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Return of the Nitrous Norton

Norton Models (not Commando or P11)

Re: Return of the Nitrous Norton

Postby lcrken » Sun Jul 09, 2017 5:02 pm

So, finally back to building the 750 engine again. I had to add a couple of 3/4" plugs of heavy metal to the crankshaft cheeks to bring the balance factor up to 62%, to make up for using steel rods instead of aluminum. This is the 75 mm stroke Maney crank with a pair of Don's (madass) steel rods.

Image

This is the Megacycle N480 cam and BSA lifters I am using. This engine is for maximum top end power for Bonneville, so I'm using the longest duration, highest lift cam I have.

Image

I'm using a stock 850 timing side case half mated to a Maney drive side half. I expected to have to open up the cam tunnel in the stock side, and I did.

Image

What surprised me was that I also had to open up the tunnel in the Maney case, but only very little. This is one of Steve's early case halves, and I suspect that the later ones have a little more clearance there. Steve experimented with the N480 cam at one time, so I'm sure he's aware of how much room it needs.

It's pretty straight assembly from here until I get to fitting the pistons. I expect to be machining the heads on my JE pistons to get a higher compression ratio, as well as making sure I have enough valve-to-piston clearance. I will probably also have an issue with valve-to-valve clearance, but can probably sort that by sinking the exhaust seats a bit. I'm also going to have to make some shorter push rods to suit the short cylinder. Stay tuned for a report on whatever unexpected issue shows up next.

Ken
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Re: Return of the Nitrous Norton

Postby xbacksideslider » Mon Jul 10, 2017 7:30 pm

Thanks Ken. Good pics. Square cam lobes are always a "tell."
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Re: Return of the Nitrous Norton

Postby lcrken » Mon Jul 10, 2017 9:45 pm

xbacksideslider wrote:Thanks Ken. Good pics. Square cam lobes are always a "tell."


Hi John. They are pretty lumpy, aren't they? I'm pretty sure the regular RD springs I've been using for so many years will not be up to it. I'm expecting to need to run it to at least 8000 rpm, and maybe 8500 rpm, to get max horsepower, and I'll be looking for a better spring package. At the moment, the options look like beehive, conical, or just some stronger conventional coils. RD has an IRL spring set that will fit that I think might work.

Ken
Last edited by lcrken on Tue Jul 25, 2017 8:54 am, edited 1 time in total.
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Re: Return of the Nitrous Norton

Postby grandpaul » Tue Jul 11, 2017 7:20 am

Glad your "vacation" is over, and this project is back on.

I think I see a kenc vs dynodave showdown in the making...
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Re: Return of the Nitrous Norton

Postby lcrken » Tue Jul 11, 2017 9:27 pm

Got the bottom end together today, and mocked up the cylinder and piston to check compression ratio and squish clearance. The in-modified JE 79.5 mm piston is .250" above the cylinder deck.



This is the piston after trimming the squish band area down by .140", leaving a beveled dome for higher CR.



I cc'd the head, and calculated the CR with the modified piston to be just over 12:1. I expect to now have to cut the valve notches deeper, so will lose a small amount there, but it should still be pretty close to 12:1, and that should be enough. At this point it's getting more difficult to raise the CR any higher, and the return for doing so is diminishing. I do plan to run it in the gas class first, and it should be fine on high octane race gas.

Next step is to sort out the valve train.

Ken
Last edited by lcrken on Mon Jul 24, 2017 4:23 pm, edited 1 time in total.
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Re: Return of the Nitrous Norton

Postby xbacksideslider » Wed Jul 12, 2017 11:10 am

lcrken wrote:
xbacksideslider wrote:Thanks Ken. Good pics. Square cam lobes are always a "tell."


Hi John. They are pretty lumpy, aren't they? I'm pretty sure the regular RD springs I've been using for so many years will not be up to it. I'm expecting to need to run it to at least 8000 rpm, and maybe 8500 rpm, to get max horsepower, and I'll be looking for a better spring package. At the moment, the options look like beehive, conical, or just some stronger conventional coils. RD has a NASCAR spring set that will fit that I think might work.

Ken


Yes, as I understand it, the beehives/conicals offer a longer wire/spring, that compresses into its center, so the uncompressed/early lift pack can be lighter while the full lift/compressed control is heavier. Dr. Taglioni, looking at hairpin springs and a valve box he designed for them, found a different way to get his valves to follow square cam profiles.
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Re: Return of the Nitrous Norton

Postby lcrken » Tue Jul 25, 2017 9:20 am

Pics of the cylinder with Timeserts and BSA lifters.





I've ordered the IRL springs from RD, but they are backordered a couple of weeks. They have a beehive spring that I might try. Zack at RD says it can be made to fit, but has a little less spring pressure. I'm a little nervous about the lower spring pressure. I have some beehive springs from Compcams (4.6 Moduular Ford) that can also be made to fit, but they require raising the collet groove on the valves, and are also slightly lower pressure. I know from other builder's experiences that the IRL springs will let the N480 cam rev high enough without float, but it's always tempting to try something new.

In the meantime, I'll be rummaging around for all the timing side bits, as well as rocker arms and such for the head. That's one of the problems with putting an engine together from parts, as opposed to starting with a complete engine.

Ken
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Re: Return of the Nitrous Norton

Postby xbacksideslider » Tue Aug 01, 2017 11:18 am

Yes, there's an appeal to figuring out how best to make what you already have work
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1973 750 #220000
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1986 Shelby GLHS #463

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