Hello guys! I've been lurking for a while, and finally I need some specific input.


Ive got an 86 F250, long bed, 4wd, super cab, lariat, with a 4bbl 351W and C6. Its got some sort of hooker long tube headers on it. Everything else, including stall, is bone stock. This motor was rebuilt about 13yrs ago, but has less than 40k mi on it since.

To make a long story short, it's a dog. It was originally built to pull trailers where the 2wd trucks wouldn't. As a result, it's just OK for pulling (as good as a small block can be) and it is S.L.O.W. And it gets 11mpg at best, so it's not along for my 90 miles-per-day commute.

I want it to be faster, something to put a smile on my face on the weekends; I still love driving this truck more than anything I've ever had.

Sometime in the next 12 months (or so), I will be putting a stroker kit in this truck. Until I do, I'd like to replace this lame-duck cam in it with something more exciting.

I've called Crane, COMP, and Lunati, plus the machine shop that originally built this motor, to get their recommendation.


Current cam:
Speed Pro CS-1084R
.050 Dur: 204/214
Valve Lift: .448/.472
LSA: Unknown

Crane:
Cam(Kit)#18005(2)
.050 Dur: 216/216
Valve Lift: .484/.484
LSA: 110

COMP:
Kit# K35-238-3
Grind# FW XE262H-10
.050 Dur: 218/224
Valve Lift:.493/.500
LSA: 110

Lunati:
Cam#10350702K
.050 Dur: 219/227
Valve Lift: .499/.522
LSA: 112
This option requires new springs and is about $2x$ the others.

The shop recommended something with a Dur @ .050 of 214/224 and an absolute max of .510 "gross lift" (what is that?).

What do you guys think? Feel free to tell me what you've used and your results with them.

Thanks!

 

If your going to buy an "off-the-shelf" cam, then I like the Comp Cams specs the best. The smaller lobe separation will give you a more "lumpy"
idle. The duration is about the max you want on a truck (you're after torque not HP). I ran an Isky cam with 108 LSA in my 460 for a while. It was real lumpy at idle and had a lot of off-idle torque, but idle vacuum was pretty low so the power brakes where not optimum.

Gross lift is "valve lift" - which is the lift at the lobe multiplied by the rocker arm ratio. A lot of cam specs just provide "lobe lift" as they don't know if your going to use 1.5, 1.65, 1.7:1 (or other) rocker arms.

 

I'm not afraid to have a "custom" cam ground. In fact, its usually cheaper, and it was my plan to bring a big companies numbers to a smaller shop and have them make a cam for me.

 

You could try a custom engine builder. I don't think a "big company" cam manufacture will spend the time with you as would a small engine shop such as:

http://www.rmcompetition.com/
or
Evans Racing Engines

You need to provide your build details such as 1) intended use; 2) vehicle weight, gearing, and tire size; 3) transmission type (converter stall for automatics); other engine mods (heads, intake/carb, exhaust, etc.).

Good luck and enjoy your ride.

 

I can tell you in my experience, changing the cam is not going to do much for you. The factory had a mild low rpm cam, and that's what you are going need also to haul loads and pull trailers.

If you want to put another cam in it when you rebuild it, then go ahead. But if you want to swap cams to get more power. I doubt you will notice any difference.

Sounds like you need to mess around with the engine some. Check the timing. Make sure it's advancing when you rev the engine by using the timing light. What rear gears do you have? What size tires are you running?

 

+100 on this, a 351 should not be that much of a slug unless there is something wrong with it or you're making it push 38" tires with 3.08 gears.

If you do go into the motor the 1st thing that has to change are the heads, this is a smog era motor so the heads have giant chambers and of course don't flow near enough for this displacement. And I'm hoping the stock exhaust and cat are long gone, if not this these things have to go, with headers and a good single or dual exhaust this motor will flow so much more air you'll have to rejet the carb.

 

Tires are 285/75-16.
Rear is open 3.55.
As I said, exhaust is longtube headers, true 2.25" (maybe 2.5", can't remember) duals with nothing in them but 24" glasspacks.
I'm not 100% sure what the heads are, like I said, the motor was rebuilt 2001ish.
I've replaced the ignition system entirely in the last year. I've tried every initial advance setting from 5deg to 12deg. I've timing-lighted it to death, the vac advance is working.
The motor runs like a top.
I'm not ruling out heads as an issue, and they will get switched for an aluminum set. But my truck pulls like a tractor to 30 or 40 and falls on its face.

 

You need heads if you want more performance.

 

Noticed you said you wanted hooker long tube headers. Stay the hell away from the 6912-HKR hookers like I have. No sparkplug issues but they have clearance issues with the C6 transmission linkages when you put a pipe on them.

EDIT: read that wrong. But still, there's a warning for everyone.

 

I really appreciate everyone's input, and it serves to convince me that my ultimate plan is best. But only one person has answered my question. What cam grind do you guys think will work best?

 

There is no "best". Everything is a trade-off.

 

Naturally. I'm willing to give up any real towing, and fuel mileage. I have to keep my factory heads and stall for now. I just want to hear opinions on what grind other members would go for.

 

Swapping out your TC (convertor) for a better/more performance oriented stall speed and gearing will give you the most noticeable and immediate kick-in-the-pants feel with your current set-up.

 

If the motor falls on it's face now at rpm then it doesn't even have the cam you think it does.. which is good and bad. Bad that you got lied to but good in that there is lots of room for improvement.
Of all the cams listed I like this one if you can get a decent set of heads on the motor.. like Eddy Performers or better. Without better heads opt for the 35-234-3.
http://www.summitracing.com/int/part...view/make/ford

 

Changing your torque converter and gears will make a big difference. BUT, doing that without making engine changes will be like trying to run a marathon full speed while having an asthma attack. Just isn't going to work right.