To H pipe or not..

[muncher]

Hi All. Well my spruce up of my 87 305 stepside continues.
Today I had a dual exhaust system made up, no H pipe. It has two centre performance mufflers only.
Would leaving out the H pipe reduce low down torque? I like the sound it makes especially at idle. Has a nice rumble/pulse. Just don't want to negatively effect the performance.
I have read lots on the www.......now have a huge headache
If anyone out there has any advice please chime in.
Cheers guys.

[rich weyand]

Either an h-pipe or an x-pipe.

The issue is that a V8 does not alternate sides in its firing order. 18436572 is LRRLRLLR. Those successive pulses on each side run into the previous pulse's over-pressure in the exhaust. So the scavenging and power from the #4 and #7 cylinder aren't as good as the others. What the h-pipe and x-pipe do is allow the extra pressure of the second pulse to vent to the other side, reducing back pressure on #4 and #7.

So either is fine. Simplest from where you are now is to put a 2" h-pipe across between the existing pipes, as far forward as you can.

[muncher]

Will I be loosing low down power without the H pipe?
Cheers

[Edahall]

Originally Posted by muncher

Will I be loosing low down power without the H pipe?
Cheers

Like at 1500 rpm or off idle? Probably not.

Is your truck suffering from low down power?

[SCOTI]

Originally Posted by Edahall

Like at 1500 rpm or off idle? Probably not.

Is your truck suffering from low down power?

It's a 305.... "Suffering from low down power" is very subjective.

[rich weyand]

Originally Posted by muncher

Will I be loosing low down power without the H pipe?
Cheers

Yes.

[Gregski]

another option would be the X pipe, I put a bolt on X pipe from Summit on my '74 350 V8 and I must admit it was a PIA to install without welding just all bolted up, I had the truck Dyno tested with just dual exhaust and stock manifolds and it tested at 195 HP I have yet to take it back in to test it after the X pipe was installed with long tube headers, but I plan on doing it soon this month I hope

[Tom]

Yes using either one will give you more power, down low and up top. How much is the question.

[kalbert]

Originally Posted by muncher

Will I be loosing low down power without the H pipe?
Cheers

Probably not noticeably.

Is an H pipe good? Yes. Can it improve WOT performance at low RPM? Yes. Will you notice? Probably not. Does it have any affect on part throttle performance? No.

[muncher]

When I drove home after the exhausts were made, no H pipe, i loved the sound but felt it was down on low end power. That's when I did a little www surfing and found arguments for and against the H pipe. It seems from the general feeling here is that a little is lost but how much is questionable.

[rich weyand]

It's a 7-12 hp difference on a 400 hp install, so on our trucks it's probably worth 4-9 hp, depending on where in the typical 200-300 hp range your setup falls.

[muncher]

Thanks Rich. I am going to drive it this week and get a feel on how it performs now. Then fit the H pipe and see how that feels. I want to keep as many of the horses as possible on my little ol 305.

[rich weyand]

Consider though that it will change the sound. If you really like the way it sounds now, you may be disappointed. It IS a gain -- it's basically free horsepower -- but it's not much.

[cadillac_al]

I am the old school type and like my exhaust in stereo. I don't mind living with a couple less horses under the hood. Just one man's opinion.

[69heavychevy]

I went from true dual exhaust to an x-pipe. I cant say for sure that I gained or loss any low end power. The exhaust note did change though.
I'm running a thumpr cam and with the duals it was annoyingly loud and choppy at idle.
The x-pipe definitely silenced and smoothed it out at idle, but it still retained some of the choppiness.

[asphaltburner]

305, or not, go with the "H", or "X", pipe if it is financially feasible. Cost is minimal,...benefit is maximal.
I built FRANKENTRUCK with this exhaust:



because it sounds great, performs great, and it provides FRANKENTRUCK's 350 V8 with the best scavenging of the exhaust "charge",...therefore enabling flow.
For your 305, this will help the engine "breathe" better (through easier exhaust,...resulting in some "pep"), you might gain a mile per gallon, and your truck might run a little bit cleaner.
You are not going to be burning rubber with your 305 by adding a crosspipe, but you, and your engine, will benefit overall. Could it improve your low-end torque? Somewhat, yes.
Good luck and have fun!
Todd.

[andrewmp6]

I would have a exhaust shop mount a H pipe for you.

[motornut]

I replaced a rotted out "stock" exhaust on my 79 305, with manifolds 2.25 duals with H pipe,short pipes to flowmaster 40s out before the rear wheels.
It seemed gutless when broken off,I'd say yes to improved off the line and nice even sound,side to side

Midas did mine

[muncher]

Thanks again for input guys. I have it booked in to add H pipe. I can give you all a back to back on how it feels next week. Also after Xmas I will be getting it tuned/chipped to see what else I can get from it.

[muncher]

H-pipe now fitted. I have to say there is a difference low down. Much better, feels crisper. Its not a major difference, just better. The exhaust note is more evened out and has a deeper tone. I have to say, for me, I like the H-pipe fitted. Next the tune up/chip reflash in the new year. Isn't expensive to do and should make the most out of the mods I have done.