Editing Pontiac V8 engine

[[File:Pont twin turbo eng.jpg|right]]
==Overview==
A look at one of the more popular GM engines.

==Bore and stroke==
[[File:Pontiac V8 bore and stroke.jpg]]

==Heads==
===6X (and similar) 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 the "good" 6X head.

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.

===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.

===Combustion chamber volume===
One of the most important things that need to be known about the heads is the exact chamber volumes. First, look to see that the secondary identifiers are the same. Even if they are, [I][B]both[/B][/I] heads need to be checked- although doing the end chambers of each head (four chambers total) will be enough to tell that the chambers are equal. This is necessary because there's no way to be sure the heads were '''always''' a pair from day one, onward. Even if they ''were'' paired from birth, one head might have had a bad head gasket that required it to be resurfaced. If '''both''' heads weren't cut an equal amount that can cause the chambers to vary. If the heads were from different engines originally, obviously they can vary due to all the above reasons plus manufacturing and casting differences from the factory.

The combustion chamber volume can be changed by milling the head deck. One cc will be removed per 0.005" removed from the deck. All heads can be safely milled 0.050". The 1971 96 and the 1972 7K3 heads can be safely cut 0.070" and the 1971-'73 round port heads can be cut 0.085". If 0.030" or more is removed, the intake side of the head should be cut equally to keep the port and bolt holes in alignment. The chamber volume should be rechecked after a valve job; most times a valve job on the same size valve (not replacing a smaller valve with a larger valve) will add 2-4cc to the chamber volume.

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 mid '75-'77 350ci; 1977-'79 W72 400ci (TA "6.6 Litre" option) 
*6X-6: 124cc, these would have been on a 455
*6X-8 and 6X-9: 101cc
*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 4, 6, 7, 8, and 9 identifiers can be found stamped on one of the vertical ribs on the side of the head. These heads have hardened exhaust seats, screw-in rocker studs and guideplates, 2.11" intake x 1.66" exhaust valves. They can be easily converted to 1.77" exhausts. If nitrous or high rpm is in the cards, this mod should be considered.

A [url= http://www.wheelspin.net/calc/calc2.html compression ratio calculator] can be used to calculate compression ratios when using different chamber sizes, etc.

===Port volume===
Then there's the port volumes. These heads have relatively small intake ports; the 6X-4 heads used on one 455 build were 158cc "stock" (these ports have also been measured at 153 cc), and they did not look to have been ported. After porting they measured 173cc. These stock sized ports would be like a ~ 125cc head on a 350 SBC. The comparison isn't as bad as it sounds because of the design of the Pontiac head/ports and the 30 degree intake valve angle, but the fact remains- they ARE small.

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.

<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.

===Studs and guideplates===
====The bottleneck stud====
[[File:Pont stk stud.jpg|thumb|500px|Stock type Pontiac bottleneck stud]]Pontiac heads like the 6X and practically all other heads likely to be used in a performance-orientated build have screw in ''bottleneck'' studs and steel guideplates. There are some exceptions to this, like the Ram Air IV and "Ram Air II" round port heads, which used a straight 7/16" stud with an adjuster nut/lock nut. 

The usual D-port stock arrangement is a "net lash" set-up. Because the stud is 7/16" OD at the bottom, the rocker arm and pivot ball is also made to fit a 7/16" OD stud. The '''top''' of the bottleneck stud is threaded for a 3/8-24 nut, to be torqued to 15 ft/lb to retain the rocker arm.  
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Net lash is affected by any of the following:
*Block deck height 
*Head deck height 
*Head stud boss height 
*Rocker arm brand/design 
*Cam base circle size 
*Lifter design/brand/pushrod seat height 
*Valve stem length
*Head gasket thickness
So if any of the above changes are made, the stock Pontiac bottleneck stud/net lash set-up may no longer preload the lifter properly. Unless the studs are changed to allow for an adjustable valve train, different length push rods may be needed to set the lifter preload. For that reason it is always advisable to use straight studs to replace the bottleneck studs. A good replacement is ARP p/n 190-4003 w/hex nuts, or p/n 190-4203 w/12-point nuts. Be aware that there can be clearance issues between the polyloc and valve cover if polylocs are used. Check the clearances carefully; you might be able to use a shorter polyloc. If possible (and the valve cover are so equipped) keep the oil drippers. The oil drippers are a separate piece from the valve covers on the RA II/IV engines.

While it is not recommended, the bottleneck studs will sometimes work as an adjustable valve train if a stock SBC lock nut is used and the camshaft is very mild. But this does nothing for the inherently weaker design of the bottleneck stud.

The stock Pontiac guideplates are fine to reuse as long as the pushrod diameter is the same as stock or if the pushrod OD is larger, the holes are tweaked to allow the pushrods to fit without interference.

===Rocker arms===
Most Pontiac engines came with 1.5:1 ratio rockers. Exceptions to this were the Ram Air IV engines, which used 1.65:1 rockers. The 1.65 rockers can be used on any Pontiac head but the push rod guide hole in the head has to be carefully inspected/enlongated at the top of the opening. More on this [ '''here'''
===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."

===Round port heads===
[[File:D over rnd pont.jpg|thumb|500px|left|D-port #13 heads above a Ram Air IV head]] 
Round port heads were long favored for high performance. But they were scarce (read expensive), and did not flow all that well.

Now that Edelbrock and others have come out with affordable aftermarket aluminum heads, the round port heads are all but ignored by the performance crowd. But to restorers, they are still highly sought after.
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==="Pete's Picks"===
Pete McCarthy 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==
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.

==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.

===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==
There are now 'cheap' but good quality Pontiac rods. Years ago, all that was available were high dollar rods like Miller, etc. or the weak factory forged rods or weak factory cast rods. Neither factory rod is a good choice if the engine will see hard use or high rpm. At the bare minimum, cast rods need to be resized and ARP hardware installed, and the rpm has to be kept under 5500.

==Cranks==
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. 

==Ignition==
[[File:PONTIAC CCW ROTATOIN ADVANCE WEIGHTS.jpg|thumb|300px|left|CCW orientation of mechanical advance weights and cam]]
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See [[Hot rodding the HEI distributor]].

==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.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:Tripower.jpg|thumb|300px|left|Tri Power induction set up]]
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==Resources==
*[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]

{{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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[[Category:Engine]] 
[[Category:undeveloped articles]]
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