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quadrajet: the fuel pump, fuel bowl, and accelerator pump

I wonder how bad icing may become with all these efforts to reduce intake charge temp? May not be an issue where you are, but others have said that removing enough heat from the intake/inlet air temp has caused icing problems.

Eliminating crossover will disable EGR, if that matters for you.

I'm running a 465, the crossover is almost resting on the bellhousing (within 1/8") no issue really tucking the 2.5" pipe up there. Making it look pretty and mating up to the collectors nicely on the other hand... :)

1% definitely differs from the 1HP per 10 degrees that is oft-quoted, but makes more sense, any increase in HP has to be proportional to the initial HP rating. And would be quite significant if you could achieve anything over 5%.
 
@dyeager535
  • I also heard icing could be a problem - a preliminary check on this is provided by what I think is a stuck thermostat. Most of the time my engine temp is maybe 160 deg F (highway is 180 F); a new thermostat is in the mail. I drilled a hole for air release and maybe it is too big, seems unlikely - I will use a smaller bit this time. Icing has net been a problem.
  • My K5 never had EGR so not a problem there.
  • Good advice on the clearance for the 465. The crossover must heat the 465 but I am guessing this has not been a problem for you.
update
  • Cold air intake/closed air cleaner project is on hold.
  • After three days it takes four attempts to start.
  • Planning to take temp readings of the fuel line and measure the fuel evaporation from the fuel bowl.
  • Gas mileage dropped, currently seeing 10 mpg around town, 12 mpg all flat freeway, 11 mpg in a ridiculous half day traffic jam.
    • The drop in gas mileage coincides with 1 more turn of APT to remove a lean buck and tuning the timing curve.
    • Before richening the APT and after tuning the timing curve I was seeing the higher 12 mpg range.
    • Before tuning the timing (lots more mechanical advance and less vacuum adv) I was in the mid 13 mpg range - but had lean bucking, and I sometimes had to feather the clutch to get going from a stop.
    • Overall my wife likes how it drives now that the timing comes in earlier and the APT is richened.
  • I plan to take the blazer into my local shop and baseline the A/F ratio with the exhaust analyzer.
Might be 6 months before any of this is done.
 
All the small blocks of early vintage, unless they have a shutoff valve on the heater core lines (which is rare on the trucks) are already bypassed. Seems like people are always able to come up with weird one off problems they've had, but the radiator cap is the highest point in the cooling system on these trucks, so they will purge air fine, unless the thermostat forms an air-tight seal under pressure, which seems highly unlikely to me. I've never seen the need to drill a hole, but that's me.

I actually have the capability to measure the SM465 fluid temp, and I've done it in the past, so I have historical data. I could measure it again, it will just take some effort and I'll have to wait until it warms up to be somewhat consistent in ambient temps. One thing I noticed with the 465 is that the fluid temps stay very consistent....if you run it down the freeway with little load, they stay quite low, once they come up from ambient temp. If you load the trans up (climbing a hill I noticed it) the temp will climb, and once it levels out, it will not shed heat long after (hour-plus) you get back to low-load conditions. I'm sure it's a function of no sort of cooling and the cast iron case, just something I found interesting.
 
A thermostat I bought had a little air bleed to release trapped air and the next one did not. So I started drilling a small hole (last 15 years) in the flange to release the air trapped when the thermostat is first installed. I noticed that without the air bleed the engine would get hot (210 deg) before the thermostat opened and the temps came back down. It was only the first startup after a new thermostat (or other reason to pull housing). I realized it must be the trapped air. I have read elsewhere about drilling a hole - a quick search found this ck5 thread https://ck5.com/forums/threads/cooling-system-qs-couple-out-of-the-norm.217254/

Nice details on SM465 temps. How hot did it get on the hills?
 
I saw 210* after pulling some good hills in 2nd gear. Not ridiculous, but it will run 100-150* all day long at 60MPH+, so a significant change.

Not really much out there I can find on what is "ok" for gear oil temp, but it *seems* that 250* is the upper end, so still within that range. But getting close, IMO. Might get interesting if the crossover is dumping heat into it.
 
Just in case it isn't in this thread, I added a pressure regulator and it has worked fine. I can see now that there was surging before while cruising. Everything is crisp now.

Fittings
  • -6 O Ring Boss 3/8" Hose Barb Adapter AN Fitting ORB
  • -10 O Ring Boss 3/8" Hose Barb Adapter AN Fitting ORB
  • -6 O Ring Boss port plug
  • 1/8" NPT port plug
Magnafuel pressure regulator PN MP-9633 http://magnafuel.com/products/carb/regulators/index.htm
 
I know this is a bit of a necro post, but I wanted to read all the way to the end, and it took a little bit.

Back when I had my big Ford F250 with a 7.3, there was always someone on the forums with hard starts and more times than not, it was air in the fuel injector return lines. Redo the entire return line system, special O rings, blah blah blah. Even with a perfect system there could still be problems, there were just too many places for air intrusion into the fuel system. What some guys did, and they swore by it, was to install a small electric pump that only temporarily bypassed the mechanical fuel pump. Some guys had it on a separate timer, some guys ran the power to the pump off the wait to start circuit, other guys ran it off the power to the starter itself. All 3 ways eliminated having to use some sort of inertia switch for accident protection since the power to the electric pump was only temporary.

What you could do, is plumb that cheap electric pump right around your mech pump enabling you to continue to use your existing fuel regulator and filter. When the electric pump is off, the mechanical pump does what it normally does.

Just a thought. And thanks for the thread, I've learned a lot and got several ideas bouncing around in my head for the Jimmy. I've got the engine running after the rebuild and cam break in and have some gremlins to squash before I go adding stuff to the mix.

Thanks again.

Joel
norcal
 
By the end of this thread that QJet starts just by thinking... 'start'

Unless it has been sitting a few days, then it is rrrr... rrrrr... Then think... 'start'
 
i think I saw well plugs mentioned in previous post. did you ever check the well plugs? After awhile the well plugs begin to leak and allow the fuel to drain into the manifold.
this sounds like it may be your issue since it normally take hours for the well to empty. when ever I rebuild a qjet I use jb weld or similar to reseal the well plugs there are four? iirc, plugs that can leak. remove carb from engine and throttle plate assembly, you will see the the lead plugs used by Rochester to seal the access to drill the passages during manufacture
 
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