Stutter at 5600 rpm

[gafletch]

440, .040 over, Holley 750 on M1 intake, Doug's headers, manual shift 727, 410 Dana. Stock 452 heads, 93 octane fuel. MSD dist.
At strip this week my 70 Cuda ran a 13.05 at 100 mph. At about 5600 rpm in all three gears it stutters or floats. About 100 to 200 ft before end of quarter.
What does your experience suggest? Heads? Gremlins, lol?
I know it can run low twelves. Thanks, greg.

 

[moparleo]

Is this the first time that you have run this combination? Or have you done any changes to your tune ?

 

[DetMatt1]

What sort of hardware you running for a valve train as far as cam, lifters, rockers and springs? Does it stop stuttering at higher rpm's?

 

[moper]

What camshaft? What was done to the heads? What convertor? What is your timing curve set up?
Honestly - I question if you have low 12s in an E body with "stock 452 heads" and bolt ons - but depending on the tune and answers to the above - you should have something into the 12s pretty easy.

 

[gafletch]

Stock 452 heads, Lunati .480 hyd cam, bought it already built. I think the stall is around 2800 . i disagree tho, about the twelves. Engine builders here say definitely so. If it does a 13.05 at 100 mph 100 yards short of the quarter but floats, it should easily drop a second if its figured out. I'll let you know. Thanks guys. Greg

 

[Cazbah362]

Just a few assumptions. If its stock rockers, need better adjustment/shimming. Valves too tight, does it feel like the rev limiter stepped in? Do you have a rev limiter? Is it adjusted?

 

[gafletch]

Cazbah (cool handle), I'm meeting our local Mopar builder Friday. I'll get back to you on those points. Thanks.

 

[Cazbah362]

Thanks Fletch - Only reason I would go right to valve adjustment is I just had that problem. Valves a bit too tight and I would get flutter like the engine hit a rev limiter at about 56/57K. But keep in mind, the symptoms you describe sound like a few other things too. Too lean (probably would get popping too), not enough timing, or starving the poor little guzzler of fuel (fuel volume), which could be pump issue or low bowl issue or dirty filter issue. So let us know, I am curious as well

 

[burntorange70]

Same thing happened to me first time out with my Dart. Thing would launch good but would crap out in the upper RPM range in each gear. I did not have my throttle cable adjusted correctly. was only getting 2/3 throttle if that with my foot on the floor. Fixed it and picked up close to a second and a half in the 1/4.

 

[gafletch]

Thanks for the help guys. First, not too lean. Second, stock 452 heads and innards. Third, I have msd distributer and coil. Could a limiter be in dist? Also have aftermarket tach. There?
,
. Fourth, Cable seems correct. Fifth, no changes since I bought it last fall. And its only after 5500 rpm.
thanks!
ps how about first names? I'm greg.

 

[Cazbah362]

Greg - how's the progress? I am a fan of the 452's, head selection is spot on in my opinion. If you have the ready to run type distributor, it has the rev limiter built in-http://static.summitracing.com/global/images/instructions/msd-8387_frm30249.pdf

The others have from the box -again assuming MSD. Should be dial or a "pill". Located on the box.

My names is Charles,

 

[gafletch]

Thanks Charles. No box but I'll check my dist model to see if its rev limiter equipped. I've heard some people say they like 452s. But a vacuum test should tell if springs need upgraded. I'll check soon. greg

 

[moper]

Which Lunati camshaft? You bought it built so you don't know what's in it for pistons or anything? What's your fuel system like? Your timing curve? Did it pull clean last year?

In terms of performance - stock the heads flow around 220cfm at peak, and at .480 lift closer to 200cfm. At best, assuimg the general "2cfm per horsepower" guideline - that's about 400hp. And that's assuming the lower end is capable of making that power level. It's simple physics -you cannot accelerate a 3500lbs car to 11s in the 1/4 mile with 400 horsepower at the crank. I think you've got a solid 12.80s pacakage as you describe. It's still no slouch and please understand I'm not trying to beat you down - but the reality is even with pulling for another 300' it won't be anywhere near the 11s.

PS - My name is Dave - nice to "meet" you Greg

 

[gafletch]

Yeah Dave, I agree that mid 12 s is reasonable. The 70 block has a nice lower assembly; Ross pistons, forged rods...
I found a 7000 rpm pill on the MSD box so that isn't the problem. I know the alternator isn't healthy. But sure runs sweet up to 5400 rpm.
Just bought an engine for the Eddy heads. We will install them later. Just got back from Mopar Nat's in central Ohio. Thanks for the input. Greg.

 

[moper]

I think i'd make sure the MSD has full battery voltage to the big red wire, and make sure the ground is good. Then I'd pull a valve cover and check the tension of the valve springs. Does it only do it in high gear or every gear?

 

[moparleo]

Ditto on the charging system. The higher the rpm the more voltage is needed to light the plugs. Make sure you have the original Champion plugs that were oe , not any Splitfire, v-fire or any other plug of the month and make sure you still have over 12 volts at high rpms.

 

[Adrian Worman]

I would have thought that if the heads were totally factory stock, springs, retainers, valves etc, that any thing over mid 5k would have caused some valve float or spring failure.