Re: Big Hemi breaks up over 6000. Valve springs??
[Re: WarEagle1]
#2935637
06/22/21 01:35 PM
06/22/21 01:35 PM
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Joined: May 2019
Posts: 713 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 713
Lake Villa Il
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Doesn't sound like enough spring to me but that isn't the only factor.
Weight is as well, so if you are running a large diameter spring I would replace it with something with more pressure, smaller overall diameter and Ti retainer. (Not that it was asked but I would prefer solid roller as well)
That being said your current spring pressure may be enough if they are beehives.
Next I would make sure you have stiff enough pushrods.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: A39Coronet]
#2935676
06/22/21 03:34 PM
06/22/21 03:34 PM
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Joined: Jan 2003
Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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You sure it's not ignition related? I'd be swapping out coil or ignition box before I pulled a valve spring unless you find broken ones (could be product of valve float). I'd rule out the ignition system first. I also agree that those spring pressures seem light for a heavy hemi valvetrain.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: an8sec70cuda]
#2935713
06/22/21 04:49 PM
06/22/21 04:49 PM
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Joined: Jan 2004
Posts: 8,307 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,307
fredericksburg,va
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Before we were smart, the Hemi we raced would shoot ducks at 6500 in the 1/4 mile, we only ran 1/8 mile tracks, we re jetted, changed plugs, wires and cap. We were running ONE holly blue with the cross ram and Hollys, was a while before the light came on that we DIDNT have enough fuel in the first place. Check your carbs and fuel supply. How did I learn? I was wrenching on the buddy’s 69 Stang with a 588 cu in Shotgun Roush engine, twin dominators at over 830 hp, popping on the top end same way (8.90 @152) a pro stock guy clued us in, you guessed it, one holly blue. In 1983 no less.
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: WarEagle1]
#2935746
06/22/21 05:59 PM
06/22/21 05:59 PM
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Joined: May 2019
Posts: 713 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 713
Lake Villa Il
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Do you have a data log or screen shot of such?
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: WarEagle1]
#2935829
06/22/21 09:42 PM
06/22/21 09:42 PM
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Joined: Aug 2003
Posts: 43,243 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,243
Bend,OR USA
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It sounds like ignition miss to me or the valve springs. I use to race NHRA stock back when we had to use the original stock valve spring and cam specs, the first motor was a 1968 Street hemi that had 125 lbs. on the seats and 325 Lbs. open with stock lift which was right at .484 lift at the retainers on the intake valves and right at .466 net on the exhaust side, we switch the first motor into a 1970 Challenger with a hydraulic lifter cheater cam and use the same valve spring specs on it, both motors would pull really hard to 7000 RPM with a Hayes S4 ignition box, now known as Stinger ignitions. I race another NHRA stocker 1970 hemi car with the early Mopar chrome box with the blue heat sink and it would pull hard to 7000 RPM also My message is to try one thing at a time but in your case I would look at the valve springs first Did you modify the oil system in the block to oil the rockers full time? If not that is worth doing , Especially on a street motor that gets the oil hot and valve springs hot for long periods of time I groove the #4 cam journal to do that and restrict the holes size to the rocker arms depending on which rocker arms are on the motor, roller rocker on the shaft get a .040 oil restrictor, non roller rockers on the shaft get no restrictor On your deal I would look at 225+ lbs. on the seats and 480 Lbs.+ open depending on how much net lift you have. If over .600 net lift look at 580 to 650 Lbs. open pressure and near 250+ lbs. on the seats you can NOT hurt a steel core solid roller cam with to much valve spring pressure, you can tear up the rollers with to little If you can see bright stripes on the back side of the outer edge of the cam lobes you don't have enough valve spring pressure
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: Cab_Burge]
#2935834
06/22/21 10:01 PM
06/22/21 10:01 PM
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Joined: May 2019
Posts: 713 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 713
Lake Villa Il
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He's on a hydro roller though ^
With smaller diameter spring, ti retainer I would guess somewhere in the 180/425 range.
I've ran more on hydraulic roller but can start tracking/damaging the cam if a 5150 core
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: dthemi]
#2935901
06/23/21 07:06 AM
06/23/21 07:06 AM
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Joined: Nov 2003
Posts: 1,840 NW Indiana
fbs63
top fuel
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top fuel
Joined: Nov 2003
Posts: 1,840
NW Indiana
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I've never seen a hydro go past 6500 in a hemi without a lot of work. I'd bet it's just that it's a hydro. More spring will help, but only to a point. This. The HEAVY valve train in a Hemi does not like hydraulic cams.
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: BigBlockGTS]
#2936308
06/24/21 08:14 AM
06/24/21 08:14 AM
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Joined: May 2019
Posts: 713 Lake Villa Il
INTMD8
super stock
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super stock
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Lake Villa Il
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What is the reason it wouldn't rev with a hydraulic?
I don't like the idea of running one on a hemi due to pushrod angularity but can't think of any reason you -couldn't- get it to 7k just because it's hydraulic
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: INTMD8]
#2936362
06/24/21 10:57 AM
06/24/21 10:57 AM
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Joined: Feb 2012
Posts: 4,454 Morristown Tn.
71birdJ68
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master
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Morristown Tn.
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The rockers with the crazy push rods are just to heavy for a hyd to handle. The spring pressures required won't work with a hyd.
Last edited by 71birdJ68; 06/24/21 10:58 AM.
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: 71birdJ68]
#2936374
06/24/21 11:19 AM
06/24/21 11:19 AM
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Joined: May 2019
Posts: 713 Lake Villa Il
INTMD8
super stock
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super stock
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Lake Villa Il
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I guess that's the reason I ask as far as what specific to Hemi as I've ran 200 seat 450 open and nearly 8k rpm on other hydraulic roller engines with 1.8 rockers and smaller diameter lifters.
With 1.8 rocker that would put 360/810 pound load to the lifter. With the same spring pressures on a hemi and say 1.52 ratio that would put 304/684 pound load to the lifter.
I could see the hemi not getting there due to mass of rockers but don't think pushrod weight should matter much. (at least I've not seen weight on the actuation side clip usable rpm range).
Either way, agreed that I don't like the idea due to pushrod angularity, just wondering if anyone has actually tried higher spring pressure and lighter valves/springs/retainers with hyd roller on a hemi or just didn't as they assumed the lifters couldn't take it.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Big Hemi breaks up over 6000. Valve springs??
[Re: INTMD8]
#2936377
06/24/21 11:32 AM
06/24/21 11:32 AM
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Joined: Oct 2004
Posts: 3,097 back in Georgia
dthemi
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master
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back in Georgia
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I guess that's the reason I ask as far as what specific to Hemi as I've ran 200 seat 450 open and nearly 8k rpm on other hydraulic roller engines with 1.8 rockers and smaller diameter lifters.
With 1.8 rocker that would put 360/810 pound load to the lifter. With the same spring pressures on a hemi and say 1.52 ratio that would put 304/684 pound load to the lifter.
I could see the hemi not getting there due to mass of rockers but don't think pushrod weight should matter much. (at least I've not seen weight on the actuation side clip usable rpm range).
Either way, agreed that I don't like the idea due to pushrod angularity, just wondering if anyone has actually tried higher spring pressure and lighter valves/springs/retainers with hyd roller on a hemi or just didn't as they assumed the lifters couldn't take it.
A wedge with a hydro roller is a completely different animal, and no where near the same load on the valve train. Weight, compound angles, length, length of rocker ect. When you start going to ti valves, retainers, locks, spread lifters, and tons of oil management to make a hydro work, you're already where no one wants to go. Better to buy a high quality set of solids, a small mechanical, and rev to the moon whenever ya want. I get the desire to run a hydro on the street, but beyond that, it seems like wasted energy to me.
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