Hey there. Thanks, but I did try an aluminum sheild along with a Phenolic spacer. I had the same results. It only happened during the summer on hot days. The oem carbs and Holleys that are not made of aluminum are not affected.

Ranger: losing my bottom end was a major concern of mine. I had a guy on the forum help me out to 'design' a custom cam that would give performance and retain the low end torque that the inline crowd loves. Oh boy. Well, I'm going to try a Quadrajet with small primary bores to see if that will give me back a bit of the bottom end. If not, I'm considering doing a cam swap. However, because of my piston choice and chamber size, if I want to stay under 7.5 dynamic compression ratio, my choices are limited.

 

I sure hope you figure it out soon. When you do, please let us know.

 

Not necessarily related to the issue, but 7.5 dynamic is a pretty good number. I bet it's pretty snappy on crank up. What did your static compression ratio work out to?

 

The static cr was 9.3, dynamic 7.17.

I was reading through the link the other member posted regarding Holley carb tuning, and found this: Increasing cam duration requires more jet. A dual plane manifold can use a much bigger carb. If you decrease the metering signal, you need to increase the jet (as you do when converting from a dual plane to a single plane manifold). I went from a manifold with divided ports, smaller runners that gave greater velocity and stronger signal to carb, to a single plane, open plenum intake. I also changed to a cam with much more duration. I think I am on track.

 

Larger plenum intake manifold? That's a new twist I didn't know you had. Which one exactly? I gotta say, all the components you've laid out here, say to me, High RPM Engine. Open plenum or single plane intake manifold, ported cylinder head, high lift/more duration camshaft,...that sounds like an engine designed to launch at 3000+ rpm, and run at WOT. That's the opposite of the components I pick for a street / off road performance engine.

 

The 300 has the bore of a 400 v8, but comes with a U head instead of a cross flow. Add to that the tiny oem ports, and you get an engine that is choked. I had a dual port, not dual plane, manifold on it before. The new manifold simply opens up the runners to the size of the oem intake.

Today I'll ck the mechanical advance. Yesterday I checked my main jets. Holley jets are not sized correctly. Although labeled 57, the measured .055. Even the new in the package ones from holley, labeled 60, measured .058. I tried the larger jets. I also changed from a 6.5 pv to an 8.5, which is what the carb came with from the factory. I could tell there was better acceleration, but cruise at 40 mph in 4th gear showed 12.8 afr. Today I'll try it on the freeway at 50, 55, and 60 mph.

I noticed that one side of the accelerator pump squirter seems partially clogged, is only discharging 1/3 what the other is. I tried to remove the squirter and blew air through it, but the problem persisted once reinstalled. This carb sat for 4 months, and I only changed the gaskets on the bowls when I installed it. Now I'm thinking it may be time for a rebuild.

Ha! the secondaries stuck open and the rpm hit the roof and I had to shut down the engine. I have a quick fuel adjustable diaphram. That was not fun.