Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Dreaded nozzle drip 17056200
Cliff Ruggles:
Why are hot starts "not happening"? Is it "bucking" the starter or flooded?
That tiny gap in the carb to intake gasket has nothing to do with your issues as it would compress the second the bolts were tightened down holding the carb to the intake.
12-13" vacuum is pretty "low" for the combination of parts. I would have expected closer to 14-16" and relatively smooth idle quality with maybe at most a "deep/heavy" sound in the exhaust.
Might want to go back thru the valves and make sure you don't have one that's too tight holding a valve open just a bit.
When it comes to cams Crower grinds will act bigger when compared to others as they use longer seat timing providing more effective duration. I use and prefer them as they have gentle ramp profiles and don't require a butt-ton of spring pressure like other companies that use "fast ramp" technology.
I'd also add that on the dyno Crower grinds really deliver and we've made more power with them pound for pound.
For example, in a Pontiac 400 build with unported #16 heads at 10 to 1 compression the Crower 60916 (221/229/112) cam made 419hp/453tq. With the next cam in their line-up the 60243 (228/234/112) the same engine made 424/465tq.
Idle vacuum for the 60916 cam was 14" at 750rpm's, the 60243 was down to 12" at 750rpms. This is with 10 degrees initial timing. Both cams were relatively smooth for idle quality with just a hint of "lope" with the larger cam.
I've done more dyno testing than most who will read this, and back to back cam testing on my nickel to see what works and what doesn't.
The Comp XE lobes are just pure CHIT despite the excellent advertising for them. They also have issues at high RPM's loosing control of the valve train as the seating velocity is just too quick and even using their recommended springs (which have too much pressure for street use IMHO) we still saw a quick and abrupt end to power production on the dyno right around 4900-5200rpm's every time we tried to test one.
Sorry to wonder off track but I use these opportunities to educate others.
I'm not seeing why you are having so much trouble here and still think that you have a fundamental issue someplace.
Did you degree the cam when it was installed?
What timing set was used?........
old cars:
The calculator you used may have been for seat to seat intake closing . Your cam card may be intake closing at .050" spec. Try this one
https://www.gofastmath.com/Compression-Ratio-Calculators/Static-And-Dynamic-Compression-Ratio-Calculator
68rs/ss:
Cliff, Thanks for the reply. After taking a couple days off to get some other stuff done, found cause for problems I was having. I suspected leaking intake on bottom side and was confirmed today after I took it off. 7 of the 8 ports were sucking air/oil from the bottom. Checked intake machined flange and found one side to have high spot where heat riser port is. Will be sending this new intake back for refund. It never fit properly from the beginning, with filing bolt boss's and holes to fit. One would think, with everything being new there would be no issues like this. I did use a brand name gasket and torqued bolts to proper torque and order in progressive higher settings till proper torque value was reached.
Will be using cast Q-jet intake in its place. Modified plenum to make two sides and smoothed out corners. Only disadvantage is the thing weighs a ton. Hopefully this will work OK.
I kind of enjoy Cliff sharing his knowledge here. Most of us learn by either reading or with someone's help.
When this is running again, will post update.
Thanks for the guidance and suggestions. learned some stuff.
Phil
Cliff Ruggles:
The factory cast iron intakes are excellent, especially the early high rise variety.
Don't sell the later "flat" big block intakes short either. I've helped out quite a few folks in FAST and Pure Stock using them and they make great power.
Not that long ago I helped a customer from Canada with his 1970 Chevelle 454 being built for FAST Class racing. He must use the stock flat iron intake. The engine was stroked to 496cid, well prepared heads, high compression and I provided the carb and helped with the cam selection.
It cranked out over 580hp and nearly 600ft lbs torque with the "flat" intake and no spacer under the carb! I know a lot of folks who ditch those intakes for an aluminum "high rise" intake on engines making a LOT less power thinking they are helping the engine out someplace. Then they loose even more power "cobbling" things up to get the air cleaner to fit under the hood or their Cowl induction to fit, etc.......
Cliff Ruggles:
I still remember the last Edelbrock intake I installed on a 454 Chevy engine. It didn't fit for chit and required taking an angle grinder to it so it would sit down and seal the gaskets. I'm not all that fond of them right to start with and even less when you have to modify them to make them fit......FWIW......
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