[superdutybob]

Mark:

As you can imagine, I will be a well wisher for the SD. I think it will be around 412HP and will match your 530TQ.

I know Paul as well and have seen his car run a few times at Martin and Mid Michigan. Can't wait to see and hear the results. Keep us posted.

[Lloyd-TX]

That's gonna be a neat deal, Mark.

I'm going out on a limb - 425 corrected BHP and 535 corrected TQ.

Even though I'm a die-hard HO guy, I hope I'm right, LOL!

[Larry Navarro]

I have this NOS Speed Pro cam that seems to be right in line with a #744.
Any opinions?

[2manyT/A'S]

I've had a 744 (knock off) blueprint cam in my 71 HO stick car for about 8 years now.
I thought it was a Melling or Wolverine brand,NOT Pro speed,but they're are ALL probably selling the same one in a different box.

I'm REAL HAPPY with the way it works. My car is pretty much stock & original,(cam,exhaust & tires being the exceptions of note)
Exhaust note is AWESOME,it pulls like a FREIGHT TRAIN & I can even get it through SMOG with a detuned Q-jet)

As i recall,it ran a high 13 on my day at the track.

[giles]

Originally Posted by Mark Weymouth

We will be using a 744 profile as that is what the rules require.

The 041 cam within the confines of our rules and max compression for an SD would actually hurt it. That has been one of the current problems with the SD's. To much .050 duration for the compression.

Pontiac needed a cam half way between the 068 and 744 in duration for the HO and SD. That would have been perfect in conjunction with their compression ratio's.

Mark

Mark, if you don't have to live within the confines of "rules" what would you estimate the minimum acceptable CR for a relatively stock HO or SD with a 744 cam to be? 9, 9.5, 10?

[Mark Weymouth]

Within the confines of the rules Paul's SD can make it to 9.5:1 and that seems to be area on the computer where the 744 cam starts to work well. If you want to stick with a pump gas motor and have that cam work the 9.5-10:1 range seems to be a honest location to start from what we have seen.

Wolverine and Melling have been our best picks for over the counter items. I have Mellings in several cars.

One the RA IV's we have dyno'd everyones RA IV option and they spec out on paper the same usually but not in the motor. So far the Melling has been the best option there.

Mark

[Jim Rotella]

Hi Mark,

I've been really enjoying all of your expert input to this 455 HO thread. It's not often that we get to see a builder's comparison of these two great engines in in pure stock form. I've got one question. Within the confines of the rules, if a 9.5:1 compression limit is in effect for both engines, I would think that the SD 455 with the stock 744 cam would benefit quite a bit more from a compression boost of over a full point than the 455 HO with the stock 068 cam. What's your thoughts on this? Thanks again for keeping us up to speed on your progress.

Jim

[OVERULD]

Originally Posted by 2manyT/A'S
I'm REAL HAPPY with the way it works. My car is pretty much stock & original,(cam,exhaust & tires being the exceptions of note)
Exhaust note is AWESOME,it pulls like a FREIGHT TRAIN

What exhaust are you running?

BJ

[2manyT/A'S]

Flowmaster American Thunder.
It's a 2 1/2" aluminized (transverse muffler),H pipe system with full radius bends & provides EXCELLENT ground clearance for an early T/A's that may be a bit lower to the ground than they are supposed to be.

Another forum member here (Goathead455) has this style of exhaust on his early HO powered T/A.
His car is VERY stock appearing & has likely had over 50 low 12 second passes in it.
You would be hard pressed to find ANY aftermarket speed parts on it (except exhaust & sticky tires) & I don't believe it EVER rode to the track on a trailer .

Perhaps he will read this & tell us a bit more about it. ( Camshaft???)

[Formulabruce]

Originally Posted by 2manyT/A'S

Flowmaster American Thunder.
It's a 2 1/2" aluminized (transverse muffler),H pipe system with full radius bends & provides EXCELLENT ground clearance for an early T/A's that may be a bit lower to the ground than they are supposed to be.

Another forum member here (Goathead455) has this style of exhaust on his early HO powered T/A.
His car is VERY stock appearing & has likely had over 50 low 12 second passes in it.
You would be hard pressed to find ANY aftermarket speed parts on it (except exhaust & sticky tires) & I don't believe it EVER rode to the track on a trailer .

Perhaps he will read this & tell us a bit more about it. ( Camshaft???)

BUT..... that exhaust is so darn LOUD!!!, the exhaust pipes exit WAY far forward and run below the rear quarter as it goes up in the rear. If Flowmaster had put a RATING on it like they do others (40,50, 80) and made it clear, I would be a little heavier in tha wallet, now I have more metal to recycle.
Sorry just had to get that in!! ( its on a 8.5:1 455H/O semiclone)

[2manyT/A'S]

Originally Posted by Formulabruce

BUT..... that exhaust is so darn LOUD!!!, the exhaust pipes exit WAY far forward and run below the rear quarter as it goes up in the rear. If Flowmaster had put a RATING on it like they do others (40,50, 80) and made it clear, I would be a little heavier in tha wallet, now I have more metal to recycle.
Sorry just had to get that in!! ( its on a 8.5:1 455H/O semiclone)

The tailpipes on MY system sit pretty close to stock location & I actually don't think it's THAT loud. (they DO exit PAST the lower valance.)

I cut the ends at the same angle as the original tips & had the last 2 feet of them chrome plated,so they actually look real STOCK,just a BIT fatter!

[goathead455]

Exhaust is such a subjective thing.
I think it sounds GREAT!!!!!
In fact,with a stock RA III,I think it is a little on the quiet side.
The cam in my engine is a Crane H-296-2 and it works very well with my combo.
.473 intake .488 exhaust 234 @ .050 intake 244 @ .050 exhaust 112* lobe sep
The best ET is 12.06 @ 112 MPH through exhaust manifolds and full exhaust.
It would run 12.teens all day in the heat of summer.
Car is a 70 T/A auto with 3.73 rear and weighs about 3800 lbs.

[Mark Weymouth]

Jim you are exactly right the SD would be helped more by compression then the HO. But Pontiac and the NHRA being what they are have granted the HO the ability to essentially hit 10.0:1 compression.

The smaller duration cam and compression sure help the HO generate a bunch of torque and the hp is not bad.

Mark

[Lloyd-TX]

Originally Posted by Formulabruce

BUT..... that exhaust is so darn LOUD!!!, the exhaust pipes exit WAY far forward and run below the rear quarter as it goes up in the rear. If Flowmaster had put a RATING on it like they do others (40,50, 80) and made it clear, I would be a little heavier in tha wallet, now I have more metal to recycle.
Sorry just had to get that in!! ( its on a 8.5:1 455H/O semiclone)

Bruce - the Tom Hand developed PYPES true dual crossflow system (with a 17276 Dynomax muffler) is THE way to go.

Better flow AND less "raucous" sound levels than the Flowmaster system.

[2manyT/A'S]

Originally Posted by Lloyd-TX

Bruce - the Tom Hand developed PYPES true dual crossflow system (with a 17276 Dynomax muffler) is THE way to go.

Better flow AND less "raucous" sound levels than the Flowmaster system.

Lloyd
I'm a little confused here.

You are claiming that the Dynamax crossflow (with Pypes system) is THE way to go,but you DON'T have one on YOUR car?

I see that your posted ET is 12.93 @ 106 mph & you list some prototype muffler that you are currently running.

We KNOW that a Flowmaster will do a 12.06 @ 112. (see goathead455's post above)

Perhaps your choice of muffler/exhaust is what's holding you back?

I realize that there are LOTS of other variables in the equation,but maybe you need to try the Flowmaster system on YOUR 72. (it can only get FASTER,right?)

Do you know of anybody that is ACTUALLY running a Dynomax crossflow (on a similar car through exhaust manifolds) for comparisons sake?

If so,what sort of times are they running?

Just curious.

[Lloyd-TX]

Originally Posted by 2manyT/A'S

Lloyd
I'm a little confused here.
You are claiming that the Dynamax crossflow (with Pypes system) is THE way to go,but you DON'T have one on YOUR car?
I see that your posted ET is 12.93 @ 106 mph & you list some prototype muffler that you are currently running.
We KNOW that a Flowmaster will do a 12.06 @ 112. (see goathead455's post above)
Perhaps your choice of muffler/exhaust is what's holding you back?
I realize that there are LOTS of other variables in the equation,but maybe you need to try the Flowmaster system on YOUR 72. (it can only get FASTER,right?)
Do you know of anybody that is ACTUALLY running a Dynomax crossflow (on a similar car through exhaust manifolds) for comparisons sake?
If so,what sort of times are they running?
Just curious.

OK, guilty as charged.

The short answer to my Formula's performance is - yes - I'm confident that my car will pick up at least .40-.50 and 4 to 5 MPH with the Tom Hand / PYPES exhaust system. There's a lot "holding" my car's performance back (i.e.: the cam is very, very mild), but the exhaust system is probably near the top of the list.

I have one of the first run PYPES systems for my Formula. In fact, I was one of the 25 or so who put $$$ up in advance to convince Chris to go ahead with the project.

But, I haven't made the time to install it on my car yet. I REFUSE to do exhaust work myself - I'm too fat and old, plus I'm no damned good at it. The muffler shop I used to install my current system has since gone out of business, and I have yet to research another good muffler shop.

The system currently on my Formula is a hodge-podge of sorts. I was involved with Tom Hand when he was prototyping his first crossflow system. Full Boar manufactured two prototype mufflers, one with Tom's design for the louvered internal tubing and Tom's spec packing material, and another using perforated internal tubes and Full Boar's packing.

Tom asked me to install the system first with his muffler, then run chassis dyno and track testing, along with my own subjective evaluations. PYPES supplied me with the 2.5" downpipes, X-pipe, and the over-axle pipes. Tom sent me both mufflers, and I sourced the tailpipes locally (Dynomax F-body tailpipes, which are darned near duplicates of the '73-'74 SD tailpipes), and a pair of PYPES 2.5" repro chromed tips. All pipes are mandrel bent.

I had the system installed (using Tom's muffler), chassis dynoed and track tested that system. Unfortunately I ran short of time and never got to install the Full Boar muffler for a comparison. Tom needed one of the mufflers back for a POCI convention, so I'm unsure of the whereabouts of the Full Boar muffler.

Anyway - VERY long story, but Tom and a buddy local to him tested the "new" system, and he assured me that it will FAR outperform my current system. When using the Dynomax muffler have a pleasant exhaust note as well. Tom has also related that the Flowmaster system is far more restrictive (and noisier) than the PYPES system, again when using the 17276 muffler.

Hope this helps!

[RicksGTO]

very timely post as I'm looking at exhaust system choices for the Formula and want to make sure I understand the Dynomax option correctly. Does the current Pypes cross-flow system come with the Full-Boar perforated stright thru muffler or is there an option thru Pypes to get the Dynomax 17276 unit? I have looked at the 17276 and still am not sure of the flow path on it, is it reversable so that it can work with the Pypes tails and axle conncections now? I also spoke with Waldron and Gardner but don't feel like they will match up with this engines power level as well as the mandrel bent 2.5" pipe so I'm leaning towards the Pypes.

[Lloyd-TX]

Hey Rick:

Purchase the PYPES system, less muffler. Source the Dynmax 17276 locally, it will fit. The PYPES muffler choices are TOO loud and sound awful to me. Larry Navarro here in town HAD the PYPES muffler on his - AWFUL!

PYPES has their mufflers manufactured by someone other than Full Boar.

No option through PYPES for a Dynomax muffler, unless they've changed recently.

[RicksGTO]

ok, thanks for the info Lloyd, I just wanted to make sure. It's nice to have this problem, as on a lot of things for these cars, a few years ago we had only a couple of choices so it's nice to see more companies offering exhaust systems and components.

[Mark Weymouth]

I have one of the initial Pypes X pipe systems with their muffler on my HO that Scott Tieman always races. It was running consistent 12.60's @ 111 this fall on a slippery Stanton track at the PS race.

Lloyd is correct, it sounds AWFUL!!!! I simply hate the sound. It is like a wounded 2bbl car huffing out of a to small single exhaust. Not a prefered sound.

Pypes must have changed the muffler since the original run though. We have the same basic set up on a 350 HO bird and on my '70 RA IV T/A. They both sound like one would expect a Pontiac to sound.

We have not been able to get Pypes to give us a straight answer on this yet.

Mark