7mpg gas drinking beast!
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 493
From: Salmon Arm, BC
Two things I'd check. Those ngk plugs seem to be too cold of a plug, check with another supplyer to make sure they are correct. I always thought the '75-'80 sbc's had projected tip plugs. I once put a set like the ngk's in my motorhome by mistake, and the thing ran like crap.
The other thing i'd look at is the catalytic converter..... if you still have one. It could be almost plugged.
The other thing i'd look at is the catalytic converter..... if you still have one. It could be almost plugged.
Thread Starter
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Joined: Dec 2007
Posts: 79
Likes: 1
From: Redmond WA
Hi Fabio,
Are you saying that when you set the timing to a reasonable 10°-12° with the vacuum advance disconnected and then when you hook up the vacuum advance, you cannot get the idle speed down to 700-800 rpm with the idle adjust screw on the driver side of the carb?
If I understand you correctly, something is not right. Have you checked your throttle cable to see if it is keeping the throttle slightly open? If it's not the linkage, then start looking for a vacuum leak as others have suggested.
Are you saying that when you set the timing to a reasonable 10°-12° with the vacuum advance disconnected and then when you hook up the vacuum advance, you cannot get the idle speed down to 700-800 rpm with the idle adjust screw on the driver side of the carb?
If I understand you correctly, something is not right. Have you checked your throttle cable to see if it is keeping the throttle slightly open? If it's not the linkage, then start looking for a vacuum leak as others have suggested.
The symptom is: If I set the idle speed to minimum the car don't shut down! And that might be ok right? Instead idle bottoms on what sounds like 500rpm on ported vacuum, on full mainfold vacuum it sounds like 750.
The cable is ok, I had to fabricate the linkage and build a way to adujst the cable slack as you can see on the pics.
My tach is not accurate so I don't have a precise reading of the idle...
The vacuum leak is not ruled out,I still have to investigate it further.
So the harder the better(as long as it don't cost me more 
)
Originally Posted by glenkov48
I once had a Pontiac that the secondaries would open at about 2500 rpm in normal cruise mode. The milage went up drastically after adjusting correctly.
Originally Posted by sstocker31
Two things I'd check. Those ngk plugs seem to be too cold of a plug, check with another supplyer to make sure they are correct. I always thought the '75-'80 sbc's had projected tip plugs. I once put a set like the ngk's in my motorhome by mistake, and the thing ran like crap.
And yes this plug specs are colder that all the others, it's even hard to find them as in 76 they went back to the projected tip ones. This car already has a higher comp ratio an I saw improvement from increasing the timming, the spark plug gap, now the spark plug itself, the car is definetelly running better and sounding differently now, lets see how it reflects on mileage.
Originally Posted by sstocker31
The other thing i'd look at is the catalytic converter..... if you still have one. It could be almost plugged.
it has 2" duals all the way to the back, the last section and mufflers look beaten up, I'm considering a upgrade to 2.25" or 2.5", not sure about H link, cheap summit headers? Suggestions???Zwede, I have some pics for you, I'll post back once they are online.
Thanks guys!
Fábio.
Thread Starter
Advanced
Joined: Dec 2007
Posts: 79
Likes: 1
From: Redmond WA
Let me know what you think...
The Holleys are always jetted a little rich as they don't know what engine you're putting it on and a rich engine still runs good.
You'll have to tune the holley to get max economy. If tuned right it will not loose any response or power, just improve economy. But it can get tricky to do them right and I highly recommend a wideband O2 meter.
You'll have to tune the holley to get max economy. If tuned right it will not loose any response or power, just improve economy. But it can get tricky to do them right and I highly recommend a wideband O2 meter.
I'm excited about playing with a new tool but is it really necessary? Any other guys with Holley StreetAvenger on vettes around??
Thanks,
Fábio.
Le Mans Master
Joined: Apr 2005
Posts: 6,359
Likes: 428
From: Seattle Area WA
Fabio,
As I recall Lars has found these carbs to be jetted very lean. Here is one of his threads.
http://forums.corvetteforum.com/show...street+avenger
As I recall Lars has found these carbs to be jetted very lean. Here is one of his threads.
http://forums.corvetteforum.com/show...street+avenger
Thread Starter
Advanced
Joined: Dec 2007
Posts: 79
Likes: 1
From: Redmond WA
Fabio,
As I recall Lars has found these carbs to be jetted very lean. Here is one of his threads.
http://forums.corvetteforum.com/show...street+avenger
As I recall Lars has found these carbs to be jetted very lean. Here is one of his threads.
http://forums.corvetteforum.com/show...street+avenger
My SA dont seem to be suffering from these problems but I'm just a rookie on this you know... I'll investigate further...
Fábio.
