N/A engine questions
06-08-2005, 03:39 PM
#46
Drifting
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No I had all 4 plugs in when I was rotating mine...i never really forced it to turn when I felt the resistance, i just would turn it slowly in little increments, not one fluid motion. this is why I think it's just all the vacuum. its like when you compress a shock and try to pull it up with all your might. Its really hard to do because the shock piston is doing it's job. but if you pull the shock up slowly, you find you'll get it up easier.
in response to the piston question, there are a number of reasons why his piston is like that and your pistons are not...is your 951's fuel system completely stock? the first thing i'd guess is that you are running a chip which is making you run richer....did you notice the position of his spark plug electrode in relation to the intake valve?
in response to the piston question, there are a number of reasons why his piston is like that and your pistons are not...is your 951's fuel system completely stock? the first thing i'd guess is that you are running a chip which is making you run richer....did you notice the position of his spark plug electrode in relation to the intake valve?
06-08-2005, 04:15 PM
#48
Race Director
We should also figure out the exact feel of this resistance that 944CS gets from compression is one that slowly builds. Then at the top, it's kinda spongey and rubbery as you compress the air by hand. What does your resistance feel like? Is it sharp and sudden, like when you were turning the cam?
06-08-2005, 08:08 PM
#49
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Danno you described it pretty well, the resistence builds and close to tdc i can give the wrench a "powerfull" tug and it will feel rubbery, it does not feel like I am hitting something and the crank thus does not want to turn at all
06-08-2005, 09:18 PM
#52
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I am not sure feel is the correct way to go to solve the problem...I have now turned 3 motors by hand and all three felt close to what is described here.
1. My 87 easy to turn and then hard with a pop at TDC (it runs strong)
2. The 83 I parted took the same amount of pressure just about all the way around with a small pop at TDC I never saw it run, but the head and gaskets looked to be in good shape when it came apart.
3. The 85 that I am now replacing the head gasket in was easy to turn with the same pop at TDC and two of the cyl. were 1/2 full of coolant.
as much as it sucks it may be a good idea to pull the head and look at the pistons. Better now then to be doing it all over again in the future. just my .02
1. My 87 easy to turn and then hard with a pop at TDC (it runs strong)
2. The 83 I parted took the same amount of pressure just about all the way around with a small pop at TDC I never saw it run, but the head and gaskets looked to be in good shape when it came apart.
3. The 85 that I am now replacing the head gasket in was easy to turn with the same pop at TDC and two of the cyl. were 1/2 full of coolant.
as much as it sucks it may be a good idea to pull the head and look at the pistons. Better now then to be doing it all over again in the future. just my .02
06-08-2005, 09:39 PM
#54
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After reading all these posts I think its a good idea to pull the head. The HG is paid for and will be at the dealer tomorrow. If the valves are fine then I just have an odd engine like Patricks. At least my car will benefit from a new HG if the valves are ok. I can have the head off in less than an hour based on what I have removed to far. Ill update everyone on my findings. One thing to add, I have always found my engine very difficult to set at exactly tdc...who knows why. It would kill me to put the engine together, start it then have the head get even more trashed. Might as well check it now well I can. Whoever invented interference engines deserves a kick to the jaw.
06-08-2005, 09:42 PM
#55
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I was just thinking about what moves in the motor...if it is still 'hitting' something then the list is short
1. a valve out in the chamber
2. a piston binding in the block or impacting debris in the combustion chamber
3. the crank rotating into something
1. a valve out in the chamber
2. a piston binding in the block or impacting debris in the combustion chamber
3. the crank rotating into something
06-09-2005, 12:20 AM
#57
Race Car
Thread Starter
patrick, that's exactly the list I had in my head, and why this has been such a melon-scratcher. It seems so simple to pin down, yet this one just isn't. At this point, the most likely candidate is a bent valve.
We changed the rod bearings, so one of my fears was that perhaps it was the rod shoulder hitting the crank girdle, although there should be quite a bit of clearance there, the reason I shot that down, was since that would happen 1/2 way between TDC and BDC, not at TDC and BDC like this is happening. It crossed my mind that it could be some kind of piston problem, but everything looked perfect from the bottom, and soon we'll see how it looks from the top, but it just doesn't quite seem to fit the problem.
The fact that when we removed the cam tower, that it became easier to turn I think re-enforces my current hypothesis that it must be one or more of the valves giving us this trouble.
Now, thinking back, I am reasonably certain that when we changed the timing belts last, we also were not able to set the engine to TDC. It would just pop from one side to the other, and it was a rather hard resistance. Most definately not compression. I've done timing belts on more than 1 or 2 944's now, and even with the spark plugs in, if you turn the engine slow enough, it will settle at TDC.
The resistance we are meeting is very sudden, and hard. Not at all like compression. I am stopping by tomorrow night, and we're going to take a look-see in there, hopefully shedding some light on the problem. If I am smart, I will even take some pictures
car_slave, to answer your question, the car is not in gear. Another thing that crossed my mind, was that perhaps it was something in his transaxle, so we tried pushing the clutch in while turning, no difference
I would really like to see this 944 running, and out tearing the road up with all the other Porsche's out there. So I hope we can pin this problem down soon, and get this thing running!
We changed the rod bearings, so one of my fears was that perhaps it was the rod shoulder hitting the crank girdle, although there should be quite a bit of clearance there, the reason I shot that down, was since that would happen 1/2 way between TDC and BDC, not at TDC and BDC like this is happening. It crossed my mind that it could be some kind of piston problem, but everything looked perfect from the bottom, and soon we'll see how it looks from the top, but it just doesn't quite seem to fit the problem.
The fact that when we removed the cam tower, that it became easier to turn I think re-enforces my current hypothesis that it must be one or more of the valves giving us this trouble.
Now, thinking back, I am reasonably certain that when we changed the timing belts last, we also were not able to set the engine to TDC. It would just pop from one side to the other, and it was a rather hard resistance. Most definately not compression. I've done timing belts on more than 1 or 2 944's now, and even with the spark plugs in, if you turn the engine slow enough, it will settle at TDC.
The resistance we are meeting is very sudden, and hard. Not at all like compression. I am stopping by tomorrow night, and we're going to take a look-see in there, hopefully shedding some light on the problem. If I am smart, I will even take some pictures
car_slave, to answer your question, the car is not in gear. Another thing that crossed my mind, was that perhaps it was something in his transaxle, so we tried pushing the clutch in while turning, no difference
I would really like to see this 944 running, and out tearing the road up with all the other Porsche's out there. So I hope we can pin this problem down soon, and get this thing running!
06-09-2005, 08:28 AM
#59
Race Director
Yeah, having someone hold the wiring harness in the back away from the head really helps. I find removing the water-passage for the heater-hose really helps too. And it's actually possible to remove the headers as well without having to yank any of the studs. But I usually pull the head with the headers attached anyway... just a little extra weight. Those guys with bad backs would want to keep that in mind.
06-09-2005, 01:21 PM
#60
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Before you pull the head, check down in the hole in the top of the bellhousing (the one you use to check TDC)... if you drop a bolt in there, it will bind up between the teeth of the ring gear and the bellhousing. The engine will turn a little until the bolt becomes wedged and then it will seize. And please, someone ask me how I know this.