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My friends call me Phish
 
Join Date: Sep 2010
Location: Newport Beach, CA
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to Machine or not to Machine

I have about 20k miles on my build and just recently there's been blue smoke up on start up and driving it around at operating temp it has the smell of burnt oil. I believe it's the valve seals are letting oil in. I almost daily my car and once a month I autoX it, so there's a lot more ware and tare then usual.

The Build.
2.7 E 9.5:1 Webers

My last compression test 11/2/18 -17,502 miles
1 - 119 PSI
2 - 118 PSI
3 - 120 PSI
4 - 120 PSI
5 - 120 PSI
6 - 130 PSI

On the 3/14/18 - 15,581 miles
1 - 130 PSI
2 - 130 PSI
3 - 130 PSI
4 - 130 PSI
5 - 130 PSI
6 - 130 PSI


So here is my question

Since I am thinking of taking the top end apart to check the rings/valve seals do I need to machine the rockers and cam if I change out the P and C's to a 10.5:1 or can I leave them the same? I will send the heads out to get twin plugged.

or

If I don't change out the P and C's and just have the heads redone, do I need to machine the cams and rockers?
Old 03-09-2019, 10:25 AM
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1) Do a leak down to see where that 10 PSI went on #1-5. If you can't purchase (under $100)a leak down gauge, figure out how to connect an air compressor hose to your spark plug hole to get a decent seal, and just blow 100 psi or so air in at TDC firing. Listen to the intake, exhaust, and the inside of the engine via the breather. You can tell where the air is leaking out that way - intake valve? exhaust? Or past the rings into the case - there is always some leakage there. If your leakdowns are good, you might want to reconsider the top end tear down - unless boosting the CR is something you are going to do anyway. My compression testing protocol is bad - I forget if I did it hot or cold, and often forget to prop the throttle butterfly open.

2)Machine rocker and cam? What do you mean? Are you asking if the cam you have will work with your new aftermarket pistons, I'd ask the manufacturer if an E cam will work. Otherwise it is up to you to do the testing to see that you have adequate valve clearance, and if not, to machine the pockets to get it - giving up some CR in the process.

But if you specify the piston maker, maybe someone here knows the answer.
Old 03-09-2019, 11:03 AM
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If you are careful to keep track of were each rocker came from and they go back in the same location then you do not need to do any machining. If you find pitting on a rocker it should be replaced or resurfaced. If you find pitting on the camshaft then you will need to have the camshaft reground and you should do the rockers as well.

john
Old 03-09-2019, 11:17 AM
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It could be the seals or even the rings. The big question is does it use oil between changes? If it is not using more than a quart say every 1000 miles, you may want to let sleeping dogs lie.

A blue puff on start up is not unusual. Every time? After sitting a while? After parked on a hill?

When fully warm and idling, is there smoke coming out the exhaust?

In some cases, the ring gaps can let oil into the combustion chamber when the car is sitting. This is made worse when the oil tank is filled up to maximum or when parked on a hill.

The smell sounds like a leak dripping on the exhaust, AHIK.

As far as the cams and rockers go, keep them in order, so each rocker goes back on the same lobe. As long as there is no pitting or obvious wear there is no need to have them resurfaced.

Re-ringing is a subject for an entire thread.........
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Last edited by Trackrash; 03-09-2019 at 11:22 AM..
Old 03-09-2019, 11:18 AM
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My friends call me Phish
 
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Thanks everyone for the replies.

I am adding a quart every 500 miles There's Blue smoke every time I start it no matter what. When it's warm there's some smoke, but also the car runs on the rich side too.

I just want to clarify, I should be able to use the same rockers and cams as long as they stay in the exact location, pit free, even if I change the P's and C's and have the heads resurfaced?
Old 03-09-2019, 09:19 PM
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Quote:
Originally Posted by pemz0r View Post
. I believe it's the valve seals are letting oil in.

My last compression test 11/2/18 -17,502 miles
1 - 119 PSI
2 - 118 PSI
3 - 120 PSI
4 - 120 PSI
5 - 120 PSI
6 - 130 PSI

On the 3/14/18 - 15,581 miles
1 - 130 PSI
2 - 130 PSI
3 - 130 PSI
4 - 130 PSI
5 - 130 PSI
6 - 130 PSI
I would think you should have at least 150+ lbs from a decent seal of rings and valves. Under 125 is very bad. From the poor compression numbers, the problem has to be more than the valve guide seals. Way too much oil loss. If you don't have or want to buy a leak down tester, compression testers can usually allow for the gauge to be removed and an air line connected. You can then listen to see if the air is leaking past the rings or valves with the piston at TDC.
Running rich will also wash away the lubrication and contaminate the engine oil
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Old 03-10-2019, 06:14 AM
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Compression numbers change depending on cam overlap. Need to look for consistency between cylinders not how high or low they are.


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Old 03-10-2019, 06:01 PM
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I keep hearing about 150+ psi compression numbers. I've never seen that on my engines, though. So I satisfy myself with looking for consistency, and good leak downs.

The oil consumption does look like worn valve guides.

If you change pistons to something with higher compression, you for sure need to confirm that you won't have valve to piston interference issues. This is normally done by doing a dry, partial assembly of the engine, and measuring clearances with clay. The same is usually done for the piston to head clearance, especially the quench area at the circumference - too little may lead to interference at high RPMs and an inadequate quench ares. Too much leads to an inefficient quench. However, maybe someone has done this for the piston (you need to specify what it is)and cam and head (yours are the stock E?). If you have the head mating surfaces machined to true them all, you can compensate for this by using thicker cylinder base shims. Are these mating surfaces damaged? Clearance/quench issues can be dealt with by adjusting base shim thickness, or in some instances by machining the piston or head in this area. However, maybe your combination has none of these issues.

Absent pitting or obviously unusual wear, reusing the rockers on their same cam lobes is pretty common. However, it is not all that expensive to send the rockers off to be refaced and rebushed. At that point you don't need to worry about which rocker worked which valve. I had Cgarr do this for a bunch of mine. He sent a couple back because they were too damaged or far off to be reground.
Old 03-11-2019, 02:18 PM
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Quote:
Originally Posted by pemz0r View Post
Thanks everyone for the replies.

I just want to clarify, I should be able to use the same rockers and cams as long as they stay in the exact location, pit free, even if I change the P's and C's and have the heads resurfaced?
Believe the concern above is whether the E cams will provide the clearance necessary to avoid valve overlap with your new pistons (i.e. would not push the valves down into the piston heads at TDC) -- this can only be confirmed by the folks making/specing your new pistons.
Old 03-12-2019, 12:54 PM
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Have you tried reducing the oil level in the tank? Also, try RSR rocker seals on each rocker - that should stop dripping on your exhaust (if that's the problem).

- Rob
Old 03-13-2019, 04:51 AM
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Quote:
Originally Posted by Robert59095 View Post
Have you tried reducing the oil level in the tank? Also, try RSR rocker seals on each rocker - that should stop dripping on your exhaust (if that's the problem).

- Rob
True. I think there is a group of respectable folks that also suggest torquing the rocker shafts tighter than what Porsche originally suggested to prevent leaks on "worn in" cam carriers.
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Old 03-13-2019, 06:57 AM
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Of course all this is just speculation, and the real answer will be known upon examination.
You lost a bit of compression in just the last 2,000 miles. Oil consumption has gone up significantly. Pressurizing the cylinders with air and listening for air leaks can help. Sound from intake- intake valve not sealing, sound from exhaust- exhaust valve not sealing, from the case- rings not sealing. Worn valve guides can give off blue smoke when letting off the gas at higher rpm as engine braking sucks oil past the guides. If you could get a hold of an inspection camera, you could pull a spark plug and check for scored cylinders.
You say there are 20,000 mi on your build. Can you tell us some details? Top and bottom end, just top end, parts replaced? How many blade fan are you using? The 2.7's tend to run a little hot. Did you install a fender cooler? What exhaust system?
I'm not sure, but I think the original 2.7 cylinders may have been Alusil, which do not take well to new rings. Also, you mention running rich, which can wash away the oil film and score the pistons and cylinders.
Oil smell can be oil from the triangle of death, or leaky valve covers dripping on the exhaust.
Walt, my '73 2.4 runs happily at 135psi with over 120,000mi. My '86 3.2 has over 180psi after top end rebuild and 2,000mi break in. Both have mild original cams, and a performance cam with more overlap and such may have lower pressure from a compression test, but high dynamic pressure in the upper rpm range.

As for the rockers leaking, I installed the RSR seals in my 3.2 when rebuilt, and used a slightly higher torque. If your rocker shafts were not removed in the last build, they are probably fine. If they were removed there is a chance they might have loosened, but I can't see that causing you to lose a quart every 500 miles.
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Old 03-13-2019, 01:14 PM
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Cylinder 4 isn't happy, 10% percentage leakage and the plug is angry. I just realized that the last test I did was exactly a year...

On the 3/14/19
1 - 130 PSI - 4%
2 - 120 PSI - 3%
3 - 120 PSI - 4%
4 - 120 PSI - 10%
5 - 121 PSI - 4%
6 - 121 PSI - 4%





Last edited by pemz0r; 03-13-2019 at 01:36 PM..
Old 03-13-2019, 01:32 PM
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Where was #4 leaking? Rings ?
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Old 03-13-2019, 01:38 PM
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It sounded like rings.
Old 03-13-2019, 01:39 PM
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Rings always leak some, so there is always some noise there, sort of like background radiation. However, if you heard sound X from the other cyliders, and 2X or something from #5,those rings are a good suspect. Assuming you heard nothing from the intake or exhaust.
Old 03-13-2019, 02:14 PM
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There was more air coming out that cylinder than the rest of them. Now, the question is what should I do.

Should I just take a part the right bank and repair cyl 4 or new P and C's with higher compression...
Old 03-13-2019, 02:17 PM
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Show us a picture after you get the heads off. But I think you already know the answer.
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Old 03-13-2019, 02:36 PM
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Quote:
Originally Posted by E Sully View Post
Of course all this is just speculation, and the real answer will be known upon examination.
You lost a bit of compression in just the last 2,000 miles. Oil consumption has gone up significantly. Pressurizing the cylinders with air and listening for air leaks can help. Sound from intake- intake valve not sealing, sound from exhaust- exhaust valve not sealing, from the case- rings not sealing. Worn valve guides can give off blue smoke when letting off the gas at higher rpm as engine braking sucks oil past the guides. If you could get a hold of an inspection camera, you could pull a spark plug and check for scored cylinders.
You say there are 20,000 mi on your build. Can you tell us some details? Top and bottom end, just top end, parts replaced? How many blade fan are you using? The 2.7's tend to run a little hot. Did you install a fender cooler? What exhaust system?
I'm not sure, but I think the original 2.7 cylinders may have been Alusil, which do not take well to new rings. Also, you mention running rich, which can wash away the oil film and score the pistons and cylinders.
Oil smell can be oil from the triangle of death, or leaky valve covers dripping on the exhaust.
Walt, my '73 2.4 runs happily at 135psi with over 120,000mi. My '86 3.2 has over 180psi after top end rebuild and 2,000mi break in. Both have mild original cams, and a performance cam with more overlap and such may have lower pressure from a compression test, but high dynamic pressure in the upper rpm range.

As for the rockers leaking, I installed the RSR seals in my 3.2 when rebuilt, and used a slightly higher torque. If your rocker shafts were not removed in the last build, they are probably fine. If they were removed there is a chance they might have loosened, but I can't see that causing you to lose a quart every 500 miles.
It was a complete rebuild. Split the 7R mag case and machined, bypass/shuffled pinned/honed to standard. New crank/c-rod bearings, intermediate gear and timing gear. I reused my Cylinders and added new 90mm 9.5:1 JE pistons, E cam, single plugged, M and K exhaust with a set of Webers.

I believe I have a 11 blade, it's def not the 5 blade. There is a fender cooler with a fan.

I just saw there's a P and C for 92mm which would jump me up to a 2.8 with 9.8:1, Would this work with my case as a slip in?
Old 03-13-2019, 10:36 PM
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