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Teksid 2V Tech Article (Must Read)

Bill

Well-Known Member
Staff member
Donator
Sounds like the discussion we had back in post #4. I'm really glad you are measuring everything. I've seen engines built a lot tighter than what Comp Cams gave you, but those numbers should be easily achieved with a mild notch. Take good pictures. I promise there is someone out there trying to duplicate the build you are doing that doesn't want to have to measure everything. I saw a couple of these at Ford Nationals last weekend, but wasn't able to talk to the owners.
 

Kmax

Active Member
Here are a couple pictures of my PTV clearance issue. I used a piece of aluminum flat bar to see how close the intake valve is to the head deck, and it looks like about .068". The piston to deck clearance is about .006", so if my intake valves are open .050" at 4 degrees BTDC (which is what the cam card specifies), you can see the problem...
 

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Bill

Well-Known Member
Staff member
Donator
I'm guessing you already know this, but for the sake of less experienced/diligent readers, when you have them notched, be sure to clean up the sharp edges of the machine work to keep from creating a hot spot on the piston. We don't like premature detonation under load. I like a piece of sand paper (800 or finer) just to make me feel better about the work.
 

Kmax

Active Member
Good suggestion, i'll make sure there aren't any burrs. Do you know offhand what the "valve drop" (distance between the lip on the factory intake valve and the head surface) measurement is, or should be? I'm wondering if these heads have been aggressively shaved before i bought them. Do you (Bill, or anybody) currently have a set of heads on the bench? I can't find any information about it so far. ...regards, kevin
 

Kmax

Active Member
I decided to check the combustion chamber volume on cylinder #1. I repurposed an old CD case, sealed it to the head with grease, and eventually filled the combustion chamber with about 43cc of isopropyl alcohol, using the very precise measurement tool in the photo. So, it looks like the heads have not been cut down by any significant amount. I've been chatting with Dale from ModMax, it looks like their stainless intake valves don't have the deep dish and raised shoulder that the factory intake valves have, and would give me the PTV clearance i need. I'll need to lap them in the heads, but that'll be easier (and cheaper) than pulling out the pistons, driving about 300km to and from a machine shop, paying to cut the pistons and re-installing them. I hope. The factory exhaust valves have significantly more PTV clearance than the intakes, i'm not worried about them.
On another note, here's a photo of an exhaust port with the exhaust gasket opening marked with a sharpie. Bill, is there any advantage to matching the long side of the port to the gasket/header, or would that reduce exhaust velocity? ...regards, kevin
 

Attachments

Bill

Well-Known Member
Staff member
Donator
I decided to check the combustion chamber volume on cylinder #1. I repurposed an old CD case, sealed it to the head with grease, and eventually filled the combustion chamber with about 43cc of isopropyl alcohol, using the very precise measurement tool in the photo. So, it looks like the heads have not been cut down by any significant amount. I've been chatting with Dale from ModMax, it looks like their stainless intake valves don't have the deep dish and raised shoulder that the factory intake valves have, and would give me the PTV clearance i need. I'll need to lap them in the heads, but that'll be easier (and cheaper) than pulling out the pistons, driving about 300km to and from a machine shop, paying to cut the pistons and re-installing them. I hope. The factory exhaust valves have significantly more PTV clearance than the intakes, i'm not worried about them.
On another note, here's a photo of an exhaust port with the exhaust gasket opening marked with a sharpie. Bill, is there any advantage to matching the long side of the port to the gasket/header, or would that reduce exhaust velocity? ...regards, kevin
Love the CCing tool set :) I have never done a gasket match like that, so I don't know how much value there would be. I don't think I would be worried about exhaust velocity with removing that little bit. I don't know how thick the aluminum is there. I'm hoping someone will chime in and give us the benefit of their experience. I like the idea of gasket matching, as it would increase flow and give you the opportunity to control the exit swirl of the exhaust. I agree that you should have plenty of PTV clearance on the exhaust side. I am interested to see the new intake valves.
 
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