Chevy Springs Mod + Port/Polish Qs
- Thread starter theKnifeArtist
- Start date
Call Comp Cams direct...they are $31.92 for 12
http://www.compperformancegroupstor...=CC&Product_Code=975-12&Category_Code=SPRNGSI
http://www.compperformancegroupstor...=CC&Product_Code=975-12&Category_Code=SPRNGSI
nice thanks!
question: these springs are stiffer right? wouldn't this cause more valvetrain friction?
and also, do i need to get a 3 angle valve job? and are there 2 or 3 angles on the exhaust valves?
question: these springs are stiffer right? wouldn't this cause more valvetrain friction?
and also, do i need to get a 3 angle valve job? and are there 2 or 3 angles on the exhaust valves?
theKnifeArtist said:
Yes, the springs are stiffer, that's the whole point
. You shouldn't have to worry about the valve train or friction when you shim it after putting these in and you are using proper oil for your engine and running on a healthy, relatively free flowing oil system.A Valve job is always something good to have done while you're at this stage. And screw the 3 angle, go 5 or more
.
5 angle valve job? that not overkill? how much would a valve job cost me. ...oh boy here it comes..
If you go more than 3 angle make sure you specify at least a 1.5mm wide seat if not you'll be redoing it in 3000 miles. (trust me on this one)
do i really need anymore than 3 angle? and does the stock exhaust valves has 2 or 3 angles? do you know how much this would cost me?
3 angle is fine there's NOT a lot of HP to be had compared to reduced service life with narrow seats.
NFI on machine shop prices there sorry I'm sure one of the US based guys will have an idea, as with everything though you get what you pay for and a good job will cost more than a mediocre one.
NFI on machine shop prices there sorry I'm sure one of the US based guys will have an idea, as with everything though you get what you pay for and a good job will cost more than a mediocre one.
300 for the valve job, 175 for the valve adjustment (for brand new valves). That's what I paid in labor 1 month ago. I wouldn't waste the time on a valve job using old valves, I'm sure I have pics of my 130k mi valves somewhere...
so i think the intakes are reusable because they look real good, so im assuming i'd need to replace the exhaust side right? how much would these 12 valves cost me? would i have to get the new valves cut if i was gettin a valve job?
well, im not looking for anything special, stock ones will be fine. how much? where can i get em?
Adjuster
Supramania Contributor
Personally, unless you have a valve that is burned or warped, and that's not very likely, I WOULD NOT DO A VALVE JOB.
Keep all your shims and buckets seperate for each valve. (Use an egg carton and label it with a sharpie pen.)
If you do not mix up the valves/seats/shims/buckets, you don't need to adjust anything..!
Just replace the seals, do your port work, but do not nick the valve seats... (If you have a used intake and exhaust valve laying around, this is a good time to use them as a guard to protect your seats when your blending your combustion chambers...)
Tape up the seats with 5 layers of masking tape at the seat. (That way you hopefully will not nick them if you get wild with the die grinder.)
Blend all sharp edges, and as noted, don't port out your exhaust the whole way, unless you then port open the manifold 1mm or so wider. (You want the sharp lip there to create a barrier to gas going back into the port, makeing it a one way hole so to speak, and this helps to improve low end tourqe without losing much on top if anything for flow going OUT of the head.)
I ended up doing a little of both. Ported closer than 1mm, and then opened up the exhaust manifold a 1mm or so larger than the gasket, with it then tapered back to the manifold runner size like a venturi.
Seems to have worked, my tourqe is very good. (But then again, I'm running 6.5mm more stroke, 1mm larger valves, and the CR is 9:1)
I don't remember the exact numbers at the moment, but it was up near 400lbs at close to similar HP levels.
Dr. J port matched his exhaust, and has said that he thinks his low tourqe results were connected to having no lip there. (His HP numbers were pretty dang good, so the engine was running well.)
Just my .02, and yes IJ, just about any valve springs can be broken, but I don't think the Comp Cams are going to be a problem with anyone running stock TCCS rev limits.
Keep all your shims and buckets seperate for each valve. (Use an egg carton and label it with a sharpie pen.)
If you do not mix up the valves/seats/shims/buckets, you don't need to adjust anything..!
Just replace the seals, do your port work, but do not nick the valve seats... (If you have a used intake and exhaust valve laying around, this is a good time to use them as a guard to protect your seats when your blending your combustion chambers...)
Tape up the seats with 5 layers of masking tape at the seat. (That way you hopefully will not nick them if you get wild with the die grinder.)
Blend all sharp edges, and as noted, don't port out your exhaust the whole way, unless you then port open the manifold 1mm or so wider. (You want the sharp lip there to create a barrier to gas going back into the port, makeing it a one way hole so to speak, and this helps to improve low end tourqe without losing much on top if anything for flow going OUT of the head.)
I ended up doing a little of both. Ported closer than 1mm, and then opened up the exhaust manifold a 1mm or so larger than the gasket, with it then tapered back to the manifold runner size like a venturi.
Seems to have worked, my tourqe is very good. (But then again, I'm running 6.5mm more stroke, 1mm larger valves, and the CR is 9:1)
I don't remember the exact numbers at the moment, but it was up near 400lbs at close to similar HP levels.
Dr. J port matched his exhaust, and has said that he thinks his low tourqe results were connected to having no lip there. (His HP numbers were pretty dang good, so the engine was running well.)
Just my .02, and yes IJ, just about any valve springs can be broken, but I don't think the Comp Cams are going to be a problem with anyone running stock TCCS rev limits.
We just tested the seat pressure on a old set of stock springs, it was 40lbs. The Comp Cams 975 springs were 55lbs, and the BC springs were 53lbs. Our head builder recommended 75+ lbs seat pressure for a high reving engine that will see 20lbs of boost or more. The only problem is that all the springs with that high seat pressure are about 10x the price. I really can't see spending Ferrea prices when you can get 1mm os valves and TI retainers from Brian Crower. No one here is building a money is no object race engine. 40lb stock springs will rob hp at high boost levels. Think about it, if you're running 20psi at 6500rpm, the boost is trying to keep the valve open, plus the weight of the valve, bucket, and shim gets incredibly heavy for the spring to close at high rpm. Just because you don't hear obvious valve float does not mean the valves are closing properly.
The whole 5 angle valve job thing is not going to do anything better then a 3 angle except cost more. Our machine shop uses a Serdi valve machine. Most machine shops don't have one because it costs around $35,000+. It is far more precise then a standard machine that uses gringing stones, making a purfect seal every time.
The only way to know if you need a valve job or not is to do a pressure test on the head. If you have leakage then you probably have pitting on the valves. Part of the reason for that is the low stock spring pressure. Carbon is very hard, and if the spring pressure is too low the carbon does not get broken down and removed, it gets stuck there and impregnated into the valve and seat, causing pitting and leakage.
The whole 5 angle valve job thing is not going to do anything better then a 3 angle except cost more. Our machine shop uses a Serdi valve machine. Most machine shops don't have one because it costs around $35,000+. It is far more precise then a standard machine that uses gringing stones, making a purfect seal every time.
The only way to know if you need a valve job or not is to do a pressure test on the head. If you have leakage then you probably have pitting on the valves. Part of the reason for that is the low stock spring pressure. Carbon is very hard, and if the spring pressure is too low the carbon does not get broken down and removed, it gets stuck there and impregnated into the valve and seat, causing pitting and leakage.
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good info guys! thanks!! well i havent gotten to cleaning up the valves a little bit but when i do, scotch brite would be safe to clean off the angled part of the valves right?
from playing around with bikes and whatnot almost all my life, that is normal. look at the space in between each "loop". its just not settled.