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| Stiffer valve springs - anyone have them? | |
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| Tweet Topic Started: Feb 10 2010, 12:19 AM (2,399 Views) | |
| puckett02 | Feb 10 2010, 12:19 AM Post #1 |
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I am going to be rebuilding my motor starting with the head. It is my belief that the weak factory valve springs are mostly at fault for the tendency for burning valves. May not be but since I have it apart its worth doing if they are available. I didn't search parts places extensively, thought this place would be the place to ask first |
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| mwebb | Feb 10 2010, 12:47 AM Post #2 |
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FOG
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hmmm i do not know a source for stiffer valve springs but would be interested to know what you base your theory on ? are you planning on using your engine at very high RPM ? |
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| dimetrodon | Feb 10 2010, 12:57 AM Post #3 |
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Hmmm. This reminds me of a discussion I had with a physicist a while back. I mentioned that some folks recommend stainless steel valves for the Metros because the stock ones tended to burn through. He pointed out that SS has a very low thermal conductivity and therefore might tend to get hotter than normal steel valves. This begs the question of valve springs. If they pull harder one might reasonably expect more heat transfer from the valve to the valve seat in the cylinder head. There are probably experts who have done real-world tests. |
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| mwebb | Feb 10 2010, 01:07 AM Post #4 |
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FOG
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i was thinking that a sloppy valve spring will delay the valve closing time at high RPM as the valves will float open while the spring slowly gets around to closing them .... |
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| starscream5000 | Feb 10 2010, 01:31 AM Post #5 |
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Got 70 MPG?
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On the supras we found an unlikely, very cost effective upgrade from the stock springs. Inner valve springs from a small block chevy available from Summit. Someone (don't remember who exactly) measured up the dimensions of the stock spring, along with the measured spring pressure (probably called something else) and found a near identical match in the SBC inner valve spring. They were slightly wider, so you had to ream out the seat a tad bit (and I mean just a tad, not much at all) and they would fit in the head just fine. The spring pressure of the stock ones was like 52 pounds and the SBC's were like 70 something. They cost less than 100 at Summit, quite a bit less than new OEM springs, and several hundred less than Ferrea (sp?) Dual valve springs. Now the only thing you need to do is measure up the stock spring and measure the seat pressure, then go shop around and do some research to find a match. I bet there's a spring out there that will fit that is stiffer than the OEM ones and for a good price to boot
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| puckett02 | Feb 10 2010, 04:21 AM Post #6 |
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Higher rpms is not my goal, but that would be a positive side effect. My theory is the heat transfer from the valve to the seat. A higher pressure spring (maybe 30 percent higher rate or less to keep from damaging the cam and lifters) should provide better seating of the valve. When I get the head out ill measure them up and get looking around. |
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| billy508 | Feb 10 2010, 07:36 AM Post #7 |
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billy508
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I have never used stiffer valves springs in a OHC engine. But in pushrod engines there is a chance of accelerated cam lobe wear. Was not uncommon to flatten a cam lobe. But that was then, maybe todays cams are much better. Just a thought. Also we were using solid lifters which I think maybe contributed to cam wear. It was hard to find until it wore down enough to be noticed. Good luck you may be on to something.
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| dimetrodon | Feb 10 2010, 07:57 AM Post #8 |
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Higher spring pressures will increase the tappet wear, increase the load on your timing belt, and possibly decrease your gas mileage. Don't do it if you are not sure your valves are floating. |
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| puckett02 | Feb 10 2010, 09:58 AM Post #9 |
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Higher spring rates will definitely create more work for the cam therefor potentially more wear. But a mild increase in spring rate will not cause lobe damage and definitely won't create any measurable load on the motor All I'm wanting is to get springs with a normal rate. Being able to remove the keepers from the valve by applying pressure with your fingers is not enough force (for me anyway) If I were wanting to get seat pressure over 100 lbs and open pressure over 250 lbs I would say your right that would be too mixh for the cam, but I think a little more than what's current is no problem I don't know the specs on the factory spring but compressing them by hand is proof of being weak (imo) |
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| Murf 59 | Feb 13 2010, 02:38 AM Post #10 |
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Try SRD he has the springs. With inners and outers too. Is that a word? If you do, Get the SS valves from 3TECH. |
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| Dallas | Feb 13 2010, 03:39 AM Post #11 |
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for what its worth, my springs of unknown condition took lots of hard miles on 28psi to 8500rpm in my 3cyl... so I think they do the job |
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| Murf 59 | Feb 13 2010, 03:52 AM Post #12 |
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I'm with you guys Dallas. The only reason I am running new springs on the Starr. Is its almost 13 to 1. And its only gonna live at the high end. For 99% of the Metros out there, stock spring will work great. Forever |
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| bennie442 | Feb 14 2010, 08:09 PM Post #13 |
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I know that the issue here is valve life as related to seat pressure( contact pressure to dissipate heat ) but, since the seat pressure will be increased, won't the same pressures apply to the lifters as well? It may well mean that the lifters won't be able to open the valves to full spec because of the added spring pressure, thereby reducing the camshaft profile to a smaller dimension IF the lifters can't fully pump up to spec. Just another fly to add to the ointment.
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| Dallas | Feb 15 2010, 04:30 PM Post #14 |
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but 28psi translates to much more combustion pressure than a n/a 13:1 would... I dont see a need to ever ever put upgraded springs in a 3cyl. |
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| 3tech | Feb 15 2010, 05:01 PM Post #15 |
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Keep in mind that's 28 psi on the wrong side of the valve (coming into the intake port) when the valve is closed. |
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Just another fly to add to the ointment.
1:54 PM Jul 11