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  #1  
Old January 13th 2007, 16:07
1500SBR 1500SBR is offline
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Cam ramp design

Guys, I have been trying to obtain more information on the differences between the Engle´s W and FK series (aside from the fact that the FK are meant to be used with high ratio rockers).

I tore my alky 1835 and treated it to an 82 crank and 94 pistons. The engine is great and all, made 217 hp but I hear some gossip about the fact that I use a W140 and that such cam is so, so mild in terms ramp design. That the FKs (89 or 97) are the ticket. Crisper acceleration and the willingness to rev past 7000 rpms.

I assume the engine is not bad (after all it makes 217hp) but at least some 30hp is due to the fact that it runs a very high compression ratio.

Does anyone have any information regarding the subject.
Additionally, there is a huge difference in spring pressure from the Engle duals and the Chevy style ones (from 230lbs to about 500), does anybody know of anything in between?

What do you guys use in terms of cam and springs? How many rpms are your engines seeing.

Thanks, regards
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Old January 27th 2007, 10:38
beetle1303 beetle1303 is offline
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I got a 1776cc t1... the max revs iv seen was 6500 rpm with power ending just about 6k. The engine is in very good working order, but not the best due to restricted budjet. New istons (Acralite), cylinders(Mahle), rings (totalSeal), heads(044), ignitor and coil. Used AS41 case, crank and conrods (all from the same engine), 40mm dual Webers and a custom made exhaust. Just added bolt on rocker shafts, due to a washer that broke from revving too high...

Chris
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  #3  
Old February 17th 2007, 16:43
Tony Z Tony Z is offline
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I have 2 cams at home, one is an 86B and the other a 121/125. What I noticed when comparing the two is that the 121/125 has much steeper ramps and the base circle is cut a lot lower.

If you run the thought process thru your head....
A high ratio rocker adds 27% more lift than a stock one. Which means that the lifter has to move less and so does the pushrod. Less intertial weight to overcome by the springs to push them back (plus you also have 27% more spring pressure pushing them back) which means yuo can rev the engine a fiar bit higher, given the same lift. Remember, you have less distance to move the components, as well as less inertia to overcome because their speed is less, but then you have the double effect, as your pushrod and follower is now "seeing" a higher spring pressure. So in theory, you could run a slightly lower spring pressure for the same revs assuming the same lift and opening profile.

The cam profile can be slightly milder on a ratio cam, but the rocker will enhance the speed of lift, thereby keeping a fast lift profile. This can work one of 2 ways, either the cam can keep the radical ramp and the valve will open even faster, or the ramp can be made "softer" for long life and the valve will still follow the non ratio "opening profile".

Dont forget that your cam lobe is also trying to push the follower down (or up depending on cylinder), not only outwards. So by having less lift on the cam, friction is slightly reduced. If your cam profile is slightly softer, you will prob find a few extra hp if the valves open on the same profile.
Too steep a cam profile does cause wear, as I found out in my old 1600...


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Old February 18th 2007, 18:51
1500SBR 1500SBR is offline
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Tony Z,

Thanks for the reply, I hear you. But in practical terms I understand I shouldn't go through all the trouble of replacing my W140 with 1,25 rocker and Engle 6602 springs with a FK 87 with 1.4 rockers, because I would have to stick with the 6602s anyways right??

I mean in theory there is benefit to a certain extent, but my question now is: how much? would it actually make a difference in my engine. Would it live longer? Would it make some more power? Or it is just something to keep in mind when building the next one?

It's good to exchange ideas with someone like you, I understand you speak from experience. Here in Brazil the culture is not to build engines for long life, which I understand but I tore my engine with 2000miles on it and did not like some of the things I saw.

Best regards,
Marcelo
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Old February 19th 2007, 07:02
Tony Z Tony Z is offline
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I honestly think an FK87 would make your engine live slightly longer, but I am guessing here, I have never tried anything like a W140 w 1.25s

You would prob surprise yourself, get a set of Titanium retainers and the new aluminum pushrods and you should be able to run stock duals.
Once again, I am guessing here, but I honestly think that if your cam and rocker combo can do what it is, I think that switching to a 1.4 ratio setup will not require changing your springs - depending on the final lift you achieve.
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