Cylinder Head Upgrades on a Budget
Cylinder Head Upgrades on a Budget Today I received my heads back from the machine shop, so I thought I'd post the before and after pics. I picked up these 862 castings locally for less $60 to go on my turbocharged 4.8L build They're NOT the Castech castings that are prone to crack, and they DO NOT have the notch in the deck, so no special head gaskets are needed. They looked like this when I got them.
I sent the heads off to my local machine shop and had the heads cleaned, milled, and the valve job cut for larger 2.00" intake valves and the stock 1.55" exhaust valves. They only skim cut the deck so the compression should be about 9.5:1 on the 4.8L. They look a lot better now.
So far, I have a whopping $330 invested.
I sent the heads off to my local machine shop and had the heads cleaned, milled, and the valve job cut for larger 2.00" intake valves and the stock 1.55" exhaust valves. They only skim cut the deck so the compression should be about 9.5:1 on the 4.8L. They look a lot better now.
So far, I have a whopping $330 invested.
TECH Resident
Joined: Apr 2010
Posts: 926
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From: Central Texas
I have a set of 862 with the coolant erosion really bad .Does that hurt anything they weren't leaking and the shop I took them to wouldn't try and clean them up (mill). I think I will try and weld them up if it is that important. Your thoughts?
As long as it's over the water jackets in the block, I wouldn't worry about it. If it crosses over to make a potential leak path, then I would worry.
A lot of machinists use it to check the concentricity of the valve and valve job after it's been done. It's a nice visual for the customer to see too, IMO.
I measured the venturi to see what the minimum cross section is. The handy little tool shows me the diameter, and using basic math, I can calculate the area.
The intake port is at 2.35sq in while the exhaust is 1.37sq in. I'll be opening the intake up to about 2.54sq in and the exhaust to about 1.52sq in.
The intake port is at 2.35sq in while the exhaust is 1.37sq in. I'll be opening the intake up to about 2.54sq in and the exhaust to about 1.52sq in.
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TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
On edit, is it me, or did they even get a little bowl work done in there while they were at it?
TECH Senior Member
Joined: Jun 2016
Posts: 22,306
Likes: 3,621
From: Central Cal.
I measured the venturi to see what the minimum cross section is. The handy little tool shows me the diameter, and using basic math, I can calculate the area.
The intake port is at 2.35sq in while the exhaust is 1.37sq in. I'll be opening the intake up to about 2.54sq in and the exhaust to about 1.52sq in.
The intake port is at 2.35sq in while the exhaust is 1.37sq in. I'll be opening the intake up to about 2.54sq in and the exhaust to about 1.52sq in.
That $ 330 does that include the cost of the heads , so you spent approx $270 in machine shop work ? So your going to take the throat diameter close to 1.80 intake ..... and the exhaust to 1.39 ?. Iirc I thought the exhaust should be approx 86- 87% of valve diameter , looks like your going close to 90% is that because it's going to be turbo ?
