I'am a mud bog racer we race thru a 200ft pit.Looking for more power in second gear heres a few discriptions of the truck, 77 f-150 frame, dana 70 rear detroit locker with 513 gears,dana 60 front, tracksion lock 513 gears, 205 transfer case with 1.98:1 gears, we use low range in transfer case I run 40 and 44 inche tires not to bad in second gear in 40s but could use a little more it needs lots more in 44 inche tires has ranger body on it, automatic transmission with 3500 ART CARR stall convertor. The thing about mudbog racing is you need lots of wheel speed so the more horse power the better. WAS THINKING ABOUT CHANGING CAM AND INTAKE BUT WOULD LIKE TO GET YOUR THOUGHTS.

Heres some description of the engine, 69 428 Cobra Jet block the letter C casted on the back of the block, bored .060 over. Block has been hard blocked to the bottom of the water pump holes, 1U 428 crank shaft bought from Guess Ford Cobra Jet turned .010/.010, Clevite 77 Bearings, DSC Motorsports H-Beam Connecting Rods, Sealed Power Forged Pistons, Sealed Power Moly Rings, ARP Main Studs, Precision Oil Pumps high volume high pressure oil pump, Milodon 8 QT. rear sump oil pan also been ceramic coated.

Now for the top half of the motor DUI Distributor, Victor Intake, set of 406 Low Rise Heads castings numbers are C3AE-C they have stainless steel under cut swirl polished valves 2.09 intake 1.66 exhaust also has harden seats and bronze guides installed. Precisions oil pumps heavy duty harden rocker shafts, also billett center and end stands harland sharp roller rockers,dsc motorsports push rods, ARP head bolts, Mickey Thompson valve covers, special ground crane mechanical tappet cam shaft advertised duration IN 302 EX 308 duration @ .050 is IN 254 EX 268 valve lift is In 530 Ex 539 RPM range for cam shaft is 3800-6800 valve float is 7400, also has roll master double roller timing chain.

 

Ok, first a few questions.

What carburetor are you running?

What head gaskets are you using?

How much deck clearance do you have on those pistons?

Do those pistons have a dish or valve reliefs, and if so, what volume are they?

What is the lobe separation angle and intake centerline of that cam?

What's the combustion chamber volume on those heads?

 

Thanks for the reply

850 double pumper its been Carb Shopped Flowed to 994 CFMS

standard Fel-Pro head gaskets

.005 five thousands

The book says 10.66 compression ratio with 68 cc head -10.3cc .085 dish with 4 valve reliefs also my heads I think are 67cc casting numbers on the head are C3AE-C and i had .050 milled off them

 

We really need to get the exact compression ratio figured out. My book lists the C3AE-C heads as late 1963 heads for use on 6V 406 motors. It also lists the combustion chambers at 56.4 to 61 cc's.

Really, your compression ratio determines what cam you should run. The reason is dynamic compression. Think of it this way, your motor doesn't start building compression until the intake valve closes. So if you have a motor with too low of compression and a huge cam, performance will not be good. This is because the motor pumps some of the intake charge back into the intake manifold! Less charge in the cylinder = less power. I think this might be what you're experiencing when you hit second gear. At higher RPM's the ram effect kind of makes up for it.

Switching to a smaller cam would restore your low end torque, but it would also sacrifice top end horsepower. A better solution would be to increase compression. A .020" thick steel shim head gasket will definately increase compression, but with only .005" deck clearance I'd be concerned about the pistons hitting the cylinder head at higher RPM's.

But I'm kind of jumping the gun here. We need to figure out exactly what compression you're running now before we go making changes.

Oh, another question:
Are you running exclusively race gas in this thing, or pump gas, or what?

 

Yes I think the compression is up there pistons are supposed to be 10.66 with 68 cc chambered heads and if the cc in my heads are smaller that would raise the compression also I have .050 milled off my heads this thing also takes high torque mini starter to start it regular starters burn up in a hurry. Also I run 110 Torco racing fuel.
Any help is greatly appreciated.

 

I'll guess you have 60cc chambers then.

Currently, I've calculated you're running about 12:1 compression.

Well, here's a few ideas:

Mill the piston tops .010", and run the .020" thick steel shim head gaskets. This would give you about 12.5:1 compression. Since you're running race gas, compression is your friend. The reason for the milling is to keep the pistons from making contact with the cylinder heads.

Upgrade some valvetrain components and run a roller cam. I suggest the Crane 349541 if your block still has provisions for hydraulic lifters.

Port the cylinder heads! FE heads respond extremely well to porting, and those heads are already good. A professional porting job will make a world of difference.

Edit: What oil are you running?

 

Hows this cam sound this is a lunati solid roller camshaft the specs on the cam are The intake duration @.050 is 272 and exhaust @.050 284. It has a 108 degree lobe separation and a 106 degree intake centerline. The gross valve lift is .707/int and .711/exh. This is a camshaft that will make big power and will run up to 8000RPM. Valve lash specs are .022/int and .024/exh.

 

have you considered. maybe a turbo or a supercharger? or NOS.

 

would love to run it but cant with class rules

 

I dont think I'd go that big on the cam. I'd keep it around 300 degrees seat to seat duration. Take a look at the Crane 348821.

I'll run some desktop dyno simulations. I dont know how close the numbers are, but it should give a good indication. I am using flow numbers for medium riser heads, since I dont have flow numbers for low riser heads.

Where you're at now:
513hp @ 5500rpm, 514ft-lbs @ 4500rpm.

With head porting: I dont have flow numbers for ported low or medium risers, but I do have flow data for ported standard FE heads, casting number D2TE-AA. I'll use that. It'll give you and indication of what can be had from porting FE heads. Your heads should flow a lot better after they're ported.
583hp @ 6500rpm, 545ft-lbs @ 5000rpm.

With head porting, and the increased compression mentioned in my last post:
592hp @ 6500rpm, 551ft-lbs @ 5000rpm.

With the head porting, compression increase, and a Crane 348821 roller cam:
636hp @ 6500rpm, 590ft-lbs @ 5000rpm.

Same as above but with the Lunati cam:
622hp @ 6500rpm, 555ft-lbs @ 5000rpm.

As you can see, big gains can be had from head porting and a roller cam. If you believe Desktop Dyno anyway. And if you're going with one of those high lift roller cams, dont even think of not checking valve to piston clearance!

 

I have to agree....when I read your first post.. I noticed your heads werent ported...Going to a bigger cam wont do anything if the heads wont breath...

Got to get the heads Ported....A guy thats real good and very cheap for the work is Les Shmader up in PA, he is very good with FE heads.. JMO..

Russ

 

I'll be the first to admit I'm no expert... so, take with a grain of salt.
Cam notes indicate min. rpm of 3800, and you have a 3500 stall...
I'm wondering, if when the trany shifts from 1st to 2nd if the rpm drop is significant enough to drop below ~3500, and I wounder if the stall really does ramp up to 3500 on the shift?
I also notice that most of the combo's Kurt has ran make peak tq up over 4500rpm...
I wonder if a combo designed to make peak tq right handy to where your gear change/rpm drop occures would help with keeping tire speed up on shifts, rather than bogging(no pun intended) into the next gear?
Porting the heads seems a good idea.
The cam you are running does not seem to have really aggressive ramp rates, at least looking at the spring spec's... from what little I know about cams,

Again, I'm no expert, but, thought I'd throw some things out there for discussion/consideration.

Good luck.

 

And I agree. Based on the torque curve I'm looking at in Desktop Dyno, moving up to a 4000 to 4500rpm stall torque converter would probably be the way to go with the above mentioned mods.

Although, according to Desktop Dyno again, with the above mods it would still be making 523ft-lbs at 3500rpm. But yes, a slipperier torque converter will help.

 

I dont think it will matter that much..cause once the tires start to spin in the mud..its should stay in the cam Tq curve..... JMO..

Russ

 

i do quite a bit of the mud drag scene around here where i live and found some neato tricks... one of the biggest helpers to me was the grinder and gas axe.. i cut, shaved and smoothed all my differentials and frame from anything that didn't need to be there- less places for mud to stick on and weigh you down, also a good mud release agent before you statrt helps.. baby oil from a weed sprayer works pretty good.. what kind of tires do you run? i went from standard tsl's to boggers and it was a night and day difference... JMO a few non motor suggestions..