Pontiac V8 engine
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There were three sizes of combustion chambers on 6X heads. For most builds, the small chamber head is what is wanted. The late large chamber 455 heads on a 400 will put the compression ratio in the 7.8:1 range, even with a 0.040" quench. The small chambered 6X and similar head on a 0.030" over 455 with a 0.040" [['''quench''']] will result in a CR of about 9.75:1. On a 400 the CR will be around 9.2:1. | There were three sizes of combustion chambers on 6X heads. For most builds, the small chamber head is what is wanted. The late large chamber 455 heads on a 400 will put the compression ratio in the 7.8:1 range, even with a 0.040" quench. The small chambered 6X and similar head on a 0.030" over 455 with a 0.040" [['''quench''']] will result in a CR of about 9.75:1. On a 400 the CR will be around 9.2:1. | ||
| − | *6X-4 and 6X-7: 93cc (have been seen to be as much as 95cc). The 6X-4 heads were found on | + | *6X-4 and 6X-7: 93cc (have been seen to be as much as 95cc). The 6X-4 heads were found on mid '75-'77 350ci; 1977-'79 W72 400ci (TA "6.6 Litre" option) |
*6X-6: 124cc, these would have been on a 455 | *6X-6: 124cc, these would have been on a 455 | ||
*6X-8 and 6X-9: 101cc | *6X-8 and 6X-9: 101cc | ||
| − | *There are also 1973-'74 casting 4X heads that have | + | *There are also 1973-'74 casting 4X heads that have 98cc chambers and screw-in studs, but the intake port size is about 5cc smaller. |
*The 1975 casting 5C heads have 101 cc chambers, but they supposedly have about 7cc smaller runners than the 6X heads. Bigger is better, in this case. | *The 1975 casting 5C heads have 101 cc chambers, but they supposedly have about 7cc smaller runners than the 6X heads. Bigger is better, in this case. | ||
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Usually a stock or mildly reworked D-port Pontiac head doesn't need lift in excess of 0.480". That is a little past where maximum flow is reached but before any port stall occurs, given the rpm range of a 455. Combining that w/a duration @ 0.050" of around 234-236 degrees or so will be about right for a strong street engine that will run mid 12 second ETs at the drags and can be driven daily, anywhere, without issue, on 89 octane gas, and using a 2.73 to 3.31 gear ratio is all that's needed. | Usually a stock or mildly reworked D-port Pontiac head doesn't need lift in excess of 0.480". That is a little past where maximum flow is reached but before any port stall occurs, given the rpm range of a 455. Combining that w/a duration @ 0.050" of around 234-236 degrees or so will be about right for a strong street engine that will run mid 12 second ETs at the drags and can be driven daily, anywhere, without issue, on 89 octane gas, and using a 2.73 to 3.31 gear ratio is all that's needed. | ||
| + | |||
| + | ==="Low compression" heads=== | ||
| + | Be aware that published figures often differ. The only sure way to know what the combustion chamber volume is, is to actually measure it. This will take everything into account: previous valve jobs, milling done to the decks, manufacturing and casting tolerance creep/stack up, etc. | ||
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| + | <table border="1" cellspacing="1" cellpadding="1"><tr><td colspan="5" align="center"><h3>Pontiac Cylinder Head Applications</h3></td></tr><tr><td><strong>Casting</strong></td><td><strong>Stamping</strong></td><td><strong>Valve Size (inches)</strong></td><td><strong>Chamber Volume</strong></td><td><strong>Original Application</strong></td></tr><tr><td>4X</td><td>1/1H</td><td>2.11/1.66</td><td>112 cc</td><td>'73-'74 455ci 4-bbl</td></tr><tr><td>4X</td><td>3/3H</td><td>2.11/1.66</td><td>98-99 cc</td><td>'73-'74 400ci 4-bbl manual trans.</td></tr><tr><td>4X</td><td>4/4H</td><td>1.96/1.66</td><td>98-99 cc</td><td>'73-'74 400ci 2-bbl</td></tr><tr><td>4X</td><td>7/7H</td><td>2.11/1.66</td><td>98-99 cc</td><td>'73-'74 400ci 4-bbl auto trans.</td></tr><tr><td>4C</td><td>5/5H</td><td>1.96/1.66</td><td>96 cc</td><td>'73-'74 350ci 2-bbl w/A.I.R.</td></tr><tr><td>4C</td><td>8/8H</td><td>1.96/1.66</td><td>98 cc</td><td>'73-'74 400ci 2-bbl w/A.I.R.</td></tr><tr><td>46</td><td>6/6H*</td><td>1.96/1.66</td><td>96 cc</td><td>'73-'74 350ci</td></tr><tr><td>5C</td><td>4</td><td>2.11/1.66</td><td>92-94 cc</td><td>'75 350ci</td></tr><tr><td>5C</td><td>7</td><td>2.11/1.66</td><td>99-101 cc</td><td>'75 400ci w/A.I.R.</td></tr><tr><td>5C</td><td>8</td><td>2.11/1.66</td><td>99-101 cc</td><td>'75 400ci</td></tr><tr><td>5C</td><td>9</td><td>2.11/1.66</td><td>92-94 cc</td><td>'75 350ci w/A.I.R.</td></tr><tr><td>6X</td><td>4</td><td>2.11/1.66</td><td>92-94 cc</td><td>Mid-'75-'77 350ci, '77-'79 W72 400ci</td></tr><tr><td>6X</td><td>8</td><td>2.11/1.66</td><td>99-101 cc</td><td>Mid-'75-'78 400ci</td></tr><tr><td>6S</td><td>7</td><td>2.11/1.66</td><td>99-101 cc</td><td>Mid-'75-'76 400ci w/A.I.R.</td></tr><tr><td>6S</td><td>9</td><td>2.11/1.66</td><td>92-94 cc</td><td>Mid-'75-'76 350ci w/A.I.R.</td></tr><tr><td>51</td><td>6</td><td>2.11/1.66</td><td>124.5 cc</td><td>'75 455ci</td></tr><tr><td>6H</td><td>6</td><td>2.11/1.66</td><td>124.5 cc</td><td>Late-'75-'76 455ci</td></tr><tr><td colspan="5">*Some have been reported to have a secondary stamp of "2"</td></tr></table> | ||
| + | An alternative to using the larger chamber heads is to install dished pistons and use any of the smaller chambered performance heads. | ||
| + | |||
| + | ===Valve springs=== | ||
| + | Cliff Ruggles has said "We use and prefer the Crower 68404 (1.6" installed height) or 68405 (1.7" installed height) for flat hydraulic cams with Pontiac cylinder heads." | ||
| + | |||
| + | ==="Pete's Picks"=== | ||
| + | Pete McCarthey did a huge head air flow test that was originally written up in the April and June, 1991 editions of High Performance Pontiac, titled [http://forums.highperformancepontiac.com/70/9029510/the-general-discussion/to-port-or-not-to-port-heads/index.html '''The Ultimate Head: Part I''']. | ||
| + | |||
| + | ;The results<nowiki>:</nowiki> | ||
| + | *Best performance head: 1970 Ram Air IV | ||
| + | *Best intake port: 1969-70 Ram Air V | ||
| + | *Best exhaust port: 1968 1/2 Ram Air II | ||
| + | *Best D-port head: No.16, No.48, No.12 (tie) | ||
| + | *Best low-compression D-port head: No.96(1971) | ||
| + | *Best low-compression post-1972 head: No. 6X | ||
| + | *Best balanced head (exhaust to intake): 1963 421 SD | ||
| + | *Best low-lift (under .400) head: 1967 No.670 | ||
| + | *Worst exhaust-to-intake port ratio: 1969-70 Ram Air V | ||
| + | *Worst intake-to exhaust ratio: 1968 1/2 Ram Air II | ||
| + | *Biggest surprise: Intake port, No.17 350 head | ||
| + | *Biggest disappointment: 1969-70 RA V, 1973-74 455 SD (tie) | ||
| + | *Biggest "sleeper": 1975 No. 5C | ||
| + | *Most undercammed: 1963 SD, 1971 455 HO, 1973-74 455 SD (tie) | ||
| + | *Most underexhausted: 1964 GTO (No.9770716) | ||
| + | *Most potential for porting: 1973-74 455 SD, 1968 1/2 RA II (tie) | ||
==Cams== | ==Cams== | ||
| + | According to Pontiac expert Pete McCarthy, "Low-lift exhaust deficiency has been a Pontiac curse for many years. That is why all the Pontiac stock cams, with the exception of the very first profile developed (No.518111 "A"), are dual pattern, with a longer-duration exhaust lobe." | ||
| + | |||
A dual pattern cam like Comp Cams' XE series or a Lunati Voodoo would be good cams to look into. For info on Comp Cams XE series of cams you can contact Butler Performance for good solid info. For info on Crower cams contact Kauffman Racing Engines or Spotts Performance. These shops can be contacted via phone or email. | A dual pattern cam like Comp Cams' XE series or a Lunati Voodoo would be good cams to look into. For info on Comp Cams XE series of cams you can contact Butler Performance for good solid info. For info on Crower cams contact Kauffman Racing Engines or Spotts Performance. These shops can be contacted via phone or email. | ||
==Intakes== | ==Intakes== | ||
With the D-port heads, unless they've been heavily ported, an RPM intake is a good choice. It will hit harder off idle and gives up nothing to a single plane at the modest peak rpm the 455 is going to be turning (5000 rpm), built as described here; harnessing the torque by using sticky drag radial tires will give the maximum all-around performance. There might be an argument made for a single plane to "tame the torque". But that might be better left until all other avenues have been exhausted. | With the D-port heads, unless they've been heavily ported, an RPM intake is a good choice. It will hit harder off idle and gives up nothing to a single plane at the modest peak rpm the 455 is going to be turning (5000 rpm), built as described here; harnessing the torque by using sticky drag radial tires will give the maximum all-around performance. There might be an argument made for a single plane to "tame the torque". But that might be better left until all other avenues have been exhausted. | ||
| + | |||
| + | ===Heat cross over=== | ||
| + | 1972 and up cylinder heads using earlier intakes can use Felpro intake gasket p/n MS90205 or Mr. Gasket p/n 5848 to seal the exhaust crossover. | ||
| + | |||
| + | [[File:PONT HEAT X-OVER BLOCK-OFF 005.jpg|thumb|300px|left|Heat riser block off schematic]] <br style="clear:both"/> | ||
| + | |||
| + | ==Pistons== | ||
| + | Generally, using flat top pistons are the best way to go. There may be cases where a dished piston is needed, but the cost is generally higher than cast flat tops. | ||
| + | |||
| + | Because the 1967 and newer valves don't line up correctly with the 1966-back piston valve reliefs in the pistons (and obviously vice-versa), the correct piston has to be used if any sort of aftermarket high lift cam is used, or else there may be destructive valve to piston interference. There are 8-valve relief pistons available to fit all the valve angle differences used through the years on Pontiac engines. While these pistons will get the job done, from a high performance standpoint they are not desirable. | ||
| + | |||
| + | Pontiac went to 7.6:1 compression in about 1975, due in part to the design of the top of the pistons. Pontiac pistons from the low compression years have a 45 degree machined outer edge of the piston top. | ||
| + | |||
| + | {| | ||
| + | |[[File:Oem pont pist.jpg|thumb|450|center|Note 45 degree cut (arrow) to the top edge of the low compression piston]] | ||
| + | |[[File:8 vr pont.jpg|thumb|450|center|8 valve relief rebuilder-type piston, undesirable for high performance use]] | ||
| + | |} | ||
==Rods== | ==Rods== | ||
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The factory cranks are good. But if a crank is needed, it would be worth looking at a stroker to make a 400 into a small journal 455. Smaller main journals of the 400 make it a better foundation for building a high performance 455 than an OEM 455 block. | The factory cranks are good. But if a crank is needed, it would be worth looking at a stroker to make a 400 into a small journal 455. Smaller main journals of the 400 make it a better foundation for building a high performance 455 than an OEM 455 block. | ||
| + | ==Original build information== | ||
| + | Ever wondered how your Pontiac was originally equipped? A service has been established by Pontiac Historic Services, P.O. Box 884, Sterling Heights, MI, 48311-0884 to research original build information for 1989-back Pontiacs. See them on the web at www.phs-online.com. Information on your Pontiac is $65.00 ($75.00 U.S. for international orders) as of 2012. | ||
| + | ==Jim Hand tech articles== | ||
| + | Jim Hand has been a proilfic writer on the Pontica scene for decades. The following is a few articles by him; others can be found on the web: | ||
| + | *[http://www.classicfirebird.com/hand/hand.html “BUILDING A STRONG STREET MACHINE”] at Classic Firebird | ||
| + | *[http://www.pontiacstreetperformance.com/psp/rebuild455jh2006.html 474 2002 updated specs] | ||
| + | *[http://www.pontiacstreetperformance.com/psp/rebuild455jh99.html 455 w/#64 heads] | ||
| + | *[http://www.dapa.org/jhpages/pontiac-cams.htm’ On cams] | ||
| + | *[http://www.pontiacstreetperformance.com/psp/RockerArms.html Rocker ratios/mods] | ||
| − | + | ==Also see:== | |
| + | *[http://www.pontiacstreetperformance.com/psp/featuredcars.html Featured Cars & Engines] from Pontiac Street Performance | ||
| + | *[http://www.highperformancepontiac.com/tech/hppp_0506_smog_head_performance/index.html Smog Head Performance] A Technical Comparison of Pontiac's Most Common '70s Cylinder Heads, from June 01, 2005 High Performance Pontiac | ||
| + | *[http://www.highperformancepontiac.com/techarticles/index.html Various tech articles], from High Performance Pontiac | ||
| + | *[http://www.jalopyjournal.com/forum/showthread.php?t=316668 Pontiac Hemi] HAMB thread | ||
[[File:7K3 Pont HEADS DRILLED FOR HEADERS 2.jpg|thumb|300px|left|7K3 heads drilled for headers. [http://www.spottsperformance.com/ Spots Performance] also sells "L" brackets for heads like these that don't have the pad.]] | [[File:7K3 Pont HEADS DRILLED FOR HEADERS 2.jpg|thumb|300px|left|7K3 heads drilled for headers. [http://www.spottsperformance.com/ Spots Performance] also sells "L" brackets for heads like these that don't have the pad.]] | ||
[[File:7K3 Pont HEADS DRILLED FOR HEADERS.jpg|thumb|300px|left|Another view of 7K3 heads drilled for headers]] | [[File:7K3 Pont HEADS DRILLED FOR HEADERS.jpg|thumb|300px|left|Another view of 7K3 heads drilled for headers]] | ||
[[File:Open chamber head 68 up.jpg|thumb|300px|left|1968-up open chamber Pontiac machined combustion chamber]] | [[File:Open chamber head 68 up.jpg|thumb|300px|left|1968-up open chamber Pontiac machined combustion chamber]] | ||
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[[File:Tripower.jpg|thumb|300px|left|Tri Power induction set up]] | [[File:Tripower.jpg|thumb|300px|left|Tri Power induction set up]] | ||
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<br style="clear:both"/> | <br style="clear:both"/> | ||
==Resources== | ==Resources== | ||
*[http://www.secondchancegarage.com/public/611.cfm 1946-'55 Pontiac engine specs] from secondchancegarage.com | *[http://www.secondchancegarage.com/public/611.cfm 1946-'55 Pontiac engine specs] from secondchancegarage.com | ||
| + | ;Hotrodders Knowledge Base | ||
| + | *[http://www.hotrodders.com/kb/pontiac-engines Pontiac engines] | ||
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| + | {{warning|Be sure to verify '''all''' Pontiac info found on the internet, in print, or by word of mouth. There is a LOT of erroneous and misleading info out there- even from so-called experts, pros and gurus.}} | ||
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