 Question for all you head guru's |
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| rtalich |
 Oct 14 2006, 10:09 AM
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#1
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Member  Group: Members Posts: 279 Joined: 25-September 06 From: Bellevue, WA Member No.: 6,913 Region Association: None  |
Can anyone tell me if these heads have been modified and/or why they have a little 'step' bored into them? The first picture shows a 'normal' head. Notice the flat surface shown circled.
 These next two pictures are the heads in question. Have these been machined/modified in any way? If so, why?   Thanks, Rob |
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Replies(1 - 19)
| Bleyseng |
Oct 14 2006, 10:40 AM
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#2
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Looks like a piece of metal was loose in that one head.
They were "step cut" for improved head sealing I think.....gotta watch your deck ht when that is done! |
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| JPB |
Oct 14 2006, 11:18 AM
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#3
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The Crimson Rocket smiles in your general direction. Group: Members Posts: 2,927 Joined: 12-November 05 From: Tapmahamock, Va. Member No.: 5,107 |
The one middle picture looks like they have cracks at the plug holes going in opposite directions but don't seem to be bad enogh to fix unless you want them perfect.
(IMG:style_emoticons/default/beer.gif) Nice and clean though and wondering about the combustion chamber size of the cut one and if it would increase the compresion slightly if they are smaller? Are you ballancing these heads yourself? |
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| rhodyguy |
Oct 14 2006, 11:32 AM
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#4
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,090 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
i think *other* head people do the same cut. "quench area improvement"?. i can never keep it all straight.
k |
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| JPB |
Oct 14 2006, 11:37 AM
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#5
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The Crimson Rocket smiles in your general direction. Group: Members Posts: 2,927 Joined: 12-November 05 From: Tapmahamock, Va. Member No.: 5,107 |
(IMG:style_emoticons/default/laugh.gif) Ahhh, I zee.
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| rhodyguy |
Oct 14 2006, 12:10 PM
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#6
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,090 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
geoff, do you mean in the top picture with the valves? aside from the small cracks, these valveless ones are nice heads. nwcr wants to remove the *shoulder* area (what ever that means). that's why i suggested rob start a thread about them.
k |
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| sixnotfour |
Oct 14 2006, 12:28 PM
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#7
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914 Wizard Group: Members Posts: 10,434 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains 
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Is it possible it is a later revision head that doesnt require the sealing ring? for deck heigth?
the first head ,flat would require sealing ring or if left out thicker base shim? for deck heigth ? I cleaned the heads for Kevin and they didnt appear to be machined . CC em and see. Why cut more than you need to ? AsK Len or Jake before you cut em. Just thinking out loud wiating for a 12 year old birthday party to start . |
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| Bleyseng |
Oct 14 2006, 12:57 PM
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#8
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
first of all I wouldnt have Jerry at NWCR work on ANY 914 2.0L heads.....
send them to Len for a quality repair. they will be trash if they go to Jerry IMHO due to his seat install method. In this picture there are small dimples that look like a small chunk bounced around in there where the red is circled. I have only seen the "step cut" once and that was to help seal the head to the cylinder...otherwise I don't know. Attached image(s) 
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| rhodyguy |
Oct 14 2006, 01:18 PM
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#9
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,090 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
that's not one of my exes, or robs newies pictured in that shot.
k |
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| Bleyseng |
Oct 14 2006, 01:27 PM
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#10
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
QUOTE(rhodyguy @ Oct 14 2006, 11:10 AM)  geoff, do you mean in the top picture with the valves? aside from the small cracks, these valveless ones are nice heads. nwcr wants to remove the *shoulder* area (what ever that means). that's why i suggested rob start a thread about them. k this is why I commented on NWCR and heads. I don't know who's heads are in the picture. I would have the heads flycut |
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| messix |
Oct 14 2006, 02:02 PM
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#11
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AKA "CLUTCH KILLER"! Group: Members Posts: 6,995 Joined: 14-April 05 From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada Member No.: 3,931 Region Association: Pacific Northwest |
if you use them you should measure the piston height at tdc, and the 'step' of the head to make sure that the piston and head don't make contact.
cc'ing the tdc of the piston/ cylinder and the head [you will have to find a way to fill or subtract the volume of the grove for the cylinders] to calculate the comression ratio. this is important! those heads might have been used on a high compression engine [11-13 to 1] bad for the street! |
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| rhodyguy |
Oct 14 2006, 02:09 PM
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#12
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,090 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
rob, give me a call when it's convenient.
k |
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| sixnotfour |
Oct 14 2006, 02:52 PM
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#13
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914 Wizard Group: Members Posts: 10,434 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains
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QUOTE CC em and see. QUOTE AsK Len or Jake before you cut em. |
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| rtalich |
Oct 16 2006, 07:37 AM
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#14
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Member Group: Members Posts: 279 Joined: 25-September 06 From: Bellevue, WA Member No.: 6,913 Region Association: None |
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| rhodyguy |
Oct 16 2006, 07:53 AM
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#15
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,090 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
rob's heads were NOT used on a high comp engine. i can assure you of that.
k |
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| Bleyseng |
Oct 16 2006, 08:42 AM
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#16
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Heck, for all I know those could be virgin heads that haven't been flycut at all. I can't remember what the only virgin set I have had looked like.
flycut head Attached image(s) 
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| davep |
Oct 16 2006, 10:03 AM
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#17
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914 Historian Group: Benefactors Posts: 5,152 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada  |
Len Hoffman is member 'HAM Inc'
You may want to email him a link to this thread to get his attention. He is busy doing a lot of heads for us right now, so his online time is very limited. BTW, Jake has the archives of the 4th Dimension radio files. Anyone rebuilding an engine should download these 'broadcasts'. They are truly a wealth of information. I was part way through doing my own heads, ready to install new guides when I decided to send one set to Len. The other set will wait until I decide what kind of an engine to build. I could not see any cracks in my 4 2.0 heads, but I'll wait for the masters prognosis. |
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| HAM Inc |
Oct 16 2006, 12:19 PM
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#18
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
Rob the head with the step has been flycut. Stepcuts were never std with any O.E. T4.
I am a big fan of the step cut. The biggest reason being that more material is left in the head in the weakest areas of the chambers: 1) beneath the ex. studs 2) on the side plug heads (1.7 and especially 1.8's) the area closest to the spark plug. By cutting a step you increase compression with out removing as much material from the head. The head seal seems to hold up better over time with a step as well. If you have a .75mm (.030") step in the head you need a .25mm (.010") deck ht in the cylinder, for a total deck ht of 1mm. The deck ht. volume in the cylinder and the head can be calculated. A 1mm total deck ht in a 94mm bore will be 6.94cc's a 96mm bore will be 7.24cc's. The heads in the pictures have not been cut too deep as the top shoulder has not been cut to prevent cylinder fin interference. The heads will need new seats and some crack repair to be made reliable. I do offer a 10% labor discount to all 914 club members. |
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| anthony |
Oct 16 2006, 02:06 PM
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#19
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2270 club Group: Benefactors Posts: 3,107 Joined: 1-February 03 From: SF Bay Area, CA Member No.: 218 |
QUOTE(HAM Inc @ Oct 16 2006, 11:19 AM) I do offer a 10% labor discount to all 914 club members. Awesome! |
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| sixnotfour |
Oct 16 2006, 05:25 PM
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#20
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914 Wizard Group: Members Posts: 10,434 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains
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HAM Inc (IMG:style_emoticons/default/flag.gif)
Thanks for clearing it up (IMG:style_emoticons/default/thumb3d.gif) |
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