Ol' Ugly 507 update... it's getting unleashed.. ulp.

[novi2krt]

Welp.. my project as some know has been on the road for 5,000 miles or so..

here's what I found today after I finished the rear end swap..

in checking timing more closely and carb. details.. I found way to much total advance for my engine combo/fuel supply.. yanked the MSD, and swapped to the large black bushing.. then let the rate come up real strong and fast, light silver and light blue spring.. set the initial back up at 10 degrees from 4 where I had it.. used to sound like a tractor at idle.. now purrs like a kitten..

also found that while playing with the throttle, the vacuum secondaries wouldn't open much at all.. two reasons I found.. linkage of the vacuum lock out doohickey to short a lil.. and spring is to heavy to get a real quick response on them.

Tweaked linkage a bit.. not sure what to do about spring..

BUT!

Between the timing curve changes, added air from a bit more secondary opening, larger air filter, and 3.4 to 3.7 gear swap..

the engine has become explosive!!!!!! I was impressed with it the way it was.. but evidentally.. I had not experienced what a 10.5 compression, 507, with MTS #10 cam, Edel intake, long tube headers, true dual 3" exhaust had to offer.. dohn think I have it all unleashed yet.. will once I get the EFI swap done on it..

but DEEEEEEAAAMMMMNNNNNNNNNNNNN tap the throttle the slightest and the front suspension instantly releases and shoots for the sky!!!!!!!

Man I love this truck!!!!!!!!!!

[onovakind67]

What kind of carburetor has vacuum secondaries with a lockout?

[novi2krt]

the stock Q jet from a 71... hehehe.. I haven't bothered swapping to a different carb since I am planning the EFI conversion for it. But didn't realise this one was not giving me full giddy up..

got 'spicious when it laid over at roughly 4000 at the track.

Kinda ran like my 440 Dart did with the temporary 650 Carter on it. LOL

[onovakind67]

The Q-jet actually has mechanical secondaries with an air valve. The air valve will rotate if the engine is loaded, but I wouldn't expect to see much action out of it while you're under the hood.
You can adjust the release time of the vacuum pull-off dashpot by drilling out the orifice to roughly .025".
You can adjust the spring tension on the air valve by loosening the set screw under the passenger side of the valve and turning the adjustment screw to set the desired tension.
Car Craft has a reasonable picture of this procedure:

http://chevyhiperformance.com/projectbuild/148_0403_quad/index3.html

[novi2krt]

the air valve is what I meant by vacuum secondary.. my bad.. I know the main plate is mechanical. I will play with it some more and see about getting it to open faster and sooner.

Thanks.

I am by far more used to EFI tweaking and tuning using stand alones.. but am not quite ready to build the new setup for this one.. wanna play with the OE (sorta) setup a bit first.

[novi2krt]

ps..

thanks for the link!!! I was studying the air door adjustment..

one.. I like EASY!!! hehehe

two.. my air door tension is definately NOT light.. fairly stiff actually. I will play with this and see how it reacts.

I have a couple other sets of metering rods to play with as well incase I start starving the engine on top with the secondaries open.

I think I will find my vaccum gauge and hook it up to see what kind of vaccum I am getting at different throttle positions as well.. get a mental image of what the blades are doing that way.