66 GTO lacking power - Pontiac GTO Forum
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post #1 of 16 (permalink) Old 01-09-2011, 03:35 PM Thread Starter
 
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66 GTO lacking power

I bought my first muscle car(66 gto) about a year and a half ago and have invested quite a bit of money in it with little results. It has a 72 400 in it, but has been bored .40 over, i've had hedman shorty headers put on, and had a high energy comp cam installed. It has a 750 edlebrock carb, magnaflow 2.5 full exhaust. It has been checked over with a diagnostic machine, and said to be running great. I'm just not impressed with its power at all. I guess to put into perspective, I feel my wifes 3.8 litre V6 has more get up and go. I would love to have 350-400 horsepower and feel with this set up, it is possible. Am I wasting my time with this engine? If anybody has any ideas or similar set up with advice with what they have done, I would love to hear from you. Thanks, Neil
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post #2 of 16 (permalink) Old 01-09-2011, 03:44 PM
 
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what heads are you running with it? what is the compression ratio? , what is your timing set at? cam specs? 72' was the start of detuning for emissions standards did it mainly with larger chamber volume, could be as simple as a head swap to get you to around 9.5:1 and a tune from a good PONTIAC mechanic. more details are needed.
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post #3 of 16 (permalink) Old 01-09-2011, 04:00 PM Thread Starter
 
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As far as I know the heads are stock. Now this is Japanese to me but the info I got on cam is, range(1500 to 5500) valve timing (0.006) duration (268) duration @ .050" (218)
valve lift ( 0.454) lobe lift (0.302). I'm not sure about the compression. I think the mechanic who ran the diagnostics told me it's around 16 on the timing, If I remember right. I know he said I had 20" of vacumn and steady(if that helps). I live in central Indiana. Do you happen to know of any good pontiac mechanics in this area?
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post #4 of 16 (permalink) Old 01-09-2011, 04:14 PM
 
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Buy the book How to Build Max-Performance Pontiac V-8s from Jim Hand. I suggest reading this book cover to cover before you throw any more money into this engine.
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post #5 of 16 (permalink) Old 01-09-2011, 05:34 PM
 
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you arent wasting time with a 400 but you must have a poorly tuned or mismatched combo. sounds like whoever is tuning/recommending parts purchases may not be real knowledgeable about pontiacs. they are kind of tweaky.


Shane Doss

66 tempest
64 el camino
02 mullis dragster
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post #6 of 16 (permalink) Old 01-09-2011, 07:57 PM
 
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best advise for mechanic is find a local pontiac club, join and ask the members who does theirs, or talk to people on cruise night. maybe someone on here is in your area and has "gotta guy". would think it could take more advance than that but i am no mechanic. i sent PM with a suggestion on help
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post #7 of 16 (permalink) Old 01-09-2011, 08:53 PM
 
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Heads

They started dropping the compression in 71 to just a little over 8 pounds of compression Check the number at the center exhaust ports. Probably 4X-6X on 73 to79 cars.Some later cars had big valves but large chamber CC's. Or numbers starting with nines or sevens If so you need to find some 10:5 are 10.75 heads. Pontiac made heads starting in 67 with larger valves. 2.11/1.77. Made them 67 thru 70. The good heads are #16--216--61--62--31 are RA-1--37--96 is round port RA-2--48--12 auto trans--13 auto trans--12 RA-3-614 round port. RA-5 is a tunnel port #44
722-614 RA-IV,forget these you'll never find them and if you do very costly.
In 71 the most horsepower you could get was a 455 with 335 hp. In 72 the most horsepower you could get was a 455 with 300 hp.
All round port heads have to have round port exhaust or round port headers.
I have to stop writing this is to much information and confusing.LOL
I have a really nice set of 61 heads if anyone can use them. Can't put them on any of my 455's they will kick the compression over 11 and can't run pump gas.
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post #8 of 16 (permalink) Old 01-09-2011, 09:18 PM
 
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Heads

Best heads for 66 is 092--093. Neither have the big valves.
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post #9 of 16 (permalink) Old 01-09-2011, 09:25 PM
 
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wonder where Bear's been he usually weighs in on engine problems....hmmmm
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post #10 of 16 (permalink) Old 01-09-2011, 09:58 PM Thread Starter
 
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If I am reading the correct numbers on center exhaust port, im reading 1 on left side and 7 on right.
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