[n2ogpsj462]

what are the benefits of both? are there perticular combos that will work better with a single pattern?? just asking because i have an opportunity to purchase a single pattern comp solid. 248 duration/525lift. how would this be different from the crower 247/252 duration 507/517lift i planned on using. 462 252cfm 6Xs 9.3:1, rpm, 850 in a heavy car with a power adder.

[BLANK1]

If you are using a solid type cam adjusting valve lash up or down can sometimes help. I am running an UltraDyne solid in my 463. Specs are 255/268 @ .050, .540/.552 lift and 112 LSA. The rocker arms are Comp Cams 1.52 Magnum roller tips. The cam card called for .026 lash(hot) on both I/E. On KRE's dyno Jeff changed just the intake lash to .020 and it picked up another 15 horsepower so I keep the lash set there. I've never tried any other cams as this one seems to work good with my combo.

[Lloyd-TX]

Well, prolly thinking about another Bullet solid flat-tappet. Use my current exhaust lobe on the intake and go up one step on the exhaust.

Remember, my exhausts flow only 64% of my intakes!

Intake: F265/333 235 @.050" 145 @.200" .333 lobe lift .012 lash @ lobe CTA lobe profile

Exhaust: F269/333 239 @.050" 149 @.200" .333 lobe lift .012 lash @ lobe CTA lobe profile

If I were to spec this cam, I wonder what LSA I should request, and what intake CL?

[Lloyd-TX]

Cliff and Jim - excellent information, thanks!

FYI - my engine was dynoed with STOCK 2.25" outlet SD exhaust manifolds and non-mandrel bent 2.25" down pipes. I wanted as close a comparison to the as installed configuration as possible. Skip brought a set of RP headers to the session for me to try, but time was short due to all of the difficulties we experienced so we didn't get to make any pulls with the headers.

Cliff - tell me how to calculate average numbers, and I'll do the math and post the results - just for fun.

Jim - I have been contemplating a camshaft swap once my exhaust system is upgraded - Ron's Tri-Y headers and the PYPES / Tom Hand X-pipe true dual transverse system. As it is now, the car seems to "run out of breath" at around 5400 RPM or so. My theory is that the camshaft is too small, ground on too tight LSA, and/or the exhaust system is too restrictive. Prolly a combination of all three!

When suggesting a camshaft, some thought needs to be given to my combination and desires. When Dan ordered the current cam, he told me that he picked the tight LSA for a couple of reasons - bleeding off some low speed cylinder pressure to help avoid detonation (10:1, iron heads and 93 octane fuel), and I believe he mentioned that it could help with reversion?

A cranking compression test I ran a few months ago yielded an average of 210 PSI!

[n2ogpsj462]

my 6x4s flow 252/217 which is 86%. and im running nitrous. so in my case a dual pattern would be better with more on the intake??? you dont see many advertised cams with more on the intake usually vise versa. the crower i wanted was 247int 252exh. with a 112LSA. with 1.65 rockers. some say the rockers will change the duration slightly is this true?
thanks- scott

[buwalda]

Cliff,
Please do not take this as being offensive, as it is not meant to be. I suggest you spend the $$$ & get a custom ground cam, with 235-240 @ 050 on the intake with 7-10 degrees less on the exhaust. Not much more to spend than a shelf grind; the custom grind I have now is a Comp Cams XE hyd flat tappet & it cost $180 two years ago. Otherwise, you will do as I did, always wonder...

[Skip Fix]

While thinking about this at lunch in engine theory a power adder (N2O,boost) are basically giving the motor more intake duration by forcing fuel/O2 in the motor.They use more exhaust duration to let out that extra burnt mixture. In a NA motor why not give more time via rocker ratio or cam duration to do the same thing since we are using atmospheric pressure to fill keeping the exhaust duration the same?

I can post the real dyno numbers later from Wednesday to show more intake duration on the same cam same motor does make more hp.

[n2ogpsj462]

what are the benefits of both? are there perticular combos that will work better with a single pattern?? just asking because i have an opportunity to purchase a single pattern comp solid. 248 duration/525lift. how would this be different from the crower 247/252 duration 507/517lift i planned on using. 462 252cfm 6Xs 9.3:1, rpm, 850 in a heavy car with a power adder.

[Skip Fix]

Real world times, but on some RAIV 400 with a hp peak with the 288/296 UD of 6200 and not D ports or a 455, "normal dual pattern" cams one solid with only 4 degrees difference to the .01 the same times and mph through the exhaust. Different advance and retard on the bigger hydraulic(304/312-247/255). Smaller 292/286(242/236) on a 110 picked up 0.2 seconds and 1-2 mph and less reversion in the intake. After the smaller headers ran the same uncorked vs mufflers which the others didn't.
My 455 just made 5 more hp with more ratio on the intakes on its dual pattern cam. Just food for thought.

[Cliff R]

Lloyd, when I get time, I'll locate some dyno charts we have here from engines dyno'd at KRE and see how they compare?.....Cliff

[Skip Fix]

Pontiac Jack, I think if you flowed some ported Pontiac iron heads(and even most aluminum) you would find the intake is the low side. Shoot even a good aftermarket SBC head designed to feed 350-400ci flow as good as what we have to feed 455ci!Depending on the intake to exhaust ratio on actual head flow different cams will work better. Just pocket porting some 6Xs and adding 1.77 exhausts and blending them got the intake to exhaust in the 85% range. My RAIVs are the same way.

75% or less split pattern 80% look at a single pattern, 85% or more maybe more duration on the intake side.

[slowbird]

Wider lobe seperations lower cranking compression, tighter will raise it. Also tightening the L/S will cause more reversion since the overlap time is increased.

[mike leech]

scott try straitline again, you won,t be sorry.scott can get to be hard to reach,try between 9am-noon or 3pm to 5pm.he seems to get swamped around 1-2.fwiw i,m 80% with lots of split.

[Skip Fix]

Some blower and old hemi cams had more intake duration,mine was a custom.Remember it doesn't cost much more(especially in the total price of the motor) to get a custom cam whatever lobe you like often different lifts same duration available, and whatever lobe sep and advance you want from any of the cam companies.

I'm not a nitrous expert but what I understand nitrous since it is injected/sprayed with the additional fuel is equivalent to way more intake flow so you need the additional exhaust duration to let it out. Also need a wider lobe sep 112-114 to decrease the chance of that extra exhaust blowing back up the intake during overlap.Maybe one of the N2O guys will make cam comments.

Add "equivalent" duration @ 0.050 of 2 degrees per .1 additional ratio over 1.5.

[Skip Fix]

Lloyd my Moroso slide says at 106 mph and 3850(I guessed) about 355 hp.

[buwalda]

Cliff,
I have tried quite a few cams. I had a RAIV cam, with the standard 230/240 @ 050 duration. I had a cam ground that retained the same intake, but less exh duration, 230/223 @ 050. The engine pulled stronger to 5800 rpm, you could feel it seat of the pants; it also idles smoother, as expected with the reduced overlap, but was stronger in the midrange. I have not run it at the strip, but Jim Hand has kindly run my current cam through his desk top program. Current cam is 240/230 @ 050, 110 LSA, 102 ICL. For this, he got these figures: Peak T= 582; Ave T=525; Peakhp=486; Ave hp= 396; For a single pattern 240/240 cam, all else the same he got thse numbers: 579; 523; 485;397. What those numbers don't show is the improvement in idle & low end from the reduced overlap. When you look at the I/E % figures for Pontiac iron heads, they seem to at worst 65-70% & as high as 90% at some lifts. Alot better than some other brands.

[n2ogpsj462]

74t/a motor is 462 6x4 heads i had done and the porter said he did the short turn for good low lift flow. flow was 247/197. after the 1.77s in the exhaust were added and RAIV ferrea valves were installed flow was 252/217 at 550 lift. headers are rons tri-Ys, rpm intake i opened myself to 2.20 and i planned on milling the secondary like jim hand does. carb is still in the air but 850 mighty demon was first choice only because i cant afford a 4150HP series 830. bottom end is strong. crower rods,srp pistons and stock crank 10 under. 700R4 trans with a non lockup 3000 converter. flashed at 3000 with the previous 400 motor and about 3400 on the 125 shot i ran last yr and thats the max i will be using this yr also. 71 grand prix wieghed 4000 out of gas. 12 bolt with 390 which i planned to reduce to 342s. and im sure the converter wont be quite right but im gonna try it first. the cam me and jeff kaufmann liked was the crower 247/252 at 50 and 505/517 lift on a 112LSA. i like the 112 for the nitrous and also overdrive trans and heavy car. tell me what you think but i was pretty convinced from what kauffman explained to me about a nice flat torque curve and street ability especially since without milling my heads alot im only getting 9.3 to 1 comp. my heads cc'd at 99. they're 6x4s but were high for some reason. also zero deck. thanks - scott

[WDCreech]

I remember reading, years ago, to run a dual pattern cam with D-port heads and a single pattern with round ports. But as Skip Fix stated, it all has to do with the flow ratio! I was running '68 RA IIs when I read this and have used a single pattern cam since with RA IVs and Wenzler High Ports. For D-port engine, I would look closely at the intake/exhaust flow numbers.

[Cliff R]

Mike, the biggest let down we had with direct testing was swapping out the iron intake for the Holley Street Dominator. The "seat of the pants" meter has the Holley intake a SOLID winner against the iron intake. The power curve is BRUTAL with the SD intake, it will tear your head slam off from 3500-5500rpm's and "pulls" noticably harder up near the shift point that the iron intake. In constrast, the power curve from the iron intake is somewhat boring. It just pulls hard from right off idle to the shift point, sort of like a locomotive, strong, but no big rush of power anywhere. Even so, at the track the iron intake is near .2 and 2mph better than the single plane intake, every time!

I'm come to learn that the "rush" of power provided by the single plane intake is a LOSS of power below 3500rpm followed by a CONCENTRATION of power above 3500rpm. We feel the TRANSITION between the two and the seat of the pants meter tells us that it's an improvment. In reality, with my car, having conservation gearing/converter more power is transmitted to the pavement for the entire run and we go thru right at 5100rpm/115mph...so we don't benefit from any improved top end charge from the single plane intake. As some have noted, a "looser" converter and a gear change might improve performance....but....for our daily driven vehicle it is NOT going to happen as it would degrade driveability and reliability.....Cliff

[n2ogpsj462]

also a 3" x-pipe with tail pipes is being used. prob either flowmasters or the pro-v's