Ironhead Cam installation problem

[Scott]

I feel like I'm doing something incorrect that is obvious - I just can't see it. I had a well-respected company (to remain anonymous for now) install new lobes on the shafts from my '81 in an XR1000 configuration (building an XL mongrel with XR top end). These shafts and gears, with their original lobes, worked fine when the '81 was stock. Just got the cams back, and number two and three lobes are smacking into the casting reinforcement around the pinion bearing. I have posted a few photos below, and my 11 year old son just helped me upload a video to YouTube. Yes, I know my skills with a camera phone are limited. What the hell am I missing? Are the lobes I had installed too wide? I wish I had a photo of the lobes that were on the cams when I sent them out. They were stock Q cams. Drawing in the FSM don't show this reinforcement around the pinion bearing.

In the first photo I'm pointing to the reinforcement in the casting that is causing all my problems. Second photo shows number three lobe smacking into that area. Link immediately below is to the crappy video I made. Yes, the cam plates are in place. No amount of shims could realistically get the lobes to clear the casting reinforcement area.

https://www.youtube.com/watch?v=c2JoQw3XSSA

[big andy]

https://www.youtube.com/watch?v=-7fEqz5F7ts

[Davo_137]

You have to clearance the new lobes. Got a dremel?

[Davo_137]

Oh wow.. just looked at your video. That’s looks bad. I don’t think grinding that out is good.

[rejeanprimeau]

Clearance by grinding the boss and the cams. Big lift need room to pass. If you're too afraid you're not up to this.
Are they small circle lift ??? Might also be your problem.

[Scott]

Thanks for the responses. If I got these cams for free, I would be willing to do some clearancing of the cam and the case (I think both would be necessary). I paid good money for these, though, and think I'll contact the company. This never happened with the stock Q cams, so I think the new lobes are just too wide (left to right wide, when you're sitting on the bike). I wanted to be sure I wasn't missing anything obvious before contacting the company. Just for kicks, I'm going to measure just how much clearancing would be necessary once I'm done with my coffee.

[Scott]

I just went to measure, just to cover all bases. The amount of shimming necessary to have nos. 3 and 4 clear would have the cam barely in the bearing. Now I've done my due diligence.

[Maxeffort]

Custom engine building is making parts that don't fit together, work.

I don't build ironhead Sportsters, but plenty of automotive stroker engines. Grinding and machining for clearance is frequently required.

It looks as you will have to grind the case and the edge of the cam lobe to fit.

I doubt it's a small base circle with zippers welded on lobes, but a small base circle helps with clearance issues. It's very common to use small base circle cams in V8 stroker engines for that reason.

[Scott]

I'm not sure what a small base circle is. I wasn't going to mention the company name, as I haven't even spoken to them yet and given them the opportunity to right this (you mentioned the name, though). I'm willing to do some case grinding but if I just grind the case to get the necessary clearance, I'd have to remove far too much material and seriously compromise the case, as the interference would continue until the lobe hits the pinion bearing race. If the cam lobes have to be ground/narrowed, I'd rather have the manufacturer do that. The stock Q lobes worked fine without interference. These lobes aren't hitting because they're a terribly aggressive grind. I think it's just a width issue (I wish I had measured the Q lobe width before sending them off).

The purpose of my post was to show this to more knowledgeable eyes to be sure I haven't done something blatantly wrong (before I contact the company). I sent them a note this morning. This problem aside, they've been great to deal with - especially because I'm doing a pretty unconventional project and they were willing to take on part of it (and be nice in the process). I'm not worried about them doing their part; I was just afraid of looking like an idiot who has no idea what's he's doing when I contact them.

Thanks again to everyone who spoke up. You can't buy the level of knowledge on here at any cost.

Originally Posted by Maxeffort

Custom engine building is making parts that don't fit together, work.

I don't build ironhead Sportsters, but plenty of automotive stroker engines. Grinding and machining for clearance is frequently required.

It looks as you will have to grind the case and the edge of the cam lobe to fit.

I doubt it's a small base circle with zippers welded on lobes, but a small base circle helps with clearance issues. It's very common to use small base circle cams in V8 stroker engines for that reason.

[seajay]

Small base circle cams have a low top dead center lift. Example, my TDC lift is .197 intake and .186 exhaust.