[Matt Meaney]

I'm no expert, just googled up something.

dave at sd performance advocates a wider lobe separation for manifolds.

"Early on we learned that camshaft selection is very critical when using the Ram Air Exhaust Manifolds compared to headers, tighter lobe seps along with long durations just don't work since they need the exhaust scavenging of a longer primary tube runner which are found only in long tube tubular headers.

When using the RA manifolds we suggest a cam with a minimum of a 112 lobe sep if not more, along with keeping the duration on the smaller side to reduce overlap."

http://www.sdperformance.com/moreTech.php?newsID=39

[pastry_chef]

Originally Posted by Matt Meaney

http://www.sdperformance.com/moreTech.php?newsID=39

At the link:

Years ago we tested a 467ci 9.5 to 1 OEM D-port headed engine in which we were running an Ultradyne Solid Flat Tappet cam with 263/271 dur. @ .050 on a 112 lobe sep, the engine made 502hp with 1 3/4" Hooker SC headers when we switched over to A-body Ram Air manifolds, peak hp dropped to 457hp and at 6000rpm we saw close to a 75hp drop.

IMO that entire cam was a poor match, too much duration (reversion monster). Dial back duration and narrow LSA, same 500 horsepower. Say single pattern 250 @ .050 with 108 LSA.
All the other examples, all around 500 HP and indicate little loss between manifolds and headers. I see speculation about the LSA factor, not evidence.

There have been many other dyno results here that show a good Pontiac exhaust manifold (ramairrestoration.com) will support 500 HP anyway.

[krisr]

Haven't there been many advocates for the monstrous exhaust lobes over intake lobes with wider LSA (and many forum e-arguments over it) simply because "That's how the factory did it", but now were starting to see the opposite? What changed?

Sent from my SM-G930F using Tapatalk

[pastry_chef]

Originally Posted by krisr

Haven't there been many advocates for the monstrous exhaust lobes over intake lobes with wider LSA (and many forum e-arguments over it) simply because "That's how the factory did it", but now were starting to see the opposite? What changed?

For many owners nothing has changed.
Here is a comment from Chris Straub on bucking trends

Math does not discriminate, it doesn't care if it a Poncho or a Mopar. The numbers have been listed. Based on the demand set by the piston speed, the potential fill and evac of the heads, the math will not lie to you. It will provide a "smart brain" for the engine....the camshaft is the brain of the engine.

Years ago when I was in my 20's, I would hesitate when the math was totally opposite to what was considered the norm. The first time I got the balls to hold my ground was a Super Stock Hemi guy. The math's result was met with, "Hemi's only run on XXX LSA". I can't remember exactly what I said but it was to the tune of "Doing what everyone else does is following." That didn't work but what did was if the cam didn't work it was free. If it did he paid for it. She made more power and she was quicker at the track. From that point I followed the math. Even with a local guy here in TN when his BBC 540 needed a 26 degree split favoring the exhaust I stood with the math. That engine had an I/E ratio in the low 50's. Power gain on the dyno was 146HP with cam change.

My experience is follow the math, its does not mix words. This engine and any other NA engine with that kind of I/E ratio needs a reverse split camshaft. Hell the Japanese figured this out 3 decades ago.
Chris Straub

Great read on intake to exhaust ratio math.
http://www.chevelles.com/forums/13-p...dont-read.html

[Cliff R]

"I was never aware that "decades of time" could invalidate performance results. I don't think so."

Right to start with you have absolutely no idea whatsoever as to how Mike Davis's car runs on the street and next to NOTHING about that engine compares to the one in question here. Mike knows how to exploit a 428 to make great power, and successfully campaigned that car for many years racing it in. I have raced with him at the same track when his car was set up in that configuration and watched him crank it up in hot weather to make a pass. It roared to life and sounded pretty much like a Pro-Stock dragster engine with 14 to 1 compression! EXTREMELY "rough" idle and the power it made was very impressive.

Nothing about that engine compares anyplace to the one here, period. Googling up tons of information w/o doing it yourself often leads to these sort of things. I keep seeing all that horse crap about tightening up the LSA to pull power down but in actual use one can very quickly run into issues with detonation on pump fuel if you engine already has decent compression.

I've tried going clear down to 108LSA on these engines and for sure if you are evaluating power by the seat of your pants they feel pretty impressive. Throws ALL the power at you right off idle and slams it right into the mid-range. I actually built a 455 years ago and tried a "hefty" 247/254 @ .050" cam on a 108LSA in it. It was also topped with #62 heads same as being used here. That engine bar none "felt" the strongest of any that I've done here once placed in service. Idle was "nasty", very rough and the power was nothing less than "explosive" when you hit it hard. I literally thought it was going to run into the 10's in the 69 Firebird we put in into.

Instead with good traction we were rewarded with 12.20's at 112mph and despite all tuning efforts were unable to get that car to go any quicker.

We ended up replacing the cam and having Dave at SD port the heads for us. He supplied his "Road Paver" cam on a 112LSA. The engine idles with a slight lope, very mild at a glance, but went 11.30's at 118mph with no other changes! Despite how well the car runs after the cam change it was actually LESS impressive on the street when you drove it. Instead of literally ripping your head off like the much tighter LSA cam did, the power was now somewhat "boring". Sure it pulled really hard everyplace, would have to running nearly into the 10's, but the power was so smooth and linear you really didn't think it was going to run any quicker than the when it was using the big cam on a much tighter LSA.

REAL WORLD learning with this sort of thing, the kind you aren't going to dig up on a Google search, especially when you are trying to find folks who agree with your line of thinking more than anything else.......FWIW......Cliff

[Steve C.]

This may not directly apply here but it might be of interest. Here is a comment from Ken Keefer (Pontiac Dude) that relates to lobe separation topic......

"I have found in my experiences tied to track results that higher compression and then having to go to longer LSA to kill the compression/bleedoff has resulted in lower ET's at the track. Just from my experience. I would rather run less compression and the slightly tighter LSA and more cam profile, then up compression with a wider LSA. Dyno numbers will look better but track ET's won't show it. Been there and done that. And not knowing what is in the pump from Summer to winter. Better safe then sorry. Make up compression hp loss elsewhere. There is a point of too low an LSA for the bore/stroke and rod ratio deals too. And we aren't talking aftermarket super high flowing heads in this post. Just basic Pontiac iron head technology. Peak HP doesn't win races."


.

[steve25]

When you run Exh Manifolds if your doing any head work you need to max out low lift Exh flow numbers
!
As rpm goes up you need to use the Exh port area you have as fully time wise as possible .

Making greater power when you can not rely on a tuned header system to make a negative depression in the cylinder / chamber ( read VE numbers above 100 %) means getting out more Exh when the Exh Manifold area you have is not packed up already, and this translates directly in to getting better low lift flow.

As Cliff has kindly posted the Cam can help you out big time in maxing out what you have .

Also big on this list is to not have done a gasket match on the Exh side of the heads because when your Exh Manifolds are at the flow point of being choked off and producing reversion you want the head flange to form a lip the curtails some of that back pressure.

[Cliff R]

"This may not directly apply here but it might be of interest......

Steve, we have seen exactly the OPPOSITE with this sort of thing. With these street engines the more compression we run in them, and bigger the cams on wider LSA's, the faster they are everyplace.

Besides, lowering compression then smaller cams on tighter LSA's sort of goes against the laws of physics with these things. It's difficult, if not nearly impossible in the World we currently live it to "do more with less" with this sort of thing......FWIW

Of course I'm using mostly my own experiences here, but my car started out running low 14's at 99-100mph, and has had many engine changes since, but very little done to the drivetrain. Each time I increase the size of the engine, the compression and put more cam in it, I'm nicely rewarded with greatly improved track performance. Going clear back to my first 455 which when first installed pushed my 3600lb car to mid to high 12's @ 108-109mph and did so very successfully for quite a few years.

With every change in compression, and or more camshaft that it's received, ET and MPH have improved at every single point on the track....and this has happened using the exact same converter and gearing. So I can't see where lowering the compression and smaller cam on a tighter LSA would do anything/anyplace for my combination, except slow it down a full second or so at the track!........Cliff

[Steve C.]

Cliff, I'm reporting on what Ken stated here on PY. Personally I have no back-to-back engine dyno testing to compare different lobe separations. Nor changes with different lobe separations in the same engine combination and then track tested. That said over the years many of my successful combinations used a 108 lobe separation recommended by Harold Brookshire when he ran UltraDyne cams, Chris Mays engine builder /sales at Comp Cams and later by Bullet Racing Cams.

In my Trans Am counting the original engine; 7 different engine combinations and twelve different cams. Three hyd flat tappet and nine solid roller cams.



.

[locomotivebreath]

My 406 basically put up those numbers with a much smaller bullit roller and 230 cfm out of the heads and ram air manifolds . Stock 68 qjet and Intake with no mods . Torque was actually 485

[pastry_chef]

Originally Posted by Cliff R

Right to start with you have absolutely no idea whatsoever as to how Mike Davis's car runs on the street and next to NOTHING about that engine compares to the one in question here. Mike knows how to exploit a 428 to make great power, and successfully campaigned that car for many years racing it in. I have raced with him at the same track when his car was set up in that configuration and watched him crank it up in hot weather to make a pass. It roared to life and sounded pretty much like a Pro-Stock dragster engine with 14 to 1 compression! EXTREMELY "rough" idle and the power it made was very impressive.

Nothing about that engine compares anyplace to the one here, period.

The UD 288/296 solid flat was highly successful for a ALL different engine families it was used in and one of their most popular cams.
I'm not even slightly surprised about Davis results with the cam.
Yup, I use search tools to reference information top pros shared.
EVERYONE should do the same for their own learning.

Cliff's cam "feelings" contradicts what you will learn everywhere else.
A few nice PMs this morning
One reached to Mike Jones, Mike recommended 108 LSA as I said.

[pastry_chef]

Originally Posted by Cliff R

Besides, lowering compression then smaller cams on tighter LSA's sort of goes against the laws of physics with these things.

Originally Posted by Steve C.

over the years many of my successful combinations used a 108 lobe separation recommended by Harold Brookshire when he ran UltraDyne cams, Chris Mays engine builder /sales at Comp Cams and later by Bullet Racing Cams.

In my Trans Am counting the original engine; 7 different engine combinations and twelve different cams. Three hyd flat tappet and nine solid roller cams.
.

Get the RIGHT duration and the RIGHT LSA for the combination.

YES, as Steve noted.
Lower compression ratio - prefer narrow LSA.
Higher compression ratio - widen LSA.

More comments from some of the very best in motorsports. CamKing, Nitro2 and Maxracesoftare etc.
http://speedtalk.com/forum/viewtopic.php?t=8513

[Formulas]

Back to the original post engine, Less than a stock intake, modest bump in head flow, XE cams act smaller than the .050 numbers would lead you to believe due to shorter seat timing, Iron exhaust manifolds, Exactly how far from stock would one expect it to dyno? Me? Not very much.

[pastry_chef]

Originally Posted by Formulas

due to shorter seat timing,

http://www.compcams.com/Company/CC/c...csid=1205&sb=0

Dur @ .006 is 284 intake 296 exhaust
There is LOTS more untapped power in that cam.

[Formulas]

Not arguing potential... analogy you cant take a kmart stereo change one component and expect concert hall performance the overall pile of parts isnt that far from stock and one change is in reverse of performance

[TCSGTO]

Originally Posted by Formulas

Back to the original post engine, Less than a stock intake, modest bump in head flow, XE cams act smaller than the .050 numbers would lead you to believe due to shorter seat timing, Iron exhaust manifolds, Exactly how far from stock would one expect it to dyno? Me? Not very much.

X2. Put a stock intake on it and tune the Q-jet. LSA isn’t the problem. A cam with that much duration on a 108,110,112 in a motor like the op has might show 20HP difference max worse to best. You’d have to have a very sensitive butt to feel that on the street and a well set up car to see much of an ET difference. Been there,done that, got the t-shirt. Once in the car his engine as is will probably run really well.

[Cliff R]

I certainly agree that LSA is NOT the problem here. A 240 @ .050" cam should make the grade, even on a 110LSA. If it's a "short seat timing" version it may come a bit short on power.

I witnessed a dyno session once (waiting in line) of a 455 with ported 7K3 heads on it, single plane intake, 1" spacer, 850cfm carb and Comp XE284 camshaft. They pulled and pulled on that engine doing EVERYTHING to bring the numbers up, and had trouble getting past 400hp and 499tq. With ALL the stops pulled out it finally made around 430hp and a little over 500tq.

Pretty much on par with the engine in question here.

Now there was a LOT of things I didn't know about that engine, including the quench distance, exact head flow, where the cam was installed, etc. All I do know is that it was one of the first dyno sessions I witnessed with an XE camshaft and was not the least bit impressed with it anyplace, except for the nice sound at idle.....FWIW....

[Steve C.]

"I just had an Engine done and am a bit disapointed in the results,after having it dynoed it made 430 hp and 507 lbs of torque.The engine is a 455 thirty over with a set of 96 d-ports ported to around 240 cfm at 500 lift with a comp.xe284h cam Rpm intake and 850 Dp.The cam was installed straight up.The numbers are not what I expected,do you think if I advanced the cam that would make any differance??"

http://forums.maxperformanceinc.com/...48#post1677148


"I finally got to run it out the back legally. I got a roll bar welded in place and put the interior back in the car just in time to make the race yesterday. The Thumper has about 25 passes on it now. I think it might have a little bit more performance to find."

1969 Firebird
3650 lbs with driver as raced

My new engine "the thumper" went 11.14 @ 120MPH

455 +035 srp's
sportsman rods
N crank 10/10
62's and a XE284H cam
RPM intake, 800CFM Q-jet, tuned by the master
T-400, 3500/TCI, 355 gears
9/30 radial hoosiers

http://forums.maxperformanceinc.com/...68#post1701668


.

[73ta]

Originally Posted by 69428HOj

Well I could have but it is a matching number engine, wanted to keep it stock as possible. 475 hp is what i was told to expect and that was good enough. Stll has 750 cfm Qjet, iron heads, long branch manifolds. Only diff is performer intake.

Get rid of that intake, very restrictive. Stock intake would be better.

[flamedabone]

Do you have any A/F or timing data? Lots of power to be won or lost in these two items.

-Abone.