Comp Cams 918 springs
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Most of the time people had no right installing or doing what they did, or in your case intentionally or unintentionally went way beyond the intended limits of the parts and broke something. THEN DONT WANT TO TAKE ANY RESPONCIBLITY!!!! Its like watching Judge Judy, no one gets it....
This thread should say "I over-revved my car tonight and blew it up
" That's it, maybe a little about what happened and how bad it was for everyone to console you a little, but not to throw out excuses on why you don't feel responsible and the parts are to blame
This thread should say "I over-revved my car tonight and blew it up
" That's it, maybe a little about what happened and how bad it was for everyone to console you a little, but not to throw out excuses on why you don't feel responsible and the parts are to blameI'm not too sure how you get off jumping to conclusions about how old I am, nor if I am or am not willing to accept responsibility for the damages to MY car. I mean not even sure what that conversation brings to the thread at all. Bottom line is I missed a shift, yes. BUT the springs were not pushed outside their suggested operating parameters.
Granted, I am not a valve train expert. But I did follow build instructions and I DID measure the PTV clearances.... which most folks don't even bother to do.
Just as the head shops I've called have stated... it's pretty obvious that the clearances were a bit too close and that was made obvious when I over rev'd the engine.
End result, get off your high horse about responsibility this, excuses that. I took it apart myself, I'm paying for the repairs, and I'm putting the thing back together myself. I came out here looking for what products I should use to avoid this happening again in the future, not be lectured on some guy who woke up on the wrong side of the bed and felt like taking his frustrations out on some random e-person.
My $.02
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I'm hearing .090-.120 PTV clearance #'s. Once I get all the parts back together, I'll check it again and see where its at.
Since (again) I'm not a engine builder by trade or anything, which way would the cam timing have to be adjusted to afford additional PTV clearance?
Since (again) I'm not a engine builder by trade or anything, which way would the cam timing have to be adjusted to afford additional PTV clearance?
Thanks for explaining that. I figured it was a give and take scenario. Also like I said before your cam may have been ground a couple degrees off so it may actually be in the wrong place right now so moving it would make it right.
However, retarding it will put the exhaust valve closer to the piston as the valve is open later in the stroke, as advancing the cam puts the intake valve closer to the piston.
My recommendation to you is first get your heads fixed, use the spring the cam manufacturer recommends (or one with similar specs). Next I would measure the PTV clearance on both your intake and exhaust valve again. From there I would adjust to see if you can find a point where both intake and exhaust clearance is sufficient (I use .090 as a bare min) try using 2deg increments. (Remember to use a solid lifter, and an old compressed head gasket when checking)
FWIW, If this were my car I would look at fly cutting the pistons. The reason for this is because valve timing has an effect on how the car runs. When you change it one way or the other the results could be better or worse. This way you can run the cam it the place where it makes the car run the fastest
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When you change cam timing it affects both intake and exhaust. You must pay special attention to the clearance after every change you make.
However, retarding it will put the exhaust valve closer to the piston as the valve is open later in the stroke, as advancing the cam puts the intake valve closer to the piston.
My recommendation to you is first get your heads fixed, use the spring the cam manufacturer recommends (or one with similar specs). Next I would measure the PTV clearance on both your intake and exhaust valve again. From there I would adjust to see if you can find a point where both intake and exhaust clearance is sufficient (I use .090 as a bare min) try using 2deg increments. (Remember to use a solid lifter, and an old compressed head gasket when checking)
FWIW, If this were my car I would look at fly cutting the pistons. The reason for this is because valve timing has an effect on how the car runs. When you change it one way or the other the results could be better or worse. This way you can run the cam it the place where it makes the car run the fastest
However, retarding it will put the exhaust valve closer to the piston as the valve is open later in the stroke, as advancing the cam puts the intake valve closer to the piston.
My recommendation to you is first get your heads fixed, use the spring the cam manufacturer recommends (or one with similar specs). Next I would measure the PTV clearance on both your intake and exhaust valve again. From there I would adjust to see if you can find a point where both intake and exhaust clearance is sufficient (I use .090 as a bare min) try using 2deg increments. (Remember to use a solid lifter, and an old compressed head gasket when checking)
FWIW, If this were my car I would look at fly cutting the pistons. The reason for this is because valve timing has an effect on how the car runs. When you change it one way or the other the results could be better or worse. This way you can run the cam it the place where it makes the car run the fastest
Yep, I typed that too quick and had them backwards. Thanks for the correction. I deleted the incorrect portion from my post so as not to confuse people who reference this thread in the future.
http://www.compperformancegroupstore...Category_Code=
I still don't understand why people want to run that spring over .600" valve lift. It just doesn't have the capacity. And I've also never read it advertised by Comp that the spring is good for xxxxRPM (not to say 7500 isn't do-able with the 918's, but the rest of the valvetrain has to be chosen properly as well).
Regardless, this isn't a spring problem. When an engine is mechanically over-revved like this, a bent or valve or two is fortunate IMO!
I still don't understand why people want to run that spring over .600" valve lift. It just doesn't have the capacity. And I've also never read it advertised by Comp that the spring is good for xxxxRPM (not to say 7500 isn't do-able with the 918's, but the rest of the valvetrain has to be chosen properly as well).
Regardless, this isn't a spring problem. When an engine is mechanically over-revved like this, a bent or valve or two is fortunate IMO!
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Totally agreed, I got off easy.
I'm going to put Patriot 8501s in now. At least I'll get the double spring safety net and I'll have a bit more spring pressure over the 918s.
I'm going to put Patriot 8501s in now. At least I'll get the double spring safety net and I'll have a bit more spring pressure over the 918s.
Comp has said in press releases that they will take .625 lift and they really do. I just set up my 26918s at .060" from coilbind on a .607/.621 lift cam and had to shim every single spring.
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http://texas-speed.com/shop/item.asp?itemid=208
Beehive Shape Ovate Wire Springs
The 26915 and 26918 Valve Springs are specifically designed for the LS1 Chevrolet cylinder head and
can be used as stock replacements or in performance applications all the way up to 0.625” lift and at engine speeds to 7500 RPM. Engineered to fit stock heads with no machining, utilizing the stock valve seat and spring retainer. This valve spring can also be used in all applications with the specifications list-ed.
Installed Load: 105 lbs @ 1.800" 130 lbs @ 1.800"
Open Load: 293 lbs @ 1.200" 318 lbs @ 1.200"
Spring Rate: 313 lbs/in 313 lbs/in
Coil Bind Height: 1.085" 1.085"
Outside Diameter: 1.290"/1.060” 1.290"/1.060”
Inside Diameter: .885"/.656” .885"/.656”
Retainer: TI 772/Steel 774 TI 772/Steel 774
Part # 26915-16 26918-16
Description GM LS1 Spring High Load Spring
The 26915 and 26918 Valve Springs are specifically designed for the LS1 Chevrolet cylinder head and
can be used as stock replacements or in performance applications all the way up to 0.625” lift and at engine speeds to 7500 RPM. Engineered to fit stock heads with no machining, utilizing the stock valve seat and spring retainer. This valve spring can also be used in all applications with the specifications list-ed.
Installed Load: 105 lbs @ 1.800" 130 lbs @ 1.800"
Open Load: 293 lbs @ 1.200" 318 lbs @ 1.200"
Spring Rate: 313 lbs/in 313 lbs/in
Coil Bind Height: 1.085" 1.085"
Outside Diameter: 1.290"/1.060” 1.290"/1.060”
Inside Diameter: .885"/.656” .885"/.656”
Retainer: TI 772/Steel 774 TI 772/Steel 774
Part # 26915-16 26918-16
Description GM LS1 Spring High Load Spring
I'll have to get a Comp rep in here. I wasn't aware our site said that, and I wonder if those are the specs they used a year or so back when they were about to switch to the 26928 part number? If those are current, I would have expected Comp's site to be updated with the same info. I'll see if I can get some clarification, and I'll check a few Monday morning to see which specs they match currently.
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Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Why would you want to be so close to the limit of the springs capabilities? Not arguing just asking. I tend to overbuild things a little and therefore err on the side of caution.