Installing Custom Roller Cam per FABO reccomendations

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bschubarg

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The current 318 standard bore with ported #302s has the Comp Cams 20-212-2 Flat Tappet.

Lobe Sep: 110*
268*/268* Adv.
218*218* @.050
.454/.454 Lift

59* degrees overlap.

Best cylinder pressure is 130 psi.
Using the Wallace Calc I get a V/P of 98..... Horrible.


New Cam:
Custom Roller 111.5 Lobe Separation
214*/214* @ .050
.474/.474 Lift

38.8* degrees overlap

Wallace V/P Dynamic Calc resolves V/P to 131.... better.

But this is all just on paper. I know how the Comp Cams run in my '87 Chrysler Fifth.
After install this weekend I will give you my impressions of the new custom Roller with 30+ V/P Index.

Ought to be interesting.
 
This is with the super low rear axle ratio, right? Yes, ought to be interesting.

Where are you timing the ICL on the new cam?
 
2.21 Rear and all I'm doing is advance the cam 4* degrees....Yes, it will be interesting. If I can light up the tires from a stand still, then for me it is a win....
 
cam2.jpg
Comp Cams 212-20-2 after 12K...
2018-06-09 16.21.14 (1).jpg
2018-06-09 16.21.14 (1).jpg
cam2.jpg
2018-06-09 16.21.14 (1).jpg


cam.jpg
 
Jim at Racer Brown will custom grind a cam for you that will out perform any out of the box cam any day of the week.
 
You could stand to advance that cam down around 103. Jes sayin.
 
gliderider,
He just got a new custom roller cam and you're advising him to call someone to grind him another new custom roller cam?
 
gliderider,
He just got a new custom roller cam and you're advising him to call someone to grind him another new custom roller cam?

Sorry, I misread his post. Somehow I read that he was thinking of getting this cam and these were the numbers on paper. Sorry for my confusion.
 
No worries glider...like you, everyone told me to get a custom grind and that is exactly what I did... hopefully installation will be completed today.....
 
true of shelf chevy grinds, not true for modern grinds unless Racer is channeling new profiles
No Ultradyne hyd profiles from Harold either
 
true of shelf chevy grinds, not true for modern grinds unless Racer is channeling new profiles
No Ultradyne hyd profiles from Harold either


Jim has many new lobes. You have to ASK him about them. He won't sell you a new lobe for a head and intake system that is 50 years old.

90% of the guys out there won't know the difference. Especially in a street car. Much ado about nothing when it comes to lifter diameter.
 
your opinion does not pass the math test YR


What math test? It's borderline idiotic to tell everyone if you don't run a lobe designed for a .904 lifter you are wasting your time.

I'd bet my bottom dollar if I called Mike Jones right now to order a cam for my street/strip car he'd spec lobes from an .842 lifter. I know, because he did.

So would you argue with Mike about using the wrong lobe and tell him his math is off?
 
im sad to say my cranking compression is 125 on my 360 with 284/484 mp cam, jim at racer brown suggested i go 220/ 450 on 110, i think i wll wait and go the higher compression route in the near future
 
Yep, rigger.... that higher CR gives a bigger duration cam more usable RPM range.

As for the lifter diameter, I honestly don't know the answer. I find it interesting that Crane has had different sets of lobe profiles depending on the lifter diameter in their Master Catalog for a long time. There must be something to it. But I have looked at the .842 and .904 profile data a couple of times and never have been able to convince myself that that either has any great advantage. Seems like you can get fast or slow ramps with either. I need to sit down later and tabulate a whole slew of these profiles for a single advertised duration (like 270-ish) and see if there is a trend. I'll try to make that easy to put in a post and share.
 
Good move Rigger
Mike only has one .904 lobe hyd as far as I know, and it's excellent but his solids are golden and his rollers cannot be beat
and if you use a chevy cam- more to it than just the lifter- maybe I''ll post a thread
nm
Crane had the .904 lobes in the catalog but no shelf cams used them AFIK- use the Comp lobe catalog- it makes it easy as it also show intensity- you also need .200
 
nm
Crane had the .904 lobes in the catalog but no shelf cams used them AFIK- use the Comp lobe catalog- it makes it easy as it also show intensity- you also need .200
Thanks wym. That is good to know... I noticed that the cam we used in my sons' 340 was a Z series which is listed as for a .842 min diameter lifter.... one of the 2 best of their profiles IMHO for around 268 adv duration for area under the curve for hyd flat profiles. Yes, on the .200" duration.... and I'll look at the Comp numbers too.

FWIW
Here are those Crane hyd flat lobe profiles for around 268-270 advertised duration. The .842 min dia looks to be a bit crisper down to the close of the valves, but they both have some slow and fast ramps. The H218/306 and H212/306 look to be the best of the bunch and don't strike me as being all that different. .904 profile actually looks slower around the 'tails' of the ramps but faster from .200" tappet lift to full lift. Of course, this is not conclusive as to all that COULD be done with one or the other, and things may change with different tappet types, mfr's, etc.
Crane Hyd Flat Profiles 268.gif
 
you are better off with a slow .904 lifter profile than a fast .842
are you looking at the online catalog
for comp you have to look at the so called jeep profiles- there are all 4 of them
remember crane advertised duration is at .004 and comp is at .006 so an identical crane using crane method shows longer duration- sometimes a lot on a slow lobe
unfortunately Hughes does not give seat timing
Cranes profiles date from the earlier valve spring era and do not pushthe envelope
they are smooth- Like Engles the .904 will have more area under the curve- it does not try for maximum lift which would take different springs
 
Last edited:
a comparison using Mike Jones
-------------1.6--1.5-lobe-@006 @.050
Jones chev 462 434 289 256 200
Jones Mopar 491 461 307 256 202
showing difference in lift with similar seat and .050 timing

Jones Mopar 491 461 307 256 @ 202

jones ch .488 .458 305 272@ 216

Jones ch 496 465 310 276@ 220
showing how much more duration you have to use with an .842 to get similar lift as .906

here's a 256 comp XE showing just the intake note the increased "intensity" over the above
XE 256H .478 447 299 256/ 212/ 22 54in 68 20 ex IC 54.5
4x4 5900 .488 .458 .305 250@ 205 122 @200 comp .904 shorter duration still more lift

HM2063164A .506 .475 .316 252@ 206 126 Hughes

4x4 2901 .498 .467 .311 254 209 126 @200 comparable comp .904 similar seat duration
K-52HYD .489" .458" .305" 254° 209° Easy on the valvetrain Engle






 
a comparison using Mike Jones
-------------1.6--1.5-lobe-@006 @.050
Jones chev 462 434 289 256 200
Jones Mopar 491 461 307 256 202
showing difference in lift with similar seat and .050 timing

Jones Mopar 491 461 307 256 @ 202

jones ch .488 .458 305 272@ 216

Jones ch 496 465 310 276@ 220
showing how much more duration you have to use with an .842 to get similar lift as .906

here's a 256 comp XE showing just the intake note the increased "intensity" over the above
XE 256H .478 447 299 256/ 212/ 22 54in 68 20 ex IC 54.5
4x4 5900 .488 .458 .305 250@ 205 122 @200 comp .904 shorter duration still more lift

HM2063164A .506 .475 .316 252@ 206 126 Hughes

4x4 2901 .498 .467 .311 254 209 126 @200 comparable comp .904 similar seat duration
K-52HYD .489" .458" .305" 254° 209° Easy on the valvetrain Engle







Geezus.
 
Cranes profiles date from the earlier valve spring era and do not pushthe envelope
they are smooth- Like Engles the .904 will have more area under the curve- it does not try for maximum lift which would take different springs
Yes that has been my impression.... and, while it is not the topic, I kinda like them for that reason. Less stress on the valvetrain and lower contract pressures on the lifters...... less problems for break-in IMHO. Easy for a moderate build.

BTW, we have not heard from the OP? How is is going?
 
YR
what most cam tech guys miss is that chevy is a short rod motor and much more tolerant of intake close as it takes many more crank degrees to move the piston around BDC
long rod engines are much more fussy
Around TDC it's the other way around
Chevy jerks the piston away from TDC much quicker than a long rod motor so they start opening the valve earlier to get it open when piston demand needs the flow
the same degrees of overlap is not as big a deal on a short rod motor as a long rod motor
etc
using the same specs on a SBC or BBC as a SBM or BBM leaves performance (however you describe it) on the table
what's the difference in torque that .030 lift and the implied increase in duration at .200 and area under the curve indicates?
WE went through this drill with a major fleet and also with the San Jose Municipal Busses where we dropped the EGT by 800 degrees (propane) with cam optimizations while giving more power and fuel economy

nm Engle is similar- good quality, good wear, easy over the nose (no little pointy chevy lobes) both have more area under the curve
but both series of lobes are dated but we are not talking "heads up" requirements are we
 
YR
what most cam tech guys miss is that chevy is a short rod motor and much more tolerant of intake close as it takes many more crank degrees to move the piston around BDC
long rod engines are much more fussy
Around TDC it's the other way around
Chevy jerks the piston away from TDC much quicker than a long rod motor so they start opening the valve earlier to get it open when piston demand needs the flow
the same degrees of overlap is not as big a deal on a short rod motor as a long rod motor
etc
using the same specs on a SBC or BBC as a SBM or BBM leaves performance (however you describe it) on the table
what's the difference in torque that .030 lift and the implied increase in duration at .200 and area under the curve indicates?
WE went through this drill with a major fleet and also with the San Jose Municipal Busses where we dropped the EGT by 800 degrees (propane) with cam optimizations while giving more power and fuel economy

nm Engle is similar- good quality, good wear, easy over the nose (no little pointy chevy lobes) both have more area under the curve
but both series of lobes are dated but we are not talking "heads up" requirements are we



I agree. My problem is actually getting lobes that are designed for a .904 lifter. And I'm not sure for most of what most guys are doing, that they'd see a benefit with a .904 lobe.

I'd have to run through the Comp lobe listing and have a look because I don't remember many .904 lobes being under 235ish at .050 and its damn hard to convince some of these cam guys it's worth doing a .904 lobe.

I still have all the cam specs from when I built my engine a few years back. Only one cam grinder gave me a .904 lobe. That was Jim at Racer Brown. And I had better than an hour on the phone going over the junk I run before he actually decided I wasn't nuts and that netting .600 lift was actually worth doing. If I would have accepted less lift, I would have most likely ended up with an .842 lobe...maybe .875 if I was lucky.

Sometimes it's a matter of who you know, or who you can convince you aren't off your rocker. Jim was the only guy I talked to who was willing to go with that much lift for my engine.

Maybe tomorrow I'll go over the Comp lobes and see how many .904 lobes are under 235@.050.
 
The XE275HL hyd is the shortest easy to find
the others (4) are used for AMC but no reason they could not be used on a Mopar core- they could even use Ford or Chevy profiles on the exhaust
I'd really like to see a 270, 265, 260 etc
It's just so easy to stick a mopar billet in the grinder and copy what is known to work in a SBC
Lately we have had a rash of questions concerning 8:1 motors these can really be helped with a short cam
but you need as much lift as possible between 70 -112 to get the cylinder filled
their heads do not flow much better beyond a half inch lift so open, stay open, close and on the exhaust open late as low compression can benefit from working the charge longer- and a lot of overlap is not helpful especially with stock manifolds
Lunati seems to be giving MOPAR the most support with shelf profiles, and Hughes which look like they have switched from profiles that look like Engle to profiles that look like Howards
Being here in CA I have not used the back east grinders much but we did use General Kenetics for the Javelin as well as Engle (Where TRACO was fronting the R&D)
cheers
 
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