Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
17059216 new issues vs old issues
olnick:
Thanks for all the support and input, It will be great to once and for all have it running right!!
The cam info kept getting deleted in all my prior posts??
Rhodes lifters and cam. This was a package deal Rhodes had once offered back in the mid 1980's.
Per: Rhodes spec: 211 deg at .050 lift with .435 valve lift. the cam has a 112 deg lobe spread with approx 298 deg advertised duration. the cam was ground with a 4 deg advance built in. It is a single pattern cam. The built in 4 deg advance might count for the higher than expected vacuum reading?
Tomorrow, I'll pull a valve cover and get the casting #
Cliff Ruggles:
Single pattern cams are fine for SBC builds especially if you are using good heads. The dual pattern stuff didn't get popular until the "smog" years when they started making heads with very restrictive exhaust ports, like the 882 and similar castings.
Chevy didn't figure out how important head flow was, and combustion chamber shapes until the late 1980's when they started making the Vortec heads. By the mid 1990's the heads deficiencies were corrected, and power and efficiency was back........Cliff
olnick:
Head casting # 333882 Date code? "1243" right under the head casting # located between 1st and 2nd cyl. No other cast #'s on the head. heavy casting shown as 1974 head??
Cliff Ruggles:
Unfortunately those are what we call the "worst of the worst" for smog heads. Those heads were the biggest reason that 350SBC's thru 1973 made the grade and 1974 and later 350's didn't.
The biggest reason is the super-restrictive exhaust port which does not have a "double pass" down both sides of the valve guide. The tiny opening left by all that additional material makes them flow very poorly.
I think the engineers did that to help provide some additional "natural EGR" for emissions, but that's just a guess. The first attempt to improve emissions came in 1970 when they took the EXCELLENT 041 and 186 castings and opened the chambers up to 76cc. The result was the 441 casting. Several similar versions of the 441 followed in 1971, 72 an 73, most were 336, 487 and finally 993's. The later 487's and all 993's had factory hardened exhaust seats. ALL of those castings had the big ports like the earlier 291, 461, 462, 186 and 041 heads. Although the chambers were bigger, opening them up unshrouded the valves a bit and the later heads are actually EXCELLENT from a performance standpoint, it's just more difficult to obtain optimum compression ratios with them.
I found out about those heads way back when I first got into this hobby and traded for a set ready to go for my 1970 GM truck. The original heads, casting #441's were slam worn out. That engine otherwise was a very strong runner, got excellent fuel economy, etc. All I did was bolt on the 882 heads and it absolutely KILLED that engine. It felt like it lost at least 100hp if not more!
Back then I had to fart in my pocket to have a cent, had just got married and starting a family, but took the 441 heads to a machine shop and paid the price. Put them back on the engine and power was restored and then some, with no other changes.
Looking back on it now it was a good lesson learned and I've never been one to put my hand on a hot burner more than once!
Sorry for the bearer of bad news, no intention to put a big black cloud over the project, but using those heads is costing a LOT of power and efficiency.........IMHO.......Cliff
olnick:
Well: I'll be looking for some heads! the 041 you mention do not have accessory holes! I need my A/C P/S and Alternator!! I have not seen any 441 heads listed anywhere either??
How are the 487 heads? would I just be better off going with a set of vortec?? and find an intake that will mount the Qjet?
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