[pastry_chef]

Originally Posted by Cliff R

and how much torque was still being made around 4900-5000rpms.

Usually with a high peak number the LSA will be 110 or tighter, it will occur around 3400-3600rpms, and the numbers out near 4900-5000rpms will be considerably lower than if a wider LSA cam was used.

Torque at 4900 would be around 485

Be concerned about durations and the centerlines.
Even better opening and closing events, at the valve is best.
LSA will take care of itself.

https://ls1tech.com/forums/generatio...-t-matter.html

[Cliff R]

So one guy in the other corner of the universe believes LSA doesn't matter.....really?

How about a link to the last Pontiac 455 he built with "smog" 6X heads on it, including the head flow numbers, dyno numbers, and track results after it was placed in service? If he did those things and made it that far how about the intimate details of the vehicle that it was installed in including race weight with driver....tks............Cliff

[pastry_chef]

I'm not surprised you don't know Chris Straub.. LOL

When you can tell an SS racer with decades of experience to adjust the intake lash a bit this way and then the exhaust lash that way.
Then he runs 2 tenths quicker..

Ain't NOTHING special about Pontiac! Thinking this only holds the community back.

Or call Mike Jones, Kip Fabre or Bullet Cams and ask them.. LOL

[dragracerx2813]

LSA doesn't matter? Since when ?

[pastry_chef]

Originally Posted by dragracerx2813

LSA doesn't matter? Since when ?

Read the first post of what he says, ideally read for a few pages.
Get the valve events correct and LSA falls into place.

If you have two cams on 110 LSA, first durations are 215 / 225 the second durations 220 / 220 - just random selections.
Running engines will not 'see' the common LSA of 110. Valve open / close events and overlap vary and these are what an engine responds to.

[dragracerx2813]

Originally Posted by pastry_chef

Read the first post of what he says, ideally read for a few pages.
True facts. Get the valve events correct and LSA falls into place.

Tell that to every Super Stock racer in the country !

[Formulajones]

Actually Paul has shown and posted at least a half dozen dyno sheets of Pontiacs he's built over the last couple years that shows how those Voodoo cams have a nice broad flat torque curve despite their tighter LSA. They don't run out of steam early like a typical tight LSA cam.

[pastry_chef]

Originally Posted by dragracerx2813

Tell that to every Super Stock racer in the country !

NOPE,,
Only ask the record holders!

Originally Posted by Formulajones

Actually Paul has shown and posted at least a half dozen dyno sheets of Pontiacs he's built over the last couple years that shows how those Voodoo cams have a nice broad flat torque curve despite their tighter LSA. They don't run out of steam early like a typical tight LSA cam.

Paul understand the deal! One of the best cam guys on this forum.

[dragracerx2813]

I will agree that Changing LSA is going to make a huge difference in most cases. But to say LSA will fall into place is kinda silly. Next we are going to say valve lash doesn't matter ! Or it's only 2 jet sizes! It might not make a big difference! But it does make a difference.

[dragracerx2813]

[QUOTE=pastry_chef;5827846]NOPE,,
Only ask the record holders

Trust me I have .

[pastry_chef]

Originally Posted by dragracerx2813

But to say LSA will fall into place is kinda silly.

You don't understand how correct valve events will dictate LSA?
Please read that link.
Maybe not everyone can understand, I'm not sure.
My mind is visual mathematician, it lends well to this.

Originally Posted by dragracerx2813

Trust me I have .

And?

[dragracerx2813]

[QUOTE=pastry_chef;5827851]You don't understand how correct valve events will dictate LSA?
Please read that link.
Maybe not everyone can understand, I'm not sure.
My mind is visual mathematician, it lends well to this.

Let me ask you this? How many people get the correct valve events for every engine. In a perfect world LSA wouldn't matter. But they just pick a cam from a manufacturer. They don't work with a cam grinder. They don't work with a engine builder. They just pull a cam out of a book or online.

[Cliff R]

"I'm not surprised you don't know Chris Straub.. LOL"

Never heard of him, mostly because you won't find me Googling this shi@ to death just to find folks who agree with my line of thinking just to satisfy my ego. Don't have time for it and much prefer to go out and get dirty and learn the old fashioned way. If and when I want advice I'll call someone like Dave at SD Performance and compare notes.

Anyhow, take a look at the dyno sheet below and tell me that the cam manufacturer knew how to recommend a cam for a 455 Pontiac engine with 9.3 to 1 compression and 250cfm #96 "D" port heads. Yes, the engine builder called them for cam advice in his first ever 455 engine build, and they told him to use the XR276HR cam in it. Besides not making much power it would NOT manage pump fuel on the dyno with "normal" timing and fuel curves in it, and when they tried to advance the timing to make reasonable power it pounded the rod bearings out of it.

I got a call only because EVERYONE from the dyno operator to the janitor was blaming the Q-jet. Instead of talking about the carb, which was fine, I told them to throw that POS cam down over the hill and install one that I recommended instead.

I told them to have Comp grind it on a 114LSA and install it at 110ICL.

I got a call after the cam swap, engine repairs and new dyno runs. They also noted that it idled better than the smaller cam on tighter LSA that it replaced. Defies the laws of physics IF you buy into the BS we continue to read on these Forums about cam selection.

LSA is not only important, long stroke undersquare 455's with heads having not much more runner cross section than an average SBC head are very sensitive to the intake closing point, size of the cam and the lobe positions.....but you'd only know this IF you built a lot of these engines and dyno'd them, then installed them in vehicles to see how they behave on the street, then take them to the track and get real numbers on them.

That's what I do here vs googling these topics in vain just to try to find someone who agrees with my line of thinking.......FWIW......Cliff

[pastry_chef]

Originally Posted by dragracerx2813

Let me ask you this? How many people get the correct valve events for every engine. In a perfect world LSA wouldn't matter. But they just pick a cam from a manufacturer. They don't work with a cam grinder. They don't work with a engine builder. They just pull a cam out of a book or online.

Exactly, simple generic compromise.
Many people don't degree their cams either.
Most do the same for other engine components, grab something off the shelf. Or worse, fall to bigger is better syndrome.

[dragracerx2813]

Cliff, was the only change between the cams just the LSA ? That's a HUGE difference between the two dyno runs .

[pastry_chef]

the XR276HR cam in it. Besides not making much power it would NOT manage pump fuel on the dyno with "normal" timing and fuel curves in it, and when they tried to advance the timing to make reasonable power it pounded the rod bearings out of it.

I got a call only because EVERYONE from the dyno operator to the janitor was blaming the Q-jet. Instead of talking about the carb, which was fine, I told them to throw that POS cam down over the hill and install one that I recommended instead.

I told them to have Comp grind it on a 114LSA and install it at 110ICL.

Hmm, MAYBE the fact that the smaller cam had 145 @ .200 duration vs the larger cams 160 @.200 played a role?
How about .335 lobe lift to .380 lobe lift?
Then there is the seat timing.

Talking about LSA in your example is playing in the field without a ball.
The bigger lobes on 110 would have dyno'd BETTER yet.

Originally Posted by dragracerx2813

Cliff, was the only change between the cams just the LSA ? That's a HUGE difference between the two dyno runs .

LMAO, nope see the figures I quoted.
Misleading isn't it ?

[glhs#116]

Well, for my purposes if overlap will be my enemy for good emissions the 703 will definitely have more because it is going the wrong direction in two ways. Both the longer duration and the tighter LSA will increase overlap. I feel like people are talking past each other here. Of course LSA, overlap, duration and all these things matter. But if, for example, you are simply changing the LSA on a cam with the same lobes then you can use LSA as a proxy for overlap. We all do things like this when talking about complex subjects. I have no doubt that the 703 would perform well. I also have seen nice broad dyno charts. But I do doubt it would pass emissions unless someone has experience to tell me otherwise

[Cliff R]

"Talking about LSA in your example is playing in the field without a ball.
The bigger lobes on 110 would have dyno'd BETTER yet."

That statement just proved to me that you have absolutely ZERO experience with these things, and I'm going to have to stay up another half our or so because I'm LMAO!

My example shows what happens when you install the wrong cam in a 455 build and how much power you leave on the table, plus it pinged on pump fuel and it idled like crap. The WORST cam you will ever put in your 455 street engine will be a relatively small cam on a tight LSA with an early intake closing event.

My example isn't misleading anyone, you just have the need to down-play the EXCELLENT results instead of noting that the new cam outran the first one in every single category, and it was on a 114LSA, which you continue to disregard.

So let's talk about your completely useless and meaningless post earlier about LSA doesn't matter. Let's take my cam recommendation in the example above and put it on a 110LSA and install it at 106ICL. Now you have a complete TURD for a 455, worse than the Comp XR276HR cam because is has WAY too much overlap, doesn't idle for shi@, sluggish off idle, no real power in the "normal" driving range, etc etc. You'd have to raise the static compression ratio at least full point before it would ever start to even act like it was going to work, or, as I did move it out on a 114LSA and enjoy a real pump gas 455 engine with decent idle quality, great street manners, pump gas friendly, AND it made nearly 90 MORE HP than the camshaft Comp recommended for it in the first place........Cliff

[Cliff R]

Your thinking on the subject is spot on Sam. Folks have recommended the 703 and even given you examples, but don't forget the basic rule of thumb with these things. If the 703 is a "home-run" in a 455 build at 9.5 to 1 compression, for example, it is NOT going to be the same deal in your much lower compression 455. For every full point of compression lost you need to loose 10 degrees of seat timing to have it act the same way at idle, off idle, and low rpm's. EVERYTHING would suffer in terms of vacuum made at idle speed, idle quality, throttle response right off idle, and efficiency in the lower rpm range. That's where those who are seriously lacking in direct experience with these things continue to make very poor recommendations for camshafts here........FWIW........Cliff

[Formulajones]

Originally Posted by glhs#116

So, in another thread, I basically have to replace my cam in my mostly stock 1971 455HO because of wear on the cam gear. Naturally, if I can step up at the same time I would want to. I chose the Lunati Voodoo 10510702 basically because I hear good things about the Voodoos and it seems still not too far off the spec of an 068 (.05 lift duration). Other considerations are that I need to still pass emissions and intend to get a manual overdrive one day and obtain decent economy. It is primarily a fun daily not a racer. But I see so many people putting the bigger 703 and 704 in smaller engines that I am a little worried. After all, I know that too small is just going to be a recipe for detonation and finicky tuning.

Is it too small? There is a decent 2.5 exhaust with H pipe on the car and I do have good Harland Sharp rockers on the BBC rocker studs with poly locks.

Sam

Originally Posted by Formulajones

I certainly wouldn't be afraid to try it in a stockish 455.

Is yours still a low compression ratio? 8:1 or so?? If it is this cam will work fine and shouldn't pose any detonation issues if everything else is up to par. I'd PM Paul and ask him where he would prefer the install position. If I remember right he says they work best about 6 degrees advanced or a 106 ICL on this one.

It says choppy idle but looking at the specs I doubt it will make much noise in a 455, especially installed on a 106 ICL. Would work nice with a stock converter and mild gears.

Originally Posted by gtofreek

That cam will have a smooth idle in a 455. The 703 has a smooth idle and makes plenty of vacuum in a 455. The 702 will probably be all done by 4800-5000 RPM. It is small, IMO, for a 455. If you go with it, I would install it on a 106° ICL.

Originally Posted by gtofreek

I put the 703 in a 9.2:1 455 that was basically stock with iron D-port heads. It made 400 HP from 4700-5200 RPM, and made like 528 ft. lbs.. According to the customer, it makes 14" of vacuum at 5000 ft. elevation. Works his brakes good. It has a real good idle also. The Lunati description of the 702 cam as being choppy idle is totally wrong. I put that cam in a 328 and it wasn't choppy. It will be baby smooth in a 455. The 703 was smooth in a 455. The 704 has a slightly noticeable idle in a 455. The 702 will probably come out somewhere in the 108°-109° range if you install it straight up. But there are so many variables that could affect the cam timing that it is best to degree them. The Voodoos are especially sensitive to where they are installed. They like to be advanced at least 4-6°.

Originally Posted by gtofreek

Not sure why anyone would think the 703 at 227/233 would be considered big in a 455. It is small by my standards, and idles really good in a 455. The 110 LSA isn't going to cause an issue in that engine, but it could always be ground on a 112 if you like. Either way, it would be fine. It would have a mild lope in a 400, but not in a 455. I put it in a 428 and it wasn't even lopey in that.

Originally Posted by Gary H

I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. The customer really wanted low end power and couldn't care less about the upper RPM range. He does't hot rod the car much, just likes to lay into it from stop light to stop light occasionally. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque. Very responsive on the street and with the seat of the pants feel, but it's done power wise at around 5000 rpm. Really what he was looking for in this situation.

I feel all these quotes really tells you all you need to know. The biggest factor is that engine passing emissions and it's a pretty low compression ratio is really the only concern I would have with cam choice. Because there isn't one of them listed that I consider big for a 455. But you've stated fuel economy a concern and emissions a concern.
If it makes you feel better, Paul stated you can order that 703 on a 112 if you wish. As far as emissions is concerned, if you want to really push the envelope with cam choice it's probably going to be trial and error on your part because you are treading into an area that 99% of us don't have to deal with on our classic cars over here in the states.