Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

7028276 air fuel ratios at cruise 15.9

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Cliff Ruggles:

So my advice to the builder is to remove the camshaft and replace it with a slightly larger cam on a wider LSA and I provided the lobe numbers and told him to put the ICL at 110.  They follow my advice and no other changes.

Back on the dyno it goes and no more detonation, plus it cranks out considerably more power everyplace and they noted it actually idled better with the larger cam out on a 114LSA than with he smaller cam on a 110LSA. 

The actual dyno sheets are at the bottom of the last page.

Not saying that this is exactly what your problems are, but I suspect that the engine isn't happy with the small cam and VE is too good at lower RPM's making it finicky for timing and fuel.  With that said I'll also bet it's close to being unhappy at full load as well and I'd be careful not to ping it and cause engine damage even though you have it pulled back to 8 initial and 30 total.  Those numbers are pretty low for a 9.3 to 1 455 on 93 octane fuel with those particular open chamber heads on it.........Cliff

Stripes:
Thanks Cliff. I agree it needs a new cam. The rear seal is leaking also and thus i'll have to pull it out, and I guess I've been avoiding doing that with the good weather here...

Cliff Ruggles:
In the mean time just be very careful with timing, and give the engine the fuel it wants to be happy.  If it's not wanting any additional timing from the VA then it's pretty close to detonation on the mechanical as well, especially at full load.

Related to your thread I have a customer with a 455 and mild cam.  He's got it in a later T/A with 2.5 something rear gears.  He has an A/F gauge and monitors it for tuning the APT system on his later Pontiac carb.

He told me a while back that at part throttle (primaries only) it will range from mid 13's to as high as 17's depending on engine load, throttle angle and vehicle speed.  He also spent quite a bit of timing tuning with the vacuum advance as well and found the "sweet spot" was to use a can that starts around 8" and all in by 12" vacuum and it adds around 16 degrees timing.  He also drove it several hundred miles to the T/A Nat's at got over 17mpg's and the car doesn't have overdrive.  That's pretty darned good for a 455 in my book........Cliff

Stripes:
Hi Cliff,
My 469 with the 7k3 heads and the very mild cam finally broke a valve spring and its time to replace the heads and move to a hydraulic roller.

I plan to use a set of d-port Edelbrock 87cc non ported heads on the 469, iron intake, long branch exhaust. Stock crank and cast pistons.  My 69 Firebird convertable weighs about 3300 lbs, has a 700r4, 3:55 rear gears, a 2200rpm convertor, and a quadrajet.

I know you like more duration in a big 469, and a wider centerlines. So, I'm torn between a 230/236 @50 hyd roller on a 112CL, or a 236/245@50 on a 114CL for a street fun type vehicle, not a race car. So really the stump puller or the old faithfull? I've got power brake, AC, and power steering.

I feel like the 230/236 would be enough duration, but with my past issues, I'm unsure.

Cliff Ruggles:
230/236 with at least a .360" lobe on a 112 LSA would be plenty for the big 469 with unported E-heads, especially with a 2200 stall converter....IMHO.

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