I have a 1975 Scout II 4x4 with the 304. I have upgraded to the 4 barrel aluminum intake along with a 4bbl 600cfm edelbrock carb. The heads are at the machine shop and will be milled to achieve a 9:1 compression ratio. Everything else is stock and the engine was rebuilt less than 50,000 miles ago. My question is, is it mechanically sound to upgrade to the lower end torque cam found at ihnorth with the mods I am doing to the heads or should I change the order on the heads or replace anything else while I am there (meaning heads, lifters, etc...). I want to avoid a complete engine rebuild if possible. All I want, is lower end torque with better compression. I am also running stans header if that makes a difference in the cam choice.
Choosing Correct Cam??
- Thread starter weddle
- Start date
Robert Kenney
Super Moderator
I guess I would have to ask what cam do you have now as a referance point and which one would you be instelling?.
In general 9-1 compression is ok with a small cam (202 intake duration @.050 tappet lift and less) but could require the use of mid grade fuel in order to run a good total timing say 35 degrees. Otherwise you May need to back that ff to 33-34 to prevent ping.
The only parts you would need to change other than gaskets would be the lifters, so they bed in to the new cam properly.
The headers won't help low end but they most likely won't hurt either. You May be able to run a few dergees more initial timing with them.
Sounds like a good project.
In general 9-1 compression is ok with a small cam (202 intake duration @.050 tappet lift and less) but could require the use of mid grade fuel in order to run a good total timing say 35 degrees. Otherwise you May need to back that ff to 33-34 to prevent ping.
The only parts you would need to change other than gaskets would be the lifters, so they bed in to the new cam properly.
The headers won't help low end but they most likely won't hurt either. You May be able to run a few dergees more initial timing with them.
Sounds like a good project.
Your help is greatly appreciated...thank u
my stock cam size? Good question. Unless International used more than one cam size for the 1975 Scout II 304, then it is whatever the stock is. The stock size would be good to know now that u mention it. I will replace the lifters and gaskets. This project started out as a new carb and turned into a bit more. One of those, "while im there I should do this" type of projects.
Just as long as the lower torque cam wont interfere with the milling of the heads I hope I am fine...as u can probably tell I know a little but not a lot about this topic. I will also upgrade to the dui hei distributor from ihnorth. Since the cam I want is sold by ihnorth im sure it will work for my application. And since the only major head mod is the milling, the compatability is my biggest concern.
If u do know the stock cam for the 1975 is the low torque cam I want much of an upgrade?
Do I need different push rods after the heads have been milled to 9:1 from 8.19:1?
my stock cam size? Good question. Unless International used more than one cam size for the 1975 Scout II 304, then it is whatever the stock is. The stock size would be good to know now that u mention it. I will replace the lifters and gaskets. This project started out as a new carb and turned into a bit more. One of those, "while im there I should do this" type of projects.
Just as long as the lower torque cam wont interfere with the milling of the heads I hope I am fine...as u can probably tell I know a little but not a lot about this topic. I will also upgrade to the dui hei distributor from ihnorth. Since the cam I want is sold by ihnorth im sure it will work for my application. And since the only major head mod is the milling, the compatability is my biggest concern.
If u do know the stock cam for the 1975 is the low torque cam I want much of an upgrade?
Do I need different push rods after the heads have been milled to 9:1 from 8.19:1?
Last edited:
Robert Kenney
Super Moderator
Weddle,
I May have misunderstood you. I see now that you have a stock cam and are upping the compression and installing a larger cam e.g. One with more duration.
The stock cam is about 185-188 degrees intake duration @.050. This equates to a lower rpm torque peak than a cam with 202 degrees intake duration. Like 500-700 rpm earlier to the peak. The stock cam will run ok with 9-1 compression but will require 89+ octane to be optimum.
The 202-202 or 202-208 duration comp cams from comp that Jeff sells need 9-1 compression to give optimum low end torque. So that is the way you plan on going and perfect and will most likely run on pump regular. Headers will help high rpm hp so even better.
After your cam header change, jet the primary and secondary main jets up .005 and .010 respectively. May need a bigger pump shot also but drive it first after jetting up.
I May have misunderstood you. I see now that you have a stock cam and are upping the compression and installing a larger cam e.g. One with more duration.
The stock cam is about 185-188 degrees intake duration @.050. This equates to a lower rpm torque peak than a cam with 202 degrees intake duration. Like 500-700 rpm earlier to the peak. The stock cam will run ok with 9-1 compression but will require 89+ octane to be optimum.
The 202-202 or 202-208 duration comp cams from comp that Jeff sells need 9-1 compression to give optimum low end torque. So that is the way you plan on going and perfect and will most likely run on pump regular. Headers will help high rpm hp so even better.
After your cam header change, jet the primary and secondary main jets up .005 and .010 respectively. May need a bigger pump shot also but drive it first after jetting up.