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Discussion Starter · #1 ·
I purchased a set of Summit racing Vortec heads back in 2012, installed and ran until disassembly this year. I took the heads in to get a valve job and they milled them too. Now I am ready to reassemble and ordered a kit to cc my heads since the milling. They were advertised as 67cc, but now I’m getting 74-75cc. Is it possible for a simple valve job to add 7cc to the heads since the valves get recessed slightly? Called the machine shop and he said it should add anything, especially considering they were milled. This leaves the issue that it’s possible Summit shipped me 74cc heads instead of 67?! Kinda confused and looking for some feedback...thank you!
 

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Doing a valve job sinks the valves deeper in the seat adding a little volume in the range of one or two. Milling the head should remove that addition and maybe more. I’m inclined to think you didn’t get heads with 67cc chambers or the valves got wickedly sunk into the head.

Bogie
 

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Discussion Starter · #3 ·
Doing a valve job sinks the valves deeper in the seat adding a little volume in the range of one or two. Milling the head should remove that addition and maybe more. I’m inclined to think you didn’t get heads with 67cc chambers or the valves got wickedly sunk into the head.

Bogie
is there anyway for me to figure out how sunk the valves got? I’m also thinking I didn’t receive the 67cc heads. Looking at before and after photos the valves don’t look noticeably lower. 7cc is a lot of volume...
 

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This is one of those places a picture is worth 1000 words. Some of us may recognize the chamber volume just by looking at it.
Post up a handful of pics of the chamber, from several angles.

At 2.02"/1.6" valve size they would have to sink both valves nearly .085" to drop 7cc volume....and that isn't even allowing for how much would be gained back by the milling, depending on how much was milled off.
If you guess that milling took 2cc off(.014" milled) than you are talking they would have to have sunk the valves .100"+ to reach a final 7cc added.

It should be obvious if the valves have been sunk that far.
 

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This is one of those places a picture is worth 1000 words. Some of us may recognize the chamber volume just by looking at it.
Post up a handful of pics of the chamber, from several angles.

At 2.02"/1.6" valve size they would have to sink both valves nearly .085" to drop 7cc volume....and that isn't even allowing for how much would be gained back by the milling, depending on how much was milled off.
If you guess that milling took 2cc off(.014" milled) than you are talking they would have to have sunk the valves .100"+ to reach a final 7cc added.

It should be obvious if the valves have been sunk that far.
My late brother-in-law purchased a set of new iron SBC heads from a high performance place in Tennessee. I was putting the engine together and we had installed the new at the time Total Seal rings. With the heads on, I wanted a leakdown number as a comparison for after getting the engine broken in. I of course expected some leakage past the ring package but was stunned when I had air screaming from every exhaust port (no valve train installed at this point). I showed him what was going on and he sent the heads back for replacement. Instead of sending a new set - they sunk the hell out of the valves on exhausts AND intakes! I showed him this but he didn't want to fool with them anymore - so on they went. This was a dual purpose car and it really hurt it's performance. BTW this high performance place in Tennessee, home of Elvis, finally went out of business.
 

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Discussion Starter · #13 ·
This is one of those places a picture is worth 1000 words. Some of us may recognize the chamber volume just by looking at it.
Post up a handful of pics of the chamber, from several angles.

At 2.02"/1.6" valve size they would have to sink both valves nearly .085" to drop 7cc volume....and that isn't even allowing for how much would be gained back by the milling, depending on how much was milled off.
If you guess that milling took 2cc off(.014" milled) than you are talking they would have to have sunk the valves .100"+ to reach a final 7cc added.

It should be obvious if the valves have been sunk that far.
Valves are the originals that came with the heads. You can see the matte finished area around the head which is from the original casting, then the new shiny area from the valve job. Unfortunately I don’t have good before pics that I can share but I did find one grainy photo when new and confirmed.

615006
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615009
 

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Discussion Starter · #16 · (Edited)
That’s a small chamber head with deeply sunk valves and these valves are relieved center which adds a couple cc’s.

Bogie
So I can assume this guy sunk the valves so low that it added 7cc? These are the original valves. Included crappy original photo

Don’t have much ground to stand on, he can’t mill them down enough to make up for it or I’ll have intake sealing issues and probably other problems. This guy has been hard to deal with, very condescending. How do you advise I go about bringing this up to him and what type of solution should I be expecting?
615013
 

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I meant originally with deep sunk valves. I suspect that the 67 cc measure is the as cast chamber before machining the seats. This was probably a 71 to 73 cc chamber to start with when you bought them. To some extent this is a not an uncommon thing with lower cost heads.

If nothing it shows the need to check what the actual chamber volumes are before assembly of the engine.

Bogie
 

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Discussion Starter · #19 ·
I meant originally with deep sunk valves. I suspect that the 67 cc measure is the as cast chamber before machining the seats. This was probably a 71 to 73 cc chamber to start with when you bought them. To some extent this is a not an uncommon thing with lower cost heads.

If nothing it shows the need to check what the actual chamber volumes are before assembly of the engine.

Bogie
I tend to agree with you. I swung by another machine shop I’ve used in the past and they said the valves don’t look sunk and he didn’t think there was anyway they gained 7cc from the valve job especially considering the milling. Said it looked like he did good work.
 

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Put me in the camp that they chambers weren't 67 to start with.
I don't see anything alarming to the seat work. Both valve margins are pretty close to flush, which is a tiny bit lower than typical but common enough. The intake is a little lower than the exhaust, again common. 7cc would put the valves so far in you wouldn't see the margins at all plus another .060 or so, you would probably see some tooling marks around the seats.
I can't say for sure someone mixed up heads OR most likely, they were a bit bigger than advertised by the PN.
Sometimes the blue prints call for 67cc and they get cast that way at the foundry perhaps even with a tolerance error built in that might make them 68-70 and then the machine work is done at the assembly line making it around maybe 70-72 and valves with depressions installed and you get 72-76ish. That's just the game an how it's played with cheap heads. I'd run it as is and quite worrying about it.
 
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