How much boost can stock valves handle?
- Thread starter white05gt
- Start date
a friend of mine ran 22lbs through a 76mm turbo for over a year on stock valves
I´ve been asking the same for a while now, since I have the stock 24 valves the ported heads came with, though most of the people tell me its ok to use the stockers, the only big suggestion is to change the guides to bronze, since even aftermarket valves tend to fail with stock guides.
Dex, I'm not so sure I agree with this statement. How many posts have you seen where folks with FI cars have had a valve failure with stock valves? The materials the factory used for the stock valves are actually really good. These aren't your basic steal valve in our engines.
If you say the stock rods are a "weak point", you will get nothing but a bit "AMEN!" from me. But the stock valves? I not so sure about that...
Do you have any hard evidence to support your claim?
How many guys have 600+rwhp on stock valves that you know of?
I have no evidence personally but someone I know may. I'll see what I can dig up. Either way, point is dont skimp on anything to save a few hundred dollars.
I have no evidence personally but someone I know may. I'll see what I can dig up. Either way, point is dont skimp on anything to save a few hundred dollars.
Mike@PowerHouse
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The stock valves are better than most give them credit for. I ersonnaly have made over 600rwhp with stock valves for over a season, no issues what so ever.
The springs would be more of an issue than the valves themselves. And that depends on the cam profile that you choose.
The springs would be more of an issue than the valves themselves. And that depends on the cam profile that you choose.
Personally, from what I know of the construction of the stock valves, I'll only replace them when I go with ported heads and larger valves. To me, it's sort of like the block. On our cars, that aluminum block is VERY strong and won't really become an issue until you are coming up on the 800 to 1000 hp level. Definitely NOT a weak link.
I guess it all boils down to the fact that I don't see the point in replacing GOOD parts when I could be spending the money on replacing other weak or marginal parts.
Of course, how many people are running around with FI on a stock bottom end even AFTER all the posts on the assorted posts on what can happen when a rod lets go???
NastyStang113
Made in U.S.A.
I agree ...
EagleStroker
N/A Junkie
Personally, from what I know of the construction of the stock valves, I'll only replace them when I go with ported heads and larger valves. To me, it's sort of like the block. On our cars, that aluminum block is VERY strong and won't really become an issue until you are coming up on the 800 to 1000 hp level. Definitely NOT a weak link.
I guess it all boils down to the fact that I don't see the point in replacing GOOD parts when I could be spending the money on replacing other weak or marginal parts.
Of course, how many people are running around with FI on a stock bottom end even AFTER all the posts on the assorted posts on what can happen when a rod lets go???
This is the only time I've seen a stock block fail:
http://s197forum.com/forum/showthread.php?t=10593
That being said, I still kept mine and have faith in it, although I'm running over sized valves.
Right. And in that post, he even claimed that the problem was caused by a manufacturing defect (core shift). I won't have any trouble keeping a stock block when I get to build my engine the way I want either. I'll even keep the stock valves. Unless, of course, I go with a set of ported heads that have larger valves...
US-1
Banned
Horsepower is not the damaging factor for a stock valve. Heat and detonation are the main factors that cause the stock valves to fail. Detonation will cause the stock valve to fracture and chip. Keep the tune up correct, run good fuel, and you should be in good shape.
Now if you are going to the trouble and cost of ported heads with aftermarket springs and/or cams then I highly recommend doing an aftermarket valve. You can go with the +1mm sizing which will, of course, increase airflow. Not just from the size. You can add a back cut to the upper face of the valve to help the air "transition" to the seat cuts. Can't do that with a stock valve.
Now if you are going to the trouble and cost of ported heads with aftermarket springs and/or cams then I highly recommend doing an aftermarket valve. You can go with the +1mm sizing which will, of course, increase airflow. Not just from the size. You can add a back cut to the upper face of the valve to help the air "transition" to the seat cuts. Can't do that with a stock valve.
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