cam tight on reassembly.

[theiceman]

Originally Posted by john walker's workshop

No issue. Just need to set the engine on TDC and have the cam keyways facing up when you install the assemblies. Way faster and easier.

thanks John
what is the significance of having tbe keyways up.? and i assume you mean having cylinders one and four at top dead centre when puting each respective bank on ?

is it because you are setting your valve clearance on the bench too, and with one and four at top dead centre and the keyways up all valves on that bank will be closed when you are installing the assembly ? ( just a guess)

[john walker's workshop]

1&4 @ TDC. Keyways up because that's basically where the cams would be @ TDC #1. Adjust #1 intake clearance, set up dial gauge, set left cam timing, Adjust #4 intake, set right cam timing, Adjust all the valves, find TDC #1 and install the distributor, install all covers.

[theiceman]

Originally Posted by john walker's workshop

1&4 @ TDC. Keyways up because that's basically where the cams would be @ TDC #1. Adjust #1 intake clearance, set up dial gauge, set left cam timing, Adjust #4 intake, set right cam timing, Adjust all the valves, find TDC #1 and install the distributor, install all covers.

lol wow that's awesome ...

just wrapped up my engne in about 8 seconds ... all good advice .. and appreciated.. il do the very thing you mentioned , mor elike 8 weeks for me tho.

[911pcars]

If you need another nudge to confirm the straightness of the cam, this is one more. Resist the urge to remove perhaps unnecessary material before making sure it's straight in the first place.

My reground cams had (as I recall) a .003" bow in it, enough to create a slight rotational bind in the cam housing. I took it to a cam regrinder and they fixed it in about 3 minutes with a certain technique.

Sherwood

[camgrinder]

I tape off the bearing journals before I parkerize camshafts. I don't recommend coating the journals.
Sounds like this one either has a knick in a journal or is bent. Easy to fix.

[rs-vic]

John Dougherty knows his stuff. I've been using his cams for over 10 years with excellent results. On a different note, can 3.0/3.2 cam housings (4 bearing cams with larger journals) be used on a 2.7? How about a 2.0 with the narrower valve angles? Not that I want to, just curious.

[Walt Fricke]

RS-VIC
While the heads don't interchange due to the different stud spacing, the cam carriers (housings) have the same bolt pattern in the 2.7s as in the 3.0/3.2s.

Pretty sure the earlier ones do, too. Other than things like center oiling of the cams, and the switch from a 6 to a 9 stud exhaust valve cover, not much change. Of course, cam journal numbers and diameters have changed, but that's not a problem with the right cam.

[proporsche]

Hi Iceman...your quote....
"a related question. I have been reading how many of the experienced engine builders now put everything together on the bench. heads housing cams and rockers , then pop it on the studs. "..

I have been doing it like this since ever...much easier on assembly as JW said just set the cams before install...my 1st engine on my own 1st 911 back in the 1980`s, i did not and opss i bend the valves on cyl 3...that was at 5 pm so i worked whole night and at 3 am engine was running like a clock;-)

Ivan

[rs-vic]

I did some more research regarding the cam housings. According to the parts book all cam housings from 68-77 are the same part number. I then measured the valve angles on a 2.0 head and a 2.7 head and both are identical. I got 27.5 degrees on the intakes and 32 on the exhausts. The 3.0 and 3.2 heads have smaller angles due to the wider combustion chamber and larger valves. There's a lot of conflicting information about valve angles. I'm going to try and measure some 3.0 heads sometime this week.

So I would say that the 4 bearing cam housings won't work with the 2.0-2.7 heads due to the different valve angles.

[rs-vic]

I got a chance to measure a 3.0 and 3.2 head. Both are right on spec.
Intake = 25.5 deg and exhaust = 30.25 deg

[Walt Fricke]

"So I would say that the 4 bearing cam housings won't work with the 2.0-2.7 heads due to the different valve angles."

How would the cam carriers differ, other than having 4 larger ID integral bearings for the larger bearing cams? A different position for the rocker shafts? Higher or lower so the elephant foot kept adequate contact with the tip of the valve stem?

The rockers for sure didn't change dimensions.

If you were actually going to do this I'd dig out an early cam carrier to go with the one I have on my desk, and an early and a 3.2 head with valves installed, stick in an intake and exhaust rocker, and see what I could see about the elephant foot on the valve.

The closest direct interest I have to these angles is to wonder what the largest valves (intake only?) I could install in my pseudo 2.8 with its 2.7 heads on 92mm cylinders might be. Not as large as the factory RSR 2.8, with its different angles, but maybe a millimeter larger diameter? 47/41?

[Travis Neff]

If you have ever watched a video on hardwelding and regrinding cams, you'll see what they do to straighten the cam back out. Doesn't look too scientific, so I imagine that you could have a bow in it.

[rs-vic]

Walt, if you get a chance to swap around heads and cam housings to see the difference let us know. Maybe even just looking at the sides of the 3 bearing vs. 4 bearing cam housings might tell us something. Maybe the rocker shafts are in a slightly different position.