[69-CHVL]

Since I have to pull these SOB's off, I was wondering if doing some clean-up work to them would be beneficial at all. Just some abrasive discs to smooth stuff things off. Its been argued that these GM rectangular heads are too big. Would I further agitate the situation by cleaning them up?

 

[GM PARTS1]

Get a good valve job and that's it.

 

[ChevelleRob]

Having a good valve job and some bowl work would increase air flow, and velocity with minor a increase in volume, and help performance. No real need to touch the ports with abrasive anything.

 

[69-CHVL]

What do you mean by valve job? These heads have about 1k miles on them.

 

[mr 4 speed]

What do you mean by valve job? These heads have about 1k miles on them.

Vince,I am not sure how many angles the factory does on their heads,but you may only have a 2 angle valve job.

 

[GRN69CHV]

Unless these are quite different from the heads that were on the 502HO, they had 3 angles on the seat. Biggest gains are to be made working the seats into the bowl area of the port, especially in the exhaust ports. When you disassemble these heads, there is about 1/8" of port sticking out past where the seat was machined - huge potential for gain by cleaning that up.

 

[BillK]

Dont know if we are talking about cast iron or aluminum heads but I just bought a pair of cast iron ones for a marine 502 I am building and I am really disappointed in the exhaust port especially. The port goes straight down form the 45 deg seat angle. Nothing you can do about it at all. They have hard seat inserts in them and the port below the insert is actually bigger than the seat ! Maybe its an anti reversion step Looks like the intake port can use some work, but dont know if the exhaust can be helped. I have also seen these heads come from the factory machined for 2.250" intake valves even though they are supposed to be 2.19's.... make sure that the intake valve size matches the valve seat

 

[69-CHVL]

These would be the 088 casting, which I think is also used on the iron-head 502/450HP motor. I think the marine heads are a little different that the auto right? Iconnel valves?

 

[GRN69CHV]

Pretty sure they are the same except possibly fot the exhaust valve material. There is a fair amount of port material that can be removed just past the seat insert (exhaust port) to give the valve seat a clean shot to the port.

 

[427L88]

If its anything like the old 074's , the short side radius of the ex port is horrible. Only fix is to weld up that floor and recontour it.

 

[79943]

Unless these are quite different from the heads that were on the 502HO, they had 3 angles on the seat. Biggest gains are to be made working the seats into the bowl area of the port, especially in the exhaust ports. When you disassemble these heads, there is about 1/8" of port sticking out past where the seat was machined - huge potential for gain by cleaning that up.

sometimes i hear the expression "unshrouding the valves" is this what you mean? i bought my heads already prepped and i dont know a lot of details about how they were machined. i just know they had 2.250 intakes installed and were machined on a serti machine. is that machined area around the valve periemeter (see pic) what you are talking about or is that just normal valve seat grinding?

http://www.chevelles.com/showroom/79943/101_0589.JPG

 

[GRN69CHV]

Unshrouding refers to opening up the combustion chamber around the valves - just as you have indicated. I am refering to the area under the valve seat, where the seat enters the exhaust port. THe heads have a hardened seat insert. THe opening in the seat insert is a lot sider than the opening in the actual port - lot of metal can be removed in the exhaust port.