1971 400/300hp - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 08-23-2009, 08:46 AM Thread Starter
 
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1971 400/300hp

Hey Guys. Newbie here. I am a 1972 Buick GS455 owner (we are all A-body cousins anyway right!!). I am helping out a buddy with a newly purchased 71 GTO 400. What are some common upgrades/products/part #`s to get a "smogger 400" up in the h.p #`s. Nothing crazy here, maybe 350-360 street horsies on pump gas (91-94 octane). A little bowl work/porting on the heads?..Scrap the heads?.. Cam?.. Intake?.. Headers? Not sure what works best on these Poncho motors. It appears to me that the 69-71 400`s use the same engine hardware except heads and intake..?? This is a TH400/3.23 car so I think a 2500 stall converter should work with this driveline. Any input is great!! Thanks!! Later,Tony.
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post #2 of 6 (permalink) Old 08-23-2009, 09:44 AM
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Tony, Pontiac changed the chamber sizes in the heads to tweak compression ratios...the pistons and blocks are the same in a '79 as a '69....So, if you want to "upgrade" on the power, a little more compression would help. You need to google Wallace Racing, Butler Performance, and Jim Hamd to learn about these motors. Be warned that if you install '70 or earlier heads, don't use less than about an 80cc combustion chamber....You'll find that 95% of all '70 and earlier heads are about 72cc, which means about 10.75 compression, and PING CITY on less than about 98--100 octane. Edelbrock makes a nice aluminum 87cc head. YOu can mill the current heads, up to .050", and you will lose one cc of chamber for every .005" milled from the head. The 1971 #96 head and the '72 7K3 heads can be milled .070". Your '71 GTO, if fitted with the stock heads, should have about a 96cc chamber. So, if you mill the heads .050", you will have about 87cc's, good for about a 9.2 compression ratio. Know that a '71 GTO, if it still has the stock heads, will have the big valves. So, if milled and cleaned up, these heads could be very workable for minimal cash outlay. On a '71 GTO, if it were mine, I would install the HO cast exhaust manifolds, install an HO cam (068) install it advanced 4 degrees, and make sure the quadrajet and distributor are working as intended. I've said it before and I'll say it again, a stock Pontiac intake and Quadrajet will usually beat the crap out of aftermarket "upgrades". I can't tell you how many modified GTO's we used to smoke with our "stocker's" back in the day. Leave the rear gearing where it is. Congrats on the Buick thing....Buicks are THE most underappreciated and one of the BEST performance cars!!
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post #3 of 6 (permalink) Old 08-23-2009, 03:41 PM Thread Starter
 
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Thanks for the reply. Great info too!! Good news about those heads, some headwork and shaving sound like the ticket,should bring up compression a bit more. He will probably go with some headers and a 2.5" exhaust. The 068 cam..is there an aftermarket with the same specs?? What to use? And I am a big fan of the QJ, I run a 800cfm on my 462 BBB. Using the stock carb, intake an recurving the dist should help out too!! Should get close to 350 h.p I gather. And you have some good lookin Goats there!! Congrats!! Thanks again!! Attached my GS for you. Later,Tony,
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post #4 of 6 (permalink) Old 08-23-2009, 08:54 PM
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Nice GS, Tony. I like the color combo. I dunno about comparable cams....I'm pretty much of a fossil. I do know that the Jim Hand articles on engines and the Butler/Wallace sites are time well spent. As you know, research can save a lot of money and grief. Rock&Roll engineering in CA is a good bet, too.
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post #5 of 6 (permalink) Old 08-24-2009, 01:14 PM
 
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Originally Posted by geeteeohguy View Post
Nice GS, Tony. I like the color combo. I dunno about comparable cams....I'm pretty much of a fossil. I do know that the Jim Hand articles on engines and the Butler/Wallace sites are time well spent. As you know, research can save a lot of money and grief. Rock&Roll engineering in CA is a good bet, too.
Might want to try Nitemare Performance in Connecticut as well.

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post #6 of 6 (permalink) Old 08-24-2009, 01:49 PM Thread Starter
 
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Thanks Guys. I will check those out. So.. comp cams for example..any good grinds? Us Buick guys have on own niche supplier many of us use over the big name companies. Later,Tony.
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