Hi Jim

These numbers were come up with by someone whom they work with and they would look for some one to cut it. When I stopped by I saw the assembly man checking the spring strength while on the phone talking to the man. They are suppose to be special winston cup springs recommended by Brodix that I am suppose to be fortunate to have but I do not remember the manufacture's name.

They have described him as somewhat eccentric about getting all the power that can be had and I am all for that but I am also already over budget and need to stay within some permitters.......... otherwise I would be jacking up the body, adding a tall single plane, Toms everything, etc etc.

Also somewhere I think I read that .700 lift is about all that is recommended with those heads. I know looking around that other site where your friend is I did not see anyone else with that much lift with those heads. Even with TD 1.7 shaft rockers I had to use 2 gaskets to get the low billet valve covers I already have up enough to clear the 660 lift of the first cam. I have an vintage air unit that I still want to be able to use and it needs the low covers.

BTW Brodix said that the way they would cut the head the port match would remain the same. That is something I would consider mandatory to maintain but they said no problem and not to bother shipping the intake

Doug

 

Did you ever give Harold Brookshire a call? He is grinding cams again (used to own Ultradyne...designed the Comp High Energy's and the Lunati Voodoo's among many others). I'd spend some time on the phone with him and see what he comes up with after hearing your whole story.

I think you *could* make the power with a 255-260*@.050 cam....but it will need to be an *aggressive* one. Not a part hurter...just a good serious cam. If you're springs are limited to .700..then we'll deal with that. The big power is going to come from when it opens and how fast it gets to .680 or whatever.


You're on the right track.....just spend the time to research the cam. I'd like to see some .200 duration numbers in the 175*+ range for a 255-260* cam with adv duration under 300*. A 112 LSA will smooth it a little...might make a couple less peak HP....but will pull like crazy and drive a lot nicer.

JIM

 

I’m a fan of the Comp Extreme Energy line of street rollers. Running their 4877 lobe on the intake and 4878 on the exhaust will give you 260 degrees intake and 266 degrees exhaust @ .050” respectively. Lift is a nominal .666” intake and .677” exhaust w/ 1.7 rockers. Switching the intake rockers to 1.8 will increase lift to .705”. If you want to calm the idle a bit, have them grind it on a 112 LSA. Their off the shelf XE solid rollers are ground on a 110 LSA.

How do you like your current cam’s idle characteristics? How much vacuum does it make?

 

Hi Mark

I am a little confused with the numbers you are quoting from Comp Cam. In the online catalog that I am reading the next one up from mine is a XR 292R with duration @50 of 254/260 and lift with 1.7 is 660/666

Right now I have the 286R that is about 6 degrees less across the board.

I do not remember the vacuum but the idle was about 950 and sounded like a M-60 being mated to a snare drum......... I thought it sounded pretty good.

With a 5 finger clutch I am going to need a little extra rpm at idle or so I figure

Doug

 

 

Thanks Mark

I guess I am dealing with some outdated info. I know the builder is looking at the same info I am and they stop at the 292 R. Those ones you posted present a whole new ball game and I will copy and print them......... Then go see if I can have a Saturday morning chat:

Thanks again

Doug

 

You're actually not dealing w/ outdated information -- Comp only goes up to the XSR292R in their off the shelf cams. But as you can see, the XE lobe series extends well past their listed cams.

Good luck,

Mark

 

i just read this saga today.
when it 1st said 155 psi
nobody did a leak down test?

 

Hi Matt

Thanks for weighing in.

I think your question is valid however with all cylinders reading exactly the same and the vacuum remaining rock steady I have not considered leakage. Also with the math showing less than 10.0 compression rather than over 10 there was going to be a teardown anyway. Then again if there was to be a duplicate low reading when the heads come back from being milled, I can just about guarantee there will be leakage............. from a .44 diameter hole

Doug

 

my newly rebuilt 355 in my 72 was 125!
so i drove it for awhile
3000 mi later i was ready to pull it
and i rechecked it
was 165!
changed heads from 76cc to68cc, now it is 185-190 9.7:1
it was just slow to seat!

 

See,,,there you go! Perfect group of cams to pick from. Take a look at the .200* and adv numbers on these cams and then go to the *shelf* cams from Comp and other and compare.

These are sweet powermakers!


JIM

 

Hi Mark

I was very impressed with those #s you put up and after some discussion with the builder that is the choice that was made and it was ordered in steel billet. For others reading that particular cam is "off shelf" versus the over counter catalog cams and the duration is @50 260/266, Lift @1.7 is 666/677 and the LSA is 111.

Cost was $328 and I think I would have been happier with the comp springs rather than the Nextal ones because their tension strength is a 690 lift limiting factor. However I am told that as long as I am under the 690 lift I will be fine. The heads should be back here within a week (11.0) and that corresponds with the expected time for the cam to arrive so maybe by next weekend we will have things back together for another run at the dyno

Doug

 

Good deal!

Actual valve lift will be .640-.660 or so at best...so you should be fine. But please check anyway!

Also have them check PV clearance real quick just to be sure....these cams move things a LOT faster. Better safe than sorry.

BTW- do your heads have seals on intake and exhaust? When I ordered mine from Brodix I had them add exhaust seals.

Current thinking is that valve springs work best when squeezed pretty tight at full lift.....almost stacking up..but just short of it. Double check coil bind and retainer to guide/seal clearance during assy.


I think you're going to like that cam!


JIM