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  #1  
Old 05-19-2002, 02:08 AM
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cageman cageman is offline
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Default Valve float Valve spring valve crazy

I have had this problem probably for some time now and it has become apparant the problem after I changed to a deaper gear, I always wondered why at a 3/8 track I couldnt turn over 5500 rpms, well I went to a 6.30 gear ( had 6.00) and guess what All I can do is 5500. So I think gee it must be the valve springs, another Dodge racer says hes turning 6000 with 6.00 gears and says he has some springs I can try that he used last year, so today at a 1/4 mile track I change valve springs at the track (boy was that an experience) to a spring thats good to a 500 lift (ive got 455 lift cam, should be good) and the darn thing wont turn more than 5000 rpm. I went backwards.
So my question is, where do I go from here. Would this thing need a stiffer spring. Im checking my old ones tomorrow to see what the rate is and I will compare with one or two of the ones I installed today

Also would me having 202 160 and they have smaller valves be what is causing my problem, There is another guy in a 4 barrel class that turns his 360 7000 rpms and he has smaller valves too, the rest of their motors are alomost Identical to mine too so now what
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  #2  
Old 05-19-2002, 02:16 PM
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DYNO360 DYNO360 is offline
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Default Valve Float

CAGEMAN, It sounds like you might have a cam going south, and it may not be the springs. In another thread you mentioned that your cam was a custom ground piece from Ultradyne, that was smooth at idle, but ran real good out on the track. They may have put an extreme profile on that cam to give you the best of both worlds. You can't get something for nothing. The cam may be wiped! Put a dial indicator on a rocker as you turn the engine over by hand. Zero the indicator at the base circle of the cam and see what the lift reads. If it is off from lobe to lobe, you may have a bad cam. Pull a couple of lifters and look at the contact surfaces too. Also, look at your oil for metal fillings. I hope it is something else, but whatever it is, I'm sure you'll get it running by next weekend.
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  #3  
Old 05-19-2002, 02:24 PM
sanborn sanborn is offline
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Default

I was sorta waiting to see if someone else answered your question because unfortunately I don't know the exact answer.

The purpose of a valve spring is to maintain the lifter in contact with the camshaft at all times. When a spring is too weak it allows tolerance(slop) to occur in the valve train. This allows "valve float" and just as important it allows the valve to "bounce" on the valve seat in the cylinder head. Both situations can allow a loss of power.

I don't know what type of camshaft you are using(solid lifter or hydraulic) but there is a specific range of valve spring pressures you need to maintain good valve train control. Generally the valve spring pressures required are in the following range:
Hydraulic lifter-100 lbs. seat(minimum)-300lbs. at full open lift.
Solid Lifter- 125 lbs to 150 lbs. seat pressure, usually 350-375 across the nose(full lift) for high RPM use.
Roller Lifter- 200 lbs. to 250 lbs. seat pressure, up to 575 lbs. across the nose for high RPM use.

I have a "gut" feeling your problem is not enough seat pressure. Lack of "valve open" pressure usually makes the engine "flutter" at high RPMs. You haven't mentioned that occuring. If the valve is bouncing around on the seat it just allows intake reversion and loss of combustion pressure. The engine just runs "lousy"!

I suspect you need to check installed height of the springs. You probably need to add some shims. Just about any kind of valve spring will control the spring at full lift to turn 5500 RPM.
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  #4  
Old 05-19-2002, 02:39 PM
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DYNO360 DYNO360 is offline
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Default Valve Springs

Sanborn, you brought up some good points, but CAGEMAN said his rpms had fallen off, before he changed springs. Upon putting in a different set of borrowed springs his rpms fell another 500. ??? I hope it is the springs. Shimming the springs would be cheaper and easier than replacing the camshaft.
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  #5  
Old 05-19-2002, 11:08 PM
I8URACING I8URACING is offline
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Default Could it be ignition related?

Looking at spring pressure and cam profile are likely good places to start but and ignition problem can give similar results.
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  #6  
Old 05-20-2002, 02:00 PM
340king 340king is offline
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Default Coil Voltage

Cageman, I agree with I8U. Swapping the springs should have eliminated the valvestprings as a culprit. I do have some concerns with lifter pump-up. Do you use adjustable vavletrain on the hydraulics? I assume so. That should eliminate that.

I had two things cause symptons similar to this. Frist, I had too small of a fuel line in my old street stocker, way back when. I struggled to get it over 5,500 rpm. Then one day I (got) spun in the middle of the corner and had to start form a dead stop. Funny thing was, I hit 6,500 rpm that first lap. Then it went down hill after that.

In my mod, I built a cool 360, just like Roundyroundman's. His turned 7,500, mine just 6,500. Changed gears, no difference. Changed from a chrome box to a MSD box and instant 7,000 rpm, in hot laps. Wow, what a difference.

I have in the past floatied my valves to an extreme extent. In doing so, it sounded like a machine gun going off under the hood. Maybe you have never shot a machine gun, but imagine it anyway. It would run well, even with severe float, until it reached 250°. Then the power went away. I would run way out front in the feature, until the heat went up. Then they woudl drive by like I was tied to a fence post. You should know if you are floating the valves that much. Look into the intake. If there is a bulidup of soot on the intake valve, then you might be floating. Ohterwise, I think it might be fuel or ignition related.

OBTW, coil voltage should be around 8.5 volts for most applications. Check with your coil manufacturer to see what they recommend. Good luck
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  #7  
Old 05-20-2002, 10:02 PM
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I have 1/2 inch fuel line, that cant be
I have a new msd blaster coil, works fine,
Iam going to pull the intake and check the cam and lifter maybe before Ill just pull some lifters
Iam thinking the cam is like that and it looked good on paper, not reality, so Im thinking of putting in a new, and a little better cam
I only have single spring s so doubles are not an option, the ones I had were comp, dont know the number but I put P5249847's in (480''--535'') and it got worse and that still boggles my engine builder's mind.
I raced in Minot on sunday, 3/8 like hometrack and I put the 600's back in and it did just the same, ran like a top till 4999 rpm and as soon as it hits 5000 flutter flutter flutter.
One lap it went to 5300 till it would go, and that was the last lap, so I couldnt back it up with the next lap, so if Iwouldve had the old springs in maybe I wouldve had 5500 at least.

So you think I should just order up a cam that is 484/484 lift at284 duration, It says centerline at 106, how will I acheive that though when I think mine is installed 3 degrees advanced allready, will I need offset keyways or what?
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  #8  
Old 05-20-2002, 10:11 PM
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cageman cageman is offline
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Sanborn I reread your post and my head builder asked me to measure the installed height and hes checking my springs tommorrow too, he said that they should be like 1.62 or something like that and Im reading the mopar parts book and the valve springs I have installed say inst height is 1.68-1.70, I dont know off hand what my heght is though, The guy I got the springs from measured it and said it was OK but Iam curious now.
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  #9  
Old 05-21-2002, 06:20 PM
340king 340king is offline
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Have you measured the voltage at the coil? Even the best coil will not create enough spark without adequate input voltage. I ran the Blaster 2 on my mod with a chrome box and could not get over 6,400 rpm. The 6AL MSD box woke it up.

As for the valvesprings, mine were capable of running up to the 5,500 to 6,000 rpm range before severe float stopped acceleration. They were in the 35 to 75 lbs at seat pressure range. You could push some of them fully open with just your thumb. So I don't think it is your springs. I was running the 340 hydraulic cam with anti-pump up lifters.

Before you get wondering why I would do such a thing, I was in college and had this engine given to me from a co-worker. It was laying upside down in his backyard when he moved into his house. It ran pretty well for about 15 nights of racing, not counting the valve float deal. I did have a set of double springs, but didn't want to disassemble the engine to cut the spring floor$. Funny thing was, the outer springs were way more spring than I needed to make the thing really fly. I would have killed them in the feature had I put the outer springs in. Oh well, just another story about shoulda, woulda, coulda!!
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  #10  
Old 05-22-2002, 02:53 AM
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cageman cageman is offline
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340 KING what is the best way to check the coil voltage and where do you hook what up, It may sound dumb but I want to be sure, do you rev it up too when you check it or is it at idle. I dont think its the coil but I will check er out to be sure. I put a GM alt on this year and she puts out a steady 14. something volts so that is nice, unlike the dodge alt.

I checked my old springs and they had 110 at my installed height that should be fine even with my new cam I ordered, took out 8 of the borrowed springs and Im checking them wednesday
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  #11  
Old 05-22-2002, 10:08 PM
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Im putting 30 thou shims and trying that on the valve springs, well see on friday
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  #12  
Old 05-26-2002, 02:31 PM
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cageman cageman is offline
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Thumbs up

Sanborn you were exactly right, Thank you.
I went to my head builder and asked some questions and he made it sound like he thought they were mopar springs in the heads and he set the inst height for them, when in actuality I had Comp cams springs and they needed another 30 thousandths to be where they are supposed to be. I now have 110 at installed when all I was running befor was 78 pounds what a diff 30 thou makes, Now Im thinking of how much money I spent trying to find this problem, I always thought it was fuel or ignition or other so untill I put more gear in it and the valves were floating bad, it was very obvious what the problem was, Just the answer took a little time.

Thanks for the help to everyone who replied.
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