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  #1  
Old April 5th, 2006, 04:42 PM
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Stephan Laputka
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Cam SHaft Questions...

I have a 4.6 in my defender and I am looking to get some more power out of it. I was thinking about changing the cam shaft to and RPI version.. any thoughts? Has anyone done this if so did you notice a difference? Lastly how hard is it to change it, never done it before. Are there any write-ups? THanks.
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Old April 5th, 2006, 07:15 PM
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Greg
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Piper makes a nice cam(RPI), but it all depends on what you mean by "more power". There are a few companies stateside that will make a grind for any application. Crower and Isky are a couple that stock a variety of cams that will increase your performance. If you want to be really fussy they'll even make you one with a custom grind. Is this something that you drive daily, or is it off road only? How hot are you looking to go?
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Old April 5th, 2006, 07:33 PM
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Changing a cam isn't "Hard", but it is very involved of a change when the engine is installed and running. You need to pull the whole intake manifold off, the rocker shafts and pushrods need to come out, and the entire front end of the engine also needs to come off. Give yourself a few days if you are good with a wrench, at least a week of solid work if you're not. AND make sure to get help from friends who know how to do it, since there are a lot of little things that need to be done right if you want it to last.

You definitely need to change the lifters at the same time, and while it's all apart you might as well do a new timing chain as well.

-Hans
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Old April 6th, 2006, 06:56 PM
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Stephan Laputka
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I am mainly looking to get some more power on the road. The car does a lot of cross country driving (Moab is in the west and I live near NYC) and loaded with gear in fifth gear i can barely get 65. We won't talk about I-70 in colorado... Anyhow she does a lot of wheeling all over the country and a lot of driving to get there. So if i do the piper cam, what are my power gains? Also, what should I look to change while the engine is apart, lifters, timing chain, what about head gasket? Any good write ups or pictures of this kind of work?
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Old April 6th, 2006, 09:51 PM
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The optimmax and RP4 would work well for you. They increase power from idle to around 4500 RPM's. The thing that is nice about the RP4 is that the lobe center is a little thicker so you'll get better vacuum and smooth idle. If you are set on RPI than I would suggest the RP4. You can plan on an increase of 15bhp or better. Do some homework on the lifters you choose as they are not all created equal. You may gain some extra torque there as well. Depending on the mileage it may be a good time to do head gaskets and check your deck, 3 angle grind valve job etc... The headwork in conjunction with the cam will be a very noticeable difference. Good luck.
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Old April 6th, 2006, 10:29 PM
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Stephan Laputka
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Thanks for the info
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Old April 6th, 2006, 11:00 PM
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Wierd, I though I had replied to this thread again..... odd.

How many miles on the 4.6? Going from just the cam, to also doing the heads as well isn't too much more work, just a matter of a couple more brackets and the exhaust manifolds, then unbolt the heads themselves. The cam will be the largest part of the work. I did new head gaskets and re-cammed about a year and a half ago, though I didn't have time to research cam choices at the time and just replaced with a stock cam and lifters.

If the mileage is kinda high, you might also want to consider either a new set of injectors or sending your existing ones out to be cleaned and rebuilt. If some are partially getting clogged and the flow rates are all over the place, that can cause all sorts of issues.

-Hans
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