[Tinkerer]

Can a direct comparison be made regarding valve overlap between the tight LSA fast ramp cams and the lazy lobes on a wider LSA?

I am finding that even though the fast ramps in question (XE's et al.) have a tight LSA, there is less valve overlap than the lazy lobes with the longer seat timing. Would not the short overlap cams be smoother at low rpms?

Or is the short overlap offset by the faster valve opening, therefore there is actually more flow during the overlap despite it being short?

I understand the issue with the early intake closing event and the noise created by the fast ramp design. However, I would like clarification regarding the overlap. There is much said in the negative for a tight LSA, but with the fast ramps, the overlap is actually less (by the numbers) than the wide LSA-lazy lobe configuration.

For example:

SPC-7 (which I currently have in my 455)
212/225 @ .050"
Intake closes at 75.5 ABDC
Overlap 60.5
LSA 115.5


XE268
224/230 @ .050"
Intake closes at 60 ABDC
Overlap 54
LSA 110


Thanks,

Bill

[Bobs78TA]

Thanks for an informative thread on cam selection for a Pontiac 455. When I called about a cam with PB,PS, AC, etc., I was recommended to use a UD 288/296 HR. I had it ground on a 112CL to reduce the lopey idle. Skip, I'm interested in your combo has you have a UD HFT very close to my specs. You have about 5 more degs. duration @ 0.050", but the roller has 8 more on intake and 1 more on exhaust @ 0.200". ICL is 106 degs also. I would like to communicate further with you regarding your combo outside of this thread if possible.

[Jim Moshier]

Wow, what a great read. A lot of good information....thanks for everyone's input and questions it helped me in my quest for knowledge. now to decipher it all! :-)

[1funride]

Ran a model of the UD 288/296 110 and the Crower 60919, the curves pretty much overlay one another. This with a 462, 10.5:1, dual plane, both with 1.65 rockers, and stock edlebrock D ports flowing 262 @ .600 and 157 @ .600 (as per Edelbrock literature). These cams seem to perform about the same, build torque about the same, and fall off about the same. I believe the 60919 is the bigger cam and has always been recommended with rhodes lifters especially in this thread. This thread seems to indicate the 288/296 has better street manners.

Q: Is my observation of these cams being essentially the same performance wise correct for the above example?

Q: Is my observation of the 288/296 110 being more street friendly correct?

I have 90% of the items to build my 462 this winter, which includes the 60919, edel heads, crower hft lifters, performer rpm intake, etc sitting on the shelf. The car has a 2500 stall (possibly to small for the 60919), and 3.42 gears. Its a 68 firebird.

After reading this I have a little reservation on using the 60919 with the 2500 converter, 3.42 gears, and standard HFT lifters (the ticking will drive me nuts). Will the UD grind suit a little better without the use of rhodes on the 60919?

[STEELCITYFIREBIRD]

If I recall correctly you have a 1975 557 block, correct?
This is like a case study of how a 557 will hold up with a longer stroke and some hard runs, with traction.

[Cliff R]

Rhoads lifters are NOT required with the 60919 camshaft in a 455 with 10 to 1 or higher compression...IMHO. I ran that cam in my last 455 without them for quite a few years and it was fine. I installed them late in the life of the engine just to see what they would do.

I saw right at 2" more vacuum at idle speed, and smoother right off idle. The car ran exactly the same at the track, probably due to the 10" converter that flashes to about 3500rpm's.

That engine was 468cid, 10 to 1 compression, and it made about 10" vacuum at 750rpm's. With the Rhoads lifters right at 12", and noticeably smoother. The base timing was only set at 10 degrees BTDC.

We also built a 455 with unported 87cc Edelbrock round port heads, and the 60919 camshaft. It made 505hp on the dyno and put a 3900lb Firebird to 11.50's at 118mph in full street trim, driven to the track. I consider that pretty stout performance for unported heads and a pump gas street driven combo.......Cliff

[Steve C.]

To add to the confusion you can also throw the Lunati Voodoo hydraulic flat tappet lobes into the mix....

Part Number: 10510704
( Previous Part Number: 60904 )
Advertised Duration (Int/Exh): 276/284
Duration @ .050 (Int/Exh): 233/241
Gross Valve Lift (Int/Exh): .504/.527
LSA/ICL: 110/106

Similar .050" duration as the UD 288/296 & Crower 60919 cams but with less seat timing and additional valve lift. And some will suggest the Voodoo lobes are quieter than UD grinds, and especially the Comp XE lobes.


.

[1funride]

There are a bunch of manufactures that make 041 like cams, at least 4 and a bunch others have in the past. They all seem to net the same results (modeled) with "very" little difference. I guess that makes sense since they are actually very close or exact copies with a little more lift. I seen a post by UD Harold that indicated that the UD and Vodoo cams were not the same. He indicated that the overall advertised duration and lift was dictated by Lunati, but the lobe was of his design.

I have wondered if that meant the Lunati cam was an improvement in his mind, or was he held to more design constraints at Lunati, which forced him to ramp the lobe up quicker? Was the UD cam a better design with less constraints?

In any event, all seem to fall in the same range of performance as other 041 like cams. The question could be, which is better from the aspect of less valve train wear and tear, idle vacuum, and driveability?

[Steve C.]

At one time I assumed all or most of the UltraDyne lobes were the same as the Voodoo lobes. Then Paul Carter corrected me within a post here at PY. That was much appreciated and with his explanations as to why they were not. A better design by Harold while at Lunati. I enjoy reading, and trust Paul's comments regarding the Voodoo lobes with his experiance using them, and his association with Harold Brrokshire. Seek out his posts on the topic. Or contact him direct.

That said, like many here I purchased UltraDyne cams from Harold when he owned and operated the origional company, and while he was at Lunati. Then later from Bullet Racing. Still a fan of UltraDyne cams

Keep in mind a engine will respond to additionl valve lift.

Paul Carter
Carter Cryogenics
www.cartercryo.com
520-409-7236
Koerner Racing Engines
520-294-5758


.

[bullheimer]

Can anybody give me a link to a thread on this same topic (lots of Ultradyne cam experiences) with a 400 engine? in particular, iron heads with a c.r. in the 9:1 range? if so, thx.!

[1968GTO421]

Subscribed!

[STEELCITYFIREBIRD]

A good read on this topic.

https://www.hagerty.com/articles-vid.../13/horsepower

[STEELCITYFIREBIRD]

When did HP #'s switch from crank to @ the wheel?

[ponyakr]

Originally Posted by STEELCITYFIREBIRD

When did HP #'s switch from crank to @ the wheel?

Looks like the rating system changed for '72 year models. A 4-barrel 400 dropped from 300hp to 250hp.

http://www.wallaceracing.com/enginesearch4.htm

Then, as CR dropped below 8:1, hp dropped below 200. Smaller cams & exhaust valves may have also played a part in the lower hp ratings.

http://www.classicalpontiac.com/cgi-...bal/engine.cgi

[Bob70Goat]

now I'm REALLY confused.. 1970 455, # 64 mildporting , currently have a RAIV copy , wanting to make more low end power, better vac,, better economy and less fumes - was considering a 068 copy but with so much information and dis information .. who knows now

[tom s]

IMO a 068 is too small for a 455.Tom

[ponyakr]

It's been my experience that all you need with a RA4 copy is Rhoads lifters. That's what I ran in most of our 455 bracket cars. Launched from an 800rpm footbrake idle, with a stock 13" converter, and ran 60ft times in the 1.60's.

BUT, given what you say you want, an 068 clone may be all you need. That's the cam that was used in that engine, with a manual trans. The auto trans engines used an 067 cam. Even the 455HO engines only used the 068.

http://www.wallaceracing.com/enginesearch4.htm

But, if you go this route, you might as well at least go with a Summit 2801. It's sort of a higher lift version of an 068.

https://www.summitracing.com/parts/sum-2801



"...good sound and great low end torque and power..."

Since you added the words "good sound", I'd say that eliminates an 068. The idle will be dead smooth, in a 455.

I'd say the next step below the RA4 clone might be a Crower 60243. I've seen it recommended mostly for 400's. But, it might work for what you want.

https://www.summitracing.com/parts/cro-60243

Below that might be the Summit 2802 & RA3 (744) clone.

https://www.summitracing.com/parts/sum-2802

The 744 clones have only about .407 lift, which will leave a lot on the table, as they say.

https://www.summitracing.com/parts/h...w/make/pontiac

Between the 2801 & 2802, are the Crower 60242 & 60916.

http://www.cnc-motorsports.com/crowe...-camshaft.html

https://www.summitracing.com/parts/cro-60916

This Crane might fall somewhere in the middle of the pack.

https://www.summitracing.com/parts/crn-283951

This Lunati version of a 744 cam, might work. With 301/313 adv dur, it should bleed off a little compression, which might help avoid detonation. The SD455 engine came with a 744 spec grind.

https://www.summitracing.com/parts/lun-10511004

[Bob70Goat]

what would you suggest then ,, I'm open to all suggestions .. my biggest fear is raising cylinder press too much and causing detonation .. none as of yet I use pump 93 .. want good vacumn , good sound and great low end torque and power .. not asking for much am I?

[Bob70Goat]

thanks I currently have a ra4 copy , rhoades lifterts as well .. love the sound but as you know does really devolp power until the upper rpms, and for a weekend cruiser that occasionally gets romped on .. converter is a 2600 ( if I recall ) which may be part of problem but will be going 2004r , have 373 in rear

[pastry_chef]

Originally Posted by Bob70Goat

thanks I currently have a ra4 copy , rhoades lifterts as well .. love the sound but as you know does really devolp power until the upper rpms, and for a weekend cruiser that occasionally gets romped on .. converter is a 2600 ( if I recall ) which may be part of problem but will be going 2004r , have 373 in rear

Static compression?

Maybe something like Lunati Voodoo 10510703


Hydraulic Flat Tappet Cam. High performance street/strip cam for 350 c.i. motors. Excellent cam for 400- 455 c.i. touring type vehicles with 9:1-9:5 compression ratio. Use 2200-2400 RPM stall converter with 3.23-3.42 rear gears. Very noticeable idle quality.

Advertised Duration (Int/Exh): 268/276
Duration @ .050 (Int/Exh): 227/233
Gross Valve Lift (Int/Exh): .489/.504
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1600-5800

http://www.lunatipower.com/Product.aspx?id=1776&gid=287