[78w72]

lots of good info cliff, thanks for educating us all. however i do have a question regarding these "bigger" cams you recommend for 455+ engines, i always see you mention the heads are ported to benefit from these cams in your examples, does the same logic apply to NON-ported head engines?

reason i ask is because i posted a similar thread recently asking about what HR cam is best for 100% street engine with stock 6x heads, majority of the replies i got said to use the stump puller or old faithfull size cams... yet, SD & butler both said to NOT use those cams or anything that big because the heads dont flow enough to benefit from them & will require longer valves set up on a taller installled height. & ironically butler & comp both suggest that xr276 comp cam for a stock head 9-9.5 462 (stroked 400) engine... both said a lower compression engine doesnt need the bleed off of a wider lsa cam.

just trying to understand the reasoning why one would want such a big cam with stock heads, low(er) compression & lower stall speed (~2500) or does this "big cam" logic only apply to guys with ported heads & 3000+ stall speed? my understanding is you want to match the cam to the rest of the cars specs, in otherwords dont overcam it just because it may make more max hp on a dyno if the rest of the car wont benefit from or perform well on a bigger cam.

[Skip Fix]

NHRA stocker guys run some BIG duration cams stock lift(by rule) in non ported head motors. One RAIV stocker I knew used a 274@ 0.050 cam!

[screamingchief]

Originally Posted by Steve C.

Where the heck is Screamingchief? He could do a doctoral dissertation in this thread

Originally Posted by i82much

X2
Where the heck is Screamingchief ? He could do a doctoral dissertation in this thread.

I'm never too far away,just not feeling especially long winded today.

Plus I dont have much to add here except that any talk of seat timing should also make some mention of where said seat timing is being rated at.

I say that as Harold B. was a big fan of shorter seat timing for all applications,just look closely at the progression of his lobes thru the years and that's obvious to see as they got shorter and shorter in seat timing as they evolved (ie: the VooDoo lobes are shorter than the UD lobes).

And if you look at the UD hydraulic lobes you need to note that he rated those @ .0045" vs. most everyone else rating their lobes @ .006",and when you look at the UD lobes @ .006" they drop a few ° of seat timing making them look shorter in seat timing than most folks see as SOP.

Me,I dont necessarily think that short seat timing and tight LSA's are the problem,that is if one knows to account for that detail and choose the given cam accordingly (ie: they need to choose a cam that's a bit bigger than one would normally use with lazy lobes on a wider LSA),but that does'nt always happen in the real world,so yeah folks often have problems as it confuses the cam selection process for many less informed buyers.

It's the same deal with solid cams,that old "add 10° to compare to a hydraulic" axiom is'nt always true,often it'll take 20° (or more) to find a comparable solid cam to any given hydraulic cam,especially when other factors are thrown in like specific lobe choice,LSA and ICL differences and such.

Fact of the matter is cam selection just is'nt as simple as we would like it to be.

I do agree that I'm not a huge fan of "fast" lobes myself,I say that as I've mostly stuck with the old Crower stuff as SOP,so I got no stake in this debate one way or the other,but I do feel there is always some merit to any given approach if the practical application of said tactics are based in sound reasoning.

FWIW

Bret P.

[Steve C.]

A fwiw.... statements by Paul Carter here on PY....

I have two friends with 455's in their cars, that drag race them. Both are iron heads, and both run pump gas.

One 455 is a budget build with ported iron heads[6X-4, 249/209 CFM], has 9.9:1 compression, runs a Harold cam ground on a 108° LSA, and ran 10.90's in hot Phoenix air, on pump gas.

The other is a 455 with mildly ported d-port heads[#16's, 228 CFM]. It is 9.4:1 compression with dished pistons, has a solid flat tappet Harold cam ground on a 110° LSA, and runs 11.50's on pump gas in hot Phoenix air.

455's can run fast with tighter LSA's, with the right lobes, and person designing those lobes.


.

[screamingchief]

Originally Posted by Skip Fix

NHRA stocker guys run some BIG duration cams stock lift(by rule) in non ported head motors. One RAIV stocker I knew used a 274@ 0.050 cam!

Yep,generally ground on tighter LSA's as SOP to somewhat mitigate the additional duration they use.

It's all a game of give & take.

Stack the deck too much one way or the other,and yeah the whole deal can get away from a person.

IMO those fast lobes were largely meant to address the age old problem of folks "overcamming" their engines,allowing them to THINK they were getting cams that were bigger than they really were,and that's the cruxt of their problem,as nowadays people seem to be a bit more educated than they were in the past.

But you know what they say,a little education is a dangerous thing,LOL

Bret P.

[Skip Fix]

I just like a "3/4 race cam" myself

[Steve C.]

As Screamingchief eluded to... my old UltraDyne catalog on hand shows two separate sections for hyd flat tappet cams, one based on .0045 duration for the seat timing and the other based on .006 duration for the seat timing.

I'm not suggesting these two as examples are apples-to-apples, but here goes:

Rated at .0045" with 280 degrees, 223 degrees at .050", 132 degrees at .200" and .3088" lobe lift.
Rated at.006" with 280 degrees, 229 degrees at .050", 139 degrees at .200" and .3200" lobe lift

As typical both the sold flat tappet cams and solid roller cams were rated at .020". That's why comparing a hyd cam to a solid cam can be difficult. Screamingchief has pointed out on numerous occasions how to do so with the timing events.

And related to lobe separation many cam experts have stated similar, but here is what Lee Atkinson stated regarding the subject:

FWIW, I have not used "LSA" as a factor in cam design in years. I get the opening and closing events where they need to be, and LSA is just a by-product. When you use exhaust lobes that are more than 10 degrees bigger than the exhaust, the old LSA "rules" no longer apply.

The Link I posted previously here to Tilden Technologies goes into some details regarding this.


.

[Steve C.]

Well thank you, it's only been on the track a few times with the 505 and only to confirm it's a legitimate 10-second street car. I'm sure there is more in it with converter changes, gearing, tuning, tire pressure changes, good weather, etc., etc.

But I have no intentions to try for a faster time nor do I care. And it's not a light car set up for the track. It's a 10:1 pump gas car to cruse around in only and to enjoy. And with a 'small' cam !

And 'no answers', again just conversation for interest. As stated previously... take it or leave it.

And at a light 3360 lb race weight like yours ....my ET / MPH computed is 10.02 seconds and MPH of 134.87 MPH.

And if your comment was not directed at me personly, my sincere apologies to you. But I felt it was since you posted right after me. Sorry for any confusion.


Have a good day

[Cliff R]

"i always see you mention the heads are ported to benefit from these cams in your examples, does the same logic apply to NON-ported head engines?"

We've built several of these engines without touching the heads anyplace and the same logic still applies. A big cam still makes big power even with stone stock heads.

We built a 455 with untouched #46 heads from a 350 engine and it was only down 15hp from an identical engine with 230cfm ported heads.

We also built a 455 with a pretty "hefty" cam in it with the smaller chamber #46 small valve heads, unported, and it' pushed a 1981 Firebird to 11.90's at 112mph on it first outing it the heat of August at Norwalk.

For sure you will see some additional benefits from correct head porting with larger cams, but these engine can still run pretty well without porting the heads at all. Just take a look at the Pure Stock and Stock Eliminator cars.

"reason i ask is because i posted a similar thread recently asking about what HR cam is best for 100% street engine with stock 6x heads, majority of the replies i got said to use the stump puller or old faithfull size cams... yet, SD & butler both said to NOT use those cams or anything that big because the heads dont flow enough to benefit from them & will require longer valves set up on a taller installled height. & ironically butler & comp both suggest that xr276 comp cam for a stock head 9-9.5 462 (stroked 400) engine... both said a lower compression engine doesnt need the bleed off of a wider lsa cam."

I've had several of those engines brought in here for us to tune using that cam, it's a complete TURD in a 455 build at 9.5 compression with ported or unported heads. One of the engines brought here was a 455 Super Duty using that cam, with the compression raised to 9.5 to 1. It was a complete DOG, and very octane sensitive as well. Hated "normal" timing and fuel curves, and really wasn't trying to make any power no matter what we did for tuning.

I would also mention here that I never once said or even tried to indicate that you can't run well with a "tight" LSA cam in one of these engines. I'm telling folks in this thread that "tiny" short seat timing cams on "tight" LSA's work poorly, and you are leaving a LOT of power on the table choosing them for these engines......Cliff

[Squidward]

Originally Posted by hurryinhoosier62

Good info, gentlemen, but you know the "keyboard experts" are going to tell you that "my buddy, this magazine I read, etc. (ad nausem) said this" instead of reading and LEARNING from REAL world professionals.

My buddy read in a magazine about someone who sim'd this cam on a computer dyno. He said it would run awesome.



No, for real. This is a cool thread, even tho I don't play in the big cube sandbox. Lots of good stuff.

Voodoo guy here. I'm a fan so far.

[Skip Fix]

Steve, Harold told me those two different HFT sections are different families of lobes slightly different. Kind of like the different families or rollers he had.

I picked up for cheap an old Late Model asphalt car with a 350 SBC with an UD NF series solid FT lobe that is a pretty strong little motor-pretty wild sounding with the 180 degree headers too. Those are a different family than their regular solid FT lobes.

[Steve C.]

Thanks Skip. That's why I stated probably not apples-to apples. And you know me well enough that my comments are just conversation and I presume some might find them of interest. I'm retired and have nothing better to do


.

[screamingchief]

Easiest way to see the difference in the UD lobes @ .0045" & .006" is to look at the listings for the UD lobes in the Lunati lobe catalog,as they got a set of those UD master lobes when Harold went to work for them,and in the Lunati lobe catalog you'll see that Lunati lists those UD lobes with the .006" rated duration per their SOP.

Cam is the tried & true 288-296 UD hydraulic:

UD lobes H5/H15

UD seat duration @ .0045" = 288°/296°

Lunati lobes UH5/UH15

Lunati duration @ .006" = 282°/290°

That's a 6° difference in seat timing,and that's often enough to be considered one "step" change in terms of cam "size".

Which often can be enough to throw off the results of a fellas cam choice if said choice were "on the edge" in the first place.

Also gotta watch for this on flat solid/hyd-solid roller lobes too,many are rated @ .015" and not .020",especially the milder comp lobes.

As far as "stock" heads are concerned,the first issue anyone will run into is lift related,not duration related,as stock heads with OE valve lengths often max out right at/around .525" lift or so when using OE valvetrain hardware (and remember you need to leave .050"/.060" for "safe" retainer 2 guide/seal clearance),that's likely why those recommendations from SD & Butler,so yeah it's not the duration of those stump puller or Old Faithful cam @ all,it's the lift they run that would be the problem with "stock" heads.

FWIW

Bret P.

[Steve C.]

See that's why Bret is missed around here. And I failed to mention many Comp solid cams are rated at 015" tappet lift. I was only talking about Ultradyne solid lobes.

Thanks Bret.

[Matt Meaney]

Originally Posted by 78w72

... both said a lower compression engine doesnt need the bleed off of a wider lsa cam.

post #2 is a good read on LSA with some additional info. as well.

http://forums.maxperformanceinc.com/...ed+compression

[Nicks67GTO]

Cliff. At what point would you want to start tightening up the LSA on a 455 past 112? At a glance it seems theres a general correlation between LSA and .050 duration on the older cam grinds.

This is also why I have no interest in picking my own cams out anymore. So much power, driveability, money, time etc can be gained or lost in the details. Thanks for posting this

[pmd400]

We've built several of these engines without touching the heads anyplace and the same logic still applies. A big cam still makes big power even with stone stock heads.

We built a 455 with untouched #46 heads from a 350 engine and it was only down 15hp from an identical engine with 230cfm ported heads.

Cliff, do u happen to remember the details of these engines? I'm currently port matching a pair of '73 #46 heads. I'm upgrading the valves to 2.11/1.77 ferrea ss valves. I love hearing about stock heads, particularly the small valves.
Thanks

[Cliff R]

We used 1973 #46 heads, Crower 60919 cam, no porting anyplace, not even a gasket match. We did open them up for the bigger valves.

The engine made 440hp/530tq on the dyno, compared to the 455 I did a few years earlier that was identical except it used 230cfm 6X heads. It made 455.4hp/540tq.....Cliff

[Cliff R]

"Cliff. At what point would you want to start tightening up the LSA on a 455 past 112? At a glance it seems theres a general correlation between LSA and .050 duration on the older cam grinds."

At about 250 @ .050" it may help to start pulling the lobes in some, as you are raising the peak HP point past the capabilities of the shortblock and in many cases the head flow.

All of the 260 @ .050" (and larger) cams we've used in 455 have been on a 110LSA, but they have all been high compression "race" engines......Cliff

[AdamIsAdam]

Ok just read this entire thread. My brain hurts now! You guys have way too much knowledge!

Seriously, great thread. I plan to eventually change me tight little cam (xe274) on my 469 with ported, 255cfm #46 heads. So I will follow this and other conversations, on and off the forums, to learn.

Thanks for sharing!