claysmoker

I have Allen's offroad sidepipes. You can hear me comin' a mile away, and if they rob a little HP, so what? They still sound badazz.

JohnZ

That's already been done, hundreds of times over the last 40+ years, and it's been well-documented; factory sidepipes are proven power-robbers compared to the standard under-car system, especially with big-blocks that pump a lot of air. The cross-section of the factory sidepipe inner core is 2.40 square inches, and the cross-section of the standard 2-1/2" under-car exhaust is 4.90 square inches; that's the only math you need to compare the flow restriction.

Willie'sVette

I never would have purchased a non-side pipe vette. If I waited 40+ yrs for one, I was going to ensure that it had what I wanted. Looks was the only consideration. Truly, I never even thought about the question of whether they added or subtracted power.

Well, that settles the matter...from one who knows....they hinder power..end of discussion...for those that like them, it's for the looks & sound, eh?....I also required that there was A/C in mine...sure it robs power, adds weight, etc, ...I'd be damned if I was gonna drive one w/o it......most of us r cruisers, we ain't racing the thing.

65tripleblack

Judging by the trap speed, the only way that your discussion makes any sense at all is if your ZZ4 engine makes a lot more power than it's supposed to make AND if the driver for your posted run was very skilled. What axle ratio, transmission, and tires were used?

I can tell you this, complete with documentation:

My 327, in it's previous, 2011 configuration, made more than 353 HP at the rear wheels with open headers.
With the cutouts capped, and running through the mufflers pictured in my previous post (VettePack 3 1/2 x 2 1/2 muffler/resonator), it made more than 348 RWHP..........a difference of only 5 RWHP!

Compare pulls 1 and 3 below:

MarkC

Joe, what happened on the 2nd or red pull. It was tracking better than the 1st and 3rd and just drops off at 5800. It looks like you had a problem and just let off the gas. I see it is in 4th where the other 2 are in 3rd. Strong numbers for a 327.

Mark

65tripleblack

That's a great question. I don't know.

I'm not smart enough to understand how torque multiplication and gearing has more than a little effect on how RWHP numbers are calculated and output by a chassis dyno. I can tell you that the axle ratio is 3.70.

Lab dyno numbers are independent of drivetrain config/gearing............................it is what it is.................. 1:1 at the flywheel, period!

Hopefully somebody who is familiar with the algorithm used on the Dynojet will educate all of us. I would think that chassis dynos are corrected for vehicle final drive ratio.

Joe

FastEddy

Sorry. Was trying not to overload with details. Bone stock ZZ4 (355hp) with 45,000 miles on it, 3:55 rear, muncie m20, and 235/60/15 BFG TA's...and me. My first and only time on a drag strip. 3 runs = 13.2 at 106, 13.0, and then the 12.9 at 108. A few chassis dyno guys I talked to back then were quoting numbers around 300hp at the wheels for ZZ4's in 4spd muncie Vettes. The few HP calc's I've tried using 3K lb car and that trap speed show @ 300hp. (Comes to @15% loss thru drivetrain) To me it looked like my runs showed the same amount of power, but with a supposedly VERY restricted exhaust? Doesn't really matter what the true exact power of my engine was, but that those pipes were letting that much power be developed. Judging how my car ran, I would say the pipes wouldn't hurt a 327/300 one single bit, or maybe not too much on a 365 either?? I wouldn't think the difference would make it worth avoiding the sidepipes, for that reason anyway. That was my point.

When I rebuilt for more power, I went to the pipes with a 2.5" inner, and man were they loud!!!! When I raced my buddy with a nitrous'd fast burn 385 in his '68 (who can't read his tach when he races) said he didn't know when to shift cause he couldn't hear his own motor, lol

Chambered

Joe - that's awesome!!!

-Eric

Donny Brass

I get that same complaint alot....... but I also get guys stopping by the pit to tell me that out of 150 musclecars... my little L79 sounds the best rolling down the track

tjstarduster

I put a set of Hooker Supercomp undercar headers on my '66bb, then had a custom exhaust fabricated to hook up to the factory 2.5" sidepipes with a balance tube at the 3" collector. It sounds great and I don't think it cost much hp. My 496 bb goes right to 6500 rpm without a hiccup. 2 1/8" primaries and 3" collectors. Good luck, tjs

2th farmer

I guarantee you put the same person in the passsenger seat in two identical cars. (One with sidepipes and one without) and I GUARANTEE they will think the sidepipe car is WAAAAYYY faster

VetteRed1965

qwik-tripp

Well said Farmer, if we are talking about index racing a car that dead hooks and a driver that shifts like Grumpy Jenkins then 15-30hp is a BIG deal. On the street a 4speed with street tires not so much of an issue. I have tried all kinds of sidepipes for sound only. I wouldn't trade my sidepipes for 150hp, I can't hook what I have. Sidepipes are way too cool.

MikeM

When I bought my '65 Corvette in 1972, I thought sidepipes would be a nice addition for several reasons. One of them was, the other mid-year Corvettes running around back then didn't have them. Metro area population of almost a million people and never saw a single sidepipe car except in the '65-'67 era. Shortly after that, they were all gone. Saw lot's of midyears but all undercar.

Anyway, I put them on and to this day, I think those sidepipes added a little throttle response to the engine and made it a little peppier. But, it's only a 250 hp engine. It wouldn't surprise me a bit that the sidepipes really choked the BB's but so did the undercar pipes. BB cars were not real hard to beat in a drag race with one of my SB cars, on the street back then while running through mufflers. Get the BB's on the track with open exhaust on both of them and it was a different story!

Today, it seems like EVERY midyear either has sidepipes or sidepipes are a planned addition. I still have the GM issue pipes and mine aren't loud like some report unless you open the the throttle but just cruising, makes a nice sound.