Posted by Jon Gault on July 12, 2000 at 16:30:10:
I need some intelligent help on deciding how to build a 318 cid engine for
my truck. I am a proffesional Marine mechanic, but have never built up a
mopar engine before and am not sure of the peticulars of this breed. so
please bear with me.
A: THE SITUATION
I have a worn out 1974 4x4 1/2 ton short box Power Wagon that I want to build into a
dependable driver and camper hauling hunting rig for the coastal logging
roads here in Alaska. No freeways here so the highest mph that this truck
will ever see is about 55 mph. The engine is shot but the truck came with a
extra 318 engine out of a 73 chalenger or something. Figure I might as well
rebuild it with some reasonable performance and put it in the truck.
This engine is now set up with a 600 cfm Eldelbrock performer carb, a
Edlebrock performer manifold, 360 heads from a undetermiend year and engine.
But I am having trouble getting solid info about cam and head selections to
reach my goal of the best compromise I can get betweem on/off road
perfomfance, since almost all the good tech info i can find about Mopars is
about big block go fast cars.
Before I get the lectures on torque=cubes vs. rpm vs. gear ratio vs. tire
size etc. etc.,and not being able to get the best of all worlds....please
beleive that I have a fairly good understanding of these and the trade offs
associated with them. I will be adding 36" buckshot tires and lockers and will gear it right for that set up then. This truck has the 4 speed tranny with granny low.
B.SO THIS IS THE PLAN.
Fuel here being very expensive, and often very low grade and hard to get in places, I think staying with the stock 318 block I have will give the best trade off in terms of suitable power,cost,dependabilty,and fuel requirements. Because of a very personal dislike for headers I want to stick with stock exh manifolds and dual pipes even though they dont breath like headers. I also plan on kepping the compression rather stock in order to use the fuel available here.
C. SO HERES THE QUESTIONS.
HEADS: I have both stock 318 and 360 heads. Some folks say that the 360 heads and exh manifolds will breath better in the mid/upper rpm range with little effect on the low end. Others say that the 360 heads on a 318 (and epsecially with the performer manifold) will lowwer the compression and fuel velocity too much and make the engine bog at lower rpms. I'm sure cam selection will have alot to do with either option, but I need someone with real experiance with this to advise me as to the facts of this matter in a truck.
CAM: Lots of good RV type cams out there and I'm sure they all work fine. I do want to stay away from chevy look alikes and get one really made to take advantage of the ramp speed and othe characterstics availabe to mopars. I wont be raceing down the freeway nor will I be pulling the world to a stop. But I will be turning fair sized tires (with something like 4.10 or 4.56 gears)and driving to work daily between camping trips with the camper.
Seems to me that this engine/intake set-up would work good with the 360 heads if I get the right cam. The choice is simpler if I stay with 318 heads. I'd rather stay on the low side than the high side of rpm/tourqe curve but maybe I can hit it just right with some help.
I've been going over the cam specs and theory for a while and kinda like the fallowing cams.(durations @ .050")
1.Hughes Engines inc. cam # HE0914AL In.208drg/.458lft ex.214drg/.470lft 112 dgr lobe sep. high ramp speed and area under the curve.
These guys really seem to know their mopars and give very intelligent reasons why their cams should work better in my small block.
2.CROWER Baja Beast cam #31915 in.200dgr/.423lft ex.208dgr/.441lft 112dgr lobe sep. Looks like a good low end truck cam that might work well with the 360 heads.
3. Mopar perfomance "purple" #P4452757. I would like to think Mopar knows what makes their engines tick and my Mopar buddies swear by them, but they are all into cars not 4x4s.
4.Edlebrock performer cam #EDE-2177 in.&ex.204dgr/.420lft Seems a little generic but maybe Edlebrock knows a little about matching their manifold and carb.
The list goes on but you see what I'm thinking. I would like some feedback from those who have really built or played with a package like this. I've seen some good theories fall short when the rubber hits the road/dirt.
I'm probaly making too much out of this, but since I plan on building this truck as my main transportion (rather than buy a new one) I might as well do the best I can and take advantage of thoughts of some of you smart guys out there in Mopar land.
Jon Gault
addamselene@excite.com
Ketchikan Alaska
"Those who would give up essential liberty, to purchase a little temporary
safty, deserve neither liberty nor safty" -Ben Franklin