Another cam question

[vdub]

I have been thinking about this cam decision I have made and wanted to get a little more input from people.

To start out i will revisit my engine combo but first i want to let everyone know I am looking for economy out of this engine.

The engine will be a 1955 with a 76mm crank and 90.5mm pistons, It will not spin over about 5500 RPM. I plan on using basic CB 044 heads and dual ICT's.

the cam I decided on was the KF41 but i am going to use the stock 1.1 rockers. This will put the specs right in line with CB's cheater cam.

The specs for both are below.


The cheater cam is

394 lift with 274 duration and 222 duration @.050

the KF41 with 1.1 rockers is

400 lift with 269 duration and 239 duration @ .050


I was told by someone that the KF41 had a steep ramp angle and will beat up my lifter bores. Dose anyone agree with this. The specs are really close to the CB cheater cam and I don't think the ramp angle is much more then that.

Does this sound like the cam I want to use. and whats everyone's opinion on running a ratio cam without ratio rockers. Remember I am not doing this for performance I am doing this for economy. Is there any reason i should not use a ratio cam with 1.1 rockers other then the performance loss.

If so then what cam should I use. should I just send the KF41 back and get the CB cheater cam. I am also thinking that later on I could always add 1.25 rockers and dual IDF's If I want to.

[grimace007]

if you mean FK41 ???

you CAN NOT use those rocker arms and expect it to be ok.

engles FK series of camshafts are designed for 1.4-1.5 ratio rocker arms NOT 1.1 so either pony up another couple hundred bucks for a good set of 1.4s or just buy cbs cheater cam since you seem to be after its specs
_________________
Brian
68 sedan

Dallas Air Coolers

[vdub]

You know I here a lot of people say that but no one knows why.

It has nothing to do with ponying up the money.

Its not the money I am worried about, I was good economy.

Can anyone tell me WHY you have to use ratio rockers.

Will the cam break in half or flatten out of I don't.

[1432]

"'the KF41 with 1.1 rockers is
400 lift with 269 duration and 239 duration @ .050"


I don't see anything in these numbers (if actual) that are unworkable with a 1.1 rocker, using a 1.4 or 1.5 would be far more problematic in terms of valve control.

[vdub]

That's exactly what i was thinking.

But with 1.1 rockers it seams quite mild doesn't it.

[1432]

yes it is mild but given your 5500 rpm limit it's a good fit, I say give it a try you can always add rockers later but I would limit those to a 1.3 also put a decent spring on it, something around 120# x 250# (@seat /@ open ) and set the up so they have room for the added lift with more rocker.

[vdub]

I was planing on using the single spring that comes with the 044 heads. They say its good to 6000RPM.

Do you think that will work ok. I didn't want to use dual springs because off the added ware they cause to the cam.

[SRP1]

vdub,
I do this for a living, really I'm not pulling your leg or giving you bad info, I'll recap this in short for you as I may have been a little vague in my other post.

1-You can use 1.1:1 rockers with the FK-41 cam, expect the valve lift to be .400" and the duration at .050" to be 235*. The lesser duration at .050" is due to the slower valve lift with the 1.1:1 rockers, in other words it will take longer to get to .050" lift while opening, and it will get to .050" sooner while closing.

2-The FK-40 series cams are a rapid ramp design, more like a roller cam profile, hence the harshness on the lifter bores.

3-You can use single springs with the FK-41 cam no problem as long as you stick with the 1.1:1 rockers, and keep RPM around 5500 max.

4-If low end torque and economy are your number one goal, and your going to stick with the 1.1 rockers run the Engle W-100. The W-100 is upgradeable to 1.25 rockers and you will never need to change your valve springs to duals with this cam.
Engle W-100 with 1.1:1 rockers or 1.25:1 rocker arms
W-100 276ºadv 236º @.050" 0.383" @ cam 0.421" @ valve 108º LC.
Engle W-100 with 1.25 rockers
W-100 276ºadv 236º @.050" 0.383" @ cam 0.479" @ valve 108º LC.


The 100 with 1.25 rockers is a real torque monster, and gets excellent economy.


Hope this helps.
SRP1

[vdub]

I don't see how it could have that rapid of a lift with the specs so close to CB's cheater cam.

So in that case is CB's cheater cam also a rapid lift cam like you say.

[SRP1]

Different ramp profiles, I added to my above post.

[vdub]

The lift just seams to high.

I am trying to keep the cam mild and I don't want to go over 400lift.

[SRP1]

Well with the 1.1 rockers you have an advertised valve lift of .421", after hot lash of about .008" and accounting for flex your actual valve lift will most likely be around .410"
Either way .421" is considered to be a very low valve lift. At that point your splitting hairs between .400" and .421". The tiny little bit of extra lift will help with torque, and won't affect your economy, or cause any added engine wear concerns.

[vdub]

That does make since, but I am still worried about economy.

What are some other opinions on this.

because the guy I talked to at CB told me any of the W series cams would destroy my economy.

[vdub]

You know I just looked at the specs again at engles website and the W100 looks really close to the FK-41 just with less lift at the lobe.

I am completely confused now because from the specs its saying that the W100 is more of a rapid lift cam then the FK-41

[SRP1]

How about you call Engle and talk to Chris.

(310) 450-0806

[vdub]

[1432]

SRP1 said,
"You can use 1.1:1 rockers with the FK-41 cam, expect the valve lift to be .400" and the duration at .050" to be 235*. The lesser duration at .050" is due to the slower valve lift with the 1.1:1 rockers, in other words it will take longer to get to .050" lift while opening, and it will get to .050" sooner while closing."


vdub,
basic .050" duration numbers are figured on relationship of cam to lifter , rocker ratio will have no effect on duration specs on cam tag numbers, unless your cam tag states otherwise (read, checking at valve) your 239* is as stated 239* @ .050".

[SRP1]

But it will slow down the effective valve timing, I'm just giving vdub an example of things that will happen when you mix and match parts off of the normal path.

[vdub]

I haven't gotten the FK-41 yet, its still in coming UPS when it gets here I will see if it has a spec. tag.

Also I am going to cal engle on Monday and see what they think also.

[vdub]