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 ?
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.
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.
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 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?
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.