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Hi Rob,
I try not to get involved with the Politics but had to add my two cents to this one. The post above you mention X and H pipes what you dont mention is the size/diameter of the exhaust. Please correct me if I'm wrong here I'm going off of old reads and Concourse repo exhaust systems that list the ZL1 exhaust diameter is 2-1/4" headpipe into 2" inch tailpipes, the L88 Headpipe is 2-1/2 into 2"tailpipes. The PSMCDR is allowing an upgrade all Vehicles that dont have 2-1/2 and also allowing an H or X Pipe again UPGRADE! Mopars came with the 2-1/2 and H so No upgrade here!

Interesting read here from Bill Porterfield (ZL1 pioneer)regarding his dnyo testing.

The ZL1's and L88's were some of the most wicked Iron to come out of the Motor City No Doubt but without the Upgrade given to them by the PSMCDR rules they would be down how much horsepower with factory exhaust??? 147.9 Horsepower gain with Headers goes to show you how bad this combo was corked up from the factory? The UPGRADE that was given didnt apply to the Mopars that came stock with 2-1/2 exhaust with H. So how much horsepower was GIVEN to any brand that could benifit from the UPGRADE? Bill Porterfield did a nice job of Documenting.

Also to quote Bill Porterfield who has been restoring ZL1's since the 70's " All ZL-1 cars were equipped with AIR pumps and Gibbs' cars were produced with standard N10 dual exhaust."

Seems like every Reference resto I see has a Smog Pump, Yenkos,Copo's L88's, 435's I've been looking at the L88's for the last 6-7 years and every survivor car I've seen has a smog pump the Fields survivor car with 700 original miles has a smog pump. Its not just the weight of the Pump on the front of the motor the belt drag there also.Hit or Miss on the Smog Pump??? I'm calling it Smog Pump Delete must be an RPO code for that one.

All Muscle cars were not created equal the Olds got the W27 alum rear, everybody didnt get the upgrade, Studes got a Supercharger No upgrade to everyone else, ZL1's got an Alum block no one else got the upgrade, Maxies, Ford 427's L88's Some Hemi's got solid lifters but everybody didnt get the Upgrade, Lift Off Six Packs got the Hood, intake and carbs everybody didnt get that Upgrade. Smog pumps everybody didnt get that but sure deleted it quick."(RPO Smog Pump Delete).

So how much of a Horsepower Bonus is it to get the UPGRADE to 2-1/2 exhaust with an H? Could be Huge according to Porterfields webpage listed above unless your a Mopar no UPGRADE at all.

The Rules of the PSMCDR are as written I dont expect any changes and dont have a problem accepting them But the Exhaust UPGRADE is a huge Horsepower gain to those that have been given that BONUS. No Denying it, just smile and know it is an "UPGRADE".

Rob Please correct me if I'm wrong on the Exhaust diameter I'm sure you have forgotten more about Yenkos,Copo's,L88,ZL1's ect... than I'll ever know. Hope to see you at Martin!!!

Paul M Petcou
440 SixPack Challenger


Hey Paul! I'll be the first to admit to the "suckiness" of the Chevrolet exhaust...but why Porterfield took an already bad situation and made it worse by testing with the chambered exhaust is beyond me. The NC8 chambered exhaust is/was garbage...it sounded good, but was even *more* restrictive than the standard transverse setup found on the non-NC8 Camaros/Novas...it necked down in spots worse than the standard dual exhaust, but worse than that it had all of those chamber "perforations" sticking into the exhaust flow. And how do I know this exhaust sucked? Well I was dumb enough to run a chambered system on our Y-Camaro for many many years...it was on it when I certified, and I wanna say I ran +/- 8 years with it? I had it on so long that COPO Pete got tired of telling me how crappy it was...so I changed it out (I wanna say I did it for the 2nd Martin event?) with just the regular kink bent dual exhaust and picked up significantly everywhere. Anyway, the chambered option (it wasn't standard on any combo) was discontinued early in the '69 model year, similar to how the Pontiac's VOE option got canned.

I won't argue with the "why" of the H/X pipe, because I agree with you...no one asked me or cared, but I was against it when that rule was proposed and eventually came to fruition. The Mopars (and few FoMoCos) that got 'em should've had 'em, everything else without. But with that said, I know a couple of the quickest L88s were in the .50s at least *without* a crossover pipe...

Concessions have been made across the board (I still don't know why), but a lot of that came from the NHRA non-sense, as even *that* idea wasn't applied correctly, and gave away Chevy's compression advantage it had on several combos, as well as some cam specs...but again, no one cared what I thought then...and I'm guessing that sentiment is still true today!

And lastly, you're spot on with one thing at least, I have indeed forgotten *tons* of stuff! I blame it on my kids, lol!!

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also Mopar had the only duel point distributor for better coil saturation compared to most all the others with a single set of points. One thing that isnt mentioned is that at lease in 1969, Mopar had G-70-15 tires, the biggest tire available at the time, and then ALL makes were allowed a one tire size upgrade, so that negated that addvantage.


Oh boy, now we can get down to skinnin' this cat! Howdy Jim! Interesting about the dual point, I didn't realize that? I know some of the tri-five Chevys and C1/C2 'Vettes had dual point setups, but I'll admit ignorance on whether they were available any later than that...but somewhere around '63-ish GM made the K66 transistorized setup available across several brands, which would be comparable to an MSD setup...it's a pretty slick setup, and was standard on the ZL1s/L88s, but was very prevalent in the C2/C3 'Vettes. And I still don't understand the tire thing, like I didn't understand the 1% or 2% camshaft deal...I kept hearing about it, but couldn't understand the "why" of it.

Truth be told, I probably enjoyed all of this PS stuff more back when my turd was running high-12s/low 13s on pump gas...it's kind of turned into a bit of a chore lately.

Rob Clary Fat, yellow Yenko Camaro 11.75 @ 118, Pure Stock!