Anyone using a Crower 52242 Compu Pro camshaft ..

Scott are you refering to the Crower cam lobe lift spec ? I think your right it should be to first one that is faster & the #2 EZ should have slower profile.

Mark

It seems hard for the cam people to get there spec right on paper.

---------- Post added at 01:50 PM ---------- Previous post was at 01:45 PM ----------

NickEv , Yup thats what I have found I short shift @ 4800 out of low & pull right up to 5000 shift to drive & cross the line @ 5000. 12.78 105 mph ( I do run the stg-1 fuel pump & 3/8 '' line ) i am going with a 1/2'' this winter when I find time & can get a lift freed up in my shop.

mark

---------- Post added at 02:00 PM ---------- Previous post was at 01:50 PM ----------

gsgtx, what brand of fast profile camshaft are you using? mine is a scott brown & scott told me 115#/305# would work fine , If I shim for more seat pressure won't the full open # increase also ?
gsgtx ,I just dug my records out & checked my cam card .... it calls for 125# & 300 open.

I will call Scott & see what he has to say,

Mark

 

The 4 degrees is being removed at .054" lobe lift.
If you look at a lobe with .330 lift it is about 5 times longer from the .054" point to the top of the lobe as it is from that point down to the .006" lift point.

If you pull 4 degrees from the lobe width or 2 degrees per side at the .054" point, the ramp angle from .006" is decreased and the ramp angle to the top is increased.
However because of the differences in the ramp lengths, the decrease in lower ramp angle is effected 5 time more than the increase in the upper ramp angle.

In other words the lower ramp angle is decreased a lot and the upper ramp is increased a little.

Paul

 

the cam i did the shim was a comp cam xfi intake and extreme energy exhaust. 218-230 duration, advertise duration-262-280, 504-490 lift. 110 LSA with a 107 installed CL. after the shim it pulled way smoother at the high rpms, went from pulling to about 5100-5150 to a increase of about 5400-5450 rpms. you can see the cam wasnt very big to start with.yes it will give you more open pressure too. if you had one off you could see what it is really now and with shims on the spring tester. are they double springs now? a spring will have less pressure after some use, a double spring would be better for the harmonics.

 

gsgtx, just got email from Scott Brown he said that I started out on the low side & after a few heat cycles they will drop 10 - 15%. I should had known this because on our puller engines they were set up 15% higher than spec , used to do this after break in with just the outer springs. One question if you have double springs are the inner to be shimed the same ?

Thanks ,

Off to locate a spring tester

Mark

 

i had double springs in at the time and just put one shim in for the outer spring.

 

gsgtx , The springs that I used were new Poston springs for their GS 116 camshaft , I think I will look into the Bee hive valve springs , they set up a variation in harmonics providing a dampening effect & creates additional valve train component clearance. The Bee hive spring also reduces coil bind problems in application requiring larger wire dia. for high lift cams. You know it's true.... because i read it in a HP Engine Assembly Book LOL . I am going to check into these springs ,I think the low pressures of these springs may be the problem with my lack of rpm. Thanks to gsgtx for the input of this 10-15% oversight on my behalf .

Thanks Folks

Mark

 

beehive are also lighter which helps a lot, use a light weight retainer too. thats what am running now are beehive springs. the poston springs say 110 seat pressure @1.86 and yours are installed @ 1.89, so you have even less pressure. poston also says you need a 60 thousand shim to get to 130 seat pressure. dont know were your coil bind will be at. ta-has a spring with 125 seat and 295 open if the beehives are going to be a problem.

 

So that explanation makes sense. I was assuming the first few degrees (say 0 to 0.004" lift or 0 to 2 deg) were removed, didn't guess they would pull 4 deg out of the lower-middle. The benefit of this is lazier valve opening and seating, but slightly higher accel/deceleration from 0.054" to the nose. I would guess hard valve seating would lead to some stability issues (valve bounce), so they are attempting to correct that, but not as important as lifter losing contact over the nose and decel during closing.

---------- Post added at 10:11 AM ---------- Previous post was at 10:07 AM ----------

Those XFI and XE lobes are some of the faster action ones out there. No wonder more spring helped with rpm!

 

Mark

I fully understand "The Budget" and I know you have considered this but for the sake of others it needs to be mentioned.

Last time I spoke to Greg Gessler about his level 3 heads, the recommendation was to have valve lifts in the .530 to .540 range in order to take full advantage of the head potential.
You mentioned having a similar conversation.

In order to accomplish this a roller cam with roller rockers would be needed.
With the roller lobe profiles a lot of power can be made with shorter durations which means less valve overlap for good street manners.
Larry's 600 hp engine is an example.

Just Saying

I also would like to see you make the present cam work.
You are looking for a Beehive spring with a spring rate near 350 lbs/in.
It would be great to find one that can be shimmed for 125# on the seat and end up around 300# open and be within .100" away from coil bind.

What is the valve stem diameter?

Paul

 

Roller cam would be nice but not "necessary" at that valve lift. Roller cam setup is not cheap....I've run .570-.590 flat tappets with no issues.

 

I wasn't thinking so much about the lift as the dwell time at the higher lifts.
The roller profiles offer much more time at the higher lifts without the penalty of long advertised and .050" durations making a roller cam much more street friendly.

Paul

 

Right....I wish the cost would come down on the roller setup. I'd like to run it in my next motor......

 

was going to try a roller too, i think you need the head flow with the high lift roller to get full effect. now going with a tight lash solid, never run a solid before.

 

Larry, could tell us all the plus and minus of running a roller cam i know cost and a lot more spring pressure any thing else? re use the roller lifters are a big plus.

 

Gsgtx, I kinda like your fast ramp, lighter lifter solid your going to try. less spring pressure needed than a roller. Does anyone know if a mild rollar is any better than a solid flat tappet. I have read a lot of defferant thoughts on this on other forums. Any ideas here? Thanks, Bob

 

thats funny when i first read this #74 post it only had the first line and a 1/2. if the cam wasnt steel billet would you still need to run a hardened distr gear.

 

gsgtx, what valve stem dia do you have , mine are 3/8'' , what company offers a retainer for the buick valve keeper & Bee hive spring ? I removed springs off of 1 cyl (injected with air) tested @ 1.89 & @ 1.39 & here are the results 93#/264# I think new springs are in order after looking into shimming ,it would leave very little before coil bind. Looks to be about 18% seat & 13.5 % open . New springs can't hurt anything.
Mark