You have the equivalent of going bear hunting with a 22 rimfire. Until you change the gears in your diffs, you will never have the performance that you desire. With 36's I don't know that 4.56's will give you what you want with the 351. I think you might need to go deeper, especially with the c-6, unless you step up to the 400 or spring for either a doubler for the t-case or the E4OD low gearset. Right now you have the worst possible combination that you can get for performance and it clearly shows that you hate it. The cam you have is really not that big. It should perform admirably in a 351. The problem is that you have too low compression, too big of tires, too high gears, a c-6, and you use it in situations that suck a lot of power. If you change one or two of those things you still have other weaknesses. The 400 won't cure all of them just by adding stroke.

For low-end torque the cam you have will probably make a lot in the 400. If you need more low-end, then step up to roller lifters. Adding the compression is a must, but keep in mind the dynamic compression ratio. If you add too much compression and you have too small a cam you can run into some bad detonation problems. At the very least, you will want to polish the combustion chambers and keep them free of oil and carbon so you don't get detonation. That means running very good PC type oil seals on the intake valve stems and making sure that you don't run the engine on it's side or let it go upside down and get oil past the rings.

I haven't run a 262DEH on Dyno2000 but I did run a basically stock 400 with a 265DEH. With 8.0 compression, stock heads, small tube headers, 600 carb with Dual Plane intake, it peaked at 415 lb/ft at 2500 rpm, 306 hp at 4500 rpm. The torque curve was flat as a pancake till 3500, then it dropped off sharply. The HP fell flat then nosed over at 4500. At 5500 were 251 HP and 240 TQ. So you can see that it dies after 4700. If you port the heads the numbers stretch a little, but not much. So you see it's pretty easy to under-cam a 400 when you start spinning them past 5K rpm.
When I ran a 275 DEH with the same combination the top end went up and the bottom end didn't suffer all that much. Peak TQ was 400 at 3500 rpm HP was 316 at 4500. Torque at 2500 was 394 lb/ft.

Keeping this in mind, you can see that the dyno numbers are pretty strong compared to what you have right now. Real world experience has shown me however that dyno numbers are just that, numbers. What you really have to keep in mind is vacuum. If you stick your foot in a 400 with a 750 carb at 2000 rpm with a heavy load, all you will get is a hiccup and maybe a backfire. Less with a 600 carb, and almost no stumble with the factory 325 2bbl.

Once you get the motor figured out, then you have to work on the rest of the combo. The C-6 is notorious for sucking power. You need a good T/C, not the factory P.O.S. If you can't get 1800-1900 of stall out of it in deep mud then you won't ever move it. You have to be able to get over 2500 rpm once things start to move, or you will be stuck in converter stall and going nowhere. I don't recommend going over 2500 rpm stall because the driveability just sucks when you are going slow, especially with the 400. A 302 or a weak 351 can get away with it, but the 400 with a high stall will be a pain in tight situations where you want to ease around.

Once you get your combo dialed in, you won't really notice that you drive a heavy vehicle anymore. Not till you decide to stop.

Good luck and I hope I didn't preach to the choir or offend anybody. Just cruising through and thought I'd give up some of the things I've learned the hard way.

 

Torque at low RPM is mostly governed by the location of the piston in the compression stroke when the Intake Valve Closes (IVC). This is the Dynamic Compression.

A 255DEH cam has an IVC of 53.5 degrees.
A XE256H cam has an IVC 0f 54 degrees.
A XE262H cam has an IVC 0f 57 degrees.
A 265DEH cam has an IVC 0f 58.5 degrees.
A 270H cam has an IVC 0f 61 degrees.

The earlier the intake valve closes the higher the dynamic compression, thus more torque. This is with the intake runner size constant for each cam.

Performance at high RPM involves a number of parameters such as carb size, head flow, valve lift and size, cam duration, exhaust flow etc.

A 255DEH cam has an exhaust duration of 265 degrees.
A XE256H cam has an exhaust duration of 268 degrees.
A XE262H cam has an exhaust duration of 270 degrees.
A 265DEH cam has an exhaust duration of 275 degrees.
A 270H cam has an exhaust duration of 270 degrees.

So, the 255DEH should produce the best low RPM torque, and the 265DEH the best power at high RPM. The 270H is the worst of the lot. If you have a XE262 all you need to do is to advance it 4 degrees, so the the IVC becomes 53 degrees and you will improve the low end torque. The high RPM performance will drop slightly.

 

I'm building a 400 right now, its strictly a Mud Truck. 35" tires are the maximum for my class, and the truck itself is a 79 F150. We have Tim Meyers Flat Tops, a Comp 265DEH, Crane Roller Rocker conversion, Crane Roller Rockers, Comp Extreme Energy pushrods, Comp Extreme Energy Springs, .040" overbore, edelbrock 2171 intake, Demon 625 carb, Doug Thorley headers, port and polish on the heads, port matching on the headers. Tires are probably going to be Goodyear MT/Rs, and so far the tranny is going to be a B & M built C6 for racing.


I've got a lot more work to do.

 

Jfinlen, Could you bump up the cr to 9.7 and run the 265deh again, PLEASE for me that is what I'm running. Thanks, Shawn

 

Ha jfinlen and danlee thanks for those replys, i like it when people will actually sit down and explain stuff. Ya i know my c-6,36's, and 3.50's are killing me. But my motor is the big thing now. I think i will go with a higher stall converter when i put the motor in and put the 4.56's in as soon as possible. I cant go any lower than that and drive it like i do. I figure with the tires i got now and the 4.56's i would spin 2800 or so around 60mph which is as high as i would want to spin it continuously. I should have a nice combo once i get this cam stuff figured out to get my motor done and get the rest of my stuff.

 

4.56s might be a little too short... if you are buying gears, you might consider 4.30s or 4.10s

 

Well Mattsbox99 i would love to go with 4.30's i think they would be perfect but no one makes them for the Dana 44 high pinion front that i have. Unless one of you guys know where to find them at. I can only find them for the 9".

 

as a matter of fact, Randy's does make a 4.27 set... http://www.ringpinion.com/content/pr...sp?vid=1&pid=4

 

Ya they make it for the dana 44. But they do not make it for the reverse rotation that i have in the front. Since it is a high pinion.

 

You don't have a reverse rotation D44, the only vehicles that have that axle are 94-01 Jeep Gr.Cherokees with the 4.7 / 5.2 V8

 

My '79 F-250 had a 400 built almost like the Hot Rod magazine engine. I used a Carter 625 mechanical secondary carb, same as the Edelbrock. Performer intake, Crane heavy duty stamped rockers, HD push rods, double roller timing chain, and cam (same as the Performer cam but a little more lift) not sure exactly what model. Block was decked and heads trued which raised the CR, It had to have 92+ gas. I used .030 stock style forged TRW pistons, melling high volume oil pump etc. It ran VERY well. Originally had a C6 behind it with no problems then put a 4 speed in and it was even better. It had 3.54 gears and 35x12.50 BFG Radial Mud Terrain tires. I ran it to death for about 125k miles and it was idle to red line constantly, in fact probably over rev. I made the mistake of using a stock dura spark ignition and distributer. It eventually killed by the distributer advancing too much at high rpms and the cylinders would fire to far down in the cylinder cracking and breaking the skirts. I wish I could have had it dyno'd. I also used the stock exhaust manifolds and 2.5" exhaust. I would love to build another one.

 

I was checking around today, and it appears that you do have the reverse cut ring gear, and that everyone else uses the regular cut gears for their D44s.

Sorry for the misinformation.

 

I always hear reverse cut and reverse rotation thrown around when referring to these. Don't they spin in the normal direction, but since it's a high pinion and sits at a different angle to the ring gear the pinion is simply cut in a reverse pattern?

 

i went with the edelbrock performer cam and induction package. the cam has a .484''in and a .510"ex lift. duration(not advertised) is 204*in and 214*ex with a 112* centerline. i went with other goodies too to top it off but have no complaints with the whole power range of this cam. it loves the r's too.

 

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