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Pontiac motor rebuild questions


I own a 1973 sport lemans with its original  400 motor R2b carb turbo400 4x heads all stock has headers and duals just over 90000 miles . Recently it has developed a small lifter noise and over this past year has drop some oil psi at idle . But overall still runs well . I want to rebuild this motor in my garage I have rebuilt some ford 5.0s in the past . So I do have some know how on things . I want to build this motor like a 72 gto 400s specs maybe with a touch more power but not to radical . any tricks to these motors or special parts I need to purchase . I do plan to go with elt ign system for sure . 



-- Edited by Dustted on Tuesday 12th of April 2011 06:37:55 PM

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First thing lets check out the Camshafts Pontiac used in their Engines . A 400 4bbl Engine should have the 067 (P) Camshaft in it . But you could go with the Well know Pontiac Hot Rod choice the 068 (S) Cam . Problem is it goes for about $150.00 with out Lifters . And you have to be careful when Buys a Cam and Lifter Kit that you don't get Chevy Lifters . They Fit but are slightly smaller in diameter and will run Loose in the Lifter Bores and cause Lower oil Pressure and wear to the Lifters and worse of all the Lifter Bores .

 

ApplicationStamping #Intake
Duration
Intake
Centerline
1.501.65OverlapExhaust
Duration
Exhaust
Centerline
1.501.65Camshaft
Part #
1959-64 4bblD273106.407".447"55282116.411".452"529472
1965-76 V8N273107.407".447"55283116.407".447"9779066
1965-76 4bblP273112.407".447"54289113.407".447"9779067
1964 GTO 421C273113.407".447"54289113.407".447"524009
1978-79 T/A 6.6L-274-.364".400"-298-.407".447"549112
1956-62 3/2bbl6283112.407".447"60293116.407".447"524886
1963-64 421 HOL288113.407".447"63301119.407".447"9770523
1965-72 HOS288113.407".447"63302119.407".447"9779068
1966-69 RAH301113.407".447"76313118.407".447"9785744
1973-74 455SDY301113.407".447"76313118.407".447"493323
1968L-70 RAIVT308112.470".516"87320115.470".516"9794041
(1973 455 SD)K308112.470".516"87320115.470".516"480737
1969 RAV- mech.V308112.453".498"87320115.447".492"545713

 


As for your 400 Engine you have to tear it Down and see how the Cylinder Bore checks out . Maybe you can hone it out and have the Crank sent out for a 10/10 Turning . The 4X Heads really are not that much different then the much used 6X Heads are . You should have a valve Job done on them with a set of Performance Springs that will match the camshaft you run . They can be trued up milled 020" use Poly Locks for the Rocker arms . A 1968-72 Pontiac Iron Intake and Q-Jet will be in order for a 1972 GTO 400Spec Build . I would also use the Ram Air IV 60 psi oil Pump but with a Hardened shaft . HEI up-grade on the ignition too .

Now that would be how you would want to build it Like an Early 70's 400 Pontiac Mill .

I would build it some what Differently with a mix of a Lot of today's speed parts . And you want to keep Fuel Mileage in mind as well .



-- Edited by TANGO on Thursday 14th of April 2011 08:15:08 AM

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How would you build it if it was going in your car . Im looking at a few 2500 stallspeeds but have no plans to replace the 3.08 now . I thinks its positraction lays down two short marks when i brake torque it . want to reuse the stock heads and block with out reboring it out .

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I would build it Street Friendly for everyday use . With the Power Leaning on the Lower RPM Torque side and as easy on Fuel as possible with out Dog-ing any Power Down .

From what I have seen and read . Lot's of Pontiac Engine Build are very much the same . With 6X Heads Cast Iron Intakes and Q-Jets and old Pontiac Cam Grinds Like the one above . Sure it's a well known Fact that the Factory 400 4bbl Combo was a good one .

But I think some Mild Porting on a Set of 4X or 6X Heads a after Market Camshaft Like the Howards # 410021-12 447"in and 467"ex 214/224 Dur at .050" 112 L/C with good Roller Timing Chain set . Adjustable Rocker poly Nuts . H.V Oil Pump and Hardened Pump Drive shaft . And a Edelbrock Performer Intake with a 750 Performer Carb . High Performance HEI Dist with Headers and a 2 1/4" Exhaust with Free Flowing Mufflers would do it .

The G.M Iron Q-Jet Non-EGR intakes really are hard to Top on a Performance Street Build . But the Edelbrock Performer is real close to it in Performance and much Lighter and it will produce better MPG .

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