ups and downs of a Norris RX camshaft

I'm back again with a new string on Norris RX in my '72 750 combat engine. Took the opportunity to recheck cam timing while the head was off for oil leak fix. Used a really good set up this time and managed to get the intakes at 54degrees BTDC per spec. Go the whole thing back together and took a ride around the neighborhood. Loping idle was much less noticable, the mid range is back and nice power. Bad news was it ran so good I got carried away reving it too high and heard a bang. Blew a 3 inch piece of the new head gasket out the left side. Gotta go to Rabers and get a new gasket, but at least the cam timing seems to be working now.

After Raber's did a slight resurfacing of the head the front studs don't have enough threaded portion to tighten up the head. Need to put some thick washers in there to take up the space, then good to go.

Your good report and process duly noted for my own future needs. If composite gasket, do not expect another not to do similar. Any worry with gas jets hitting fuel line?

I went with a copper gasket on my combat. it works very well. I also broke one of the front studs and replaced them both with a 1 1/2" long 3/8-24 allen bolt. Works much better and a little easier on and off for the head.

common wisdom is you DON'T use a fine thread in to aluminum. don't believe me just look at how the factory did it or about any thing else threaded in to aluminum

bwolfie said:

I also broke one of the front studs and replaced them both with a 1 1/2" long 3/8-24 allen bolt.

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It's a good thing it's in the cast barrel then. I replaced the 2 small barrel studs in the front.

you are forgiving

bwolfie said:

It's a good thing it's in the cast barrel then. I replaced the 2 small barrel studs in the front.

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bill said:

you are forgiving

bwolfie said:

It's a good thing it's in the cast barrel then. I replaced the 2 small barrel studs in the front.

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Thanks, now I can sleep at night

Glad dialing in the cam helped. Any more feed back other than "it ran so good..."

Dances with Shrapnel said:

Glad dialing in the cam helped. Any more feed back other than "it ran so good..."

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Will let you know after I get the engine back together....again. Off to a four day weekend in the Sierras with the NCNOC sans a Norton. Camp out is fun even without the Commando. Specifically in the two miles it ran, the mid range power was back to normal. I should not have turned up the wick before retightening the head bolts. Got carried away.

Oh my if was me facing Norton event sans Norton with just the head to re-seal, I'd sure want to experiment sans gasket with just non-melt thread back up and hi temp goop like Hylomar. Check for clash of course but them hotter cams like their compression hi yet not detonation prone. At least we know once things are assembled decently then the RX is good for some PeterPan flings.

Hi Guys,

Back with more on the Norris RX cam. Got the cam timing correct now. Seat of pants meter says the engine is stronger than with what the previous owner put in this combat engine...a standard cam. The radical idle from the Norris is gone now with timing correction. Others have said the RX is a full race cam, but I don't notice this. It acts similar to what I recall with my first combat in '73 that was all stock. Particularly the compression braking is very noticable when letting off the throttle. Mid range power is still good and the engine wants to rev going easily passed 6,000rpm in 1st and 2nd. Exhaust sound has changed...lower pitch and more shock wave. With the good results I'm not planning to change the camshaft again this winter....good thing as I wasn't really looking forward to another total engine tear down.

Still have a pretty good oil leak from the front of the head that seems to go away after getting the engine hot. I don't think it's the head gasket, but having a hard time pin pointing the offending cause. It's also not the intake valve cover leak that's typical as no trail of oil going down into the head fins.

Glad your Norton pleases you again. Sometime fork seals blow back that far. Otherwise shorter and shorter trips after cleaning to see where it shows first.