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Old 08-15-2005, 17:34   #1 (permalink)
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2v or 4v ..i just dont know

as i read everyones post that have anything to do with heads or port plates, its seems everyone has a different opinion on whether 2v or 4v heads are better when it comes to anything under 7000rpms. i am not saying that i am goin to run out and switch my head selection, but could i have a few people's not violent, arguing, opinion on which heads would be better in my case.

.560 hyd tapped cam 245 dur matched cam. soon switching to (solid mechanical cam .605lift 248dur matched 110 lob sep)
single plane intake
long tubes with 3inch exhaust and spintech proshootout mufflers
4200 stall (launches at 3000rpms)
demon carb 850cfm (slightly oversized<i have no concern on my power from idle -3000rpms.)
9:1 cr
msd pro-billet dist and 6a box
roller rockers
and a 175 nitrous injection
rpm range is 2800-6800

i currently run a set of fully ported 4v oc heads stock valve size and exhaust portplates.
i used to run (still own) a FULLY ported oc 2v set
i dont have much access to a dyno to tell the difference and the change from 2v to 4v was very recent and havent yet made it to the track.
and i actully twisted 7000rpms out of the 2v heads and hyd cam
and when i switched to the 4v heads i can only go 6000rpms (thats why i am goin to a solid cam.)
so what do we think
go solid cam and stick with the 4v's or go solid cam and go back to the 2v's?
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Old 08-15-2005, 18:24   #2 (permalink)
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Re: 2v or 4v ..i just dont know

Quote:
Originally Posted by musclemustang8
as i read everyones post that have anything to do with heads or port plates, its seems everyone has a different opinion on whether 2v or 4v heads are better when it comes to anything under 7000rpms. i am not saying that i am goin to run out and switch my head selection, but could i have a few people's not violent, arguing, opinion on which heads would be better in my case.

.560 hyd tapped cam 245 dur matched cam. soon switching to (solid mechanical cam .605lift 248dur matched 110 lob sep)
single plane intake
long tubes with 3inch exhaust and spintech proshootout mufflers
4200 stall (launches at 3000rpms)
demon carb 850cfm (slightly oversized<i have no concern on my power from idle -3000rpms.)
9:1 cr
msd pro-billet dist and 6a box
roller rockers
and a 175 nitrous injection
rpm range is 2800-6800

i currently run a set of fully ported 4v oc heads stock valve size and exhaust portplates.
i used to run (still own) a FULLY ported oc 2v set
i dont have much access to a dyno to tell the difference and the change from 2v to 4v was very recent and havent yet made it to the track.
and i actully twisted 7000rpms out of the 2v heads and hyd cam
and when i switched to the 4v heads i can only go 6000rpms (thats why i am goin to a solid cam.)
so what do we think
go solid cam and stick with the 4v's or go solid cam and go back to the 2v's?
Wow...pushing 7K with a hydro is asking for it, IMO. I'd try to talk you into going with a solid roller camshaft and using whichever set of heads you think work the best. Your choices seem to suggest a race-only set up. What gears/tire size are you running? I'd have a custom ground solid flat or roller cut for nitrous usage on probably a somewhat different set of parameters than what it seems you've been focusing on. I wouldn't want to make any sort of recommendation without at least knowing the vehicle weight, gear ratio(s) and tire type/size, but, to more closely answer your question, I'd think that the 4V heads are going to be the better choice with nitrous making up the bottom end...assuming that you're launching on the juice. I'd like to see a set of CC 4Vs, but it isn't very practical at this point. The benefit of the quench chamber is a "good thing" compared to the rather "ugly" OC chambers.

I would definitely recommend switching to a 6AL to manage RPM limits. By switching cams, you're going to be switching springs, too. With that in mind, I'd probably be pushing for a roller camshaft since the real costs are the difference in lifter prices, a bronze distributor gear and about $100 more (than a flat tappet core) for the cam core.

Since you're using both OC 2V and 4V heads, I'm guessing that you're in the US. If that is the case, I'd strongly recommend that you seek out a camshaft recommendation from Mark McKeown of http://www.mmeracing.com/ and have him grind you up a custom camshaft for your exact application. If you're going to spend the money and effort swapping cams, get the best you can afford whether flat or roller tappets. I definitely would not use an "off the shelf" cam, as they are "middle of the road" at best, IMO. Granted, some are very good for basic N/A Clevelands, but I would be hesitant to say that the same level of R&D has gone into making shelf cams up-to-date with recent advances considering the relative age of the heads and relative lack of popularity compared to the Windsors.

HTH...

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Old 08-15-2005, 18:47   #3 (permalink)
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Re: 2v or 4v ..i just dont know

thank you very much for your opinion's and help, i am running the combo in a 91 fox hatch with a c6 trans and a set of 4.30's in the rear on 28inch slicks. i wasnt as concerned with getting the 7000rpms back as i shifted at 6500 and just liked having a little bit of a buffer zone.
i would love to go with a custom grind cam and a roller at that, but as most of us are, i am on a very tight buget and unfortunatly its not obtainable for me at this time, the solid cam by comp cams is roughly $200 with lifters and it would cost close to $700 for the roller set up,(between different pushrods, lifters, lifter guideplate and cam).also this is one of many hobbies i have and, middle of the road is about all i can finacially(sp) push. but i really do thank you for your opinion.
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Old 08-15-2005, 19:03   #4 (permalink)
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Re: 2v or 4v ..i just dont know

as far as changing the springs, the springs i have are rated for the amount of lift and there is only 1lbs of pressure difference. the only difference between mine and the ones they suggest is mine is a single spring with a dampener and the ones they suggest is a dual spring. it there a major reason i cannot use the ones i have for turning 6500-6800rpms?
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Old 08-15-2005, 20:33   #5 (permalink)
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Re: 2v or 4v ..i just dont know

Quote:
Originally Posted by musclemustang8
as far as changing the springs, the springs i have are rated for the amount of lift and there is only 1lbs of pressure difference. the only difference between mine and the ones they suggest is mine is a single spring with a dampener and the ones they suggest is a dual spring. it there a major reason i cannot use the ones i have for turning 6500-6800rpms?
I understand your previous point about being on a budget, still, you may want to consider asking Mark about a custom ground solid flat tappet camshaft, as the extra power benefit will be worth another 30-50 bucks.

I'd want to carefully check your springs before making any assertions as to their suitability for a particular purpose. If you know the spring part number, the installed (measured) height, your lobe lift and your rocker arm ratio, then it is possible to calculate everything needed. However, to put all of this into context, a "hydraulic spring" is basically one with lower seat pressure and open pressure than a "mechanical spring." High spring pressures used with hydraulic cams serve to collapse the plunger (internal valving) of the lifter and can cause all sorts of valve event timing oddities.

Higher spring pressures are necessary to control valve float at higher RPMs. This is especially true with large, heavy valves as are common with large valve Cleveland heads. Typical installed seat pressure of about 100# is common with a hydro cam, whereas 110+ is common with a mechanical flat tappet cam. For example, I have a basic, low-budget 351C with 4V CC heads and a mechanical flat tappet cam. I run 150# of seat pressure and use "cool face" lifters. A maximum of about 120-135# would be used with standard flat tappets for a streetable engine.

You need to ask yourself where your seat pressure is in order answer whether or not your "springs" are up to the task. It is not necessarily the material or the part number of the springs, but the installation details and the spring rate. Since you mentioned that the spring rate was the same for mechanical lifters, I'd be a bit suspicious without more details. Usually, springs recommended for mechanical cams have a higher rate than hydro springs, though not necessarily always the case.

One thing is for certain...you don't want to get too much or too little spring pressure throughout the entire valve operating range. Incorrect spring pressures cause all sorts of nasty problems. Too much = flat lobes, debris in the pan and really piss-poor performance. Too little = floating valves at higher RPMs, smacked pistons, broken camshaft dowel pins, sheered distributor gear teeth, bent valves and piss-poor performance.

If you don't know your spring condition, you're inviting a host of problems.

When you compare springs, especially comparing the dual versus single coil designs, you need to add the combined spring rates of the dual coil springs to get the combined spring rate. This can easily exceed a "standard" single coil spring, but, like nearly everything having to do with engines, not necessarily.

The thing that is of some interest is the harmonics involved with springs. Everytime we close the valves, we're basically hammering them against the seats. Some don't realize that the valves usually bounce off of the seats a few times before settling down kind of like dropping a BB on a glass table. Th force of gravity is like the force of the valve spring, though not quite. The hammering produces shock waves through the materials involved. These shock waves are picked up by the valve springs and can have a detrimental effect on their useful lives unless controlled.

The dampener aims to control harmonics. Dual valve springs also control harmonics kind of like the way a multi-chamber muffler controls exhaust noise.

My recommendation is to closely follow the spring recommendations of your camshaft maker. Different ramp designs will affect harmonics! Double check your spring rates using a spring tester and install them carefully to the desired installed height necessary to obtain the rate indicated by the manufacturer based on the actual measured rate for the given spring. Use proper cam break-in procedures and adequate moly lube during installation.

Another note on budgets, spring rates and cam break-in...just one wiped lobe will pay for the extra cost of a roller cam and related pieces if the flat tappet cam isn't carefully attended to...and with infinitely less frustration involved. You could sell a set of your heads to finance your roller cam. You'll make better power and be practically unconcerned with break-in...and, if you ever do occasionally street drive your engine, a roller will live so much better between stoplights than a flat.


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Old 08-16-2005, 07:59   #6 (permalink)
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Re: 2v or 4v ..i just dont know

thanks you for your very detailed information, that is probably the best information that i have ever recieved from one particular person, thank you for taking the time to educated a youngster, so many people just want to tell me how slow my car is and dont want to help. thanks again and i will look into talking to mark about a custom grind.
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Old 08-16-2005, 13:51   #7 (permalink)
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Re: 2v or 4v ..i just dont know

ok i checked the installed load on the springs i have and it reads 120#
the ones it says i need are 125#
the second height of 1.250 (2nd load) mine say 312#
suggested springs are 328#
the max lift it .660 on the springs i have, the lift of the cam with 1.73 ratio rockers is .605
are these springs goin to work for me?
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Old 08-16-2005, 16:59   #8 (permalink)
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Re: 2v or 4v ..i just dont know

Quote:
Originally Posted by musclemustang8
ok i checked the installed load on the springs i have and it reads 120#
the ones it says i need are 125#
the second height of 1.250 (2nd load) mine say 312#
suggested springs are 328#
the max lift it .660 on the springs i have, the lift of the cam with 1.73 ratio rockers is .605
are these springs goin to work for me?
I doubt 328 open will cotroll a cam revving to 7000 and 605 tho lift.
I have a 570/590 solid flat tappet that has 140 closed and 390 open that works good. Double springs with dampner. This is what the cam companys recomended me.
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Old 08-16-2005, 17:08   #9 (permalink)
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Re: 2v or 4v ..i just dont know

I had 335lbs open and it rev'd to 7000rpm no worries but when you looked at the tips of the valves after 5000 k's the valve tips were concave. Showing they were boucing but weren't audible.

My current springs are 390lbs open but I have shimmed them up 60thou. Probably find they are around 400-410lbs.
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Old 08-16-2005, 18:43   #10 (permalink)
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Re: 2v or 4v ..i just dont know

sry correction open pressure is 345 #
seat pressure @installed 125#
and the spring that i currently have are 340# open
120# installed
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