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Author Topic: Fitting 'Classic' cams to Electra X  (Read 307 times)

GBBet

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Fitting 'Classic' cams to Electra X
« on: August 26, 2014, 03:11:30 PM »
When fitting 'Classic' cams to an Electra X, is it best to notch the piston to avoid inlet valve/piston contact, or alter the valve timing? If the latter, is it advance or retard?

ace.cafe

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Re: Fitting 'Classic' cams to Electra X
« Reply #1 on: August 26, 2014, 03:22:03 PM »
It depends on the cams that are being installed, because there can be quite a difference.
However, the general rule would be that retarding the inlet cam gives more piston to valve clearance around TDC, and advancing gives less.

Retarding reduces dynamic compression, and advancing increases dynamic compression.
If you like the cam timing specs of the cams as installed on the dots, and there is piston to valve contact around TDC, then cutting some valve reliefs into the piston would be the typical answer, as long as the piston crown is thick enough to allow that.

You will also need to use longer pushrods, and remove the valve lifting(decompressor) and collar on the exhaust tappet, because the Iron Barrel type cams have a smaller base circle, and the tappets will sit lower in their guides.
« Last Edit: August 26, 2014, 07:31:55 PM by ace.cafe »
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Adrian II

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Re: Fitting 'Classic' cams to Electra X
« Reply #2 on: August 28, 2014, 11:40:41 AM »
I found that when experimenting with both the "S" cams and the Indian iron Bullet cams the stock pushrods had enough adjustment to cope with the cams' smaller base circle. The piston crown has enough metal for a shallow pocket, but
don't go crazy with that Dremel. BW machines a 2mm deep band off the piston crown as part of his squish band modifications with no ill effect. You can also reduce the seriousness of any inlet valve to piston contact by getting your local engine shop to cut the valve seats back so that their outer edges are actually flush with the combustion chamber surface. On both of the 500 AVL heads I have seen have the valve seats originally stuck out about 1mm from the casting :o That is not good.

My preferrence is to set the timing up on the marks and give the inlet valve the room it needs.

Regards,

A.

GBBet

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Re: Fitting 'Classic' cams to Electra X
« Reply #3 on: August 29, 2014, 08:34:56 PM »
Is it safe to use shims behind the cam to prevent the follower from hitting the cams?

ace.cafe

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Re: Fitting 'Classic' cams to Electra X
« Reply #4 on: August 29, 2014, 08:53:18 PM »
Is it safe to use shims behind the cam to prevent the follower from hitting the cams?
If necessary, yes. I have not heard of that being necessary before, so you might want to inspect all the areas around the cam gears to be sure there is clearance to shim it out. In any case it should be spaced only a very small amount with the shims that are used to set cam end thrust distance. Then you will need to check your end thrust clearance by putting the timing cover on, and testing for any binding or resistance to turning the engine.
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GBBet

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Re: Fitting 'Classic' cams to Electra X
« Reply #5 on: August 29, 2014, 09:11:20 PM »
Removed and re-fitted follower guides (after turning them 180 degrees) to check all is central, but when cam is installed the follower kisses the gear wheel. This is on inlet and exhaust.. Using 2 cam shims behind each allows necessary clearance. Fitted the timing case with 1 shim, all seemed okay.

ace.cafe

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Re: Fitting 'Classic' cams to Electra X
« Reply #6 on: August 29, 2014, 09:13:50 PM »
That sounds okay.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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GBBet

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Re: Fitting 'Classic' cams to Electra X
« Reply #7 on: August 31, 2014, 11:39:04 AM »
Have decided to get the valve seats re-cut, so may as well get a little shaved off the follower heads and shim the cams properly.

Adrian II

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Re: Fitting 'Classic' cams to Electra X
« Reply #8 on: August 31, 2014, 08:07:24 PM »
Saw these in nfield gear:

http://nfieldgear.com/enfield-store/improved-valve-lifters.html

They have smaller heads already, and being for the C.I. engine have tougher stems. You might be able to get the follower guides bored out to suit, though you would need to swap push-rod ends for the late C.I. type (6mm, not 1/4"). Don't know if this would cause push-rod length problems, though!

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A.

GBBet

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Re: Fitting 'Classic' cams to Electra X
« Reply #9 on: October 06, 2014, 05:52:11 PM »
Thanks Adrian, had a look at these. Fifty dollars sounded like a good price, hundred dollar postage put me off. Had some C.I. followers turned down, waiting for them to come back from hard chroming.

GBBet

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Re: Fitting 'Classic' cams to Electra X
« Reply #10 on: October 28, 2014, 07:19:12 PM »
Thanks to all for help, job done. Increase in usable mid-range power out weighs the noisier valves which I guess is caused be the sharper cam lobes.

Adrian II

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Re: Fitting 'Classic' cams to Electra X
« Reply #11 on: October 29, 2014, 08:29:00 PM »
Glad it all worked out for you, did you have any valve to piston clearance issues in the end?

A.