TeamEvil wrote:
Conflicting info seems to abound. The reason for the mechanical secondary statement is due to the second hand experiences that I've had with my friend's TR8. He always went with a mechanical secondary when he could, usually the chromed Holley carb. I've heard it elsewhere that mechanical secondaries were more sensitive to the carb needs and offered a better transition because of the precise linkage.
Still open to any and all suggestions, but starting to get confused by opinions, you know?
I guess that the 600 is the over-all choice, just have to narrow down the make and model.
The Carter AFB is almost the same as the Weber/Edelbrock offering I think. They look very much the same anyway, not at all sure of how they perform or is they're still available or even if they'll work with a drop base air filter.
Here is my input based on a lot of experience, but it is still just someone's opinion on the internet.
I hate carbs that are too big. The difference between a 390 cfm 2-barrel and a 750 cfm 4-barrel will be about 5 hp on that stock engine. Going too big will mean losing throttle response and part-throttle torque. 600 cfm is more than enough. That engine is totally done by 5000 rpm anyway, so unless you're racing and spending all your time at WOT, size it right for the street. 500-600 will be a nice sweet spot for you. Going too small means losing 5 hp between 5000-5500 rpm, but going too small could actually make it quicker on the street by improving torque in the 1500-5000 range.
Back in the 80s and 90s, Edelbrock made a few intakes for short windsors. Is yours a squarebore or spreadbore? If its a spreadbore, hands down get a Qjet. Period. If its a squarebore, don't try to adapt a spreadbore carb to it. The transitions in the adapter are terrible and will ruin airflow quality. Qjets are the most accurately metering carb available. They are a bit complex, but they have a hundred ways of fine tuning for different loads and throttle positions you see on the street. They are also truly flow-sensing. You can't oversize a Qjet. If you could graph the fuel delivery of a Qjet you would see it is a nice sloping curve. Other carbs kinda stab at mixtures offering one bulk delivery for each of the circuits; idle, primary, secondary. That graph would look like tilted steps. It doesn't usually show up as an issue on the butt-dyno but they really do miss the mark in a lot of situations.
If you want a squarebore that is super simple, Edelbrock 1406 is the way to go. They advertise "out of the box" but you'll have to get a jet/rod kit. I put one on a 389 Pontiac and had to go two steps bigger on the primaries and 5 steps bigger on the secondaries. It almost wouldn't run at anything but idle. Holleys are also a very good carb.
On the topic of vac or mech secondaries, it depends on the application. Racers tend to lean toward the mechanical because they want it open. They want to control the throttle and not a vacuum pot. Mechanicals are also often preferred in manual transmissions while vacuum secondaries tend to be preferred with automatics. In an automatic, the shifts occur without your input which means that load and demand change on their own without your foot doing anything. In a manual, you are more in control of RPM and load, so the mechanical secondaries reflect your input. (that is a very simplified way of saying it).
But to say that mechanicals are "better because my friend had one" is not really valid. If you are looking for easier to tune, street manners, and less headache, a vacuum secondary might be better. If its a street vehicle, err on the side of the less-racy version; smaller cfm, vacuum secondaries.
I always go Qjet when I can. I have spent many moons getting acquainted with them and when tuned right, they are an amazing carb. They were accurate enough that GM used them as late as 1989 and was able to get them to pass EPA regs while everyone else had to go EFI. Even after trucks went TBI, many guys swapped back to Qjets and picked up power and MPG. Really awesome carbs.
