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Discussion Starter · #1 ·
hi all,

finally got the 408 in my bronco. and it is a beast. now the cam is a solid roller, 254-260 @ .050 toploader trans, vic jr. heads and intake 488 gears, 33" tires. right now it has my old edelbrock 750 carb. when taking off it has absolutly nothing under 2000 rpm. which i am not surprised. but it feels like not enough accellerator pump. which is already at max setting.
i have never had any thing with a big cam like this so maybe this is normal. or would a holley that i could adjust accell pump squirt help. or do i just lay a big stretch from every stoplight.
thanks
 

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The cam you have judging purely on the duation numbers you posted really isnt that big of a cam for a 408* topped with vic jr heads.

I think you will find alot more performance from this engine with a properly tuned holley. Vaccum secondary if you choose, they usually yeild a little better fuel economy. Or ya Double pumper which are a little less fussy and generally produce better power at the cost of a little fuel economy.

That motor should have quite a bit of low end grunt once you find your issues.

Joe-
 

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Dump the e-brock and get a Holley. My build is similar and it tears ass even below 2K.
 

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Discussion Starter · #4 ·
what cfm carbs are you running. i am thinking 850 dp with a choke ( cold in arizona)
 

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That IS a big cam. Bigger than the one I run in my 545, and man it idles rough at 1000 rpm with 11.8:1 compression.

What are the rest of the specs on the cam?

Greg
 

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Discussion Starter · #6 ·
its a comp street roller. lift is about .625 the rest of the specs are in the garage right now. it pulls like a freight train from 2000 in any gear. way better than the 351 that was in it. just trying to pull gently from a stop light is impossible. if i keep the rpms at 2000 and feather the clutch, hold on baby.
 

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Discussion Starter · #7 ·
its a comp street roller. lift is about .625 the rest of the specs are in the garage right now. it pulls like a freight train from 2000 in any gear. way better than the 351 that was in it. just trying to pull gently from a stop light is impossible. if i keep the rpms at 2000 and feather the clutch, hold on baby.
 

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Discussion Starter · #8 ·
its a comp street roller. lift is about .625 the rest of the specs are in the garage right now. it pulls like a freight train from 2000 in any gear. way better than the 351 that was in it. just trying to pull gently from a stop light is impossible. if i keep the rpms at 2000 and feather the clutch, hold on baby.
 

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Friend of mine had a very similar combo in a Mustang (with a T5 yikes!!). It's got PLENTY of low end even though it idles at 1200. Check your timing. That can make a big difference. It comes on pretty good around 3500, but its not like a torqueless 289...it's got enough low end to smoke 'em in the first 2 gears off idle. Past 3500, it's a waste of rear tires, period but then again, that car is nothing more than a weekend cruiser so we're not concerned with traction or smooth idle, or any of that. Just lots of fun.

BTW his combo was pretty mucha duplicate of mine. 415" (.060 40
Jr heads & intake, healthy Erson solid (260-268 .600" lift on a 108 LC). His carb is my old 830 annular Holley that I built here at home originally for the race car...but it worked so well that he bought it from me when I went to the dominator and later to the injector.

I would have a good look at the timing curve. When I had mine on gas, it liked 14-16 at 1000 RPM idle and all in by 2000 RPM. Probably could have locked it out at 32 deg but it would be a bear to start it. 32 is about the max that mine would take before ET would fall off.

Come to think of it, my old truck's 514 did the same thing no matter what I did...had the same 750 Edelbrock carb too. I put the dominator on it and it was a totally different engine....but the dominator wasn't street friendly (was only a 2 circuit carb). The 750 may not be a problem, but it was weird how much mine picked up with the bigger carb. Even the low end was better.
 

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It's awfully big for a 4WD with big tires. What kind of trans and converter (auto?) does it have? What kind of rpm do you want it to turn?

My advice would be to install a camshaft around 20 degrees smaller @ 0.050" and buy a Holley 950HP. These have 750 sized throttle bores and an 850 baseplate. They don't really flow 950... maybe 800... but would work great with that combo.

The cam is just too big for a truck with big tires. That cam is for an applicaiton that you don't care what kind of power it makes under 3500 rpm in a 408. Something 20 degrees smaller will yank that thing around like a matchbox car!

Good Luck!
 

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Discussion Starter · #11 ·
it is a muscle car with a front diff. 4.88 gears and a toploader. cruise rpm is over 3000 rpm. it was built with rpm in mind.
 

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Did he just call a bronco a muscle car?
 

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The accel pump on the Edelbrock carbs is pretty weak... on my Bronco with a 460, when I had the Edelbrock 750 on it, I had to have the pump shot on max to keep it from stumbling off the line... and this is a VERY mild 460 stock heads 260/272 (advertized) cam, performer intake, 300hp tops. I'm sure if you threw a Holley 850 on there it would only get better. However, that IS a big cam, and I wouldn't expect it to pull under 2K rpm.
 

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I'd throw a big q-jet at it. Holley's suck offroad. Just too hard to keep fuel slosh under control.
 

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Luv70Fords has a good point... however from personal experience (my current carb on the 460 is an 800cfm Qjet) the fuel bowl on the Qjet is extremely small, so if you went that rout, make sure you do the appropriate mods such as getting the larger float needle/seat, keep the fuel line as un-restrictive as possible and go a little overboard on the fuel pump.
 

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I still stand by my recommendation for the smaller camshaft. It will FEEL more powerful in that bronco. Really.

Top it with an 800 Edelbrock if you are going to do much off roading, and give er' hell!


The 800 Edelbrock is a nice jump up from the 750. The 750 doesn't flow 750. The 800 comes a lot close to flowing its advertised rating. It's a good unit for an off road vehicle.
 

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It's a '70 Bronco... not exactly a heavy truck, I'd be suprised if it weighs much more than a '70 Mustang. But yeah, I'd say you're better off fudging on the small side when it comes to camshaft selection in a mostly street vehicle.
 

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I agree too much cam too. You might be able to cheat a bit if you advance the crap out of the cam (like 103-ish centerline) but my guess is you wouldnt have the valve clearance

A little less cam, actually, I'd go a lot less cam, something in the 240 @ .050 max, probably 108-110 LSA and install it on 106 or so.

You'll give up power at the peaks but it'll make incredible low end and mid range
 
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