WRONG! Small tube headers and Try Y designs work better because of SCAVENGING. Velocity for low end performance only applies to the incoming fuel charge, and one reason is because the fuel and air have to move fast enough to keep the fuel suspended in the air, too slow and the fuel begins to settle out and puddle on the manifold and intake runner floors.
The very small difference in viscosity between hot and (marginally) cooler exhaust gases is minimal and more than offset by the extra flow capacity of the larger pipe. The problem with the larger pipes is there is so much capacity that the scavenging effect is lost because the outgoing charge can suck air from so much larger a volume that the pull on the next charge is minimized.
I think I misstated the benefit of an X or H pipe, though. It is not really a scavenging effect in play in that situation, but an equalizing effect closer to back-pressure, where the pipes aren't completely filled and emptied on each fire, but some charge remains in the pipe which actually helps to slow the rate at which the exhaust pulses travel down the pipes, eliminating the pop-pop-pop of a true dual at idle. This is a benefit for extremely low end rpms only.
Back to the topic of pipe size- the overwhelmingly important role of exhaust scavenging takes place at the collectors of the headers, reducing the size of the pipes afterwards will NEVER result in any more power at ANY RPM. In fact, while scavenging has a beneficial effect on performance, the real and most performance gain is realized in the increased flow that the headers provide. And after the collectors, BIGGER IS BETTER, been proven time and again by people smarter than me who care a whole hell of a lot more about performance than me.

 

I DIDNT READ IN DEPTH THE ENTIRE POST BUT FOR THI S ENGINE THE BEST THING TO WAKE IT UP IS HEADS/CAM/EXHAUST WHICH IS RELATIVLY CHEAP. i would PM Conanski, he knows a lot of little things that get overlooked on these motors.

sry i didnt realize i had caps lock on, i wasnt trying to be loud

 

thank you all so much i am learning so much. The main thing that i was woried about was the decelleration "poping". I cut the muffler off my truck and when i put in 1st or even 2nd gear it pops and im woried that the more flow the worse the poping. will a good set of headers treat this or does the answer lye in the muffler and cat.

 

I have had that for a long time. Check your plugs and wires. We changed half the plugs (the others were too hard to reach in the cold), the wires, some of which weren't even on the plugs, and the distributor cap. There was a bunch of carbon tracking on the distributor cap. I have had basically no popping whatsoever. It's a good thing I read this again. I hated it soooo much. I hope this helps you man!!!

 

We have emmision testing here how do these exhaust mods effect that?

 

thanks rambuck. i have already change the plugs and wires and installed a new distributor cap. I did manage to reach all of the plugs, its good to be 6'5" haha.

 

Not when you try to walk through a 6' doorway. ha ha . I'm only 6' even myself, and I've had my share of head-bangers. I'll bet you trip over crap a lot, because you are always looking up to avoid the obstacles.

 

i may have some obstacles that i need to watch out for but the shorter people that are my age need to watch out for me! I can't count how many times people don't look ahead and before i know it bash their heads/faces into my shoulders hahaha! back to the discusion though, i found that short tube headers tend to be more expensive and the longer headers are cheaper. Why is this? Are the short better than the long? Im looking for all around performance gain. Haveing ridden motorcycles all my life and now owning a CR500 two-stroke (60hp@230lbs) i understand the relationship of torque and horse power. im using my truck for off road and just got 36" tires so probably lean to torque more than horses.

 

*I can't count how many times*

 

Long tube headers provide better torque. Shorties are for horsepower. You see plenty of long tubes for trucks, and mostly shorties for mustangs.

 

I looking for some budget heads for a carbeurated 351w though. Any suggestions, I am open to going to a salvage yard for some gt-40's I just don't know which ones would work best. I am building the motor to go in a mud-sand-trail truck. I need horsepower from 1500-5500 rpm. Like I said Carbeurated, rv cam, headers. Any Ideas on what heads?? Thanks

 

i have read in some readers rigs mags that 69 windsor heads work well.

 

Short answer- Short tubes suck. They are more expensive because is it harder to build a short tube header that is worth using. Therefore, the reason they are more expensive and the reasons they are harder to build should make it obvious, that unless there is some reason that requires you to use them, long tubes are the way to go. Not only are they cheaper, but way better.
Just to drive home the point, if you haven't gotten it already- long tubes generally provide more low end HP and torque.

 

I'm pretty happy with the JBA equal length shorty's that I have on the windsor in my Jeep. Yes the 69 4v 351 windsor heads are great heads, I've been running a set for about 25 years

 

1969-70 4v 351 Windsor heads are the same as 1969-70 2v heads. It was Clevelands that had different heads for 2V vs. 4V engines around this time.