Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
17057266 1977 W72 q-jet- changes necessary?
Kenth:
--- Quote from: Mr Hand on August 04, 2021, 07:13:08 AM ---Other prob is it pings like crazy at speed once I am into the secondaries. I kept the timing specs stock just to establish a baseline and go from there......16 initial, 24 mechanical, 25 vac advance. It was re-curved to be all in by 3000 RPM.
--- End quote ---
All in at 3000 rpm´s is NOT stock, 4400 rpm´s is.
I will NEVER understand the urge some folks has to get "all in" earlier than factory settings. The factory ignition curve is there for a reason. And the reason is engine design/parameters.
You do NOT help the engine by igniting a too lean mixture by ignite it earlier, the real cure is to give the engine a proper, fully combustible, mixture at factory ignition settings.
How many times do you read "i have all in at 2500-3000 rpm´s and now my engine pings", big surprise!
FWIW
old cars:
Good or bad positive stop?
Cliff Ruggles:
I've seen them done in similar fashion and it is effective.
It really doesn't provide an easy method to control how much timing is added.
Here I MIG weld up the "slot" then use a round file to precisely control the stop point, which also controls how much timing it adds at the same time.
Cliff Ruggles:
"Engine will be totally stock right down to the single exhaust with the original catalytic convertor.
Just a .040 overbore and a 066 cam which is almost identical in duration to the original W72 cam with the only difference being slightly more lift at .407 vs .364"
I'm curious as to which pistons you are going to use? All of the "builder" pistons being sold have 8 valve reliefs and end up .030-.050" in the holes at TDC. NOT a good place to be as this will reduce the compression ratio nearly a full point and even more if you use a thick head gasket.
Pontiac 6X heads have flat combustion chamber floors and are more sensitive to quench area than most others. They thrive on tight quench and will run cooler, less timing required, and less octane sensitive (detonation) at the same time. They will also make a LOT more power.
What else is being done to it to deviate from "stock"? Hopefully it's not getting a "double roller" timing set or a high pressure oil pump. We've seen nothing but issues with currently available double roller timing sets including being inaccurate and the chains stretching out very quickly. I wouldn't use roller rockers on it either, and if you venture that direction avoid anything but Crane Gold Race, Harland Sharp or Crower Enduro. Everything else we've seen used have failed miserably and/or put metal into the assembly. The WORST of the bunch are Comp Cams roller tip rocker, absolute JUNK.....IMHO......Cliff
Mr Hand:
--- Quote from: Cliff Ruggles on August 05, 2021, 05:57:46 AM ---
"I'm curious as to which pistons you are going to use? All of the "builder" pistons being sold have 8 valve reliefs and end up .030-.050" in the holes at TDC. NOT a good place to be as this will reduce the compression ratio nearly a full point and even more if you use a thick head gasket."
"What else is being done to it to deviate from "stock"? Hopefully it's not getting a "double roller" timing set or a high pressure oil pump. We've seen nothing but issues with currently available double roller timing sets including being inaccurate and the chains stretching out very quickly. I wouldn't use roller rockers on it either, and if you venture that direction avoid anything but Crane Gold Race, Harland Sharp or Crower Enduro. Everything else we've seen used have failed miserably and/or put metal into the assembly. The WORST of the bunch are Comp Cams roller tip rocker, absolute JUNK.....IMHO......Cliff"
--- End quote ---
Pistons are TRW speed pro forged.
Timing set is all NOS parts. Cam gear, crank and original style wide link chain.
Stock Melling 60psi pump.
No roller rockers, no trick aftermarket parts anywhere.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version