how to rebuild my 428 - Page 7 - Pontiac GTO Forum
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post #61 of 103 (permalink) Old 12-19-2012, 07:50 PM
 
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should be a minimum of 750cfm, and maybe higher, depends on who you ask. It will flow plenty. Here is a good thread on the discussion...

Tripower VS Quadrajet
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post #62 of 103 (permalink) Old 12-20-2012, 07:23 AM Thread Starter
 
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This is very interesting, thank you!
I really like the look of the Tri-Power so I never really thought of changing to a single carb. The sound is also great, especially after the end carbs come into play
I also have the sealed pan and open hood scoop to give the engine some cool air:
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post #63 of 103 (permalink) Old 12-20-2012, 09:23 AM
 
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I am with you there, the tri power has a high "cool factor". I was looking for a tri power for mine (it is a tri power coded car) but did not like the cost, and was having good results building my qjet with Cliff Rugles book. I am trying to keep my car fairly stock looking, but it is not a show car.
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post #64 of 103 (permalink) Old 12-21-2012, 04:26 PM
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Quote:
Originally Posted by Chris-Austria View Post
I've got another question

What if I use rocker arms with 1.65 ratio instead of 1.5? The valve lift will be higher I guess.. but can I just use these rocker arms and get more power? New pushrods will be used anyway.. but do I need different pushrods for these rocker arms? Which ratio should I use? Edelbrock says max. valve lift = 0.55" and the cam has 0.443"/0.465" with 1.5 ratio and 0.487"/0.512" with 1.65 ratio. So I can use either of them, correct?
(rocker arm example: http://www.summitracing.com/parts/cca-1452-1)
Sorry I'm late with a response...

1.65's will do two things because of the increased ratio: 1) increase valve lift, 2) increase the duration @ .050 figures. Swapping rocker arms is an easy way to effectively add a slightly "bigger" cam without actually changing cams.
It's not a huge change - it's something you can do if you like, or "keep in your pocket" in case you want to step it up a little later. As long as you stay with the same manufacturer and style of rocker arm, switching them "shouldn't" require a pushrod change but it's always safer to check the contact pattern on the valves just to make sure.

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post #65 of 103 (permalink) Old 12-22-2012, 01:30 AM Thread Starter
 
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Thank you for your response Bear
The engine builder sells me the pushrods, rockers, lifters and cam. I will know which parts are exactly used in January, until now I only know the specific camshaft and that he uses the stock ratio. Maybe I'll ask him to sell me a set of 1.65 rockers as well just to be sure to have the correct parts that I can change if I feel I want to try it. Probably after the engine has been driven a while and I go to the dyno I'll ask for 2 runs and change the rockers for the 2nd one.
I sometimes read that people like to "overcam" their Pontiac engines and for example Speed Pro recommends to use the smaller cam if there are 2 choices that look good. So I'm happy with my choice because I can't easily go smaller if I install the bigger cam, but with the rocker ratio I can go a little bigger after I installed the smaller cam.

The Scat connecting rods have already arrived, they look nice I will have a much better feeling everytime I reach higher rpm's now.. no matter if stock ones would have worked.. the $ 500 are a good investment for a comfortable feeling instead of being afraid to crush a "almost" new engine.

Last edited by Chris-Austria; 12-22-2012 at 03:55 PM.
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post #66 of 103 (permalink) Old 12-23-2012, 11:36 AM
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Sounds to me like you've got a good plan going. Can't wait to hear how it all turns out.

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post #67 of 103 (permalink) Old 12-28-2012, 08:53 AM Thread Starter
 
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Bear, do you know if the pushrod holes are large enough for the 1.65 ratio rockers?
(edelbrock d-port heads)
I tested it with a software called "desktop dyno 2000" and the results with 1.65 ratio rockers and my cam are a little better over the whole rpm range.
CompCams offers a set of pushrods and 1.65 ratio rocker arms (roller tip) for a good price. I'm wondering if this will fit just fine?! (high energy pushrods and magnum rockers are included). A set of full roller rocker arms is much more expensive.. probably they will reduce friction, but I'm not sure if this is really necessary for my street application?!
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post #68 of 103 (permalink) Old 01-07-2013, 10:31 AM Thread Starter
 
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the heads have finally arrived, now he can start putting things together.. there have been some changes again (heads are now 72cc, cam is now a compcams..)
the static and dynamic compression has been calculated.. it's 10.52 static and about 8.61 dynamic.. it should work just fine with 93 octane I guess





and here the final .pdf
Attached Files
File Type: pdf 66GTO Details.pdf (34.9 KB, 81 views)
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post #69 of 103 (permalink) Old 01-07-2013, 01:51 PM
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Looks like a nice build up!
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post #70 of 103 (permalink) Old 01-07-2013, 05:17 PM
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Good deal, Chris.... you do realize that a video of it running is a requirement, right?

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