Time for me to address the 800lb Gorilla in the room.(Engine knock thread) REVIVED!

[dan filipi]

Well I haven't given up yet.
I'm going to move the left 1200 cam to the right as a test.

 

[slabghost]

Send me the cams. I couldn't care less about the compression. I'd just install and fire it up. Might be cautious enough to set the valves way loose and adjust while running.

 

[dan filipi]

Send me the cams. I couldn't care less about the compression. I'd just install and fire it up. Might be cautious enough to set the valves way loose and adjust while running.

I'm about ready to fire it up but I want to know why this is happening first because if a valve gets bent it's going to be quite awhile before I can fix it.

 

[scdmarx]

Might be cautious enough to set the valves way loose and adjust while running.

Don't forget to post pictures! :smilie_happy: :yahoo:

 

[slabghost]

I'll do that. I got 1000 cams in the mail and I'm looking for a cheap valve cover to cut up.

 

[mcgovern61]

The 1200 cams are in.......now the big question (drum roll please :music2: ) still have any knock? :?: :whip:

 

[dan filipi]

I actually did NOT hear the knock in the higher rpms like usual but I hear what sounds something like a knock at lower rpm's, around 1500.
I need to test ride again after rechecking valve adjustments. I think at least one on the right is too loose.
I'm thinkin there may be a break in period with these 1200 cams and rockers because it seems to run better now than it did when I first put them in.

 

[wanrep]

Have you checked carb synch with the new cams?
I've seen more than one low-rpm "knock" cured with a carb synch.

 

[dan filipi]

Well I checked carb sync and they were off less than one inch vacuum so I don't think that was it but I went ahead and adjusted the valves carefully and redid the sync. They are now withing a 1/2 inch HG.

Time for another test ride but the knocking is hard to hear now when running in the garage which is much much less than before. A step in the right direction so far.

 

[slabghost]

Waiting for the next shakedown ride report. Wheres the smilie drumming fingers?
What gap did you set the valves to?

 

[dan filipi]

I set intake to a snug 4 and exhaust to a loose 4.
If I set exhaust to 6 the tappets are noisier than I like.

Right now it runs crappy until warmed up.
I think I might have a carb problem, #2. It's acted up before so maybe it's time to dive into that one.

 

[mcgovern61]

My next step though is to measure the torque needed to compress the springs on the '81. Both heads are on the engine. I am going to back off the rocker adjustments and remove the other timing belt. Then I will use my torque wrench to measure how much torque it takes to overcome the cam passing TDC and compressing the springs. I know it will be greater when two springs are compressed at the same time, but I am more interested in testing the other individual springs to check them.

Well, I finally got a chance to work on this engine. First thing I wanted to try was testing the spring compression with a torque wrench. With two springs compressed it takes 13 ftlbs to overcome them on both sides. It only takes 10 ftlbs to overcome the #4 intake, #1 exhaust and #2 exhaust. However, #3 intake cannot even be measured since it is so easy to open.

I pulled the right head and found the #3 exhaust valve stem corroded? I will post pictures in a minute and leave it open to real mechanics for analysis. Both right side exhaust valves are covered and real whitish tan yet the exhaust itself is covered in carbon. The #1 side of the head is carboned up. Pics next!

 

[mcgovern61]

Here are some pics:

 

[mcgovern61]

In this shot, I have opened up the #3 exhaust valve so that you can see the edges and seat. My guess is that it closes, but leaks by. There is not a good sealing surface that I can see. (Real mechanics, help me out here!!!)

The compression on this engine was low 150's all around if I remember. I will have to look up the numbers from my files. (Dan, this would be a good example of stuff lost in the crash. This info was in the old thread.)

 

[dan filipi]

Wow yeah, a lot of carbon on those valves.

Gerry, can you pull that weak spring and measure the length so we can compare it to spec?

This should be helpful to gauge good and bad springs.

 

[mcgovern61]

Wow yeah, a lot of carbon on those valves.

Gerry, can you pull that weak spring and measure the length so we can compare it to spec?

This should be helpful to gauge good and bad springs.

I have to make make a spring compressor to pull it. (Actually, might not it is so loose! :smilie_happy: )

I do not have a metric ruler or tape to measure with.

 

[dan filipi]

Gonna need a caliper to measure, it's a pretty close tolerance between new and servicable.
Maybe work has one?

 

[mcgovern61]

Just for information, I checked the skirts side to side and the pistons are not loose. I cranked them to just past TDC and gave a push and there is little if any play. If the lower bearings were shot and causing the knock, I would have thought there would be a lot of movement in the bearings.

The head gasket looked good and is intact otherwise. There are no signs of any damage other than the water stain in the bottom of #1 cylinder. Could all of this have been from a bad carb setup in the first place???

 

[mcgovern61]

Gonna need a caliper to measure, it's a pretty close tolerance between new and servicable.
Maybe work has one?

No, all of our calipers and tools went back to Rolls-Royce except vibration testing equipment.

 

[dan filipi]

Gonna need a caliper to measure, it's a pretty close tolerance between new and servicable.
Maybe work has one?

No, all of our calipers and tools went back to Rolls-Royce except vibration testing equipment.

Could drop it in the mail to me I'll send it back, or a good one to replace it with.