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post #1 of 11 (permalink) Old 04-10-2017, 11:57 AM Thread Starter
 
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Finally on the road again

Last August, I got fed up with the Chevy 350 that came in my '67 GTO when I bought it. In September, the 350 was pulled from the engine bay.

As of this past Saturday, the GTO is on the road again with a '67 400 under the hood. It's been a struggle - since September, I've gone through 3 different carburetors and a cam swap when I discovered that the Crane Fireball that came with the motor had a bad lobe. The final specs came out to '67 400 YS block running dished pistons, '68 #16 heads, '68 intake, 7028268 quadrajet, Summit 2801 cam, '69 timing cover + water pump, Ram Air Reproductions oversized ram air manifolds, 3.36 positrac rear end, bolted to a TH400 with what I'm told is a 2100 rpm stall.

It's not perfect - something seems a little off in the timing, as I have to let it idle out of gear at around 1300 rpm to keep it from stalling out in gear, but there's a world of difference between 'barely running at all' and 'I can at least take it down the street'.

This friday I'm going to have the exhaust hung - but for fun, here's a quick little video my parents took when I left their house in its current state, running nothing but turndowns off the manifolds.


Last edited by SSnakeAce; 04-10-2017 at 01:01 PM.
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post #2 of 11 (permalink) Old 04-10-2017, 05:00 PM
 
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Hooray!!! Sounds like a Pontiac engine pumping through those pipes. Keep working at it and you will get it dialed in.

And..... did you take it easy and short shift it for the "folks?"
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post #3 of 11 (permalink) Old 04-13-2017, 02:54 PM
 
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Congrats. Time to trouble shoot, it sounds like. Make sure your timing is set correctly and not "by ear". Also check for vacuum leaks.

One other thing and it's sort of a soap box issue for me, but make sure you are not suffering from too much fuel pressure. The Quadrajet likes only 4-5 PSI and aftermarket pumps typically put out significantly more. If you're unseating the needle from the seat, it will exhibit similar symptoms to what you describe.

When the only tool in your toolbox is a hammer, you tend to see every problem as a nail.
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post #4 of 11 (permalink) Old 04-24-2017, 10:30 AM Thread Starter
 
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Hah, no. They live on a corner lot so there's a stop sign just out of view there.

We played with the timing a bit more yesterday. It was definitely out of time - was showing 52 degrees of total (no vacuum) advance @ 3000 rpm. We got that fixed - it now shows 11 degrees @ 1000 rpm and 35 degrees @ 3000. Without the vacuum advance, it'll even idle down nice and slow. The one thing we didn't really check is the actual advance curve - we pretty much just looked for maximum timing and wanted to get some numbers to compare with. We'll get there, but we didn't see it as being necessary for getting the idle under control.

Which leads me to thinking my issue may be that the vacuum canister isn't right for the car. With the vacuum hooked up, it's showing 41 degrees @ 1000 rpm. Is that too much? With the vacuum hooked up, it gains 300 rpm or so, but we've been able to get it to sit pretty happy at 1000 rpm out of gear and it drops to about 750 in gear.

For reference, the HEI unit + vacuum canister I'm using came from Butler Performance. http://butlerperformance.com/i-24453...tegory:1234791

On the fuel pump, it's an Airtex unit I bought from NAPA. It's rated for 3-4.5 PSI.

Thanks guys!
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post #5 of 11 (permalink) Old 04-24-2017, 02:19 PM
 
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You may have already seen this thread, but if not, Lars did a good job with it and many members chimed in with advice. Best of Luck with your '67!

https://www.gtoforum.com/f170/gto-tun...up-tips-13052/
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post #6 of 11 (permalink) Old 04-28-2017, 02:10 PM
 
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Just dump that adjustable vac can and get a standard motor parts...SMP VC 302...Rick auto has em or your local auto parts will cross it for you,...put that on pulls 10 degrees at crank...hook it to full manifold vac and take a spin, with your other numbers you will be real close
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post #7 of 11 (permalink) Old 05-06-2017, 01:34 PM Thread Starter
 
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Lemans guy, thanks for the heads up on that vac can. It made all the difference in the world. Took it out today and put 20 miles on it, and it's almost perfect. It's certainly happy to engage positrac!
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post #8 of 11 (permalink) Old 05-06-2017, 05:52 PM
 
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Originally Posted by SSnakeAce View Post
Lemans guy, thanks for the heads up on that vac can. It made all the difference in the world. Took it out today and put 20 miles on it, and it's almost perfect. It's certainly happy to engage positrac!

Need another video.
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post #9 of 11 (permalink) Old 05-08-2017, 03:26 PM
 
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cool...so what you really have is 21 BTDC at idle....11 base and 10 from the vac can.....

you had 35 degrees total advance you said...base +Centrifigal all in at 3000 RPM....

your centrifigal starts at 1000RPM....

Butler did you right they have the right springs in there....

I would just set that base to 12 and have 36 degrees Total (vac is not considered Part of Total)

with the vac at 10...you have 46 at light throttle cruise....perfect on today's reformulated gasoline...

If I was setting your curve on my Sun distributor machine....it would come in right there!

try twelve and test drive always listen for pinging as you don't want that, if so you can cut the base down a couple of degrees.

But I have found those settings to work real well and they came from Lars,...I go by his stuff and set up my freinds cars like that....

really makes a difference..enjoy the cool idle and responsive light gas pedal!

super car
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post #10 of 11 (permalink) Old 05-14-2017, 08:53 PM
 
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@SSnakeAce - That's just simply brilliant! Incredible sound. Sounds like a freakin Tyrannosaurus rex! You are one lucky man sir. Salute!
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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