408 low revs
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408 low revs
Here's the set-up; a 408 stroker, Vic Jr. heads and intake, 850 Demon carb, 253/260 @.050 cam w/ 109 lobe seperation, and 1 7/8 primary 4 into 1 headers. Why would this motor pull from 2,500 -5,500 and top out at 5,500? Shouldn't it turn at least 6,500 and why wouldn't it?
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This is not my motor, I figured the 210 cc Vic Jrs. probably came with adequate springs, This is the second ignition system the guy has (MSD), cam is timed straight up. Don't know what static timing he's running. He's looking into the fuel delivery question now, feeling that maybe g-force from acceleration is restricting fuel flow.
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Hemieater- The guy failed to mention that he was running a Crane ignition that crapped out, and he has yet to make a pass with the MSD. I'll let you know what I find out. Thanks for the input. Kemicalburns, If I get a chance I'll ask him a little more about the cam, I suspected he'd gotten a mispackaged grind, but he claims to have degreed it and it to be right on. His immediate thinking is that its acting smaller because of the stroker set-up, but it seems like that wouldn't tone it down that much.
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Get him to put a fuel pressure gauge on it , install it where he can see it during his run. I have put them on the wiper arm with tape..... my truck would pull first to 6500... slam second and it would only go to 4500 and fall off fast... I put the gauge on it and the fuel pressure was gone before I shifted into second. My little 302 would empty the bowls faster than the pump could fill them.
get the timing to 36 38 degrees at max advance, check the distr find out how much mech advance it has... if it's got 20 mech then set the timing to 16 to 18 at idle.. I use an adjustable timing light, set it to 38 and rev the motor up to 3500 to 4000 and set the timing marks to 0 degrees on the balancer.
the valve springs should be replaces with better springs... most manufacturers will use cheaper springs...
what does it do... does it just fall on it's face?
pop throught the carb?
stumble?
That cam should pull it up way past 5500..
get the timing to 36 38 degrees at max advance, check the distr find out how much mech advance it has... if it's got 20 mech then set the timing to 16 to 18 at idle.. I use an adjustable timing light, set it to 38 and rev the motor up to 3500 to 4000 and set the timing marks to 0 degrees on the balancer.
the valve springs should be replaces with better springs... most manufacturers will use cheaper springs...
what does it do... does it just fall on it's face?
pop throught the carb?
stumble?
That cam should pull it up way past 5500..
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He said it pulled strong all the way, just hit 5,500 and quit going up. By the time I talk to him again, he may have it figured out, but if not, I'll pass on the recommendations. I haven't even asked him what kind of pump he's got, since he's looking into it as a possible problem. Might tell him about the windshield pressure guage, though, slick idea.
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Make sure the choke flap on that big 850 is not sucking itself closed,it has happened to me before running a big block. It was hard to find because it ran perfect and pulled like crazy then just died at 5600 rpm,as soon as rpm dropped it was perfect again. Just wire it open and try.
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