I a building my heads on my 04 cobra . What are the best valves and springs and valve guide for running no more than 25 pounds of boost ?
Best valves for a built 04 cobra heads
- Thread starter onefastcar
- Start date
Stock valves
PAC 1223 springs and R312 retainers
PAC 1223 springs and R312 retainers
What RPMs are you turning and what cams do you have? There's no reason to change the factory springs unless you've got aggressive cams with more duration and lift. Even high RPMs above 7k RPMs don't need a spring change. GT500 cam followers will help north of 7k RPMs but the benefit is minimal for the cost.
Malcolm, the factory springs have only ~62 lbs of seat pressure when new. Add 15 lbs of boost behind the intake valve and your in the high 40's which is not real comforting. Chances are his springs were installed at the factory 12 years ago which by now have lost some of their resiliency. Replacing them with a higher rate springs is a good idea which will do a better job to ensure the rockers accurately tracks with the cam profile at high rpm's. The 1223's have 95 lbs of seat pressure which is not excessive and is a nice bump for added insurance. I like the idea knowing my valve train is good past 8K and with a stock cams will be rock solid. On any built engine I can't see myself installing OE valve springs.
I agree on a built motor but he really didn't give any details so we're shooting in the dark. Sounded like a stock short block getting the heads freshened up but who knows. I ran 27.5 PSI to 7k for a couple years on stock springs as do many with no issues. I'm not sure our ECUs even support 8k. All the cars I've seen turning 8k plus either go with the older (I think 97-98) ECUs or stand alone ECUs. The older ECUs had less features and over head and allow for higher RPM.
The thing is we really don't know what the valves are doing at high rpm and big boost. If the springs can't keep-up with the followers will result in valve float. I am sure the factory springs are fine where you can violate the rev limiter. But on an engine taken to the next level I think it's prudent to upgrade the springs and the PAC springs don't have a "stupid level" of seat or lift pressure. When these springs start to loose their resiliency they will still be better than the stock rate chances are you will never need to replace them ........ theoretically speaking.
BTW: PAC and Associated are the 2 major suppliers of valve springs to the OE. If your buying Comp or Tooley springs chances are your getting either PAC or Associated which is a good thing. The science behind valve springs is more involved then most realize.
BTW: PAC and Associated are the 2 major suppliers of valve springs to the OE. If your buying Comp or Tooley springs chances are your getting either PAC or Associated which is a good thing. The science behind valve springs is more involved then most realize.
I agree with SlowSVT .
There was a many page discussion about springs, seats, seat pressures, oversize valves and so on over on ModFords a few years ago.
Consensus was stock valves. New guides, properly honed and sized. The stock guides are a known problem with terrible concentricity (valve not centered in the opening). Springs with not enough clo0sed seat pressure. And with the pressed in valve seats falling out and destroying an engine. The fix for the seats it replacement seats with a greater interference fit when they are pressed in. There is no way to fix the stock seats.
Here is where people are getting their valves with great success. http://www.briantooleyracing.com/50...s.html?page_context=category&faceted_search=0
This is a good read on valve seat materials. https://www.highpowermedia.com/blog/3054/valve-seat-materials
Consensus was stock valves. New guides, properly honed and sized. The stock guides are a known problem with terrible concentricity (valve not centered in the opening). Springs with not enough clo0sed seat pressure. And with the pressed in valve seats falling out and destroying an engine. The fix for the seats it replacement seats with a greater interference fit when they are pressed in. There is no way to fix the stock seats.
Here is where people are getting their valves with great success. http://www.briantooleyracing.com/50...s.html?page_context=category&faceted_search=0
This is a good read on valve seat materials. https://www.highpowermedia.com/blog/3054/valve-seat-materials
I think the valve guide concentricity issue can be traced to "shifting" on a brand new casting once the engine is put into service. The powdered metal guides are pressed in a die which should hold very tight tolerances or the tool wouldn't work very well. I remember reading a short passage in Sean Hyland's book where he broached the issue of poor seat registry to the valve on a new castings after it had been run for a while. Once he pulled the head and re-cut the seat the problem was resolved. This makes sense, a brand new aluminum casting after being exposed to varying temperature differentials especially around the exhaust side (much of the guide is exposed unlike most engines), expansion and contraction and clamping forces that may shift the geometry in the heads a little. At the time I didn't give it much though until I was inspecting my valve seats and heads with 16K on them and noticed the wear pattern on a lot of them did not encompass the circumference they had a shiny crescent appearance. They weren't real bad none of the valves were burned they just need a "kiss cut" but you could tell this problem started at the factory.
As you know when you re-cut the seats your using the guides to register the cutter which will re-true the valve seats to the guides which is something I would not be the surprised if Ford cut the seats independent of the guides. A well seasoned head will have lost all of it's manufacturing and internal stresses long ago and should do a much better job keeping everything aligned.
I don't hear to many problems about the valve seats falling out in this car I would not yank them out without a reason. On a high-end turbo car that is going to be flogged without mercy then the term "seat retention" would cross my mind a bit more.
The thing I hate about this head are those fragile cam baskets
As you know when you re-cut the seats your using the guides to register the cutter which will re-true the valve seats to the guides which is something I would not be the surprised if Ford cut the seats independent of the guides. A well seasoned head will have lost all of it's manufacturing and internal stresses long ago and should do a much better job keeping everything aligned.
I don't hear to many problems about the valve seats falling out in this car I would not yank them out without a reason. On a high-end turbo car that is going to be flogged without mercy then the term "seat retention" would cross my mind a bit more.
The thing I hate about this head are those fragile cam baskets
I hadn't heard of that either but when I took my heads in for work my exhaust valve seats where done. When they attempted to machine them for a valve job one just spun around in the head and was ready to just fall out. Some others they hit just crumbled and fell apart. All the exhaust seats were toast. They replaced all my exhaust seats, intakes were fine. When I enquired about this they told me it was very common on these 4 valve mod motor heads and assured me there was nothing wrong with my motor or heads. They apparently see this frequently.
That's been known to happen. I think the seats are PM, the shop broke it digging it out of the head. PM is the "bomb" for valve guides but hardened steel seats would be preferable.
Powdered Metal
I am turning no more than 6500 rpm . At the moment I have factory cams I am probably going to go with a aftermarket cam now. Yes I sill have the stock bottom end . What happen is I burnt a valve guide and I just want a set of heads that will handle any I through at it .I have a tvs with a 2.8 upper and 4lb lower I run this on 116 I don't want to have to do a another head job cause I didn't buy the right parts
The heads are at the mercy of your tune and the integrity of the valvetrain. Unless your going turbo the factory heads are hard to beat. The OE valveguides are best next to steel (do not install bronze guides in this head). If they have 4 thread spark plug holes get timeserts and install colder plugs to compensate for the loss of heat transfer.
The factory head is fine. Have an intelligent shop perform a good valve job, replace the seats as it is only a matter of time before they come loose. I like BTR springs as they are affordable and are PAC springs but easier to find and typically cheaper. Stock valves are fine unless you are wanting to get into the 3/4k CNC'd head work. The aftermarket valve guide is commonly made from bronze. Bronze performs amazingly well and keeps lubricated better than the factory PM but at the cost of faster wear. It's up to you or your shop to decide which way to go. The 4 vs 9 thread head is almost complete crap, I've run 4 thread heads to hell and back. As long as you aren't an idiot when you replace plugs it's a non-issue. If you want to switch to 9 I prefer lock and stitch and make sure they use the correct insert.
Heat transfer in the extra 4 coils? Are you honestly trying to tell me that you think the few extra coils is enough to change temperature range on plugs?
Heat transfer in the extra 4 coils? Are you honestly trying to tell me that you think the few extra coils is enough to change temperature range on plugs?
No, what I'm saying is steel inserts won't pull heat out of the plugs nearly as well as aluminum which is why you should run a step or two colder with steel inserts. 9 threads have twice the contact area as 4 threads for even better transfer but that's not what I was getting at. To answer that question the word would be "yes"
So you recommend replace all the valve seats regardless, install bronze guides despite the fact they wear out quickly and don't worry about torquing spark plugs into a hole with 4 aluminum threads.
Why in the world would I put a steel insert into an alum head? Why wouldn't I use the proper alum insert?
Yes replace the seats. Most head shops will require you to replace them if it's on a high performance motor as they are terrible from the factory and tend to literally just fall out and destroy engines. I never suggested bronze guides I simply told him it's up to him to decide which he wants because not EVERYONE builds a car one way regardless of how you feel about it. This is a place for information not to demand people what to do. I offered ALL the information and options. You tend to give only what you do to your car and pay zero attention to the other side or what other people might do. It's really frustrating to watch and is one of the reasons this site gets made fun of so much by the more technical places.
For your last comment if you could read, which at this point I honestly question. I said DONT GO CRAZY when isntalling your plugs and you won't have an issue. Know how I know? Because I've done it. For thousands of miles on multiple seats making well into the 800-900rwhp
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