[Half-Inch Stud]

Cliff, Roger than statement, as your have been consistent thereon.

Question: Do you factor Rhoads-in as -10degrees (10degree early) on Intake closing?

[screamingchief]

Steve C.'s old 462 combo made 600 hp with a victor and a 254°/108° LSA cam,and it did so @ a miserly 9.7:1 CR to boot (due to a mistake computing CR).

That mill made 580 hp with the RPM intake in place.

That combo had the peak power around 5800 RPM IIRC,torque @ 4400 RPM was like 589 ft.lbs. or so.

Sounds healthy enough to me...

His was a single pattern grind,IMO a dual pattern grind with practical I/E split should have helped add to the high RPM output slightly as well.

IIRC that combo was good for 10.88's @ 3700 lbs race weight.

IIRC he was using the XE lobes on that cam.

There is absolutely more than one way to skin a cat,ya' just gotta understand the nature of the beast,not fear it.

Why can some make it work,while others can't,well that may be a mystery we never answer.

BTW,I can think of more than a few 290b6 455 based "long stroke" combos that run very strong too,,,cant imagine why a rolller version of that cam would loose anything either...

Those combos dont really need a high CR to run well either.

[Steve C.]

My friend Bob Davis 3500 lb '64 Tempest ran 10.40 at 128 mph with his single pattern XE254 solid roller using a 110 lobe separation and ported 72 cc Edelbrock heads. At that time I don't think he claimed it as a true 'street car' due to the compression ratio and the need to mix in race gas, but he did drive ir around some on occasions.

He later made changes that included a smaller single pattern XE248 solid roller and ran high 10's.

Now today for the most part it's a full time pump gas street car running a Comp Xtreme Energy XSR 242/248-110 solid roller and REALLY likes it. This new combo now with a overdrive transmission has run 11.11 at 120 mph, and if conditions are right will probably dip into the 10's.

It's a cool car, more info here if interested:
http://www.popularhotrodding.com/fea...tom/index.html

[screamingchief]

Yeah,there seems to be a wide variety of views on the whole LSA thing.

IMHO.

The tight LSA mimicks a "smaller" cam for a given duration.

The wide LSA mimicks a "bigger" cam for a given duration.

You cant really play with the LSA much without carefully adjusting the duration accordingly to suit the LSA change,as those two items are inter-dependant on each other.

That is often where some get into trouble.

They think hey,,,if for example a 247°/254° (@ .050") 112° LSA cam would work well enough for their application,,,then maybe I'll just tighten up the LSA a bit to boost the midrange power,,,or some such reasoning,,,well that's not gonna get the fella what he's after likely...

The fella would also need to add some duration to make that work the way most folks would want it to work,often that fella would need to add more duration than he would ever think he would need to add to account for that change.

And no doubt there are always a ton of other considerations to take into the equation.

I would tie LSA to the SCR of a combo more than I would tie it to the stroke of the combo.

The closer to the edge you run the SCR,the more one will benefit from the wider LSA.

And to a lesser degree,I would consider the RPM range the combo will primarily operate in.

Stroke would be among the last things I would tie my LSA choice to.

Though I do admit there is some small relationship between the two (LSA & stroke).

But that mostly is used to keep the hp/trq peaks @ the same basic RPM when choosing cams for various strokes.

If one is not overly concerned with the slight shifts in those peaks when a given cam is to be used with a specific stroke,than often that is of little concern.

Power band width and average power,that's a whole other discussion.

But I digress.

[tempest455]

Ditto what Cliff said.

My old E head 455 was 11.5:1 and I ran on pump gas (92 octane) for years. Of course, I had a big solid in it to bleed off some cyl pressure.

[BVR421]

I dont know if 600hp will happen with GS4s 1 3/4" headers
I think 1 7/8" bare minimum for 600

[Half-Inch Stud]

Careful now, gotta use Cliff's advice as a darn good baseline for the reason of getting the 60foot time.

I'm convinced these BIG CAMS make big power at hi-RPM but they also LOOSE power off-idle. Worst-case is stock converter (who does thaat anymore) but a 2800-3200 stall may not be enough either. When a fella says over-cam in the 254@.050/108LSA they are ALSO needing a 3900+stall converter to get the 60foot into the 1.5's. That is not Street-able.

So I'm trying to bend the deal here with the Switch-Pitch.

[issach428]

i am running the same cam that mr. pbody refered to that was in fronkensteen, only two trips to the track but ran an 11.29 at 119 first time out. Should be in the 10's this spring.

[screamingchief]

Originally Posted by BVR421

I dont know if 600hp will happen with GS4s 1 3/4" headers
I think 1 7/8" bare minimum for 600

That deal would probably be the strongest argument for the wider LSA cams here if you asked me.

If I were going to opt for a wide LSA cam to get these sorta goals,I'd select a HR cam just a bit bigger than the current one,maybe low to mid 240's @ .050" probably on a 112° LSA or something of that nature.

I'm not single minded about one approach or the other,either one can work.

But do note,that 70 lucerne lemans runs the 310 KRE D's with a 290b6,and it seems to run pretty well (9.92 best I believe).

Though he may indeed have some bigger headers as you point out BVR,also IIRC he runs with an open exhaust too as his deal is race only.

He also runs more SCR,12.5:1 or so IIRC.

If you go that route (tight LSA/high SCR),race gas is a must,no argument on that from me.

I will state for the record here that I generally dont care much for solid cams (flat or rollers) on wider LSA's (> 110°),that is not untill you get into some seriously big SR cams (270° + @ .050") and higher RPM (7000+) applications.

Though some smaller solids on a wide LSA seem to work ok in some healthy street applications,but they often give up something to their hydraulic cam counterparts.

I personally would'nt waste my time with any solid roller under 240° @ .050".

A SR in the mid to high 240's @ .050" on a 110° LSA will make a good street/strip SR cam though,I just sold one like that not too long ago,that cam should have been able to get right around 600 hp in a combo like this,it was 248°/252° on a 110° LSA ground on the .406" lobes.

I also forgot to mention earlier that one other strong influence on the LSA choice is the abillity of the heads as that relates to cid,bad heads on big engines need help,good heads on most any engine does'nt need as much help from the cam.

If I were intent on using a wide LSA,I would probably stick with the HR cams as most others here have suggested.

But I just dont feel the current one will clear the 600 hp hurdle myself.

[pinballDan]

The runs I have made I have made through the full exhaust . I still was wondering if I was to install cut outs would I see any gains ? Would you install them in front of the h pipe or after the h pipe ?

[GS470]

I really appreciate all the responses, lots of great info. I wanted to see if what I was thinking was reasonable and it looks like it's not too far fetched. And as was stated in the thread, there's a lot of different ways to get the job done. I'll admit, a lot of the serious technical discussion is over my head, but I'm able to follow along to a certain extent and it's all part of the learning process.

Tom S suggested I talk to Dave to get his recommendation. I didn't do that right away because I wanted to see if there were any strong feelings one way or the other on the KRE vs. SD ported KRE D-ports. Looks like sticking with Dave is a good idea, so I'll be following up with him to get his thoughts, too. This post gives me several specific things to ask him about. Including the potential ring seal issue. My motor's really low mileage, so hopefully I'll be OK there.

1050goat - I look forward to seeing your results and combo. Good luck!

Darby - Hopefully I'll go forward with this stuff and see you at the Rock this summer where we can both test new combos.

Silver Judge - You're so right. There is no way to rationalize this need for power, but it sure is fun reaching for more.

Thanks again. I'll let you guys know what I end up doing.

[ponjohn]

what I can add to this thread is based on sim data, speaking in great depth with Steve C and Bruce Wilkie.

My "testing" sims only, as mentioned the wider lobe seperation does produce a lot more power along with as much lift as possible. On the advice of Bruce I began changing cam specs and averaging the hp from 4k rpm to 6500. I was very surprised at the results.

If I chose the cam that produced the highest peak hp, I would have sacrificed nearly 20 + avg hp from the given rpm range. The average hp I ended up at is 609 AVG hp from 4k-6500. ( one might argue the 6500 rpm. as noted in another thread the belief is that the sims can raise peak hp by as much as 300rpm).

When I started researching cam profiles I was told to use a 280@50 cam. This to me was unacceptable an unecessary.

The cam profile I thought was the best spec'd as so....252/259@50, 112 lsa installed @110, 702 lift. This sim'd at 714 hp @6500, 636 tque at 5k rpm. This produce and avg hp of 609.6. This is an UD lobe.

The cylinder head flow I used was Moneypits 325cfm d-port flow numbers. This is on a +35 455 @ 11-1.

I am currently waiting for Dave at SD to get settled. Once he does I expect avg flow numbers from his cnc 315 cfm d-ports.

[Skip Fix]

Mine is on a 112 LS and 107 IC 10.25:1 aluminum heads and 93 octane. No problem with power brakes, a little lumpy in gear at idle but not bad even with that tight 10" Continental convertor and no noise Rhoads either.

That time is with slicks but with full exhaust and tailpipes.

[screamingchief]

Originally Posted by ponjohn

what I can add to this thread is based on sim data, speaking in great depth with Steve C and Bruce Wilkie.

My "testing" sims only, as mentioned the wider lobe seperation does produce a lot more power along with as much lift as possible. On the advice of Bruce I began changing cam specs and averaging the hp from 4k rpm to 6500. I was very surprised at the results.

If I chose the cam that produced the highest peak hp, I would have sacrificed nearly 20 + avg hp from the given rpm range. The average hp I ended up at is 609 AVG hp from 4k-6500. ( one might argue the 6500 rpm. as noted in another thread the belief is that the sims can raise peak hp by as much as 300rpm).

When I started researching cam profiles I was told to use a 280@50 cam. This to me was unacceptable an unecessary.

The cam profile I thought was the best spec'd as so....252/259@50, 112 lsa installed @110, 702 lift. This sim'd at 714 hp @6500, 636 tque at 5k rpm. This produce and avg hp of 609.6. This is an UD lobe.

The cylinder head flow I used was Moneypits 325cfm d-port flow numbers. This is on a +35 455 @ 11-1.

I am currently waiting for Dave at SD to get settled. Once he does I expect avg flow numbers from his cnc 315 cfm d-ports.

Dont trust those sim programs blindly John,I suggest you go take a look at what it took Walter Lansing to get that sorta power with his bigger engine (525 cid).

Walter's first 525 build.

His first outing was with 370 KRE D's and a 267°/276° 108° cam.

In that version he made 749.1 hp @ 6200 and 699.5 lbs-ft @ 4500,average hp was 672.4,average trq was 668.9 according to his dyno sheet.

Not too shabby for a long stroke combo using a tight LSA,huh?

So,lets now consider that your sim is telling us with less CID,less head flow,and a smaller cam (albeit on that wide LSA) your gonna approach his numbers???

I just dont think that your combo will get to the numbers the sim suggests John,no offense intended this is JMO.

Also ponder that your sims peak RPM numbers are actually a bit higher with the shorter duration/wide LSA/small cube combo than it is with Walter's longer duration/tight LSA/big cube combo.

That's the stroke/LSA relationship I mentioned earlier.

Then you should go look at the second version of Walter's motor...

Walter's second 525 build.

Though I'll admit your two combos are'nt exactly an "apples to apples" comparison,the known combo should make you take a pause and review that sim as well as your game plan.

But take a good look @ what they did with the cam in that combo.

Now granted your proposed smaller engine is not as hard to feed,and thus the heads are'nt as pressed to feed the added cubes like Walter,but keep in mind that deal is just another small part of all this.

Like I said earlier,when one plays with the LSA he is going to employ,he absolutely must be ready to play with the duration to account for his first action,or the results suffer greatly,and understand that both of those affect the overlap you get,all three of those are entirely inter-dependant on each other,there is simply no way around that fact.

Which one of those a fella chooses first,will pretty much dictate where the rest end up being often.

Does he choose the LSA first?

Does he choose the duration first??

Does he choose the overlap first???

A smart fella can juggle cam numbers all day to get just about anything one could want.

That same fella can get there with less duration on a wide LSA,or he can do it with more duration on a tight LSA,or he can choose something between those two.

Each choice will have it's own needs and strengths,as well as it's own weakness,it's all a bargaining game,a very tricky game of compromise.

Just keep an open mind and dont get locked into one mindset.

I wish all good luck in their endeavours.

[ponjohn]

I don't necessarily trust the sim data blindly.

What I do trust is the trends they show.
The trend I see is just what Cliff's real worl data supports, this being the wide LSA tend to make more power, certainly more average power.

The problem as i see it is: I (we) do not know how many different cam profiles were tested in ANY combo before the end result was published.

What do I mean? How do I know if Walter's cam was the first or 20th choice. Do I know if he and Dan experimented with wide lsa or narrow, more or less duration, more or less advertised with the same at 050. More lift, less lift. Let's agree the possibilities are near endless.

Do I think the sim data for the 463 I posted above will make 700+ hp, probably not. I do believe this is more of an educated guess based on the trends than a "gut" feel. I am not implying your offering a gut feel.

I want to the responsible party for my next cam selection, good or bad. Then I have no one to blame but myself if I am disappointed in the power production.