Does my 451 have to small of a cam?

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Roger Price

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I have a 71GoldDuster with a 451,but it is a slow launcher and has a mild top end.The cam has little if any thump.Please help!
 
400 block steel 440 crank polished/balanced Eagle rods KB flat tops Ported/polished steel 400 heads RPM preformer intake Holley 750 Regulated elec.fuelpump Supercomp.headers 727 trany/TCI shiftkit 1500 stall 8 3/4 posi.3.91gears.All I know about the cam is 470/470 110 lobe sep.
 
What do you mean by slow launcher??Unless you have monster tire on it you should be able to fry the tires at will and launch hard. Your power to weight ratio should be excellent as the 440 Duster I had weighed 3300 lbs with my fat *** in it.

In fact, I had trouble getting the car to hook up, streets tires were a joke as far as hoping to get traction. Your package should easily make 400 plus horse power as a stock 1970 440 six pack motor had 390 horse and I think close to 480 lbs of torque and was strong enough to move a much heavier B body 13.00 flat(Ronnie Sox "Mr 4 Speed" in 1970 took a bone stock B body six pack 4 speed car and managed to get it to turn 13.00 flat.

Put a vacuum gauge on it and if it doesnt go to or near zero at wide open throttle you probably dont have enough carb. With 3.91 gears if you have about 26 inch tires on it you are probably at 6000 rpm (or more)at 120 mph thus your lack of a big top end.. 750 double pumper or vacuum secondary, possible bogging accelerator pump may need adjustment.????? With what you have you should easily be running in the 12's at 110, are you anywhere near that??

As far as the cam making the "big power sound" the cam doesn't have rock the car to make power, for example 327/350 horse chevy small block cam only had .447 lift. I don't know that the mopar 340 cams had a whole lot more than that. The old 409/425 chev motors didnt really have that "big cam" sound either.The best street cam I ever had was right around the same specs as the one you have. Start with one system at a time and troubleshoot it till you get it dialed in. If you have deep pockets take it to a pro who has a dyno. You might consider a little looser converter say around 2500.
 
1500 stall is awfully low if that is what you really have. The big, low stall factory convertors would usually flash higher than that. The proper convertor will really wake a car up. If your cam is .470 lift and 110 LSA i'm guessing it may be a Comp 270. It should run fine in there. A hotter cam would make more power but would be a dog with that tight convertor. If your carb is a VS, the sec. spring may be too stiff to allow the sec. to open all the way. Try a lighter spring and see what happens.
 
pettybludart said:
1500 stall?
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There's one big assed problem, try a 3200 to 3500 stall, cam dependent. What's your initial timing set at, what's your total not including vacuum (plug it if ya got it) and what RPM are you at when you're at full advance. I'd be looking at 12 initial, total 36 and all in at 2200 RPM. Also check that carb out good it could be as simple as the secondaries aren't opening.
 
A 1500 stall cannot be right. That would have to be some kinda towing converter for a Mopar. Mopar stock stall speeds were higher than that. Mopar has always had higher stall speeds than any of the other makers. Their factory high stalls were close to 3K. Usually, the stock stall speed was around 1K less than the high stall. So, if you really have a 1500, that's a big problem as already indicated. If all else fails, lots of nitrous. Lots and lots of nitrous.
 
Plugged exhaust? Maybe the cam is too BIG. Maybe you have a little bitty, REAL poor exhaust

Cam timing? Off a tooth? Worn plastic sprocket? Who put the cam in and how do you know where it's degree'd?

3.91's ??????????? Keeerieeps even a stocker 400 out of a C barge out to be a neck snapper with 3.91's

First, IS THE THROTTLE OPENING all the way?

What is your timing, initial, total? Is the advance in the carb stuck?

What are you running for and air filter? Did the filter get WET?

This thing out'ha be a tire burner so much that you'd have to be CAREFUL driving it not to tear 'em up
 
Cam maybe on the small side, but that stall converter rating is weird and awefully low.

You could step up the program with a bigger cam and for surely a much higher stall converter.
 
1500 stall on that motor combo makes the motor feel like you are stuck in 3rd gear..as they say, a 3200 to 3500 stall should wake it right up.
A 1500 might work on a stock 500 inch Caddy motor.
 
Thanks for all the feedback! Iam learning so all tips given will be used.Iam pos. The converter is 1500. I found the cam specs. 475/475-308/308. Like I said , I bought it prebuilt and as a learner car.I have only had it 2mons.I only made 3 passes at the track and yes, I can melt the tires in the box turning an easy 5k,but running a wimpy [email protected] feels like the brakes are on!
 
that still dont explain no top end. Thats a big bore for a 750. ithink it should have more like a 950
 
daredevil said:
that still dont explain no top end. Thats a big bore for a 750. ithink it should have more like a 950
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Yup yup that's the answer, all right. Won't run? Put a bigger carb on 'er

Hell, the original 375 hp 440's didn't come with that much carb.

My old RR, which is a HELL of a lot heavier than this car, ran 13.0's back in the day, and that was with a 3.54 gear

This was a stock sixpack cam ---a lot less cam than we have here---and a single Holley 750DP

I only ran a single 800DP on a 440 in a '70 Cuda that went 11.8's. This was before I "got out" and did not get it "sorted out." The thing had a clutch problem, and this was launching in 2nd gear, and VERY slow shifts

The carburetor, here, if it is opening WOT and working as it should, is the least of the trouble.
 
You basically have a 440 there. A 451 is a .060 over 440 in a lighter block. If the heads are ported and the compression is not as high as it should be it will feel soft. Take a cylinder pressure reading and post it. If you don't know about the engine then you need to start by pulling a head and taking a look at stuff.
 
I ran 10.9s @ 122 all day long with nothing more then a 750dp (i bought at a swap meet) in my 451 duster, so the carb is not the problem, sounds to me like you have a bunch of issues going on & mix matched parts. The cam may be on the small side, but it should still run alot faster then that. What is your Altitude & what does the car weigh with you in it?
 
All right flame away. If it doesnt have any top end it isnt the converter as mentioned and it isnt the cam as you said your six pack cam was smaller so what is it?I run 750,s on small blocks. That 451 has a rod ratio that needs to breathe is all I was saying. (stolen from Diamondback))>> Get the proper carb for your vehicle- undersized carbs, while great for response will be dead at the top end, run richer as a rule (excess velocity causes main circuits to come in wrong) and usually get worse mileage. Oversize carbs (especially vacuum / air secondary type) will have an untunable low end bog, lazy acceleration and nearly impossible idle problems. Somewhere in between is what we are looking for. A simple equation to get you close : ((Max rpm X CID) / 3456 )X V1. V1 is a variable representing the efficiency of your engine . Use .85 for a normal street engine, 1.00 for a fairly stout street engine ( we're talking close to strip car here) 1.2 for a highly modified strip only vehicle. (Yes< I know these are not the same numbers as some books show, but they work for these carbs) BE HONEST (you don't have to tell anybody) -along those lines do not use 7600 for the rpm on your hydraulic cam 8.5:1 street engine.

EXAMPLE: 440, hydraulic street , 5800 max rpm. ((5800 X 440)/3456) X .85 or ((2552000)/ 3456) X .85 or 738 X .85=627 or a 625 440, 620 lift mechanical, 6800 rpm max ((6800X440)/3456) X 1.00 or ((2992000)/3456) X1.00 or 865 X 1.00=865 or 800 (biggest) or 2 X 500
 
Holy crap!, you guys are awsome! You guys will forget more than I will ever know.DareDevil,those #s blow me away! I just got schooled!! Thanks again,I promise I will everything. Iam here to learn. I will give my cell# if more info is needed. I can call you back if needed so its on my dime.
 
Compression, initial timing, total timing,actual cam specs, what rockers; all the specs have to be known, before any help can happen.
 
That cam sounds like an old school grind. 308 degrees of duration with only .475 lift. Definetly needs a lot more stall with that much duration. Any idea what the compression ratio is supposed to be? Do the tests mentioned and report back. That'll tell us more.
 
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