I had that cam in a stock 440 Ebody.. made it a total dog, took it out and replaced with the .471 MP cam. Much better...

You really need a towing cam to make low end torque. My friend has a 78 club cab 2wd, with stock 400 auto 2 bl.. runs great plenty of power..

replace the cam, tweek the timing.

Thanks for all the input gang. Lots to think about but clearly the cam will be the best bang for the buck if I stay with the 400. I will probably put a small block stroker into it at some point but it seems like a cam change should increase the fun quotient for now.

Also gonna put the 750 carb back on and mess with the timing again, maybe will see some more improvement.

Thanks again! Will update soon.

Have u done a compression check out of curiosity? I say swap in an 833 and see how it is. For the low compression big blocks a lot of guys like the Summit cams (6400 and 6401). The gear spread on an NP435 has no place in a hot rod truck. Even with its low compression (8:1 ish) a 400 in good mechanical shape should burn the tires right off that truck. I had a '77 warlock way back with a .030 over 9:1 440, crane 282/.450" lift cam, headers, stock intake and a tiny Holley carb that would get rubber at a 30 mph roll (auto with 3.23's). The intake u have is probably the best one you can get for your application.
If you're willing to do a stroker SB, for around the same money you could put 4.25 arm in that 400 and have a 512. You're already set up for a BB, I'd stick with that.
An Edelbrock 800 Thunder series is a good carb (I know it's easy for us to spend your money lol!)

The transmission is not your problem. Yes, have driven np435 truck. It's a good off road/work transmission, not really a good choice for a hot rod/race truck. But as stated, that cam is your problem. Who ever put that cam in there made about the worst cam choice he possibly could have. A stock cam would be a leaps and bounds improvement for you. That 284/484 cam is killing your cylinder pressure and your sub 3000rpm power. You should be able to lug that thing at 1000-1500rpm without problem. Also, I suspect your distributor timing is coming in too late. For a smogger BB, you'll want all timing in by the 2000-2500 range.

OK, looked at some cams. Gotta say it's kinda odd looking at cams with such low duration. Last one I bought was a solid FT for the 416 in my Duster that is 251/259 @ .050" with almost .600" lift lol.

#1 Hughes HUG SEH1016BL-12

#2 Hughes HUG SEH1620BL-12

#3 Comp XE256H

#4 Comp 255DEH

#5 Comp 252H Says it requires 9.1 c.r.

Any other suggestions? Anyone use any of these and have any comments on any of these cams?

Will do a compression check tomorrow and see what comes up. Maybe I will do a leak down test too, there is a tick in #2.

If I was forced to pick one it would be the 252h but really a custom one is not much more and the difference would be noticable.

If I was picking from a catalouge it would be this hughes cam
http://www.hughesengines.com/Index/produ...mp;partid=30250

The extra lift hughes gives you will help keep it from choking as the RPM climbs before a shift as long as you get their recomended valve springs.

If I was ordering one from scratch I would get the hughes cam I listed, have them change the ex lobe to be the same as the intake one. That will reduce overlap and that will reduce unburned fuel going out the exhaust as well as give a couple more degrees to push on the crank before the ex valve opens.

I looked at that one too. The lobe lift is basically the same as the other ones just less duration obviously. Will talk to Hughes on Monday and see what they say.

Can you tell if Comp is measuring their lobe lift @ .020" because it's lower than the Hughes. .283 vs .315/.320.

So the 750 carb went back on, it definitely runs better. There is 2 more inches of vacuum, smoother idle, better throttle response and room for more timing without having to idle too high so it's going in the right direction. I did not reduce the jets yet, there are 70s in the front now which are stock for this model. May go down to 68s but it runs good so I'm not sure if I am going to mess with it. Has a pink pump cam in the #1 hole and a brown secondary spring, takes off great.

The reason I put the 600 on was to see if the mileage and throttle response would be better with a smaller carb but no dice, just the opposite. Like Dave mentioned in his first reply it actually ran richer, even with 65 jets. It also idled rougher and had less room for timing. Seems to defy logic a little, all the math for CFM requirements said use a 600 or less. Lesson learned.

I've traveled 100's of thousands of miles with the NP435 in a working PU. 1974 D200 with a 360. That transmission out lasted two engines... never opened up. Yes it is functionally a 3 speed in normal driving... 1'st is for creeping or getting started with a heavy trailer. That truck was peppy even fast for its day with 4.10's and ~29" tires. The NP 435needs matched up to an engine with wide torque curve.

Agree with all the comments... low compression, giant cam and tall gears do not work together.

The only thing to add, is have you considered building the 400? Make it a 451 with a 440 stroke crank and you could have a superb engine. You already have almost everything else (headers, accessories, manifold ect.) and BB Ramchargers are pretty special. With a 451 built for torque, the gear spread on the transmission and 3.23 gears would not be an issue at all. Different truck.

You know, I have been kicking around the idea of a 451. I mentioned I am a small block guy but the one big block part I have held on to is a '230' 400 block. Basically just need a rotating assembly. And some better heads... and well, you all know how that goes. I need to finish the 416 for my Duster before I start building another motor though.

Something tells me a a properly built 451 may get better mileage over the current combo.

Can't hurt to start collecting parts for now...

Assuming the basic long block isn't hurt or worn out, you can do better with a lot of tuning. Just bolting on a carb and changine jets wont cut it.

Yes as stated the cam is a poor choice. But it should do better. Is the cam timing off? Like a whole tooth? I just can see any big block not being able to run 45 mph in 4th unless something is way way off or the thing smokes like a barbecue.

A compression test (leakdown is better) verifying cam timing and some distributor and carb tuning can do wonders and is cheap.

I would like to see you put a 750 DP on it and play around with the jets and squirters. Check fuel pressure also. That carb won't make a 6 cyl run good. Too small.

I agree the 600 was too small. It has a 750 vacuum secondary on it now that is pretty much in it's original configuration from Holley - 70 jets, 6.5 PV, 31 squirter. I did change the pump cam to the pink one from the orange, (there is no bog) and changed the secondary spring from the yellow to the brown. (yellow was too light) The floats are set properly (trickle out sight plug), the transfer slot is a square yada yada yada.

Thought about going down on the jets to 68 but it seems OK right now, not sure it's necessary.

Idle vacuum is around 16", idles at 850. I have not driven around with a vacuum gauge but I'm sure the PV is in the ballpark. I definitely do not need a lower one and I don't think I need it coming in quicker.

Have not checked fuel pressure. Guy I bought it from claimed it had a 'hemi' fuel pump on it, whatever that means. Looks like a Carter strip pump. Guess I should find one of those little pressure gauges...

I put my Proform 750 DP on it briefly and it worked well but I didn't think I wanted a double pumper on it for regular/highway driving.

I personally believe vacuum secondary's are for lighter vehicles. If you have one on a truck I believe it will run poor. You need a good DP carb and I'd be going up in jets to start. I believe your truck runs bad because it's starved for fuel. My 10 to 1 360 with a 509 and a 750 DP didn't run very good until I started increasing the jets and squirters. I can't remember what they were but they were far from stock and every time I went bigger it run better and better.

I agree to an extent that some combos need more fuel than they are supplied with if things are matched properly but no way with my junk. In my opinion, a double pumper would just be dumping fuel with no real benefit.

Comparing your 10:1 small block to my 400 is not apples-to-apples either. My 400 is probably like 8:1 if I'm lucky, probably more like 7.5:1. The lack of compression in this motor is probably the biggest contributor to poor performance here, not the carb. It's why the cam was/is such a poor choice. So if that's the case, (which it is) why then would you think it needs more fuel?

Regarding vacuum secondaries, they work fine if you take the time to tune them. Case in point; under normal driving conditions, the secondaries hardly open, there is not enough signal to pull them open at lower rpms where the truck usually operates.

When I first got it a few months ago, it had a bad hesitation under any sort of load, like when I had to give it some gas going up a hill, the thing would buck like a bronco. It was because the secondaries were being opened too soon by a light secondary spring without enough signal from the motor.

The truck came with a yellow secondary spring in it which was too light. I got one of those Holley secondary spring kits to tune the timing of the opening. I changed the yellow spring out for a heavier brown spring ( 2 steps heavier) to hold off the opening a bit. It worked and made the truck accelerate crisper and much, much smoother - no more hesitation, bog or stumble and pulled to a higher rpm, was like night and day difference.

I actually went down on the jets too from 72 to 70 and my seat of the pants dyno tells me it was the right direction.

AFAIK, your assertion about double pumper carbs working better for heavier vehicles is actually the opposite - DPs generally work better with lighter vehicles. Most of your Street/Truck Avenger type carbs are vacuum secondary.

Some members here are confused as to WHAT the vehicle is. The OP never clearly mentioned it other than the -76 D100 at the bottom of the sig. Is this the truck? Is it a Ramcharger? The OP wants help, right?

Here's the money pit. 76 D100, 2wd, SWB.

These trucks are as aerodynamic as a garage door. The taller they are, the worse mileage they will get.
That is just one issue.
Low compression, wrong cam... Yeah, I agree. I had that cam in a Motor home 440 and while it screamed at WOT, at part throttle it was a slug like yours. I may have averaged 8 mpg freeway (UNloaded) with the 4.10 gear and 32" tires.

If you are trying to keep from swapping engines, milled heads on that 400 can raise the CR by about a point. Add in a stock 440 Magnum cam with better flowing exhaust and it should greatly improve. It will never be a 20 mpg truck even with fuel injection, overdrive and bicycle width tires. What numbers are you looking to get? 12 ? 14?
I agree that your transmission is a POS for a truck not used for low speed grunt work. I have the same trans in my 75 Power Wagon. I'm swapping in a 727 since I'm not a fan of manual transmissions. If mine was a 318 or a 360, I'd seriously look into a 518. There is room there for it and the .70 lock up overdrive helps. When I had a Gear Vendors in my 70 Charger, even their .78 OD made a noticeable difference in cruise rpm.
Do you hammer the truck much or is it a mild daily driver? The 833 OD is not a bad trans behind mild big blocks if you treat it right. I'll bet it has lower rotating mass than your 435 so it saves HP there. The OD is near .70 so you win again. The gear spacing is okay from 2-3-4. The 1-2 is a steep drop off though.

Oh, NICE looking truck!

Thanks for the reply.

Chrysler really saddled us with some poor engine architecture during the '70s, eh? It's like they thought low compression was the answer to everything.

To do what I want here is going to take some bucks. Have been looking at cams, heads, transmissions, gears etc. The current plan on paper is for Stealth heads, a different cam, a Passon 4 speed OD and maybe some steeper rear gears when the OD goes in. Possibly EFI down the road too.

The Passon unit has good gear splits, plus the OD, its exactly what I'm looking for. Stealth heads are just modern versions of the OE heads in aluminum but offer a pretty good option over sinking money into 40 year old boat anchors. I almost have to do it.

Never harbored the idea any of this would be cheap but if I can swing the initial cash hemorrhage it will be pretty awesome.

They were straining to reduce NOX emmisions, that was the really tough one to reduce, that is why compression was so low, also why they had EGR valves and retarded ignition timing, they just did not know any other way to reduce it quickly, cheaply and effectively. Now they have catalytic converters, aluminum heads, high swirl heads, EFI, variable cam timing... lots of tricks to allow more compresison once again. We can apply some of there strategies invented to reduce NOX to our old stuff and improve MPG and TQ.