Previous Thread
Next Thread
Print Thread
Cam selection 520ci #2486915
04/23/18 05:59 PM
04/23/18 05:59 PM
Joined: Jan 2014
Posts: 23
TN
RRandP92 Offline OP
member
RRandP92  Offline OP
member

Joined: Jan 2014
Posts: 23
TN
Putting together a 520CI RB based engine. Will be running the trickflow 270 heads with port matched indy 440-2 intake. 1050 dominator on HVH 4 hole spacer. The car should weight 3200-3250 race ready. Will be running a 727 with 4000-4500stall converter and 3.60-3.70 rear gear in hopes to get down the road. Static compression will be between 11-11.5:1 depending on the head gaskets run in hopes to run 93 pump on the road. Engine will be sprayed 150-200hp couple times a year. I have a comp 23-770-9 .690 on the self i would like to run as i already have it. I have also seen an off the self crane 688651 on a wider 112LSA. Looking for a roller that is not to aggressive on the valvetrain. Or should i get something custom ground? Very happy with a porter racing cam in another 499" but hoping to use what i have if a lot of power/reliability is not left on the table.

Re: Cam selection 520ci [Re: RRandP92] #2486920
04/23/18 06:14 PM
04/23/18 06:14 PM
Joined: Jan 2003
Posts: 13,319
Marion, South Carolina [><]
an8sec70cuda Offline
I Live Here
an8sec70cuda  Offline
I Live Here

Joined: Jan 2003
Posts: 13,319
Marion, South Carolina [><]
You said you're happy w/ a cam you got from Porter Racing in another motor...talk it over w/ Dwayne. He won't sell you something you don't need and is a wealth of knowledge w/ these types of combos.


CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
Re: Cam selection 520ci [Re: RRandP92] #2486921
04/23/18 06:16 PM
04/23/18 06:16 PM

C
crabman173
Unregistered
crabman173
Unregistered
C



Conventional wisdom is wider LSA with more cubes--OK but I have had better luck in general not going that route and staying in the 110 max range and as for Crane--the one custom I had done by them for a six pack 511 CI was a dud--way too wide LSA just no balls made 40 HP less than it should with our regular stuff with no other advantages Porter made you happy trust HIM
again--right?

Re: Cam selection 520ci [Re: RRandP92] #2486962
04/23/18 08:36 PM
04/23/18 08:36 PM
Joined: Jan 2003
Posts: 30,947
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,947
Oregon
One thing I learned the hard way is that the TF heads are easy to over cam since they have really good flow at low lift. If the lobe is too fast you'll end up with reversion and the engine will not make the power you were expecting.

Dwayne has a good handle on this since he has watched my test results. Give him a call and ask about the Comp cam that you already have. It might be fine for what you're doing.

Re: Cam selection 520ci [Re: RRandP92] #2486983
04/23/18 09:44 PM
04/23/18 09:44 PM
Joined: Feb 2017
Posts: 566
Texas
R
RustyM Offline
mopar
RustyM  Offline
mopar
R

Joined: Feb 2017
Posts: 566
Texas
fwiw_ I would concur with talking to Dwayne.
He did ours for our 511 and engine dyno made almost exactly what he predicted, within 10 hp - we made 10 more.

Re: Cam selection 520ci [Re: RRandP92] #2487032
04/23/18 11:26 PM
04/23/18 11:26 PM
Joined: May 2017
Posts: 72
WI
B
Brewzer67 Offline
member
Brewzer67  Offline
member
B

Joined: May 2017
Posts: 72
WI
This is almost the mirror of my build. I went to Bullet for their recommendation and they spec'd a custom grind of 262/269@.050 (110 lsa) and .714/.716 lift with 1.6 rockers. I wanted something that would haul the mail but not chew up valvetrain pieces. I don't have too many miles on it yet so I can't speak to it's reliability yet, but it pulls pretty strong and is very manageable on the street.

Re: Cam selection 520ci [Re: RustyM] #2487039
04/23/18 11:34 PM
04/23/18 11:34 PM
Joined: Jun 2004
Posts: 922
B
birdtracker Offline
super stock
birdtracker  Offline
super stock
B

Joined: Jun 2004
Posts: 922
no matter what cam you use, pull the heads down and check all the installed heights. I bought the " up to 680 lift " version as I planned on using a .650 comp flat tappet. The springs that came on the heads coil binded at .680. I removed all the springs. Three valves on each head had .135 of shim under them. Most had .085 and some had .035. The installed heights were close to 1.945.
Andy F had used some Comp rollers with success , I thought he would of chimed in with a few recommendations. Birdtracker

Re: Cam selection 520ci [Re: RRandP92] #2487107
04/24/18 02:58 AM
04/24/18 02:58 AM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
I Win
C

Joined: Aug 2003
Posts: 43,007
Bend,OR USA
My first pump gas 511 C.I. 400 stoker motor ended up with a set of Indy M.W. SR non ported heads on it with a 400-3 intake and a old Holley 9375 non HP 1050 CFM carb on it, I bought a Comp Cams new custom ground solid roller cam from a member on here that worked excellent, it was 260 @.050 on the intakes with .420 lobe lift, 266 @.050 on the exhaust lobes with .409 lobe lift ground on a 108 LSA installed at 106 to 107 ILC.
I switch to a set of Harland Sharp 1.65 ratio rockers after doing the first head swap from the original ported big valve 906 iron heads to a set of CNC ported Eddy RPM heads before switching the heads later to a set of Indy SR M.W port size heads(which increased the compression ratio from 10.29 to 1 to 10.78 to 1) several years later, same cam and lifters. That combination loved being shifted at or above 7000 RPM to get the best times the track no matter which heads, intake or carb sizes I ran on it shruggy
I have never used NOS so keep that in mind also work
I wouldn't be afraid to run that same combination with NOS though after discussing it with a friend who has raced a bunch of different motors and cars with NOS on them, he like tighter LSA cams than wider ones also for NOS work shruggy

Last edited by Cab_Burge; 04/24/18 03:01 AM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Cam selection 520ci [Re: Cab_Burge] #2487298
04/24/18 02:31 PM
04/24/18 02:31 PM
Joined: May 2005
Posts: 1,946
Apollo, PA.
B1MAXX Online content
top fuel
B1MAXX  Online Content
top fuel

Joined: May 2005
Posts: 1,946
Apollo, PA.
Just was reading about a small dia valve to single cylinder vol. ratio likes less distance between lobe center so that the high depression overlap cycle is longer to help the small valve. shruggy

Re: Cam selection 520ci [Re: AndyF] #2487429
04/24/18 07:10 PM
04/24/18 07:10 PM

C
crabman173
Unregistered
crabman173
Unregistered
C



Originally Posted By AndyF
One thing I learned the hard way is that the TF heads are easy to over cam since they have really good flow at low lift. If the lobe is too fast you'll end up with reversion and the engine will not make the power you were expecting.

Dwayne has a good handle on this since he has watched my test results. Give him a call and ask about the Comp cam that you already have. It might be fine for what you're doing.


Interesting there Andy


Most cam folks see that big CI and just lay the lobe to it
We have had some great running big CI units with smaller than you would expect on the cam---well...I really can say that about most every engine for street
Over the decades we have about decided that no cam is too big on a REAL race engine and smaller almost always seems to make a better street engine overall

I have always been against the" use every MM of the lifter diameter" for most guys as it gives away that safety margin Mopars enjoy and for what? a few extra HP on a unit that will have plenty? Just never made sense to me

With all the stroker stuff these days most street guys can't stick it to the road anyway and that 340 4 speed with a 410 gear walks off from them better than they thought

Last edited by crabman173; 04/24/18 07:10 PM.
Re: Cam selection 520ci [Re: RRandP92] #2487431
04/24/18 07:18 PM
04/24/18 07:18 PM
Joined: Jan 2014
Posts: 23
TN
RRandP92 Offline OP
member
RRandP92  Offline OP
member

Joined: Jan 2014
Posts: 23
TN
Thanks guys I will check with Dwayne when i get a few mins to see what he says. A Youtube video is the only reason i looked into it as a similar 512" made good power with a flat tappet with slight bit more duration and little less lift vs. the .690 comp. flat tappet 324adv. 290@.050 and .650lift VS. Roller 323adv. 287@.050 and .690lift both on a 108LSA. I would be happy with the power the 512" made on motor. Planning on the recommend harland sharps rockers also. Building this to run dragweek this year.

https://www.youtube.com/watch?v=UTqqc6Gu4ks

Re: Cam selection 520ci [Re: RRandP92] #2487463
04/24/18 08:35 PM
04/24/18 08:35 PM
Joined: Oct 2007
Posts: 4,205
New York
polyspheric Offline
master
polyspheric  Offline
master

Joined: Oct 2007
Posts: 4,205
New York
More displacement means less valve area per cubic inch = more overlap, and smaller LSA.
Those high LSA numbers are how you hide the displacement when the duration is huge.


Boffin Emeritus






Powered by UBB.threads™ PHP Forum Software 7.7.1