How would you take the flex from a hollow cam?
How would you take the flex from a hollow cam?
(OP)
I have been modifying a Ford 4.6L dohc (modular) motor for about a year now. After close study, I conclude that the stock cams cannot withstand the added stress of after market (high pressure) springs. Reason? Hollow cams.
For the mod motor, Ford perfected a method of setting cam lobes on a hollow tube by pushing a steel ball down the center. All Ford modular cams are hollow. All after market modular cams are solid. By clamping down a small amount of resistant cam friction and hand turning the crank, I have watched these cams flex enough to gall the bearings. So, gentlemen, here is my question...
What would be an effective method to stiffen up these hollow cams? Here are some wild ideas:
1) Pour lead down the center.
2) Pour a binary compound down the center (ie epoxy?).
3) Weld a steel rod inside the cam. (This idea worries me since it would probably require the cam center to be drilled before hand... which might re-loosen the lobes.)
I would be most appreciative for any insights here.
Walter Carter, Palm Springs, California
For the mod motor, Ford perfected a method of setting cam lobes on a hollow tube by pushing a steel ball down the center. All Ford modular cams are hollow. All after market modular cams are solid. By clamping down a small amount of resistant cam friction and hand turning the crank, I have watched these cams flex enough to gall the bearings. So, gentlemen, here is my question...
What would be an effective method to stiffen up these hollow cams? Here are some wild ideas:
1) Pour lead down the center.
2) Pour a binary compound down the center (ie epoxy?).
3) Weld a steel rod inside the cam. (This idea worries me since it would probably require the cam center to be drilled before hand... which might re-loosen the lobes.)
I would be most appreciative for any insights here.
Walter Carter, Palm Springs, California





RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
I don't know anything but the people that do.
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
I have a bit of practical experience in hollow Ford/Lotus camshafts that tended to break when reground to extreme lift/duration/rates with the attendant high spring rates necessary to keep things from going bang. My solution was to use cams ground on steel billets. Perhaps a slight bit more expensive up front, but satisfactory performance and no breakage in many years of racing.
Rod
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
If you really want to use the stock cam as a basis, I'd insert a steel rod through the center, right behind a ball of strong thickened epoxy which should be able to take up the radial gap. But first look at the deflection equation for a long skinny tube or round bar stressed as a beam to see how little effect it will really have.
Mike Halloran
Pembroke Pines, FL, USA
RE: How would you take the flex from a hollow cam?
Like mike says, filling the centre won't make a huge difference.
Regards
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RE: How would you take the flex from a hollow cam?
wrist-pins (.048") and filled them with 50 modules unistrand prepreg polyamide and with a .927 Chevy wrist-pin the stock one broke at 9800# while mine broke at 17200#.
That being said if it is possible to get uniformity of your windings the full length you will have as much in them as an after market cam although it will be lighter.
I don't know anything but the people that do.
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
Least awful low-buck technique I can think of is to sweat-solder a steel round in the hole. Fit it to .002 to .004" gap per side if you can.
Mike Halloran
Pembroke Pines, FL, USA
RE: How would you take the flex from a hollow cam?
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: How would you take the flex from a hollow cam?
The cost of engineering the dynamics of the valve train to utilize your OEM cams far exceeds the cost of purchasing aftermarket units. The cure for any flexure is larger diameter, and stronger material. Your ideas posted would change harmonics of the system, and may help to some extent.
RE: How would you take the flex from a hollow cam?
What will ONE blown engine set you back?
Rod
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
You'd do better to try reaming the bore and shrinking a steel rod into it... but the assembly has to be done very quickly.
Another thing that comes to mind is spacers around the od of the shaft... but they have to split for assembly, retained somehow, and they have to be a close/press fit axially between the cams and the bearing journals in order to be effective... but Comp Cams' shafts are certainly cheaper.
Mike Halloran
Pembroke Pines, FL, USA
RE: How would you take the flex from a hollow cam?
Don't try to make your own as the degree of expansion will be critical and their formulation has that worked out.
Once again, even though I suggested it, I don't recommend it. My recommendation is grind a cam on a significantly bigger diameter shaft.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
Check out the specs on this tube which you can slide in with some polyamide high temp epoxy
http://ww
Cheers
I don't know anything but the people that do.
RE: How would you take the flex from a hollow cam?
RE: How would you take the flex from a hollow cam?
Assuming the deflection is always the same direction, you could insert a solid or hollow bar that is fastened on its first end relaxed and its second end with preload. If well thought out, it could be simple, cheap, and failsafe.