Ford Muscle Cars Tech Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
I believe in the "no replacement for displacement" rule. That said: I am putting together a 408 Windsor for a '86 4WD F150 to be used towing a 2 ton camper. 3.55 gear, C-6, 31" tires. Reputable machine shop doing the balanced short block. Scat crank, Eagle rods, Hypereutectic pistons. Keeping compression under 9.5 to live on 89 octane.

Favoring aluminum heads (AFR 205) heads, but concerned that they won't take sustained heat generated, or that bigger motor will produce lots more heat. Truck will get new aluminum radiator, trans cooler, oil cooler and remote filter. Am i limited to Roush 200 or Windsor SR cast iron heads, or safe to make the top end of the motor and cooling system aluminum. The thought here is better thermal transfer, not weight reduction. Is roller cam (retrofit) and roller rockers worth the $$ upfront to cut more friction, or just more hype?

Will bottom end performance be flat with Air Gap intake, or will cubes and more converter compensate? I will not be the cat you follow 35MPH up a long hill. They will be in a bowtie!! Thanks to all blue oval faithful who might shed some light.
 

·
Registered
Joined
·
159 Posts
For that motor with that application I certainly wouldnt use the 205's. Way too large of a port volume for towing applications. I'd look more into the 185's if you want anything resembling low end torque. The aluminum heads will hold up better than iron heads in the long run with their better seat cooling. The 205's numbers look great but you arent going to be running a .700" lift cam and you want to keep the rpms under 5000 and those arent where the 205's shine. Put it in perspective. The 205's flow as good or better than stock rectangular port big block chevy heads . Would you want those on a 400 inch tow motor ?

The reduced "friction" isnt why roller cams are used . Its to open the valves faster and keep them open longer then slam them shut. If you actually had "friction" in an engine it would saw itself to death in minutes. Oil is what you use to prevent friction. You'll need more spring with a roller cam and the roller rockers will live longer at the higher spring rates.
To be honest for a tow motor I'd probably just run 185 heads with the supplied springs, a flat tapet hydraulic cam in the 230-236 @ .050" lift range , a 2000 stall converter ( NO MORE for towing or you'll fry the trans pronto ) . That will get you up the hills without losing your low end power.
Use steel roller rockers for long life and reduced valve stem wear.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Appreciate the logic and reasoning. Trying to build sensible foundation to put in street car when wife tires of camping. My toys have to do work....for now. Stroker and better brakes are cheaper than newer rig to do the job. Fun to surprise folks with a carburated small block too.
 

·
Registered
Joined
·
1,287 Posts
On 2006-12-29 10:08, mikeandnatasha wrote:
For that motor with that application I certainly wouldnt use the 205's. Way too large of a port volume for towing applications. I'd look more into the 185's if you want anything resembling low end torque. The aluminum heads will hold up better than iron heads in the long run with their better seat cooling. The 205's numbers look great but you arent going to be running a .700" lift cam and you want to keep the rpms under 5000 and those arent where the 205's shine. Put it in perspective. The 205's flow as good or better than stock rectangular port big block chevy heads . Would you want those on a 400 inch tow motor ?
I disagree with you here, the 205's on a 400+ inch motor CAN make great low end torque, it depends on your cam design. If you're running an off the shelf...you might be better with a 185 yes. If you're willing to spend a bit more on the cam, you can have great mileage, efficiency, and low rpm performance to boot.

Particularly this:

On 2006-12-29 10:08, mikeandnatasha wrote:
Put it in perspective. The 205's flow as good or better than stock rectangular port big block chevy heads . Would you want those on a 400 inch tow motor ?
You're right...they flow well, as well as the bbc heads you mentioned. With less than 2/3 the port volume, AND more importantly...cross sectional area (just a guess there, never looked up bbc rectangle port volumes, but I'm betting I'm close to right). Guess what that makes on a 400+ inch motor?

Torque.

Too many builders out there are designing motors based on the old tried and true theories, that worked with the old tried and true camshaft designs from a hundred years ago. If that's what you want to go with....throw the 185's on there, or better yet, buy a diesel and get a REAL tow motor. If you're looking for a motor that's efficient, runs great, can do a LOT more than just tow, but will tow VERY well....talk to the custom cam designer of your choice, and let them help you with your head selection. Also...there are a LOT of good heads out there aside from AFR 205's, in similar sizing. Don't limit yourself to the media hype!

Cris
 

·
Registered
Joined
·
159 Posts
I disagree with your disagreement. While I am sure the 205's will make great power with the right cam its not great power that he needs. He needs an engine that is going to see use in a very heavy vehicle towing a load using tall tires and poor gearing for performance. On top of that he needs to use a low stall converter that isnt going to help get the engine into an rpm band where the cam will help the heads breathe. The 185's are heavy hitting heads and on a 400 inch engine are more than capable of supporting 500 plus HP on pump gas . Larger cross chamber ports arent going to help him on that specific application one bit.

Don't get me wrong. I think the out of the box 205's are some of the best heads made for the SBF or any engine for that matter but in this particular instance I think he'd be more satisfied with the overall performance of the engine in his rig with the 185's which are still great heads.
 
1 - 5 of 5 Posts
Top