[steve25]

No problem!

[steve25]

Note that I have been informed by another member of the board that DV pointed out a correction to this overlap chart that I posted up yesterday.

DV did so on the Speedtalk site and I will try to find the time later to look it up.

[ponjohn]

What is meant by long ramps - low Hydraulic intensity?

[slowbird]

Originally Posted by steve25

This is what DV has in that same book Stan.

So a 455 should run roughly a 105cl? I feel like most of his charts are out in left field for Pontiacs. Just my opinion.

[Cliff R]

The "low" lift profiles work well in these engines with iron heads. I've dyno tested the cam below in a basically "stock" 455 Super Duty build. Despite having 230 @ .050" and a roller it was done pretty early. It also made a LOT of vacuum at idle speed and not the first hint of "lope". Idled dead smooth down to 600rpm's with only 10 degrees timing in it.

I see folks using smaller cams in 455 builds frequently and they are leaving a lot of power on the table.....IMHO.

Anyhow the second dyno chart is from a recent customer who used a low lift HR cam with the same type of lobes and #16 iron heads. He used a larger 236/242 @ .050" cam which is better suited to his build because it had more compression than the 455 Super Duty we did here........

[steve25]

Yup, just like those peak torque numbers at 4100 rpm show , the stock D port heads are done by then, flat out done!
But if you have a 4000 lb car with A/C and 3.23 or less rear gears that’s just what you want, especially if it comes along with a tad over 450 hp as that dyno read out shows!

[Formulabruce]

" done by then, flat out done" no offense but the work is being done well below what most people consider "done"
Seems like few , if any, build an engine like Pontiac did, for work and cruising.
I have a stock 400 that does 400lb ft of torque at 2400 rpm... its working AT cruising RPM...
Did I mention its not bad on gas?
Bet it would tow well
I would build the 455 the OP has with a Boat cam as Jeff said, if possible. Get the most TQ at the lowest RPM.
All horsepower ratings are calculated anyway, No dyno measures HP, only Torque. Hp is a calculation WITH a few variables
that can be tossed in.
Build a towing machine to its Torque, and Pontiac has it, in spades.
Note, no automatic cars have a HP converter !
Back in 1959 GM Automatics had 3 Torque converters!

[JC455]

https://www.herbertcams.com/485-500-...-center-33988/

Product Description
Cam Grind Type:HYDRAULIC ROLLER CAMS
Application: PONTIAC 55-81 265-287-301(4.9L)-316-326-347-350-389-400(6.6L)-421-428-455
Block Size: SB
Engine Make: PONTIAC
# Of Cylinders: 8
Manufactured In Year: 55 - 81
Cubic Inch Size / Volume: 265-287-301-316-326-347-350-389-400-421-428-455 | 4.9L , 6.6L
Additional Qualifier: 301=(4.9L) and 400=(6.6L) ONLY
Brand Code: Herbert Performance Cams
Dur Int-Exh: 280/285
Dur @ .050 Int-Exh: 220/240
Lift 1.5 - 1.5 Int/Exh: 485/500
Lift 1.6 -1.6 Int/Exh:
Lift 1.7 -1.7 Int/Exh:
Lobe Center: 112
Valve Lash: HYD
RPM Range: 1000-6000
Description: Low to mid-range torque and power. Good for daily driver. Good sounding idle.

[Half-Inch Stud]

Originally Posted by "QUICK-SILVER"

This thread needs the intended cruise RPM really bad. Clay

Well, since the criuse can be 2,500 rpm at 75 MPH (overdrive), and the 12.0 ET corresponds to about 4950 RPM (1:1) or less(Overdrive shift).

Assume cruise TQ needs to include 2000 rpm for best feel. At the moment the 9:1 455 pulls rather well with the "big" 236/244 cam and i expect an improvement with a smaller Roller.

[Half-Inch Stud]

Originally Posted by ponjohn

What is meant by long ramps - low Hydraulic intensity?

Long, slow ramps ADV duration - 050" duration is 50-70*
Medium ramps ADV -050 is 45-50*
Fast ramps ADV -050 is < 45* ( seems to be 1 cam MFGR that has hung their hat on this sort (

[steve25]

I don’t know why your taking issue with my comment to the heads being done for?
What I posted is 100% correct, that being at whatever rpm peak torque takes place at then the heads can no longer supply additional air because they are the choke point , or they are being made the choke point by what’s around them and or what’s popping the valves open.

[Steve C.]

What is meant by long ramps - low Hydraulic intensity?

Long, slow ramps ADV duration - 050" duration is 50-70*
Medium ramps ADV -050 is 45-50*
Fast ramps ADV -050 is < 45* ( seems to be 1 cam MFGR that has hung their hat on this sort)


Related ?
"CAM PROFILE INTENSITY"

http://4secondsflat.com/Cam_Design.html

Now if interested, apply it to the lobes in my post #17



.

[Half-Inch Stud]

Comments;
My Iron heads are ported. I'm done with the 455 rpm way before the heads are "done".
Been a goal to run the 1/4 mile with least engine RPM at end: low 12s is good, 11's are probably there next time with 5,000-5100 rpm. low 1.7s 60-foots are good enough for 3850 Lb, and 1.6s is my practical limit.

Haven't run a small cam, nor properly sized cam since the mid-80s.
The 236/244 cam (below) pulls very well at 1700 rpm, has a classic PMD lope, and exhaust note.

This THREAD has a goal to find/specify a Roller grind with slow ramps, and reduced exhaust lift, to crack the valve open before cracking the #2 Lifter bore. Lifter Bore friendly & Valvespring friendly.

Is "Cam Profile Intensity" is a marketing term for lobe ramps (High Intensity = dished Flat HYD lifters, busted Roller Lifter bores, and Vasco springs.)

I fear small cams for ping at pull away.

[Cliff R]

I wouldn't go less than 236 @ .050" for what you are doing and the goals for the vehicle. The last dyno chart from above is from a 455 with iron heads and 9.7 to 1 compression using a "low" HR cam. It makes PLENTY of power to 5000rpms to easily put 3800lbs into the 11's so low 12's should me too difficult....IMHO.

I don't use a lot of RPM with my set-up, and shift at 5000rpms and go thru the top end around 5100-5300 for most runs......

https://www.youtube.com/watch?v=6zVdoLR-VzM

[Formulajones]

It's hard not to make torque with a 455 Pontiac using conventional Pontiac heads. Head ports are small and it has a long arm, it's what Pontiac does best. If someone is having trouble making torque with one of these engines something went seriously wrong in the build. You don't necessarily have to run a tiny cam to make torque with these things, in fact I'm in line with Cliff's thinking, anything smaller than about 230 @ .050 is a waste of time in a 455.

Here's one Paul built, with iron 670 heads and a 239/243 @ .050 cam.

This thing makes torque everywhere!! 512 ft lbs. already at just 2500 rpm. Hp peaked at 5400 rpm so there is no need at all to spin this thing tight, but it does carry the power out pretty nice beyond peak.

RPM____Torque____H.P.
1600____426______129
1700____437______141
1800____444______152
1900____445______161
2000____456______174
2100____468______187
2200____479______201
2300____488______214
2400____496______226
2500____512______248
2600____---_______---
2700____526______269
2800____536______286
2900____542______300
3000____552______320
3100____---_______---
3200____560______337
3300____566______356
3400____568______368
3500____570______380
3600____573______393
3700____573______404
3800____575______416
3900____571______424
4000____569______434
4100____573______447
4200____567______453
4300____557______456
4400____556______466
4500____551______473
4600____547______479
4700____545______488
4800____540______494
4900____534______499
5000____530______504
5100____523______507
5200____516______511
5300____512______517
5400____508______522
5500____499______522
5600____488______520
5700____472______513
5800____466______514
5900____456______512
6000____419______470

[Jay S]

Richard Guido has that boosted 65 GTO with a 500+ cube engine, MPFI and a 5 speed that gets in the low 20s mpg, and that car has been down in the 8s 1/4 mile E.T.

If you want to keep the performance of the HFT cam in the car now I would not drop below the average size of the 236 cam. I totally agree with Cliff and Jones on that. Rocky Rotella did that article several years back on his HR swap from HFT’s with some similar .050” specs between the cams in a 455. IRC the HR made a little more average power and better drivability, peak power didn’t change a whole lot. This sounds similar to his cam swap project.

Once the car has enough tq to pull itself at cruising speed I think adding more tq with a small cam or adding cubes will be a struggle in the search for fuel economy. I would focus on compression and cam design and make those things work well with the ported heads. FWIW.My street cars with higher compression (over 10:1) ported cast iron heads and cams in the effective 236-245@.050” duration range get as good or better economy and make a ton more hp than my sub 10 scr small cam cars, even on 87 octane.

I have one Pontiac cam project coming up that is running the arrow engineering kit to run the speedpro GM HR lifters, but using Rhoads V pro Roller versions of them. Might be something that would work good for your build if your going to do the slow ramp set up. I plan to keep the intake lash tightened down to about zero and run some lash on the exhaust. Up to about .010”. Hoping to gain some vacuum and economy, but mostly after gaining the short travel high rpm effects of the Vpro Rhoads lifters, hopefully without the short travel shortened life. Only one way to find out. Lol

[Steve C.]

Rocky Rotella cam swaps....

https://www.hotrod.com/articles/hppp...ller-cam-swap/

https://www.hotrod.com/articles/hppp...s-am-cam-swap/




.

[dmac]

A member here ran quite a few simulations for a low CR, low rpm , high torque and came up with using the ultradyne H5 and H15 lobes on a 115 LSA advanced 8* and it had almost 500 ft/lbs of torque at 4000 rpm. I think I gave him 8:1 cr as the target with a 4.25 stroke 4.181 bore. I don't know how that would convert to a HR cam, but it was very close to an old wolverine cam or maybe the 068 with a little more lift but with a wider LSA. Vacuum was estimated at 18psi. 288/296 adv with 231/239 at .050. I want to be able to use california 'regular' gas which is 86/87. Some reading indicated that a high vacuum has some relation to fuel economy. This set up had just about the widest torque curve he could get that was that close to 500 ft/lbs

[Formulabruce]

" Some reading indicated that a high vacuum has some relation to fuel economy"
Even Pontiac Agreed with this.. Here is a Factory Vacuum Gauge .

[pastry_chef]

Originally Posted by dmac

A member here ran quite a few simulations for a low CR, low rpm , high torque and came up with using the ultradyne H5 and H15 lobes on a 115 LSA advanced 8* and it had almost 500 ft/lbs of torque at 4000 rpm. I think I gave him 8:1 cr as the target with a 4.25 stroke 4.181 bore.

I have EA Plus and the Pro version as well. Unfortunately not near accurate enough to get correct valve timing events. EA plus loves exhaust duration, LSA out to lunch - even for Chevy engines.

Builders of other many other engine families know for a fact what works. Real back-to-back dyno testing with 4 or 5 good cams through the same engine has been done many many times. Long overdue for the Pontiac community, probably won't ever happen. IMO it would shock to many and turn years of forum talk on its head.

Imagine a dyno cam shoot-out with four cams through the same engine to obtain max power within a streetable range. See where numbers really stand.
1) A "traditional" Pontiac pick, maybe 041 or something. Typical dual-pattern - wide LSA.
2) A Bullet Cams custom pick.
3) A Vizard custom pick.
4) A Jones custom pick.