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The amber fan shroud came with the motor when I bought it as a long block for this project. I'm not sure who it came from and I've asked the previous owner but I didn't get a response.
I'd try reaching out to these guys who I believe also make the amber fan shroud:
Getty
Series 900
JWE Motorsports
Gunner Racing
GT Racing
got the motor almost to long block form. the plan is to bring it to a local Porsche gear head to help me with checking the cam timing. he has the tools and mechanical rocker.
1) Can i get good compression if cam timing is off?
2) Before going as far as checking cam timing, could i check leak down to give me a ballpark idea whether or not the cams are timed properly? For example... z1 at tdc should give me very little leak down (or least amount) for cyl 1 at tdc, z1 at 120 degrees should give me very little leak down when cyl 6 is at tdc, z1 at 240 degrees should give me very little leak down when z1 is at 240 degrees, etc. Obviously this won't be accurate for measuring actual cam timing, however, is my logic correct and can approach it this way to see if my cam timing is in the right ballpark?
If cam timing is off, you will still get good compression.
Leakdown needs to be performed with engine at operating temp or close. If you do it on a cold engine you will get leak past the rings giving a false impression the rings are bad. The rings have a gap when cold, and the gap near closes when at operating temp.
Thanks. We're currently trying to find a shaft to grind down to fit the temporary mechanical rocker in order to measure the lift using a dial gauge/z-block.
If we were to used the factory tools that attaches to the back of the cam (P9551 and P9552), which doesn't require a dial gauge, how do we know the cam is being set at 1.8 mm lift properly using this approach? Do those tools somehow align the cam to face a certain direction which automatically maxes that lift at the right crank angle (TDC)?
we ended up getting a decent measurement using a zblock and ground-down mechanical rocker.
check out how far off TDC we are when the cam is set to the specified 1.8 mm... (at least 5 degrees off TDC). i can't explain how the engine builder could have buttoned it up this way.
i shot him an email. i can't get too upset because it was the previous owner of this motor that paid him to do the work and that was about 2.5-3 years ago now. disappointing though
she's all back together now. started the passenger side 8 AM with the help of a friend. had the motor back in the car and buttoned up at 8 PM.
the driver's side was easier because we simply used a socket to tension the chain. the passenger side we improvised with other methods to get have enough chain tension to avoid removing the heat exchanger.
waiting for a weekend for another friend to help me start her up. standalone engine management is beyond me at this time.
To answer an earlier question, yes, a compression test can give an idea of how well the cams are timed.
For example, let's say it is known that a fresh engine developes 180 to 185 psi on a compression test.
However, during your testing, one bank is 180 to 185 psi, but the other bank is 160 to 165 psi.
All else being equal, more than likely, that cylinder bank's cam timing is retarded, thus holding the intake valve open too long on the compression stroke, and why the lower compression numbers for that bank.
A quick cam-timing check will confirm an improperly timed cam, and is an easy, cheap fix.
i'm not sure i'm fully understanding how compression testing on a SOHC can show lower numbers...
If there were 2 cams per bank or DOHC, then i can see the valves not opening/closing as they should when timing is off (one cam controls intake and the other cam controls exhaust valves).
However, when it's only a single cam, i feel the compression would be unaffected. if timing is off on a sohc , the exhaust and intake valves will open and close at the right timing, relative to each other (they will always respond to the lobes on the single cam which can't be effected by to bad timing), providing maximum compression reading, however, they will not be at the right timing with respect to the crank position. i might be misunderstanding it but this is how my mind is processing it.
At bottom dead center upon completion of the intake stroke, the piston will then start to rise up the bore on the compression stroke.
However, the intake valve doesn't close right away, and the piston continues to rise in the bore with a still-open intake valve. Because the intake valve is still open, the cylinder cannot generate compression-pressure.
It is only after the intake valve fully closes is when the cylinder can finally start compressing the air/fuel mixture. This is called an engine's dynamic compression ratio.
So with the piston rising in the bore, and the longer the intake valve is held open, or retarded from closing, the less mechanical compression pressure the engine can generate.
Therefore, that is why one cylinder bank may be timed correctly, and the other is not, since each cam must be timed independently of one another.
This is how a compression test can give you an idea of how well the cams were timed by simply looking at the compression results.
that was a great explanation. thanks. the missing part of my thought process was the position of the piston relative to when the valves are open/closed. i see how that can influence compression now.
interesting that i was getting 180-190 psi compression across all banks but cam timing was so far off. perhaps it wasn't that far off to influence compression but enough to make it run as poorly as it did.
03-14-2018, 03:02 PM
