Cam sizing

-
B

bbizelli

Well-Known Member
Joined
Feb 23, 2010
Messages
129
Reaction score
8
Hey guys im looking at putting a new cam in my 318 thats in my duster. I have found one that im interested in http://www.summitracing.com/parts/CCA-CL20-671-4/ its a .484 lift cam or http://www.summitracing.com/parts/CCA-CL20-672-4/ .508 cam i have a set of stock 318 and a set of 360 J heads. My main questions are would i have to change valve springs or do anything else to the heads or anything? Also ill be running a 650 double pumper with a 360 intake while i try to find a cheap used aluminum single plane intake. Any and all help is greatly appreciated im trying to make some more power out of it to run at monster mopar!!
 
What gears and converter do you have? Do you know your compression? Also you will need to change springs. I had a similar combo to what you are building. .484 cam and m1 intake. It sounded great but, wasnt very fast. Went with a smaller engle cam 216 at .050 int and ext. with .456 lift and 113 lc, and a 360 intake with the plenum milled. Car has stock converter 3.91 gears. went from a 15.05 at 88mph to 14.1 at 98mph I also picked up 5mpg.
 
I have 323s right now but im working on a deal for either 355s or 373s. A 2500 stall i believe. And its a stock 71 318 .30 over bore with a small cam. Just looking for some more pick up and a harder lope. Would it be better to run the 318 or 360 j heads also?
 
I got into this when I rebuilt the 727 behind my 340. I vaguely remember the stock 10" converter for a 340 is around a 2400 stall.
Bigger port heads off the 360 generally will loose bottom end torque on a 318 (possibly a bunch), but gain power at higher RPM if the car has the gearing to allow you to get to that higher RPM. Bigger port heads (J in this case) are going to be the best match to the 360 intake. Too much cam (duration and overlap) will give you a soggy bottom end and the J heads and larger port 360 intake on a 318 will make it worse. Spreading out the valve events (110 to 114 degree centerlines) will give less overlap at any given duration/lift and tame down any cam somewhat.
Staying with a stock spreadbore carburetor should give you just as much (or more) top end as a square bore Holley and be far more forgiving of the smaller displacement, too.
 
Both of those cams could be a bad choice for your build. You don't have the gears, converter, compression and the list goes on.

Your stock springs will not work.


It would basically be a disaster.
 
That 108 centerline ought to chop well! Nice size cam.
 
I agree those 2 cams listed in post #1 are way too big. Just to make them work you'll need to have the spring pads cut to accept dual springs and have the guides cut down to accept the lift (ok, the 1st one might be ok with the lift but it's a gamble I wouldn't take). The cam Moturbopar listed looks much better and you shouldn't have to do anything to the heads except put on some better springs. And if their in good shape keep the 318 heads on it or you'll most likely loose low end torque like tqofosho said. What little gain you'd see with the 360 heads would not overcome the loss of torque. It doesn't take much cam to make a teen lope and one ground on a 108 center will sure help it plus still have decent low end torque which you need with a small cube motor and less than 3.91 gears and 3000 stall converter. JMHO
 
What is your static compression going to be? My brother in law put the .508 in a 8.5:1 340 w stock converter and 3:23 gears. Only 100 lbs of cylinder pressure. Biggest dog you ever did see. Not to mention it wouldnt idle in gear. Instead of going the easy route and selecting a diff cam he chose to buy a 3000 converter 3:91s and it was still a dog because of the lack of compression. Eventually he put on some closed chambered heads w thin gaskets to get the compression up to 9.5:1 and we advanced the cam to 104 to get the cylinder pressure up to 140 lbs and it now goes pretty good.
 
You need to listen to Fishy68 and swinger340. The 360 heads have larger combustion chambers and will lower your compression thus you will lose power.
 
so smaller lift and better springs? And dont run my 360 heads i thought they would make it run kinda worse with the bigger chamber. Would running my 360 intake make a difference on it also?
 
You need "Cylender Pressure" Check out Hughes Engines, they have a line of "Whiplash" cams that would be what you are looking for... Nasty idle and bottom end grunt. These cams were designed for low compression motors. Also they are great to deal with, shoot them off an E-mail and take a boo on there site!
 
Using the 360 intake is a no-no too cause it has larger ports and will be a big mismatch to the 318 heads. You need a small port intake.
 
I would run the 360 heads but have them milled. my car is almost 9 to 1 and i personally think from 2000 rpm up its way stronger than if it had 318 heads.
 
1968FormulaS340 said:
Both of those cams could be a bad choice for your build. You don't have the gears, converter, compression and the list goes on.

Your stock springs will not work.


It would basically be a disaster.
Click to expand...


X 2, verbatim.
 
I usually don't....but I'm gonna wave the Mopar Performance banner on this one. I like this choice. http://www.summitracing.com/parts/DCC-4452759AC/

If you scrap the 360 head idea and use 318 heads, your compression will not suffer. That cam above was designed for the 318 as a hot street cam. There is another right above it for the 360. Those two cams work great in their designed applications. I have used both and was very pleased.
 
Its so hard to decide lol im thinking about getting the cam that moturbopar posted http://www.summitracing.com/parts/HRS-CL710991-08/ with new valve springs. And i probably wont use the 360 heads or intake i just got them on a trade and didnt know if the would be better or not. I plan on building a 360 in the winter or so but i just wanna pick up my 318 a little bit and run it at monster mopar also! How hard is it to change the springs when there on the motor? I have a valve spring compressor that i can do it with the heads on the motor but have never tried it like that. Thanks!
 
Changing springs on the engine isn't hard at all if you have all the right tools. Which spring compressor do you have? If it's the one that bolts down to the rocker shaft stands they work real good. If it's the one that has fingers that grab the spring and you crank down a wheel to compress it their not so great but will work on single springs. In addition to the spring compressor you need an air compressor and hose to screw into the spark plug hole to hold the valves in place while your changing the springs.

Hey what trans. do you have in your car? I have an extra 2600-2800 stall converter for a 727 I picked up cheap and didn't end up using. It along with that cam would really liven things up. If ya got a 727 trans. and are interested PM me.
 
Yeah i have the one you twist down one. I may be interested in the converter but after 3 days and finally getting my headers on not really looking at tackling another big project right now lol or take it to my uncles who knows much much more then i lol
 
You must log in or register to reply here.
-

Back
Top