gaskets,the piston to valve, the piston to head, etc, the cam timing from right to left. If the work is done properly, everything comes out the same. Even if you used the thicker gasket, it is only .010 thicker, which still wont get you the desired clearance, and the compression will drop as well. The best thing to do is go back and measure is all from the beginning.
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Old 07-17-2004, 02:30 PM
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Reputable?

This shop does have a very good reputation in the city I live in. They even got awarded "best shop in town" by one of the local TV stations. He has been pretty helpful so far.

I can ask him why they time one cam different than the other. It was only slightly different. His mechanic did it on purpose, I watched him do it. I paid them to time the cams because I didn't have the equipment and wanted to make sure it is done right. The prepair a lot of the autocross and race cars in town. They used to do a lot more 944s than 911s but recently they have even been doing the work on a GT3 cup car for one client.

I didn't hear from him today, he was supposed to be checking it out. I assume that means he found out what I assume, he can't fix it with cam timing. It will be interesting to find out what he finds out. If I think he screwed up my heads, I am going to want things repaired at no more cost to me. I have already spent 12,000 with them between the last rebuild and this rebuild "I" am doing. Also, I have another friend in the club who had his engine rebuilt exactly like mine about a year later. I would be interested to see what his clearance looks like. The adjuster screw method wouldn't be that hard to do on the #1 and 4 cylinders during a timing adjustment.

I looked at the Webcams documentation that came with the cams. They suggest a minimum of 1.25mm on the intake and 2.0mm on the exhaust which is pretty close to what Wayne recommends.

Thanks for all the advice.
TK
Old 07-17-2004, 10:25 PM
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The 1.25mm and 2.0mm specs are minimum clearance numbers.
1.5/2.5 would be better.
I have heard about timing the two cams different. Some believe one bank lags behind the crankshaft more than the other. Advancing this side would keep it in time. I am not sure if doing this makes any more HP.
I know its done on 928's from the factory.
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Old 07-17-2004, 11:17 PM
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More clearance is better than less. Especially if you ever miss a shift again. Yes, if you take it to 10000 rpm, it won't matter, but there is an area where you get away with things, if your clearances are conservative.

You need to be more patient, get the tools and assess the situation until you know what's going on. Then disassemble and fix it yourself. That's the only way I'd be happy and confident that I didn't put a grenade back in the car.

Cheers, George
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Old 07-18-2004, 03:05 AM
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Conclusion

The shop owner ended up retarding the cam timing and says that I now have the 1.5 and 2.0mm I need he said that the way webcams tells you to time the cams it will give you the most torque at higher RPMs. He reviewed their datasheets and said that by retarding the cam timing I will have more lower end torque but will not have as much torque up to 7500RPM which is not how I drive the car anyway. I usually am shifting at about 5500 - 6000 RPM.

He said that the reason things were tight is that the shop that worked on the heads took more than he would have liked off to clean up the surfaces.

He ended up adjusting all my valves for me just to be nice.

I hope it runs well when I get it all put together.

Todd
Old 07-19-2004, 04:46 PM
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