magnum head cam?

-
caferacerx

caferacerx

BAND MEMBER
Joined
Aug 15, 2009
Messages
3,593
Reaction score
51
Location
philly PA
what cam would you recommend for a stock LA 318 with magnum heads 1.6:1 rockers, crosswind intake, 600 cfm holly, dakota exaust manifolds, 4speed, 3:23 gears, 205/70-14's, in a 66 barracuda, just a driver
 
I have a comp cam xe268, 477/480 In my 318, comp cams says thats the largest cam you should run with a stock convertor. The rpm band is 1500 t0 5800, car runs great.
 
The XE268H with the 1.6 ratio magnum rockers is .509/.512 lift. This is about the maximum you can go on a magnum head without cutting the guides down. Also, you can't use the stock springs. When I built my magnum head 360 I used the Mopar Perfromance "R/T" spring which is good for .525 lift.

Oh yea! The XE268H in my 360 works great.
 
what's the duration on that one? 210/220? If so, I've used a very similar one in the past that had a .512 lift on both sides with a 110 degree LSA. It had a slight lope on a 360. I am sure it would be a nice cam on a 318, but I'd recommend a stall at about 2400 to take advantage of it.

When using it with the DODGE MPI system it was VERY weak up against the stock converter until the computer learned the idle, and even then it wasnt so swell. But this was a truck. Maybe the factory stall speed was different in the truck? I dunno. I will say I am so glad to be back to the oldschool again without all that efi doo doo.
 
I'd use the one size smaller cam for the lower compresion 318 in "Just a driver" car and that gear ratio.
 
Id suggest the XE256. I plan to use another XE262 that I currently run in the LA360 in my truck when I add the Magnum heads to the new 360, but I think the 268 and 262 may be a little much for a mild 318/stick with mild gearing.
 
looking for something mild, like a 340 cam, my concern is 1.6:1 ratio rockers on the magnum heads VS 1.5:1 stock LA rockers, the pistons are only about 20 thou. down in the bore with no valve reliefs
 
POS Dakota said:
what's the duration on that one? 210/220?
Click to expand...

The duration on the XE268 is 268/280 and 224/230 at 0.050. That's the advantage of these modern fast ramp cams. For a given advertised duration you get more duration at 0.050. This helps keep the cylider pressures up for low rpm torque and still make power on the top end like a bigger cam.
 
I took into account the ratio increase. I am not sure if you'll have an issue with clearance with the 268. Dave (DGC), do you recall what your piston to valve clearance was? I thought you have valve refliefs but it might help figure how close the OP's are...
 
rumblefish360 said:
I'd use the one size smaller cam for the lower compresion 318 in "Just a driver" car and that gear ratio.
Click to expand...

yep.

besides everyone always recommends the comp 268*, real generic response.jmo

I would consider a custom grind/combo of lobe profiles that fit best, which go's with what rumble is saying about cyl pressure determining most of the profile, after that..it's a give and take between lift/flow-rpm/CL/gear etc..

Thats what I do, unless building an old 'known to work/cookie cut' recipe with a specific easily obtainable et/power goal.

consider the exhaust system-exh port flow of a magnum head and weather you really need a split profile cam or not.

Remember, cam choice should be based your builds specifics, not popularity.

food for thought and nothing more.
 
moper said:
I took into account the ratio increase. I am not sure if you'll have an issue with clearance with the 268. Dave (DGC), do you recall what your piston to valve clearance was? I thought you have valve refliefs but it might help figure how close the OP's are...
Click to expand...

My pistons have deep valve reliefs. With clay it was about .1"
 
That's what I figured... He's got no valve reliefs and the vlave with the 268 cam is going 2/3 of the way down a cut relief. I dont think the .020 below deck is going to help. I think he's going to have valve to piston issues with that xe268.
 
there is a purple P4452761 cam in there now with the stock 1983 2-bbl heads and there is not much clearance between the exhaust valve and the pistons
my other thought is leave that cam in there and use a set of 302 heads to bump compression and a weiand dual plane small port intake with a 500 cfm eddelbrock or holly
 
cc'm still but 302 heads have the same if not a lil bigger chamber than the stock open chamber 318 heads.

ME?
I would maybe advance the cam a lil or degree it in to begin with if not already, run the 600 holley vac sec, and play with the timing curve and fiddle the carb to run best with the 318 heads on it OR cc/mill the magnum heads to get the same or more compression than you have with the 318 heads.
 
302 are closed chamber heads the stock 1983 are open chamber heads about 57cc for the 302 VS 64cc for the stock ones give or take so that should be good for around 1/2 point gain in compression if my information is correct or I could be wrong, just out of curiosity I will CC them both
 
my other option is a bone stock 1999 5.2 magnum motor just not sure which was to go here
 
caferacerx said:
302 are closed chamber heads the stock 1983 are open chamber heads about 57cc for the 302 VS 64cc for the stock ones give or take so that should be good for around 1/2 point gain in compression if my information is correct or I could be wrong, just out of curiosity I will CC them both
Click to expand...

ha, hey.. cc'm and let me know.
 
You must log in or register to reply here.
-

Back
Top