Pontiac V8 engine
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==Heads== | ==Heads== | ||
| − | ===6X | + | ===6X heads=== |
Casting 6X heads and similar heads from the "smog era" generally all have hardened exhaust seats, screw-in rocker studs and guide plates, with 2.11" intake x 1.66" exhaust valves. See [http://www.pontiacstreetperformance.com/psp/6XheadID.html ''How to Identify Pontiac's Small Chambered 6X Head''] for more info on ID'ing 6X heads. | Casting 6X heads and similar heads from the "smog era" generally all have hardened exhaust seats, screw-in rocker studs and guide plates, with 2.11" intake x 1.66" exhaust valves. See [http://www.pontiacstreetperformance.com/psp/6XheadID.html ''How to Identify Pontiac's Small Chambered 6X Head''] for more info on ID'ing 6X heads. | ||
When inspecting 6X head and Pontiac heads in general, check the spring installed height to be sure it is equal between the valves. The spring's seat and open pressure is also important but all but impossible to measure unless the springs are checked w/a spring gauge. There are spring gauges that can be used on an assembled head. When buying assembled heads, demand a receipt showing part numbers. That will not guarantee anything but will cut down on the BS. | When inspecting 6X head and Pontiac heads in general, check the spring installed height to be sure it is equal between the valves. The spring's seat and open pressure is also important but all but impossible to measure unless the springs are checked w/a spring gauge. There are spring gauges that can be used on an assembled head. When buying assembled heads, demand a receipt showing part numbers. That will not guarantee anything but will cut down on the BS. | ||
| + | ===4X heads=== | ||
| + | <table border="1"><tr> | ||
| + | <td align="center"><strong>Application Stamp</strong></td> | ||
| + | <td align="center"><strong>Application</strong></td> | ||
| + | <td align="center"><strong>Valve Diameters</strong></td> | ||
| + | <td align="center"><strong>Rocker Studs</strong></td> | ||
| + | </tr> | ||
| + | <tr> | ||
| + | <td align="center">1H</td> | ||
| + | <td align="center">455 4-bbl</td> | ||
| + | <td align="center">2.11/1.66</td> | ||
| + | <td align="center">Pressed-in*</td> | ||
| + | </tr> | ||
| + | <tr> | ||
| + | <td align="center">3H</td> | ||
| + | <td align="center">400 4-bbl Manual</td> | ||
| + | <td align="center">2.11/1.66</td> | ||
| + | <td align="center">Threaded</td> | ||
| + | </tr> | ||
| + | <tr> | ||
| + | <td align="center">4H</td> | ||
| + | <td align="center">400 2-bbl </td> | ||
| + | <td align="center">1.96/1.66</td> | ||
| + | <td align="center">Pressed-in*</td> | ||
| + | </tr> | ||
| + | <tr> | ||
| + | <td align="center">7H</td> | ||
| + | <td align="center">400 4-bbl Auto</td> | ||
| + | <td align="center">2.11/1.66</td> | ||
| + | <td align="center">Both*</td> | ||
| + | </tr> | ||
| + | <tr> | ||
| + | <td colspan="4" align="center">*All rocker arms are threaded beginning with Motor Unit Number 709986 assembled on or about May 7, 1973.<br></td> | ||
| + | </tr> | ||
| + | </table> | ||
===Valve sizes=== | ===Valve sizes=== | ||
Often, modified Pontiac "X" heads have 1.77" exhaust valves installed in place if the stock 1.66" and this is obviously going to be very easy to determine. As far as the rest of the work that may have been done to the heads, you can visually look to see if they both have at least 3-angle seats (that won't tell you if the seats are concentric, though). The valves can be inspected to see that they have adequate margins, seat widths, and if they've been back cut or have undercut stems. I would suggest measuring the valve guide clearances, too. | Often, modified Pontiac "X" heads have 1.77" exhaust valves installed in place if the stock 1.66" and this is obviously going to be very easy to determine. As far as the rest of the work that may have been done to the heads, you can visually look to see if they both have at least 3-angle seats (that won't tell you if the seats are concentric, though). The valves can be inspected to see that they have adequate margins, seat widths, and if they've been back cut or have undercut stems. I would suggest measuring the valve guide clearances, too. | ||
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